He uses high-resolution satellite data and drones to map glacier melt and precipitation in the world’s most rugged terrain. His findings provide the scientific backbone for assessing risks like Glacial Lake Outburst Floods (GLOFs) and the long term reliability of hydropower and irrigation in South Asia.

His impact has been recognized with top honors, including the 2024 ERC Advanced Grant, the 2026 Alexander von Humboldt Medal, and the American Geophysical Union’s Macelwane Medal.

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1. We often hear about “glacier melt,” but you’ve noted that precipitation variability is actually the largest source of uncertainty for future runoff. Do you suspect we have been over-emphasizing ice melt at the expense of understanding shifting monsoon and westerly patterns?

Yeah, I think you can say that. There’s a lot of focus on glaciers and glacier melt, but if you simply look at the area that glaciers cover in a large river basin, it’s relatively small when you look at the overall scale of a river basin. So, yeah, the amount of rainfall that falls at slightly lower altitudes is also really critical in how much water eventually flows in the rivers downstream. But having said that, if you are high in the mountains and communities that are really close to glaciers, then, of course, glacier melt is a critical source of water. And also in dry and warm periods, when there is no rainfall, then glacier melt provides a steady flow of water to the rivers. But overall, when you look at the different components of river flow, so when you compare snow melt to glacier melt and rain runoff, then, yeah, you can definitely say that rain runoff is in many basins in the world the most important component.

2. Your team is known for using drones to map glaciers at centimeter-level precision. What is one specific discovery you made with a drone—such as the behavior of supraglacial ice cliffs—that would have been impossible to see from a satellite or traditional ground survey?

Good question. Yes, so we have been working with drones on Himalayan glaciers since 2013, and we have mostly investigated debris-covered glacier tongues. So many of the glaciers in the Himalaya are covered in debris, and this debris can have different effects. So if you have a super-thin layer of debris, it means the albedo of the ice surface is lower, and it can absorb more energy, and it actually accelerates the melt. But if the debris layer is getting thicker, then it insulates the ice from melting. But still, we found that these debris-covered tongues melt quite rapidly. And as you already referred to, these ice cliffs and supraglacial lakes that you find on these tongues, they play, let’s say, a catalyst role in this, and they are super important, because usually this is dirty, exposed ice or warm water in the lakes, and that accelerates the melt on these kinds of glaciers. If you use satellite images, then usually the resolution is in the order of 10, 20, or 30 meters, and you don’t capture these small-scale patterns. So with the drones, we have, you know, we make very detailed elevation models at indeed, let’s say, a resolution of 10 to 20 centimeters, and then we repeat that every six months, and when you subtract those two, you can see in great detail where on the glacier surface the biggest mass loss is happening. And we found that those are indeed those glacial lakes and those exposed ice cliffs. And yeah, we then link that to energy balance models and atmospheric models to really try to understand and simulate that.

3. How can we communicate the “temporary abundance” of meltwater to policymakers without creating a false sense of water security?

Yeah, that’s also a very good question, I think. Yeah, we have to be very careful. A lot is written about this whole peak water concept, right? So glaciers are, when the temperatures are rising, a glacier melts faster per unit area, but after some time, the glacier starts to retreat, and this faster melt rate cannot compensate anymore for the retreat in overall glacier area. So there comes a point in time in the future when the absolute amount of meltwater starts to decrease, and this is different for every glacier. So for small glaciers, maybe we are already past this peak water. So if you look in the Alps, for example, most glaciers are far beyond that point. But in the Himalaya or in high mountain Asia, yeah, we predict that point is somewhere around 2050, 2060. So until then, it’s likely that glacier melt will increase, especially for the larger glaciers. And of course, when you look at political decision-making, this usually goes in timescales that are much shorter than 30, 40, 50 years in the future. But I think we should be very careful in investing in huge infrastructure like hydropower plants that completely rely on this water source because it will decrease in the future. We don’t exactly know when, but we need to make sure that you get a return on your investments.

4. When the river flows eventually decline after 2050, which sector—agriculture, hydropower, or urban—is the least prepared for the transition?

Yeah, I think it’s, if you look at the total water availability, in my opinion, it’s unlikely it will decline even after 2050. That’s my first point, because yes, maybe then the glacier melt will be reduced. But the rain, in general, most climate models predict an increase in precipitation. So we think that the reduction in glacier melt will be compensated for by extra rainwater. But the big challenge we will be facing is that the flow becomes really unpredictable because glaciers provide a steady source of water. But if they are gone, then whenever it rains on a rocky surface, that water is immediately in the river. So I think our big challenge for the future is how we are going to deal with unpredictable flow and extremes. And from that perspective, I think, yeah, the hydropower sector is quite vulnerable. Because we have already seen in the past decades, you know, several disasters which led to the destruction of hydropower plants, some of which were still under construction. Also, for agriculture, it’s a problem because the seasonality of the flow will shift. So now you know that, for example, in summer, the glacier melt will come. It’s predictable. It’s a little bit variable, but not so much. But if you completely depend on when rain is falling, then of course, yeah, you have to adapt to that. So I think agriculture and hydropower sectors will be the strongest hit, not because of a reduction in water availability, but due to an increase in variability.

My feeling is hydropower and irrigated agriculture. So hydropower, of course, directly depends on mountain water resources. They are usually located at relatively high locations. So probably the hydropower sector will be hit most strongly. And after that, I think irrigated agriculture. Irrigated agriculture, you see that now also in the Gangetic Plain and in the Terai, and everywhere. There’s a lot of groundwater pumping. So that can partly compensate, of course, for this decrease in glacial melt inflow into the reservoirs. But that’s also, of course, limited. So the deeper you have to pump, the more groundwater depletion you get. It’s more costly if you have to pump from deeper sources. But there is a little bit of buffer there. And I think for the hydropower sector, the impact is immediate.

5. Can the region’s underground aquifers realistically buffer the loss of surface meltwater, or are they equally under threat?

I think they can potentially buffer this. So there’s not so much known about groundwater in mountain areas. But as the glaciers retreat, then what you see is that, you know, you have these large amounts of unconsolidated sediments that remain, and then they can offer, yeah, they can serve as a kind of seasonal aquifer that can partly compensate the role that the glaciers have. So they provide a steady base flow to the rivers. But this is really a new field of research. There have been a couple of papers in the last years that looked into this. But that’s a very interesting point.

6. Can “artificial glaciers” or reservoirs truly mitigate the rise of extreme events like GLOFs?

Yeah, I don’t think they can mitigate the effects of GLOFs, because a GLOF is something, you know, yeah, it’s a glacial lake outburst flood, which happens because a glacial lake increases over time, and then the moraine dam or the ice dam collapses, and it results in a flood. But I think these ice stupas or artificial reservoirs can help at a small scale for local communities to provide an additional source of water for irrigation and for drinking water when the glaciers are gone.

7. How can scientists facilitate shared water management in the politically tense “Water Towers” of the Hindu Kush-Himalaya?

I think the role, you know, there’s a lot of sensitivity regarding water-related information, and particularly in high mountain Asia. So there are big tensions regarding this between India and Pakistan, between China and India, and yeah, between many countries. I think the role of scientists is just to promote open science, to be clear on the methods, and to make the data on which these decisions are based openly accessible, so that everyone has the same baseline and benchmark, and that there is no or limited doubt about the numbers.

8. Why has high-altitude precipitation been such a “blind spot” in mountain hydrology, and how will your new DROP project change our climate models?

It has been such a blind spot, yeah, for different reasons, mostly because of the inaccessibility. It is very hard to do fieldwork and to do, you know, to get data from these regions. So we’ve been, last year we went, for example, to an area, yeah, above 5,700 metres, and we wanted to drill an ice core there, and using that ice core we can, yeah, we’re still analysing the data, but we hope to reconstruct the monsoon patterns over the last 30, 40 years. But, you know, getting to such a site, making sure all the equipment is there, dealing with, in this case, we had a very extreme snow event just before the field trip. So these are just examples that show how complicated it is, and there are so many things that can go wrong, and in addition, it’s also very costly to organise these kinds of expeditions. So there’s just a very limited observational basis at high altitude in the Himalaya, and what you also see in the Himalaya, I mean, of course, the latitude is quite southerly, so that also means that, you know, the high altitude is really very high. So if you want to work as a scientist in an altitudinal range between 5,000 and 6,500 metres, it means you need to be very fit, well acclimatised, have all kinds of safety precautions in place to be able to actually do the work. So I think those are the reasons why there is so limited data on precipitation at high altitude in the Himalaya, and we hope to change that in our ERC drop-off project. Yeah, by installing these super advanced stations at high altitude, combining it with atmospheric modelling, and with the ice core work.

9. Having lived in Nepal and spent decades on these glaciers, what is the most profound physical change you have personally witnessed?

Yeah, personally, we have been coming to the Langtang catchment for many years, in addition to other regions. So there, yeah, we know the glaciers really well. So every year you come, it is a shock to see how fast these glaciers are retreating. I think since we started our field campaigns more than 10 years ago, yeah, one of the glaciers we are looking at, it has retreated hundreds of metres, and it has also thinned considerably. And another glacier we used to camp really close to the glacier, 5 minutes walk. If you want to reach the glacier now, it is almost 45 minutes walk. So these are just, within 10 years, you can see those changes.

10. How do you translate complex, 50-year hydrological projections into actionable advice for local farmers?

Yeah, that is a major challenge, and I do not have a straight answer. The problem with many climate models is that the uncertainty is still very large. So there are some climate models that predict an increase of 20% in precipitation, some that predict a decrease of 20%. So if you are dealing with these kinds of uncertainties, it is very difficult to give sound, specific advice to a specific farmer somewhere downstream. So I think our role is at a bit higher level, and we have to come up with these regional projections and show how the water resource availability is going to change, and also make sure that these uncertainties are clearly communicated. You know, usually politicians do not want to hear about uncertainties. They just need a number, and that is what they can act upon. But yeah, the reality is that it is uncertain. The reality is also that we do know it is going to change. Likely there will be an increase in overall water availability. And a big challenge will be to deal with the extremes and the changes in timing. And that we can predict, but with certain uncertainty bands.

11. Since mountains warm faster than the global average, does a 1.5°C global target still offer a “safe” future for the Himalayas?

No. If you see, a 1.5 global corresponds to a 2.1-degree increase in high mountain Asia and in some regions even more. That fact of elevation-dependent warming, combined with the high dependence on snow and glacial melt, makes the region super vulnerable to changes in the dynamics of water availability.

12. I am all out of questions for now. If you would like to add anything, please feel free to do so.

No, I think you prepared very well. And you had some really nice questions. Thank you. It would be nice if you could also maybe refer specifically to this DROP and ERC project because that’s something we’re really working on now. And I think it is a very important topic to improve our predictions in the region in terms of water availability. Because I’ve been doing this now for maybe 15, 20 years. And we’ve learned more about the glaciers. We’ve learned more about snow. But in the end, a major source of uncertainty always comes from the fact that we do not know exactly how much snow and rain actually fall high in the mountains. So, of course, that drives the entire water cycle. So, it’s really critical that we improve our understanding of that.

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In the corridors of power, Forster’s influence is equally pronounced. During his tenure as Interim Chair of the Climate Change Committee (CCC) from 2023 to 2025, he acted as the UK’s lead scientific auditor, holding the government’s feet to the fire over net-zero commitments. This dual role as both a high-impact researcher and a key policy advisor was formally recognized in 2026, when he was awarded a CBE for his tireless services to climate action.

In addition, Professor Forster is committed to applied environmental science through his work with the United Bank of Carbon, a project dedicated to active forest conservation and restoration.

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1. How close are we to a “weather-forecast” style system that tells the public exactly how much a specific ongoing storm or heatwave was fueled by climate change?

That’s a good question. I do think we aren’t very far off from doing it with artificial intelligence currently. I think we’re making big steps forward in this area, and with a lot of work, we can do that attribution with a degree of confidence for a lot of storms, for individual ones. And I think with artificial intelligence, it won’t take a lot of work to automate that. So, in fact, what I would say is: I think we could do it today if countries would put a bit of resources behind it. Yeah, so I think we do already have the tech; we do already have the expertise to do it.

2. Your 2025 review of climate indicators suggests that for 1.5°C, we may already be looking at a negative remaining carbon budget. At what point does the scientific community need to pivot its communication from “preventing 1.5°C” to “managing the descent” from a 1.6°C or 1.7°C world?

Yeah, we do have to do that. And I think before we manage the descent, we have to stop it going up. So, what I would really say to that is we have to stop temperatures going too far above 1.5 degrees. So, whether that’s 1.6, 1.7, or 1.8, we do really have to pivot. Explaining the first thing: once you go up, it’s quite difficult to bring temperatures back down again afterwards. There is no certainty we’ll be able to do that as a society. So, this does tell us that all the fossil fuel we’re burning do really make it worse. So, I think it’s really time we talk about all the things we can do to stop temperatures going too far above 1.5 degrees, 1.6, or 1.7.

3. Having been a lead author for decades, do you believe the current IPCC ‘Mega-Report’ model (releasing massive reports every 7 years) is still fit for purpose in an era of rapid, volatile climate shifts, or is it time for a more agile, rolling assessment process?

Our indicator publication did partly go in that direction to try and give the annual update of some of these key indicators. And we presented them as coming from that international IPCC community of kind of scientists. And that’s because, just as you said at the beginning, I think it’s important we do have this authoritative assessment coming out more frequently, and policy makers around the world do have some robust, trusted information to go on. So, I think we do need that more agile communication.

But in terms of the big IPCC reports, there is definitely a role that they do have impact. But I think there are big issues with them as they are. The first is, they take up too much of our scientists’ time now; too much literature is out there to review. And they’re a big piece of work. And the other thing is that they’re always split up the same way into working groups. And this kind of fragmentation into the working groups, I think, isn’t the best way of communicating our work. Like, if you look at our indicators, that works across the working groups. So, I think it’s important to join them up.

And if you do have a look back at some of the most successful IPCC reports, probably the one I worked on most was the special report on 1.5 degrees; that had real authority, and that had real actionable impact. So, what I think the IPCC should go towards is some kind of an updateable version. And at the same time, it could come out with these more infrequent, authoritative reports on particular topics. I think that would work well.

But I think the other thing we have to acknowledge is that the whole IPCC process has got quite political. So, there are some countries that do not want the IPCC report to come out before the next global uptake. So, I think the other thing that these more community assessments can deliver is they can still deliver that community data where we are, and you don’t necessarily have to rely on your government co-operating to be able to deliver that.

4. With the Indicators of Global Climate Change project providing annual data, is our current policy-making cycle fundamentally too slow to match the pace of warming? How do we shift governments from decadal to annual action?

Okay, good question. It’s not too slow; it’s just not impactful enough. Yeah, there’s not enough co-operation, I think. But there are things you can do. And I think now we’ve gone beyond the words, because what countries came together for before was to come up with some nice warm words that they would do stuff. But that’s a bit different than the actual implementation of policies. And that’s what we have to begin to see countries really deliver on now.

But there are definitely ways to do that. So, that goes with the other job I’ve got. I’m sitting on the UK Government Climate Change Committee. This is a government committee in the UK that really does that translation from the negotiations into what the policies are we need to implement within our country. And the good thing about the committee and the way the Climate Change Act in the UK was set up is that it has a lot of parliamentary authority. So, it can compel politicians to do things, because when we advise on a carbon-efficient target, that target becomes a legally binding target for our country. And if the government of the day is not delivering that target, they get into trouble and have to do more to achieve it.

So, I think we need to have those sorts of parliamentary and governmental mechanisms that really translate what politicians say they will do when they’re together into what they actually do when they get back to their countries. And I think we have good evidence from the UK that this longer-term thinking really works. We set budgets 12 years in advance of when they have to occur, and then they give politicians and businesses the time to change. And it worked well in the UK and EU countries, and now the Chinese, for example, are also going to the same sort of approach, where they try to set five-year targets for their countries. So, you don’t just have a 2030, 2040, 2050 target; you have an every-five-year target that you have to internally achieve for your country.

5. The UK has world-leading targets but is currently off-track for its 2030 goals. As a CCC member, how do you handle the tension of advising a government that agrees with your science but frequently pushes back on the specific, ‘difficult’ policies needed to implement it?

Yeah, so that’s a very intelligent question you’re asking. Yeah, so the good thing about the CCC working is that the government does do stuff, but you’re absolutely right that it tends to do the easy stuff and doesn’t do some of the most difficult things, particularly the ones that could be more expensive to do.

So, we have two different ways of dealing with that. The third way of dealing with it, which we have found successful as a committee, is to just keep on repeating our advice over and over again, all the time. And in fact, that eventually works because they get bored of always hearing the same thing. They eventually do something about it.

So, our top advice currently is to reduce the electricity bills for consumers. And we’re just saying it all the time now, because if you have cheap electricity bills, you encourage industry to electrify and you encourage people to buy electric stuff. So, we could go on about it all the time, and that eventually makes governments do stuff.

The other thing we sometimes do, if we think our advice isn’t working, is try and think of alternative policies that might work. So, we try not to be political, or we try to suggest ideas that could be popular with a conservative government if we have a conservative government. But if we have a more socialist government, we try and give ideas that might be interesting for that government to implement. So, we try and pitch our ideas accordingly.

And the other thing that would work well in Nepal, in particular, would be talking about the other benefits to air quality and the pollution-related benefits. It isn’t just benefiting climate; it also benefits the health of your population and helps remove pollution from your communities. We try and talk about all those additional benefits that come from taking action.

6. In your recent work on the UK’s Seventh Carbon Budget (2038–2042), you’ve framed decarbonization as a “good news story” for the economy rather than a cost burden. How do you plan to convince a skeptical public—and Treasury—that the 0.2% of GDP cost is an investment that prevents a much larger GDP loss from climate impacts?

Oh, wow, good question you’re asking. You’re asking very good questions. Yeah, that is one where we try and go over the costs really carefully. We do lots of analysis, lots of different scenario planning, lots of uncertainty tests to really show our calculations are robust, to really show that a compromise doesn’t stack up. But you’re correct, it just takes someone to say, “Oh, it’s all going to cost too much,” and then they’re always going to win the argument.

So I just think you have to turn it into narratives for the individual. I think the best thing I learned to do is talk about what are the clear benefits for an individual family. And perhaps if you can give an example—like if you get rid of the pollution for the family, and, for example, if they have a petrol and diesel car and they switch to an electric car, or in a broader case, a petrol motorbike to an electric one—the change will actually make it more economic for them instantly. And then they’re going to spend their money on other things.

So I just think you have to try and really bring all this complex economy back to the level of the individual. And the other thing to talk about—well, not good, especially today with what’s going on in the world—is that you can talk about trying to make your country more resilient and provide energy security. If you noticed what occurred when the Ukrainian-American war began, we saw a big increase in the price of gas and oil. This came as a shock to consumers. So what I try and say is one of the best reasons for converting to renewables is that you reduce those economic shocks.

7. You live and work in Leeds, a city aiming for Net Zero by 2030—two decades ahead of the national target. How does witnessing the local, ‘on-the-ground’ hurdles of retrofitting homes and transport in Leeds influence the advice you give at the highest levels of national policy?

The first thing is that we probably will not get to net zero by 2030. That target was set back in optimistic times when we thought we could. In fact, it’s going to be more challenging. But the good thing about setting targets, even if you don’t deliver on them, is that it makes people pay attention. And in fact, what’s happening currently is that people are beginning to resize their targets and are looking far more pragmatically at what we can do in our towns.

But you’re so right that a lot of the changes we have to see do come from central government decisions overseas. Then the other changes we need to make must happen within our communities. So, I think when communities come together, we can have things like community energy production. We can get things like community services. And you can ultimately improve your economy and your efficiency. You can ultimately improve your community.

But to do that, we have to get the communities talking to central government, and that doesn’t happen very well in our country. I do not know how well it works in Nepal, but this is one of the key things we want to see the government improve: internal communication.

8. Regarding “hard-to-abate” sectors like aviation and farming, are we over-relying on technological “silver bullets” like biochar or hydrogen instead of addressing the need for demand management?

Yes, is the answer. Well, I think first, if you do have a look at our committee report, we try to be quite careful not to do that. But that is something I am concerned about, particularly because quite often these technologies can be executed to just continue with what we’re doing currently.

For example, you talk about quite different sectors. If you look at aviation, it’s only a tiny fraction of the population that flies on airplanes. And the people who fly on airplanes could afford to pay a bit more for their tickets. Eventually, that industry could pay for decarbonizing. So, I think the solution there is that the industry really has to make investments to transform itself.

It’s a bit different with agriculture. Agriculture is important for everyone. Personally, I think it’s probably more important to worry about all the other things in your economy before trying to change agriculture too much. The food people eat and consume is so personal, and quite often our agriculture industry is very traditional. There are lots of opportunities to innovate.

But what I think we’re falling into a trap of doing is talking about agriculture when we should be talking about getting rid of coal. First and foremost, we should get rid of coal power generation. That is somewhere we really do have solutions that are much better than what’s out there currently. And I think quite often companies take the conversation to agriculture, which is very controversial and challenging to decarbonize, whereas by far the biggest emitter is coal burning—and for that, we really have solutions today.

9. Given that the top 10% of earners produce half of all emissions, how do you balance the push for institutional structural change with the personal responsibility of high-emitters?

Yeah, and this also applies between rich and poor countries. But recently, there are very wealthy people in every single country, and it’s those wealthy individuals who are really responsible for the bulk of the emissions. And they’re also the ones who can afford to change.

Yeah, so I think we need to see a shift in policy to concentrate on where the big hitters are, to make the most impact. This goes back to my earlier point: rather than trying to get every farmer to do something in your country, you should be really going after big industries and the big-ticket emitters in your country to try and persuade them to develop alternatives.

So, I think we need to get far more pragmatic and far more focused on what we want our society to do first.

10. The Royal Society recently released a report you contributed to regarding SRM. While you’ve stated it is no substitute for emissions cuts, do you fear that even discussing SRM provides a “moral hazard” for governments to slow down on Net Zero?

I have changed my mind on this, and I didn’t use to think I was, but I’m sort of beginning to think today that we at least have to understand it so we can potentially reject it as a possible solution. Unfortunately, countries like Nepal are right in the group of countries most affected by climate change. You’re going to be out there on the front lines, and if it begins to become an existential threat to your communities and your livelihoods, especially your agriculture, perhaps we really can’t ignore some of these possible solutions.

So, I absolutely don’t think we should be deploying them currently, but I do think we should be understanding these technologies, because there might come a time when we might want to deploy some of them. But that should not take away, of course, from trying to bring emissions down as fast as possible. That is the only thing we can do if we want to stabilize the climate in the longer term. So, ultimately, we have to do all of that, of course.

11. After 30 years of analyzing increasingly dire climate data, what specific physical evidence or emerging trend gives you the most genuine reason for hope?

Ah, it’s definitely the changing emissions of greenhouse gases we’re beginning to see now. So, I think the whole idea of “we’re going to turn a corner”—perhaps this year, perhaps next—is where we will see greenhouse gas emissions begin to decline for the first time since the Industrial Revolution. I mean, they dropped during Covid, but that was only a 12-month drop. Hopefully, we’re going to see a sustained decrease in emissions for the first time, and we’re seeing signs of it now from the Chinese—they’re reducing their energy emissions, and this will drop for the first time.

So, I think when the Chinese change, the rest of the world will change, and that puts the whole world on an entirely brand-new trajectory. That does say that, although we have a long way to go to get rid of emissions completely, they are at least beginning to go in the right direction. They’ve been going up, but now they’re starting to turn the corner, and that corner could be this year. That gives me confidence that we can change.

The other thing I want to say is that there is good scientific evidence here. If you look at the 2100 projections from before the Paris Agreement was negotiated, we were expecting five degrees of warming this century. That has now dropped to below three degrees. So, that shows it’s still terrible, but it also shows that the whole Earth can change direction. Countries can change, and we can change course.

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Cox is best known for his influential work on the potential risk of Amazon forest dieback, highlighting how climate change could lead to large-scale rainforest loss. His research showed how interactions within the land carbon cycle may amplify global warming through soil carbon release, a finding that has received widespread public attention, including features in documentaries narrated by Sir David Attenborough. In recognition of his scientific contributions, he was appointed a Commander of the Order of the British Empire (CBE) in the 2025 King’s Birthday Honours.

In addition to his research, Cox has played a significant role in international climate science and policy. He has been a lead author on the Intergovernmental Panel on Climate Change (IPCC) Fourth, Fifth, and Sixth Assessment Reports, contributing critical scientific evidence to global climate negotiations. At the University of Exeter, he also leads the Grand Challenges programme, which supports undergraduate students in developing interdisciplinary solutions to global challenges such as the transition to net-zero emissions and mental health innovation.

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1. In your work with Emergent Constraints, you often find that simple historical observations can narrow the uncertainty of complex Earth System Models. Looking forward, do you see the future of climate science leaning more toward these “top-down” observational constraints, or will the priority remain “bottom-up” complexity, such as modeling individual microbial processes?

Yeah, I think it’s going to have to be a bit of both. So, we do need process-based modeling because we are extrapolating out a sample, if you like. But I think what’s happened over the years is we’ve made calibration of models a kind of taboo, something you shouldn’t do. And I think in most predictive science, in all other predictive sciences, pretty much, you would expect to have to calibrate your model against the observational record to get a good prediction of the future. So, I think we need to break that taboo and start to think about transparently calibrating our models against observations, especially against the observational record. What the emergent constraint thing shows us is that, if you just look at the observational record, it separates the unlikely from the likely in terms of models, and that’s really important. So, I think just getting to that point means that we will not rely on relatively crude emergent constraints, but actually we’ll have models that fit the observational record as a sort of requirement, to within uncertainties associated with natural variability. So, I think that’s absolutely key, and we are working on that at the moment. It’s the idea that we just need to get the whole community to see that as the way forward.

2. The latest generation of models (CMIP6) showed a higher range of climate sensitivity than previous versions. Based on your work in constraining these models with real-world temperature fluctuations, what is your current assessment of where the “true” sensitivity lies, and what does that mean for our remaining carbon budget?

Yes, so the true sensitivity looks like, if you look at the observational record. So, we’ve done two things. One was to look at the variability of the system. That turns out not to work so well on the latest models. If you just look at the warming, say, since 1970, when greenhouse gases have been the dominant forcing factor, then you find that models that have got climate sensitivities that are above four, certainly above five, do not look like they fit that record very well. And essentially, we are reaffirming, in a way, that the most essential estimate is about equivalent climate sensitivity of three, probably plus or minus one or 1.5. I think one is more likely, so more like two to four for the equivalent climate sensitivity. That relies on what models generally show us: that the climate sensitivity doesn’t change very much through time. But in some models, there is what’s called a strong pattern effect, where the sea surface temperature warming that takes a while to emerge could change the climate sensitivity somewhat. But generally speaking, if you look at models over the historical period, the ones that look like the historical period have a climate sensitivity of somewhere between two and four, with rare exceptions. So, I would say that that is where I would still think the most likely outcome is. That’s good because, if it’s six, the system is very prone to getting hot very quickly or getting significantly hotter. And it’s closer to sort of an instability in the climate cycle system if you’ve got an ECS of six. So, I’m pleased that it’s not looking like that.

The interesting thing about the remaining carbon budget is you can get an emerging constraint directly on that without thinking about climate sensitivity, because the remaining carbon budget is essentially related to how much global warming you’ll have at peak. And we know that global warming is pretty much linear in the total emissions since pre-industrial times. And then you could just plot global warming against emissions for models, and you can look at what the real world is doing, and you could do an emerging constraint directly on that. And we have done that recently. So, in a strange sort of way, the remaining carbon budget is easier to constrain than the climate sensitivity, certainly the equilibrium climate sensitivity, because it’s what we see most clearly in the observations. And, yeah, we haven’t got much left for 1.5, if anything, and we can sort of get constraints on what 2 is. So, that’s a really interesting thing.

It’s one of the things that’s come out of climate science in the last 15 years, which is that, despite the great complexity of the system, at least for the current greenhouse gas forcing, there was an extremely strong correlation between global warming and emissions from the beginning, so the cumulative emissions. And that’s a really powerful constraint, which is why net zero makes sense, really. Otherwise, net zero might not make sense, but that does really make sense.

3. Based on your research into transient climate response, what is the magnitude of the “warming spike” we should expect as a result of global aerosol unmasking?

Yeah, I can’t give a direct answer to that. So, what’s going on at the moment in the climate system is that we continue to have CO2 concentrations and methane concentrations go up. And we have, for a while, had a counteracting cooling from aerosols, especially sulfate, sulfur dioxide that turns into sulfate. And sulfate reflects sunlight and also makes clouds brighter. So, that’s been masking some of the warming. I think the warming over the last 25 years is associated predominantly with darkening of the planet. So, not with the blanket greenhouse gases getting thicker, but with the planet getting darker and absorbing more sunlight. And that seems to be most likely due to sulfur dioxide production. So, it looks to me like maybe, and this is just an approximation, half or so of our warming, the warming we’ve had globally since 2001, is due to aerosol decline rather than greenhouse gas increases. If that’s the case, we will eventually get to the point where the aerosols are very low, and it doesn’t matter so much. But during this transition, it is quite a significant amplification of the warming. So, if you just look at that period and you don’t take account of SO2 reductions, you might assume that climate sensitivity is high, but I don’t think it is. I think it’s where it was. It’s just we’ve got another forcing factor that’s very significant.

So, if you look at satellite measurements, for example, from the Ceres satellite, we can see that the amount of shortwave radiation is being reflected back by the planet is going down. And the Ceres record starts in 2001, goes to the current day. During that time, I think it’s reflected shortwave drop by about 2% to 3%. So, that’s about 3 watts per metre squared over that period. By comparison, if you double carbon dioxide, you expect 3.7. So, it’s close to the amount you get for doubling carbon dioxide. It’s just due to this darkening. There’s two reasons why that darkening might happen, roughly. One is forcing, so most likely reducing SO2, so reducing brightening of clouds, reducing inflection of sunlight. And the other is due to feedbacks. So, climate feedbacks in models quite often lead to reductions in cloud cover, especially low cloud. And that makes the planet darker because the cloud is bright otherwise. And therefore, you absorb more sunlight. So, the question we have at the moment is, how much of the darkening, the polarity darkening we can see, is due to SO2 reduction and how much is due to feedbacks? If a lot of it is due to feedbacks, the climate sensitivity would have to be really high. And that would be at odds with what we’ve seen in the observational record. If it’s due to sulfur dioxide, it probably needs to be a bigger reduction, you know, a bigger decline in the cooling effect of SO2 than the model is currently showing. So, there is a bit of a contradiction paradox at the moment, in that the global warming record, historical global warming records, suggest climate sensitivity is about four, maybe three to four, probably near a three. And yet the darkening, if you take it on face value, might suggest it’s much higher. The only way to square those two things is to see that most of the darkening is due to sulfur dioxide reductions and not feedbacks, if that makes sense.

4. Your early simulations regarding Amazon dieback were instrumental in defining the concept of tipping points. Given twenty years of subsequent data on CO2 fertilization and forest resilience, how have the specific mechanisms of that tipping point evolved in the latest Global Systems Institute models?

Yeah, very good question. I mean, generally across the board, climate system models are getting more complex. What we had when we first published our results in the year 2000, we basically had two counteracting effects was that CO2 in that model would fertilize plant growth and, therefore, increase carbon storage in the Amazon and make the Amazon forest healthier, in a way. But the impacts of CO2 on climate, which was warming and drying, would do the opposite. And that’s pretty much what still goes on.

The additional sophistication comes in two things: that CO2 fertilization is probably limited by things other than water, for example, nutrients, especially phosphorus in the Amazon. Very few models include phosphorus. And secondly, the mechanism by which you release carbon is probably more explosive than we assumed in those models. So essentially, what happened in those models is the soil carbon would be released because the soil got heated up and decomposition happens more quickly, then you lose carbon from the soil. Whereas what’s likely to happen in the real world is happening in the real world, does happen in more complex models, is that, if it gets sufficiently dry and the dry season gets long enough, you can have fires take over, and then the forest can’t re-establish and the carbon gets rereleased.

So, what’s happened between 2000 and now is that we don’t get the large-scale dieback we saw in that single model, thankfully. But what you do see is a tendency for local dieback in lots of models, which is often mediated by fire, by drying, warming, and fire. And I think we’re seeing more evidence of that in the observations too. You know, the dry years are leading to more loss of carbon than previously in the Amazon.

5. Has the scientific community focused too much on “most likely” outcomes while under-preparing for the fat-tail risks and low-probability disasters your research highlights?

I think so, in general, I think it’s changing, but I think we have. So, the notion of tipping points, which really only was voiced in the climate community in 2008 by my colleague Tim Lenton’s paper, which has been very influential, has taken a long while to take hold in the mainstream climate science community. Now, we have quite a few projects that are using climate models and looking at data and looking at early warning signals of tipping points.

So, there was a recognition that the biggest impacts of climate change are not going to be smooth global warming, they’re going to be what that means for extreme events and tipping points. But it’s taken a long time. I think it’s probably too long. We’ve probably taken 15 years from when that first idea was out there for it to get into the mainstream. But it’s in the mainstream now, and there’s quite a lot of work going on in this domain now.

I think it’s true that the risk was certainly dominated by extreme events and tipping points. The overall impacts and risks are associated with that. So, if you want to really deal with those, you’ve got to start to look at those nonlinearities. And for a while, I think people were of a view that climate models didn’t have those, but they do. If you look at climate models, you can see localised Amazon dieback, you can see subpolar gyre collapse, you can see all sorts of things going on. You just got to look in this multitude of data to see it.

6. Given the 2024–2025 temperatures reaching the 1.5°C threshold, does the “Net Zero by 2050” framework remain scientifically sufficient, or must we now pivot to an aggressive Net Negative timeline to prevent permanent biosphere damage?

I mean, the risks just go up because of the nature of tipping points. We don’t know where they are. It’s a bit like, some people have said, it’s a bit like running down stairs in the dark. It’s dangerous, but you’re not sure where the steps are. So, the way you would deal with that is to try and slow down so you’re not going to actually move quickly.

And so, we have to reduce the rate of global warming and the ultimate level of global warming. We are not going to avoid 1.5 now. I mean, not by conventional mitigation, or by CDR to come down to a certain degree, we’re not going to do that. Two degrees is still a possibility, but there’s a challenge, as you probably know, when people run the pledges that have been made by nations within the United Nations Framework Convention on Climate Change, they come out near a 2.5 or 2.7 still even now. So, there’s more to be done.

And there’s something else rising up the agenda now. So, I think more and more people, including us, are looking at solar radiation management, geoengineering. So, if you had a really dangerous situation emerge, you weren’t sure where it was, what would you do? Carbon removal will always be too slow. Conventional mitigation will always be too slow. Could you, or would you even think about doing something more radical, like making the planet brighter for a while?

And that is becoming more assessed, I think, for a good reason, because we are not mitigating anywhere near as fast as we might. But it remains an incredibly contested area. There’s some people just against even talking about it, and others thinking we should.

7. Given your stance that land-based carbon removal is not a substitute for emission cuts, what is the realistic “sustainable scale” for global sequestration before it compromises food security and biodiversity?

So, I sort of feel that we should be doing forests for the right reason, which is biodiversity renewal and recreation and adaptation, and not for carbon storage. And that just means we’ve got to be a bit more upfront about why we do these things. If you don’t do that, of course, you can end up with forests that are rather lacking in biodiversity. Monocultures just grow fast, and you take water out and bury it or whatever you do with it.

Whereas what you really want is mature forests, and they take a while to grow, and you don’t want to destroy them when you’ve got them, like the Amazon forest, but also you want to promote diversity rather than productivity in the sense of carbon storage.

So, what’s a realistic number? That’s a really good question. I don’t think I know. I would say that the current carbon sink is around about three petagrams of carbon per year, billions of tons of carbon per year. It fluctuates quite a lot. I don’t think it would be easy to do more than double that. I think even with reforestation, you’re probably going to struggle to do more than that.

So, if you get CDR carbon dioxide removal requirements that exceed, say, five petagrams of carbon per year, I think we’re looking at other mechanisms like direct air capture, probably, which, of course, is feasible, but expensive and not yet done at scale. So, probably only roughly doubling the current carbon sink is what you might manage to do. And, of course, we’re still emitting 11 billion tons of carbon per year, so that would help, but it wouldn’t get us there.

8. What is the primary technical challenge in representing human behavior as a dynamic feedback loop within a climate model rather than as an external scenario?

That’s a really good question too. So, I think this is almost like a historical way of doing things. We have judicially cut up the climate problem into the Intergovernmental Panel on Climate Change working groups. There’s one group that does physics of climate change, of climate change projections, and so on. There’s another group that does the impacts of climate change. There’s a third group that does the scenarios of the future, you know, future world development, and what that implies for the emissions of greenhouse gases and aerosols, et cetera, and land use change. And I think that is kind of frozen in a slightly weird separation of the system.

So, humans are still in this whole process outside, almost like they make decisions about the future independent of the environment. And I think if we had them inside, we would probably get some really interesting dynamics in our models, which are really implying that certain things like very high emission scenarios, which assume very high rates of economic growth, are not consistent with the impacts of those emission scenarios by climate change on economic growth.

So, I think we’ve basically got a bit of an inconsistency in the way we do things. But putting people in models is much harder, right? Because I think humans are very resistant to being treated as equations in all sorts of ways. So, it might require something a bit more radical. We may need to use machine learning approaches to connect data, to try and put the human feedback loop in.

But I do think it’s kind of like when Earth system models go from being Earth system models with people outside, like strange misbehaving gods, to Earth system models with people inside. We’ll change our perspective on what’s possible. There are some things that are not possible, because they would require things that are inconsistent, like huge emissions and huge rates of economic growth, or they require things that are not feasible. And I think that’s the next big challenge, I think, with Earth system modeling, is to put people inside, not outside those models.

9. Do you see empirical evidence that positive social tipping points—like rapid technological shifts—can actually outpace the accelerating physical feedbacks, such as methane release, that you have modeled?

Yes. I mean, I think we can sort of see that now. So, even though there’s this backlash against renewable energy in the US and in other parts, there’s no stopping it now, right? If you look at solar energy, it’s amazingly more efficient than I ever thought it would be when I was younger, you know, when I was doing my PhD — much more efficient, much more efficient than trees, you know, in terms of amount of energy captured. And it’s therefore exploding because it’s actually the best and most economical way to generate energy in most parts of the world, even in the UK, where we hardly have any sunlight; it’s still a really good thing to do to have photovoltaics.

So, in the warmer parts of the world, it’s an amazingly efficient thing to do. So, I think we’ve already got a positive tipping point in electric technology. So, photovoltaics and things like electric car uptake — if you look at those, in fact, some of my colleagues have highlighted they are classical positive tipping points, where you’ve got exponential growth, economies of scale that really drive it forward.

And so, my hope is that in the end, the economics of it stops it being stopped, you know, that there is no stopping that once you get to the point where it makes sense, people will just, most people will act in the interest of themselves and their family and do the thing that makes sense. And at the moment, almost all locations moving away from fossil fuels makes sense. It’s almost like just a resistance to doing it, but it will happen.

So, we can see positive tipping points. I suppose one of the things that we’re interested in is whether we could promote those positive tipping points, we could prompt them in some way or not ask, but we might give advice to policymakers whether they would allow them to do those things — whether they’re incentives, or car taxes, or injections into innovation, certain types. I think there’s ways that that can be done. I think there’s hope that we can sort of see it happening in some parts.

10. Will AI-driven ‘foundation models’ eventually replace traditional Earth System Models, or do they lack the physical constraints necessary to predict a climate state the Earth hasn’t experienced before?

You’ve got some really good questions here. That’s a really hot question at the moment because of AI-based weather forecasting is revolutionizing the way weather forecasting is done. But that’s a slightly different problem because we’re generally speaking about weather regimes that have been seen before, and they’re in the data. So, the argument against doing that for climate prediction is that you are going out-of-sample for some parts of it.

So, you could imagine that, say, you wanted to do AI simulation of clouds; the clouds may still experience pretty much the same environment before. But if you wanted to look at the effects of CO2 on cloud cover, you might find it harder because you might be out-of-sample in that respect. So, this argument is still being had. There are some people that are thinking the whole of climate modeling could be done with AI. But some people are saying it must be process-based. I tend to think that we have to combine the two.

In other words, one of the reasons that we haven’t, that problem we spoke about earlier, we haven’t calibrated process-based models is because they’re too expensive to run and, therefore, too expensive to calibrate. But what machine learning and AI can do is create very fast, efficient emulators of process-based models. So, what I’d like to see is that we use emulators of process-based models, compare them to observations, used to calibrate parameters in process-based models which we run.

Sometimes we might run that process-based foundational model at very high resolution for relatively short periods, use it to calibrate an image we can then do projections with. So, I think there’s a hybrid system in which the foundation model, in a way, is process-based. But the machine learning allows you to calibrate that model and extrapolate with it. And that will allow us to do process-based models without the compromises we currently make because models have to run for, you know, 250 years, and we want to do many ensemble members. We have to constantly say, we can’t afford that, we can’t afford that.

If you did it this way, you could do that. You could say, I’m going to have a process-based model that ultimately leads to an emulator that’s very fast. So, that’s where I’d like it to go. But this is a very hot topic at the moment, and we’re working on it in various ways in discussions about where do you draw the line between AI and process-based modeling.

I think it would be a shame if we didn’t have process-based modeling because, as a scientist, I’d like to be able to make a good prediction of the world, but mostly I want to understand it. And the process-based model allows me to think about that. So, there is also a personal thing here, which is that in order for it to be a scientific discipline, it needs to be process-based.

11. As we approach major planetary boundaries, do you believe we are moving toward a period where ‘managing’ the Earth system via active intervention will become a scientific necessity, or does that risk unpredictable feedbacks in the carbon cycles you’ve spent your career studying?

I do think that we should think seriously about what we might do in an emergency. So, some of these tipping points, we might not get warning until quite late in the process. And ideally, you’d like something that just said, well, just for a moment, we’re going to do this, just for a temporary alleviation of the symptoms of the problem. You ultimately have to deal with the root cause, which is to reduce emissions. But we know that takes a long time, and you wouldn’t be able to do it in an emergency.

So, I’m very much in favour of open research on solar radiation management. And we’re doing some work in my group where we’ve looked at, for example, whether solar radiation management scenarios could save the Amazon forest from dieback, and we sort of think it could. We’ve got a paper that’s just about to come out on that. So, I think there is a case for being more upfront about that.

And because they are fast responses, you don’t need to do them now. But you do need to start thinking about what you might do under what circumstances. It’s a really tough problem, right? Because with climate change, it’s kind of like it’s an accidental byproduct of development over the last 150 years. But with this, you’re doing something deliberate, and that means that there’s a higher level of confidence required that it’s not a stupid thing to do.

So, I do think we’re going to need to think about — and even if we don’t need to, I think we should think about — what we might do in an emergency in the short term. And the only thing I can think of at the moment are solar radiation management approaches, which are promising in many respects, but you wouldn’t want to do them instead of cutting CO2; you just might want to do them to avoid some tipping point or some climatic extreme temporarily. And so we’re working on that.

And others are, I think it’s still, again, a bit of a taboo in mainstream climate science, but I think that’s changing. I hope it is.

12. Would you prefer a national government or a coalition of world governments to lead solar radiation management research and implementation? Or would you prefer private individuals, such as Elon Musk or other major business figures, to initiate the process?

Yeah, I think it would be terrible. So, if it’s going to be done, it has to be done with agreement. And that will make it really unlikely to be done, to be honest. If you think about it, we can’t even get agreement on cutting emissions, then it’s unlikely to be done, but it needs to be done with agreement.

The worst-case scenario is that this becomes a sort of underground, you know, tech billionaire toy that they play with. And at the moment, they are not interested in doing that. In fact, most of them are either denying climate change, like Elon Musk, or they are working on other things, and they’re not thinking about doing this. There are some foundations working in this space, and I think they’re doing good things. But public money is required to make sure this is all above board.

And now we’ve got a program in the UK called ARIA that’s going to be thinking about SRM, solar radiation management approaches, and I think it’s really important. It’s public money because then there is a necessity that it’s publicly available information to people. People need to know about what’s going on. So, to answer that long answer to that question: yes, it should be through a coalition of governments, and it should, above all else, be visible and open to scrutiny.

13. As a scientist who has moved from the Met Office to the Global Systems Institute, where do you now draw the line between objective modeling and active advocacy for policy change?

Very good question too. I’m still a scientist, so I want to maintain my objectivity where I can. If somebody asked me my opinion, then, like you’ve done, I will give my opinion. But in some cases, my opinion is no better than anyone else’s. In some cases, it might be better informed, but not always. So, I think it’s just a question of separating the two.

We’re human beings, right? And scientists. So, being an objective scientist is kind of a struggle against human nature, and we just have to be aware that this is a struggle that’s worth maintaining. So, I think scientists in general, their greatest value is that they sort of take a democratic oath to be objective and are assessable in things where they can.

So, I think as long as one can separate these things, I think it’s okay to be involved in both. And the GSI has some people that are really quite involved in activism, and I fully support that, as long as there’s a separation between things you say as an activist and things that you research, or where the connection is clear — you know, where there’s a reason why you say these things.

So, I think we’re going into a situation where we’re not going to be able to — well, it’s been a while — we can’t stay in our ivory towers forever; we’re going to have to come down from our ivory towers. But I think we still need to maintain a sort of sense of objective assessment because some of these things are really difficult to deal with, and they are very politically charged, and ideally, we want to avoid that if we’re going to get to any solutions.

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1. In a 2026 reality where the 1.5°C threshold has been effectively breached, has the IPCC’s rigid pursuit of consensus become a liability that masks the chaotic speed of climate collapse from policymakers?

‘I don’t—I mean, it may be that IPCC, it is the case that IPCC is cautious. And it may be that that slows down policymakers, but I don’t think it’s the major reason that we don’t have forceful policies. As I said before, I think the reason is the opposition of powerful political interests, primarily the fossil fuel companies.

And if IPCC weren’t cautious, it would be making a lot of mistakes along the way that would have been recognized already, and governments would stop giving credibility to IPCC’s judgments about what’s important to do and what isn’t. So I think it’s very good.

There are enough people running around saying, well, IPCC is cautious. That’s kind of a base, but things are actually going to be worse because of X, Y, or Z. We sort of don’t need IPCC to disrupt its reputation for being very careful, because that’s something the policymakers can count on. Then they can calibrate it based on what they’re hearing in each country from their own scientists, or from scientists in other countries that are not organized as part of IPCC, or are, but have a separate opinion and express it publicly.

And then recalibrate and decide that, okay, IPCC says that the damage done from one and a half degrees is going to be some list of harms, and the likelihood of them occurring is in that list. But others think it’s going to be worse. Maybe some others think it will be not so bad. And then the governments can make their own judgments.

But if they don’t have that baseline to calibrate from, where they know that IPCC is careful and is cautious, and that the statements from IPCC lean a little bit away from scaring people, let’s put it that way, then they can’t take that into account. If we didn’t have an IPCC, we wouldn’t be able to anchor our judgments about scientific matters at all. We’d have a thousand different voices or more expressing opinions, and no one voice that is the calibration. And that’s IPCC.

2. Does the current scientific effort to downplay “tipping point” doom in favor of immediate action risk accidentally lowering the perceived stakes for the radical structural changes required in the fossil fuel industry?

You know, my own view, as stated in a paper that I was co-author of about less than a year ago, is that the tipping point analogy is overdone. And it’s applied to many situations which aren’t a tipping point, or which people don’t appreciate are a tipping point, and where the physics underneath is really that it’s not a tipping point.

So one example would be that while the ice sheets may have a physical trigger at which they start to disintegrate faster, a particular temperature, there’s a very wide range about it, which is not going to be resolved quickly. So it hardly should be called a point. And in addition, in most scenarios, it’s not like you go through a particular temperature and all of the ice disappears. It’s probably a different temperature at various locations around the ice sheet that causes such a trigger.

And then there are processes which, even once the loss of ice is triggered in a particular region, which eventually will cause sea level rise, do not occur instantly. It’s not like this big amount of ice all of a sudden falls off the continent in the course of a few days or a few years. It takes a long, long time, even once you’ve passed a tipping point where the physics says, oh, we’re eventually going to lose all our ice on this, or a lot of it. That doesn’t necessarily occur for hundreds of years.

So it’s a metaphor which is not accurate about the processes and is not accurate about what people will see in front of them. Even if we pass a physical tipping point, which might be a good thing to avoid and a good target for policy, it’s not going to be that people are going to say, you know, ten years from now, we passed a tipping point, we’re still here, what happened? So it’s not necessarily the best way to frame the discussion, either scientifically or for policymakers, and in fact might be counterproductive, because the idea of the tipping point isn’t the way people experience most of what happens with climate change, and isn’t the way it plays out scientifically, either.

So I don’t think that that’s the problem. If I think there’s a good scientific framework for policymakers to understand how climate change will manifest itself, it relates essentially to the probability, the chances that extreme events, among other things, will occur in particular places and over a certain period of time. And policymakers can understand the language of probability. Business people can understand the language of probability, because probability is the way they think about risk. And risk is what governments think about when they think about big issues like national security or economic collapse. It’s the way businesses think about the future. Every big firm in the world has a risk manager.

So I think the way that scientists can most effectively enter the policy discussion is to frame things in terms of risk and probability. Now, you could say, well, but the average person doesn’t understand these concepts, and that may be so. And ultimately, it’s basically not scientists’ job, I don’t think, to make sure that they twerk their message in a way which is digestible by the general public. Scientists should be scientists. It’s hard to present scientific understanding in a way that the average person could understand without twisting the science.

So although I myself do a lot of public presentations, I’m very careful about making sure that they are truthful, even if they are simplified in a way that the public can understand. And that’s the job of governments also, to be truthful and to explain climate change to the people in a way that’s understandable.

And so do I think this one little aspect of climate change discussion discourse, namely the tipping point translation of the science, has been a problem in either causing governments to do too much or too little? No, I don’t think so. I think it is confusing and inaccurate the way it’s used, and I think we ought to all find better ways to communicate, even if we’re just scientists, to find ways to communicate our science better. But I don’t think it’s the main problem. I think the main problem, again, is interest groups that have an interest in avoiding action.

3. Your 2025 research suggests global averages hide local catastrophes; how can we move away from “global mean” statistics toward a “hyper-local” risk communication style that actually drives municipal budget changes?

All countries should be organized around the problems of emissions reduction, or emissions mitigation, and adaptation to climate change. Particularly with adaptation—planning for the future, or emergency response in the case of a bad event that was made worse by climate change—governments need to localize the information. They need to get people to understand how this global problem has had, and will have, effects in their neighborhood.

There are some issues with localizing some of this climate information, because we only know it at a more general level. Our models are not yet good enough to resolve things on a village level, let’s say, or even a city level in some cases. But there are ways to translate the information that’s garnered at a larger scale into probabilistic, reasonable guesses as to what will happen in a particular community. And that’s the information that governments and people should be acting on.

The governments in most countries have not done a very good job of translating the science into information that people living in particular communities, villages, towns, cities, or states and provinces can grasp and act on. They haven’t been very good at providing the funding so that communities with less money than the central government can act on it. Frequently, they just don’t have the resources to do what needs to be done—like building coastal defenses, evacuating people, evacuating habitation from areas too near the coast, or building better ways for people to escape if a storm that’s been juiced up by climate change is approaching.

The funding for that is sub-minimal. It’s got to get much better, much bigger. And the rich countries have an obligation to help the countries that have little emissions but are suffering the damage, in some cases worse than the rich countries. Those countries—the rich countries—have, in this case, an obligation to help the poor countries.

4. As inland communities face record wet-bulb temperatures in 2026, how do we ensure “managed retreat” doesn’t just trade a flood-prone catastrophe for a heat-fatality one in poorly prepared inland areas?

It’s thematic of a broader problem, which is that it’s not just managed retreat, but the whole urbanization problem. The urbanization trend is driven by economic factors: people are moving from inland areas where agriculture is not providing a route to a better life, into urban areas where there are better job prospects in many cases. But a lot of these urban areas are coastal, and they are threatened by sea level rise. It’s kind of the reverse of the problem that you mentioned, but I’m sure it goes the other way, too, in many cases.

And that is a phenomenon which is fairly widespread in terms of dealing with climate change: frequently, people do trade one set of risks for another set of risks. That’s quite common. We’re just starting to understand it. There is some evidence that people who want to move out, or are encouraged to move out, of areas faced with flood risk try to avoid other areas that have high flood risk, but in many cases wind up, maybe, in an area that has high heat risk, which is what you’re just pointing to.

So it’s a real problem that needs to be understood. We don’t have enough data yet about people’s responses. A lot of people are working on this issue, and we’ll know more in a few years. But it’s something that policymakers need to be aware of. They probably shouldn’t just be handing people money to sell their property and then get out of the way, but they should help them find a sensible place to live that has less exposure to climate change, because we know that climate change is going to get worse just about everywhere.

5. How are you advising policymakers to handle the paradox of AI being a tool to resolve uncertainty in climate models while simultaneously acting as a massive energy consumer and a tool for fossil fuel optimization?

That’s a big problem; that contradiction is very real. AI’s electricity demand is causing overall energy demand to increase. That generally causes prices to increase, and if the growth of AI is a bubble, it may burst, and the pressure may decrease. But on the other hand, it may just be that the growth of AI is here to stay, and that means a perpetually increasing energy demand. That’s another reason why governments should be speeding a transition to renewable energy, because renewable energy is the best way to get away from the fossil fuel fallout from AI’s energy demand.

Now, there’s another way: AI should be subject to guidelines and regulations about efficiency. Basically, they’re energy hogs, and like all other new industries, energy efficiency is not the first thing they think of, but they should, because in this case their energy gluttony has big global effects eventually if it continues. So that’s the negative side, and governments are very lax, doing essentially nothing about it yet.

On the more positive side, AI is very useful to scientists in trying to analyze the climate problem. So there’s what we call in the U.S. a catch-22: no matter which side you err on, somebody gets hurt, or some part of the problem gets worse. Either we know less than we need to know, or we’re just guzzling too much energy, staying on fossil fuels, causing too much global warming. We already have too much, but AI’s energy demand could make it worse.

I don’t know—it’s early days. Policymakers are slow to deal with it. They’re struggling. Some of the companies that are into AI have a lot of political influence, and they’re using their political muscle to keep the government from regulating them, at least that’s what’s going on in my country. So, I don’t know where the outcome is going to be yet.

6. As nations “overshoot” 1.5°C in 2026, how do we prevent a single “rogue” state or private actor from unilaterally deploying solar geoengineering as a desperate, uncoordinated stopgap?

You know, I think that’s a threat that needs to be dealt with. I think we need a new international agreement to address it, frankly. Essentially, it involves launching a geoengineering experiment. The most commonly discussed approach is launching sulfur dioxide—an easily made gas—into the stratosphere, where it forms particles that reflect sunlight. This has been suggested for decades as a way to cool Earth.

The trouble is that, although it would probably be effective at cooling the Earth as a whole, it would change climates at different locations in different ways. Some of those changes could make the situation worse, rather than better, for the countries in the areas where the climate gets negatively affected. We don’t know enough about these effects because current modeling is not accurate enough for us to make sensible policies.

In my view, there should be no outdoor experimentation with large-scale emissions of sulfur dioxide or particles into the stratosphere until there’s an international agreement on how to manage it and a way to stop the experiment if it produces nasty side effects. Until the science advances enough to accurately predict what would happen if an individual or a country acts unilaterally, we should do nothing that could negatively affect the climate.

Do I think some rich individual or country will act alone? No. There would be too much pressure from other countries. It’s a serious matter, and countries would not want a single country to shape the climate that others depend on—much like poor countries now resent being burdened with carbon emissions and climate impacts from richer nations. Countries acting alone would likely be ganged up on and think twice before proceeding.

However, it’s possible that if global irresponsibility continues regarding fossil fuel emissions, enough countries might eventually decide to take geoengineering action because other measures have failed. Stratospheric particle injection can cool the Earth as a whole, so some might take the risk in 20 or 30 years. I don’t think we’re there yet.

Right now, some individuals are running small experiments, sometimes with encouragement from a few governments. I hope that governments will regulate these activities before they reach a larger scale.

There are many reasons why this type of geoengineering is a poor way to approach the climate problem. The main one is that particles must be continuously pumped into the stratosphere. If pumping stops, the particles fall out within a year or two, and global temperatures would shoot up again. You’d be relying on the global system being stable and controllable, constantly pumping particles into the air. Given current international tensions—for example, the disputes between the U.S. and Europe over Greenland—it’s clear that the global system is unstable at this point.

7. I talked to one of the proponents of solar geoengineering, and he told me that in case anything goes wrong with the South Asian monsoon or other climate systems, we could stop pumping those substances into the air and everything would turn back to normal. That was his reasoning. What do you have to say about that?

That’s laughable, because if I lived in a country and somebody said, “Well, I’m going to do an experiment, and the monsoon might fail for a couple of years,” I’d be furious. It’s not instantaneous; it would be a couple of years before the particles are gone. And I’m sorry, your farming is going to suffer. I know how I would feel about that. Farmers can lose their whole livelihood with just one year of bad weather. So I think that’s cold comfort, you might say.

In addition, when you talk about these tipping points in the climate system—of which there are some—it’s possible that if you do a full-scale stratospheric aerosol injection, enough to cool the Earth and offset the 1.5 degrees of warming we’ve already had, you might cross some tipping points that make it impossible to go back along the same route. That’s called hysteresis. Some of these physical features of the system might not be able to just return to normal. We don’t know. So it’s important to be very cautious about the way we handle the atmosphere.

The atmosphere is a common good. It belongs to all countries. No one country has the right to destroy it. No small scientific endeavor has the right to do things that the world as a whole wouldn’t approve of if there are going to be global effects. We need an agreement. The chances of such an agreement now are very small because of dysfunction in the global political system. But things won’t always be this bad. I think we’ll eventually get back to a situation where governments can come to their senses and develop ways to encourage scientific research while managing the risks.

As of today, that means not allowing any experiments of significant scale in the atmosphere. There’s plenty of work to be done on computers and in laboratories. We don’t need the cowboys running around shooting things into the atmosphere at this point. Let them focus on other geoengineering research. At this stage, any experiment that’s too big—enough to threaten significant side effects, locally or globally—should not be allowed. We need the international agreement first.

8. You have advocated for an “immediate expansion in fission energy”; how do you reconcile the urgent need for this stable power source with the long lead times and high costs that still plague nuclear projects in 2026?

That’s wrong. That’s incorrect. I’ve never been a proponent of expanding nuclear fission energy, period. I’m being misquoted somewhere.

The only thing I said is that research on ways to develop nuclear energy that is safe, affordable, and resistant to the proliferation of bomb-grade material is something governments have supported and can continue to support, because maybe some genius will solve the problem one of these days. But until those issues are solved, I’m completely opposed to any expansion of nuclear energy—unequivocally. You either have me confused with someone else, or I’ve been misquoted on the web, and that’s what you picked up.

9. With 2026 legislation potentially chilling environmental criticism through litigation, should the “scientist-activist” move beyond public communication toward a more aggressive legal and institutional defense posture?

You’re asking whether scientists who are also activists—like myself—should take a more aggressive legal and institutional stance. I think the answer is yes. It’s perfectly legitimate for scientists who are politically active in the policy arena to use the legal tools available, make their voices heard, and communicate clearly and accurately so the public can understand. Activists have sometimes had remarkable influence on government actions and corporate behavior.

At this point, we should use all available levers—as long as they are peaceful and legal—to push the public and governments toward stronger action on climate change. In general, in my country and most others, the public wants this problem solved. And now we have the tools to do so: in many places, solar energy is cheaper than fossil fuels. That’s why most of the new electricity generation built worldwide in the past year was solar. Coal plants are hardly being built anymore, and while natural gas is still in use, the best investment at the margin is increasingly solar.

There are challenges, like energy storage—we need better batteries—but these technologies are evolving rapidly. Soon, we will have the tools to support a mostly renewable energy economy, with perhaps some minor backup from fossil fuels temporarily. Given that the technology and economics now align, I believe we can—and should—be as forceful as possible, while remaining peaceful, in urging governments and companies to do the right thing.

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Serving as the UK Government’s Chief Scientific Adviser from 2000 to 2007, Sir David brought climate change to the center of political decision-making, famously warning that it posed a greater threat to global security than international terrorism. He was central to the creation of the Energy Technologies Institute and helped embed environmental policy at the heart of UK governance. From 2013 to 2017, as the Foreign Secretary’s Special Representative for Climate Change, he led the UK’s diplomatic engagement ahead of the Paris Agreement, championed the 1.5°C temperature target, and launched Mission Innovation, a multi-billion-dollar international effort to accelerate clean energy research.

Today, Sir David’s work extends beyond traditional mitigation, centering on what he terms “climate repair.” As Founder and Chair of the Climate Crisis Advisory Group and the Centre for Climate Repair at Cambridge, he argues that reaching Net Zero alone is no longer enough to prevent climate disaster. Instead, he promotes a “4Rs” framework: rapidly reducing emissions, removing greenhouse gases from the atmosphere, repairing damaged ecosystems, particularly by refreezing the Arctic, and building global resilience. His recent initiatives explore bold technological interventions, including Marine Cloud Brightening to cool polar regions and ocean restoration strategies such as stimulating phytoplankton growth through engineered nutrient cycles.

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1. You stated that world leaders had just “five years left” to avert catastrophe; since that clock started in 2021 and we are now in 2026, has the window for a “safe” transition officially closed, or is “Climate Repair” now our only remaining door to survival?

Well, needless to say, that’s a very good question. I’m going to say to you that if only we had acted wisely 20 years ago, never mind five years ago, we would be in a much stronger place globally. Where we are today means that there is an enormous amount that the global community must do in order to create a manageable future for humanity. It’s as serious as that. So, what I’m going to say is we need deep and rapid emissions reduction. We should stop using all fossil fuels in every way possible. But we also now need the other three R’s. I’ve got four R’s. The first R is reduce emissions. The second R is to capture the excess greenhouse gases we’ve already put in the atmosphere. So we have to remove excess greenhouse gases. That’s the second R. The third R, we have to repair those parts of the climate system that are already tipping or are close to tipping. So, for example, the Arctic Sea region is now losing ice from Greenland at a horrible rate, and that means sea levels will rise continuously. And then the fourth R, every country, every city, every region needs to develop strategies for managing the changing climate that is happening right around the world. So, the fourth R, we also need to see that we create a safer world for all of us, given that temperatures are now rising so rapidly that we have extreme, extreme weather events all around the world.

2. With recent data showing January 2025 reached 1.75°C above pre-industrial levels, is it time for the CCAG to officially declare the 1.5°C goal “dead” to force a more radical repair conversation, or does that risk triggering global despondency?

The last three years have seen an average global temperature above 1.5 degrees centigrade, and so your question again is absolutely critically important. We understand the risks are now getting worse as we go forward in time over the coming years, such that, really, if we don’t act quickly, it’s going to be extremely difficult to see how we manage the future. 1.5, however, there’s no point in saying, okay, let’s relax 1.5 and make it 2, let’s stay below 2, or let’s stay below 3, because that is going to be unmanageable. We really have to get our temperatures down to a level which is even less than 1 degree above the pre-industrial level now, in order to manage the future. I’m going to say to you the 1.5 degree centigrade target has been breached, and as we move forward in time, we must focus on keeping that breaching as short in time as possible, and bring the temperature back down again. That’s the big challenge now for humanity.

3. So, is CCAG actually going to declare the target dead?

I don’t think anyone should declare the target as dead, and the reason I say this: that target was set in 2015 at the only meeting where 195 nations all agreed that we should all, if possible, stay below 1.5 degrees above the pre-industrial level. If we abandon that, we’re abandoning the only agreement that we have. So we should not abandon it. We have to say we must see how we can restore that target and even get better, and get down to 1 degree.

4. In your latest 2026 “Planetary Solvency” recovery plan, you argue that financial institutions are drastically underestimating climate risk; if the actuarial data is truly as dire as you suggest, is the current global insurance market fundamentally incompatible with a 1.5°C+ world?

The short answer is yes, but of course, that means that we have to work with the insurance industries of the world. It’s really done by the actuaries working with climate scientists like myself. Those actuaries work for the insurance and reinsurance industries. The biggest group of industries of that kind is here in London, and these are the people who tell their bosses what is happening. Those reinsurance industries all know that this is a big, big challenge. I’m going to say to you, scientists are very good at making good predictions. I myself am very proud of making good predictions, but the best people to analyze the risk are these actuaries, because when you’re working for an insurance industry all the time, you’re having to calculate risk. What’s the risk of your house burning down? They have to understand that so they can give you a price to insure your house against burning down, so if it does burn down, they can repay you. That means these actuaries really know what they’re talking about and what they’re saying. And, Manish, this is really important. What they’re saying is that even in 25 years’ time, the global GDP growth will be damaged by 10 to 15% every year by extreme loss and damage due to extreme weather events. That’s what the actuaries are saying, and already over the past year, 2025, it is likely that loss and damage amounts to, I’m going to say, more than half a trillion dollars. So we’re looking at loss and damage around the world, not all of it insured. Many, many parts of the world cannot afford insurance, but loss and damages are really already in the region of half a trillion dollars a year.

5. You have long called for a global carbon price of at least $150 per tonne. In 2026, with the public already struggling with inflation, how do you convince an average citizen that this isn’t just another tax that will make their food and heating unaffordable, but is actually a “prosperity plan”?

That’s a very good question again. If we look at carbon dioxide emissions, the idea of a tax is to encourage people to use renewable energy, for example, to make electricity. If you use renewable energy, you don’t pay these taxes. This is just an encouragement to see that people switch away from creating carbon dioxide when they use energy. If we look into the future, we have to see that all energy production should come from electricity, including heating and air conditioning, and we also need all electricity production to be created without any carbon dioxide emissions. That’s what we have to target, and that is the only way that we can head towards a manageable future.

6. You’ve recently identified methane as the “fastest lever” to slow heating because it is 80 times more potent than CO2. If we are to achieve the 2030 Global Methane Pledge, what is the single most effective thing the general public can do to force industries—particularly agriculture and oil—to plug these leaks immediately?

Carbon dioxide has a long lifetime in the atmosphere. So if we stop emitting carbon dioxide, the level in the atmosphere will stay where it is now. However, if we stop methane production, because methane’s lifetime in the atmosphere is only about 10 or 12 years, within a short period of time, the temperature itself will start coming down. Now, methane at the moment, methane emissions are causing 30 to 40 percent of global warming. This is not generally understood, and I think the fossil fuel industry is probably trying to keep this information out of the public domain. They want to keep producing methane and for us to use it. If we look at where the methane is emitted from, a large amount of it can be pinpointed by satellites. So we now have satellites telling us exactly where the methane is emitted. We need to reduce emissions of carbon dioxide quickly and rapidly, but we get a big win from reducing methane.

So we started by saying 1.5 degrees centigrade—is that target lost? If we were to reduce methane emissions even 30 percent, within 15 years we could see a global average temperature fall of 0.3 to 0.5 degrees centigrade. There’s the big advantage. Now you ask, what should the public do? The public, in particular, must talk to their governments. Governments in democracies are elected by the public. They need to talk to the media. They need to get the message out into the public domain so that governments can understand capturing methane and getting rid of it. You can burn it to carbon dioxide. Methane is about 100 times more effective as a greenhouse gas. It’s worse than carbon dioxide by a factor of 100 per molecule. What that means is you can just burn it. If you burn methane, you make electricity, so you get money. This is a relatively cheap way to get rid of methane escaping into the atmosphere.

7. You’ve called for Marine Cloud Brightening as a form of “biomimicry” rather than geoengineering; if a large-scale experiment over the Arctic were to inadvertently disrupt the monsoon cycles in the Global South, who is legally and ethically liable in your proposed governance framework?

So, let me say at once that if we start using marine cloud brightening, it can be stopped. Marine clouds are formed when, as you say, we’re mimicking nature when we do this. We’re creating tiny droplets of seawater from the sea itself. Those tiny droplets, when the sea is warm, are carried up by the air. As the droplets are carried up into the atmosphere, maybe when they get to a height where clouds are formed, they lose their water as they’re going up in the hot air. What is left is a single crystal of salt. That single crystal of salt then hovers, picks up water vapor again, and you get a cloud. If the crystals are small enough, the cloud will be white. If you stop making those white clouds, you will stop this whole process. So if the Indian monsoon or any other big negative happening occurs, you can stop this process, and within a week or two, the whole process will be terminated.

Now, of course, the idea is to stop the melting of ice over the Arctic Sea during the polar summer months. This would only be done for three months in the year when the sun has come back to the North Pole. In those three months, it’s possible to keep the ice that is formed over the Arctic Sea by reflecting sunlight away. Every year, the ice will grow again if we keep this up. In that way, we can stop the Greenland ice from melting as well, and sea levels will not rise as rapidly as they are now. I think the big win in this process is that it can be stopped quickly if there are negative consequences, and it saves us from high sea level rises, which would cause major problems.

8. Could you describe your proposal to regenerate ocean biomass via artificial whale excrement?

Well, that’s also a very good question, because I believe we need to remove greenhouse gases at a minimum rate of 10 billion tons a year. At the moment, we are emitting 40 billion tons of greenhouse gases into the atmosphere every year. Let’s suppose we can stop most of that. If we can remove 15 to 20 billion tons of greenhouse gases a year, we can then bring the greenhouse gas levels down to a level where global temperatures will even begin to fall.

Now, I just want to say, the process you’re describing is one in which we recover the biomass of the oceans. The reason is simply that if we use this material—and at the moment, we’re doing experiments with volcanic ash from the Tongan volcanic eruption that happened just a couple of years ago—this material has all the missing nutrients from the surface of the ocean to create large areas of phytoplankton. Green phytoplankton soaks up carbon dioxide from the atmosphere and is the foodstuff of fish larvae. What we create is many more fish in the ocean, because without phytoplankton, those fish larvae just die.

So what we can do is recover the fish in the oceans to where it was 400 years ago, and we can then see that carbon dioxide levels will be pulled out of the atmosphere very efficiently. All of that involves big experiments to be conducted to prove that what I’m saying would happen.

9. You often discuss “stranded fossil fuel assets,” but what about “stranded political assets”—governments whose entire economic stability relies on revenue from resources that your strategy would render obsolete? How do we transition these specific nations without triggering global conflict?

Let me give you an example. The country of Kenya has been one of the most successful countries in the world in switching away from fossil fuels to create electricity from renewable energy sources. Something like 90% of their electricity today is generated without any fossil fuels. The country used to buy resources because they have no coal, oil, or gas, and then burn them to make electricity. Now, they are recovering energy from the heat below the land—they’re using geothermal energy to create most of their electricity. They’ve done this in a short period of time by putting local people to work.

This has two big advantages. They’re not having to buy fossil fuels, and secondly, they’re putting local people to work. It’s really good for their economic growth. I think that’s important because most people think the only countries doing this are advanced ones. For example, Britain has now reduced its emissions by more than 50% since we began working on this 25 years ago. But Kenya is among the world leaders in slowing down emissions dramatically.

So, no, I think stranded fossil fuel assets don’t mean that companies or governments will lose money. What you should be doing now is investing in alternative energy sources—putting your resources into things that won’t become stranded assets.

10. As we head further into 2026, do you see a path where climate repair becomes a bridge for US-China cooperation, or is the technology behind “repair” destined to become another front in a green-tech cold war?

At the moment, with President Trump in place, we have no such cooperation possible on climate change issues. What happened in Brazil? I’m wandering away from your question, but I’ll come back to it. What happened in Brazil is that the United States withdrew from the meeting. Because the United States withdrew, this encouraged many other countries to withdraw their action under their commitments already made. For example, Saudi Arabia and Russia joined the United States in saying they were not making commitments.

But the big plus that happened was that more than 80 countries in Brazil agreed to continue the process of reducing emissions. Under the presidency of the President of Colombia, they will meet in April this year—the heads of governments and their representatives—to see if they can together carry through all of the policies required to create a safe future for humanity. Now, that’s a big challenge, but China is part of that group, Brazil is part of that group, many African countries are part of that group, and most European countries are part of that group.

This is an important group because if they can develop a future without using fossil fuels, they will reduce the power and grip of that industry on the global scene. I’m saying this because it is the power of the fossil fuel industries that is basically in the business of trying to stop action on climate change. Those fossil fuel industries, I think wrongly, believe that it’s the end of their business. They could switch and do the right thing, but they simply see this short-term end of business and decide to stop any action on climate change. That lobby has been very powerful.

11. In your role as Senior Strategy Adviser to President Kagame, you are working with a nation that has a negligible carbon footprint but is on the front lines of climate devastation. Does the ‘4R’ strategy in Rwanda represent a path toward African self-reliance, or is your primary mission there to help the Global South legally and diplomatically leverage the ‘climate debt’ owed by the nations that destroyed these ecosystems in the first place?

This is now quite a difficult question. I’ve been working with the government of Rwanda for many years. While I was working with the British government, I couldn’t work officially with them, but I was advising unofficially. I’m still in that place today. In 2010, Rwanda was the first of the developing countries in the world to declare a policy called the Green Growth and Climate Resilience Policy. I was the strategist behind the development of that policy, but I had to work with many, many ministers. That policy applies right across government—green growth and climate resilience. It is a crucial part of the future for that country.

I’m not saying that Rwanda is going to get involved in removing excess greenhouse gases. I do believe that the removal of excess greenhouse gases and the repair of broken climate systems is work that should be taken on by countries that can afford to do it. I’m not asking Kenya, Rwanda, or other countries that are still growing their economies to invest in that part of the program. I do think it is heavily the responsibility of advanced countries. Amongst the advanced countries, I am counting China, which today is the most progressive country in tackling the problems of climate change.

12. You used the COVID-19 pandemic to pioneer a model for transparent, independent scientific advice; if you were to apply this “shadow government” science model to a specific country’s climate policy today, which nation is most in need of an “Independent Climate SAGE”?

The United States. Yes, I certainly think the United States needs an independent advisory system to deal with climate change. For example, with methane, how do we detect where methane is emitted? In Britain, most of our methane emissions are occurring from old coal mines that are no longer in use, but they’re still emitting methane. We know that because there are two satellites pointing directly at where the emissions were coming from. One of those satellites was from NASA, the other from the European Space Agency. The one from NASA is no longer producing data.

So we’re looking at a country, the United States, which obviously ought to be leading the game in managing the climate crisis, but they are completely turning their heads away from this. They are putting their heads in the sand. They don’t want to hear the bad news about climate change. Yes, I think that’s the country that most needs and could benefit from independent science advice on climate change.

Not all states in the United States are aligned with the federal government on this. For example, California has a governor who is very, very committed to reducing emissions. So it isn’t fair to say that all states in the United States are following what the federal government is saying. But the federal government does have an influence on states, even where they don’t have a majority or a governor that supports them.

13. Is Britain well-equipped to take over the role of the United States, if it had to do so?

What is interesting, if we’re talking about climate change, is that I do believe that in the years 2000 to 2015, Britain played the leading role in the world on climate change. Why wasn’t the United States playing a leading role then? It’s because it has always seen itself as a heavily oil-, coal-, and gas-based economy. So they wouldn’t play with us. Britain, of course, developed its economy on fossil fuels, but we have now stopped using homegrown fossil fuels completely. It is important to understand why the U.S. wasn’t playing a leadership role in that period.

However, Britain is too small in its power on the international scene. The European Union is a much better target to lead the world. Your question highlights the fact that today we really don’t have a global leader among governments who is standing there saying the future of humanity depends on us all pulling together and taking the actions that are needed. Listen to the scientists.

14. You’ve used the year 2090—the age your granddaughter Lola will be then—as your moral anchor. Now that 2026 has arrived with warming hitting 1.75°C, do you still believe you are building a world for her to thrive in, or are you now just trying to manage the scale of the world she is destined to lose?

I have grandchildren. Many of us have children and grandchildren, and we are concerned about their future. I’m an old man, and I really care about the future of our global civilization. We have a long history—we can look back thousands of years. Are we really saying we’re happy to not be able to look forward to more thousands of years ahead? That we can bring our civilization to an end within the next 50 to 100 years? I don’t believe that is the right way to look at it.

My entire operation, and I head up this group, the Climate Crisis Advisory Group, has been focused, since I began working on this within the British government in the year 2000, on how we can strategize a safe future for humanity. We must never abandon that. Of course, it has already become more challenging because we haven’t taken the right action. That means we have to develop resilience against the changes that are coming. The science community can tell the mayor of every city in the world, and the government of every country in the world, what climate change risks will happen in their region over the next 30, 40, 50 years. We can tell them, and if they take that advice, they can begin to build resilience now.

Of course, building resilience will cost money. This doesn’t come free. It is a question of whether we could create a fund big enough, from wealthy countries, to enable all countries to develop proper resilience. But resilience is not the answer. We have to take the four Rs into account. We really have to do all four Rs with equal priority. People say to me, which is the most important? If we keep emitting emissions, then we are cooked. But if we don’t manage where we are already, then we are also cooked. We have to really set out a coherent strategy. And when I say “we,” I mean the global community.

15. Looking at the present scenario, what is your projection for the future?

My prediction for the future is that it’s going to be tough. It’s going to be tough because we haven’t taken the right action. Removing 15 to 20 billion tons of greenhouse gases from the atmosphere is going to be a very big challenge. But if we can achieve that, then humanity has a future. If we can buy time by cooling, for example, the North Pole region and stopping the loss of ice from Greenland in particular, if we can do these things, then we can manage a future for humanity. If not, then I think we might all just stick our heads in the sand and say, “Let’s not watch what’s happening.” Let’s look down, not look up, and not watch what is actually happening. I don’t see that as a good way for any of us to go forward.

16. Do you really predict that human civilization will be doomed in the next 50 to 100 years at the current rate of emissions?

So let me take you through a scenario that isn’t attractive. Sea levels are rising now more quickly than ever before for two reasons. One is the loss of ice on land. The ice melts and always ends up in the ocean. The second reason is the ocean itself—it is being warmed by global warming and expands. So we’ve got two reasons why sea levels are rising.

Those sea level rises mean that, for example, Southern Vietnam, in the Mekong Delta region, is very close to sea level. It was formed by the Mekong River bringing silt down from the higher land. The whole of Southern Vietnam was formed in that way. That’s where the third biggest area of rice production in the world is—the biggest rice paddy fields. In just 25 years’ time, modeling says that 80 to 90% of the Southern Vietnam region will be under seawater for at least two months a year. Once it’s under seawater, it won’t be producing rice.

Then I take you to Indonesia. Indonesia has many rice paddy fields, many of which are close to sea level. We know that the northern part of its capital is already under seawater periodically. Sea level rises are threatening these countries that are close to sea level, yet they produce rice for the whole world. The biggest rice producer in the world is China, and the northeast coast of China, where most of the rice is produced, is also close to sea level.

We’re looking at the first, second, and third biggest rice-producing countries in the world, and their rice production is going to be challenged by rising sea levels in just 25 years’ time. What does that do to the world? It’s not just the problems raised by the insurance industry about loss and damage, but also the production of food for the world. If rice production from these areas stops, it means that countries that produce rice will stop exporting it, and the global market system that sustains us year after year will be disrupted.

So, I’m just saying that within 25 years’ time, we’ve got a real crisis on our hands—unless we get enough action by governments, companies, and individuals around the world to manage the problem.

17. Why do you have so much faith in the climate models? They’re not perfect. Also, since the 1980s and the 1990s, climate scientists have been making dire predictions, such as the world would face trouble within the coming decades and that the sea levels would rise devastatingly within a few years. But none of that has happened, has it?

Manish, you’ve got that completely wrong. I’m going to contradict what you just said. For example, in 2003, we had an extreme weather event in Central Europe, particularly in countries like France and Italy, resulting in maybe 60,000 excess deaths from heat waves that summer. If you look at the climate models, that was predicted. Now, that excess heat has been exceeded every single year since 2003. Why are excess deaths not as high anymore? It’s because resilience practices were put in place—for example, old people were discouraged from going out to shop in the middle of very hot days. Simply instructing people how to behave became an important part of managing that crisis. But the models produced then are already matching what has actually happened in Central Europe from 2000 to the present.

Secondly, we’re not just dependent on models. The models are essentially based on work that was done in the 19th century. In 1824, Fourier, the great French mathematician, calculated what the temperature of the Earth’s surface would be given the energy coming from the sun. He knew how much energy was coming from the sun and thought he knew how much would be absorbed by the planet. His first calculation, however, produced a temperature far too low—about 30 degrees centigrade too low. He suggested that the atmosphere must be capturing energy and putting it back into the planet—like a blanket or duvet keeping you warm at night. To get the right number, he had to make a guess about how much energy the atmosphere absorbed.

Then, in 1860, a British scientist from Ireland, John Tyndall, did experiments by taking air from the atmosphere, putting a warm body on one side, and measuring how much energy was radiated through it compared with a vacuum. He first removed all “impurities” from the air—only oxygen and nitrogen remained—and got zero absorption. But when he repeated the experiment with air containing all impurities—water vapor, methane, and carbon dioxide—he obtained the same value Fourier had guessed. This was the discovery of greenhouse gases.

In 1894, the great Swedish scientist Svante Arrhenius calculated what the temperature rise would be if greenhouse gas levels in the atmosphere were doubled by burning fossil fuels. He was the first to recognize that humanity could change the amount of greenhouse gases in the atmosphere. He predicted that doubling greenhouse gases would increase temperatures between 2 and 5 degrees centigrade. Today, we have just doubled greenhouse gas levels, and temperatures are already rising above 1.5 degrees. If we went to net zero tomorrow and CO₂ levels stayed the same, we would still likely reach 5 or 6 degrees above pre-industrial levels. That prediction, even before computers existed, was remarkably accurate. Most of the problem was understood by the end of the 19th century.

Now we have another major source of information: paleoclimatology. This allows us to know the Earth’s surface temperature going back not just thousands of years, but millions. We can also determine the greenhouse gas levels in the atmosphere at those times. Paleoclimatologists can use this data to predict what temperature rise we would get if greenhouse gases reach a certain level. These two completely different approaches—paleoclimatology and climate modeling—produce very similar results.

The climate science community is a wise and rigorous scientific community. Just as medical scientists discover vaccines that prevent billions of deaths, climate scientists use the best science to warn us about future risks. Science is very powerful when done properly, and I can assure you, the climate science community is doing it properly.

18. I have talked to many climate skeptics, and almost all of them claim that there is no climate emergency. Some say the models do not work well, while others argue that sea levels will not rise as much as predicted. What is your message to them?

So many of these people, and I’ve heard this many times, say to me that temperatures have always been fluctuating in the past. Every 20,000 or 100,000 years, temperatures have changed. We’ve seen ice ages and warm periods, and there wasn’t human activity causing it. I always like to respond, “How do you know all of these temperatures in the past, during the ice ages and so on?” They ask, “What do you mean?” I say, “That’s the scientific community—that’s paleoclimatology. That is the scientific community that produced the information you are now quoting against.”

Of course, the scientific community understands this in fine detail. If you sit down with a climate scientist—and you’re doing that right now—you can ask all these difficult questions. They will know the answer. If they don’t, it’s because not every answer has been found. That’s why I quote paleoclimatology and models—completely different scientific approaches producing the same results. Or I quote Fourier’s theory, in which he had to use a fudge factor, a number he pulled out of the air to get the correct surface temperature of the Earth. That was confirmed by scientific measurement 40 years later.

We have so much evidence that is constantly backed up with checks and balances. So I think the question is, where are these people getting this negative approach? If you were offered a medicine to deal with a disease by the medical community, would you not take it? If you say, “I know better than the medical community,” I’m sorry, you wouldn’t have it. And here we are talking about the Earth itself. The ecosystems of the Earth have been put into a dire situation by human activity. We can manage it, but we all need to understand and listen to the scientific community. You cannot ignore them if you want a safe future.

19. Most of the skeptics are scientists as well, for example, Dr. Richard Lindzen. He and other skeptics claim that the whole climate emergency is a made-up issue, created so that the renewable energy sector—which is a trillion-dollar industry—can profit. In other words, they argue that the climate emergency is being exaggerated in pursuit of financial gain for the new energy sector.

Okay. Richard Lindzen is a scientist who was once respected in the climate field. When he first came up with his negative view—I’m just picking Richard, I could pick any of them—he based his analysis on the idea that the heat absorbed by the atmosphere changed with height from the planet’s surface. But measurements have now shown that his theory was wrong. The scientific community absorbs good science, then conducts experiments and develops theory. It’s an enormous program of work.

It’s not what you’re quoting. I can tell you that some of those climate scientists I won’t name received funding from the fossil fuel industry. Now you mention the renewable energy industry—my goodness, where was the renewable energy industry when all of the scientists I mentioned in the 19th century were working? So, this is really nonsense. We either dismiss it and do not waste too much time, or we examine it in detail to see where it goes wrong.

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His work mainly looks at how greenhouse gas emissions are changing over time, how countries measure and report their emissions, and whether current plans to cut emissions are actually realistic. He is best known for his leadership role in the Global Carbon Project, where he helps produce the annual Global Carbon Budget. This report is widely seen as the most reliable source for tracking global carbon dioxide emissions and how they affect the atmosphere, land, and oceans. A key message in his research is the growing gap between governments’ climate promises, such as those under the Paris Agreement, and the continued rise in fossil fuel use.

Peters has also been a leader in studying “consumption-based” emissions. This approach shows how emissions are often created in one country to produce goods that are consumed in another, shifting responsibility away from consumers and onto producers. This work has changed how policymakers think about international trade, carbon leakage, and who should be accountable for emissions. In addition, he was a Lead Author for the IPCC’s Sixth Assessment Report, contributing to research on how the world could reach net-zero emissions and the technical challenges involved.

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1. You’ve been outspoken about removing the stigma around admitting we’ll likely miss 1.5 °C. Inside climate science itself, is there a culture of optimism that discourages researchers from publishing their most pessimistic, and possibly most realistic, conclusions?

I don’t think so. The 1.5-degree thing is a little bit different. Out of all the people doing climate research, there’s only a very few who will look specifically at questions about whether we’re going to cross 1.5 degrees, and when, and so on. But many researchers have formed a view, based on their knowledge of the climate system, of whether we would cross 1.5.

And I’d say, yeah, 99.9% of people, if you spoke to them in the cafe, over a coffee, or in the pub with a beer or something, they would say, hey, we’re going to cross 1.5 degrees. That’s 100% certainty in the next 5, 10 years. But whether they say that in the public domain, that’s a little bit more nuanced, because in the public domain there’s the whole politics surrounding 1.5 degrees.

Countries are signed up to 1.5 degrees. Many companies and countries have net zero targets in 2050, etc. And if you say 1.5 degrees is dead in that context, if you’re not very careful with the way that you communicate that we’re going over 1.5 degrees, I guess there’s a fear that companies or countries might start to say, oh, no, well, we’ll drop our 1.5 degree ambitions, and that type of thing. So it’s a little unusual dynamic.

If I think of politicians in Norway, for example, and this is true in many countries that I’ve noticed, the politicians will say we’re still going for 1.5 degrees. 1.5 degrees is our ambition, etc. We’re not going to change that. So it’s this sort of situation where politicians lock themselves into this 1.5 degree narrative, perhaps partly from pressure from scientists, and now it’s very difficult to unwind it.

But I’m happy to say in public that we’re going to shoot over 1.5 degrees. I think it would be scientifically incorrect not to say that.

2. How many degrees do you project the planet would be overshooting in the coming decades?

Yeah, so let’s say in a globally average sense we would cross 1.5 degrees, let’s say within five years, probably, when you consider all the variations. If emissions stay on the current sort of trajectory, or if emissions are fairly flat out to the end of the century, then I’d say we’ll head up around 2.5 to 3 degrees by the end of the century, that sort of territory.

And then, of course, after 2100, next century, temperatures keep rising, so it keeps getting worse from there. So unless there’s a fairly dramatic change in policy, we’ll probably head in that sort of 2.5 degree territory by the end of the century.

You can look at it a little bit from a positive or pessimistic direction. If technology costs keep going down, ambition keeps going up, and climate policy keeps getting stronger, then we’d edge towards the 2 degree end of that spectrum. And if things slow down, or the climate system is more sensitive than we thought, then you would head up to the 3 degree end of that spectrum.

So that’s sort of where I’d say we’re heading. So 2 degrees maybe around the 2050 period, plus or minus some decades, depending on where emissions go, et cetera. So things are just going to keep going up unless there’s a dramatic change. Recent carbon budgets, such as land and ocean sinks, are already weakening.

3. Recent carbon budgets suggest land and ocean sinks are already weakening. In your modeling work, is there a point where these natural sinks stop helping and start accelerating warming, and are today’s Net Zero timelines actually accounting for that risk?

Yeah, so this is a very difficult question. Broadly speaking, to answer the second part of that question, models do consider the way the carbon cycle changes as temperatures go up or down. I’ll come to that in a minute. So broadly in the models, how accurate that is, that’s a little bit uncertain.

And part of that uncertainty relates to the period that we’ve lived. Over the last 200 years, emissions have been rising, so concentrations have been going up and temperature has been going up. All our models are calibrated based on this rising emissions. If the world starts to reduce emissions, then concentrations go down and temperature stabilizes. We’ve never really been able to calibrate the models or check them against real data on how they would work in that situation.

And also, we’ve not been able to test the models in a real world with, let’s say, two degrees of warming. So it’s very hard to validate the models. You have to go to process understanding experiments that you could do in a lab to check models and so on.

But broadly speaking, the current understanding is that if we continue emissions going up, then the carbon cycle will become, you could say, less efficient. So for a given emission, if you emit one ton, then slightly more would stay in the atmosphere than today. But there’s also some unusual behavior when emissions go down. When emissions go down, the sinks actually get weaker because you’re putting less carbon into the atmosphere, so the sinks take up less of that carbon. So you also get this effect, but in a different context when emissions go down.

The models broadly account for these processes, but how accurate and how well it’s represented, you could say there’s a lot of uncertainty. So that’s, I guess, every year as time progresses, one of the things that I’m very interested in looking at: how is the carbon cycle responding to continued emissions?

Because so far, the carbon cycle has broadly kept taking up carbon. The natural land sinks have kept taking up carbon, even though we keep emitting more and more. There are different processes going on and different things with efficiency, but broadly speaking, the carbon cycle so far has been fairly resilient to increasing emissions. But we don’t expect this to go on forever.

4. Dr. Peters, does the carbon concentration rise first, followed by the temperature? Or does the temperature rise first, followed by carbon concentration? I’ve heard a lot of skeptics state that first the temperature rises, and then the carbon concentration rises. What is this all about?

Yeah. So if you get into the paleo record, going back thousands, hundreds of thousands of years, then related to these orbital cycles, you do get the temperature driving the carbon. In the current situation, it is reversed: the temperature is rising as a consequence of the carbon. Ways that you can determine this are through measurements of concentration in the atmosphere, lab experiments on the way the concentration influences radiative forcing, the energy imbalance, the temperature profiles through the atmosphere, and so on. It’s not my core area of expertise, an area that I’ve sort of researched as such.

The other way you could look at it is by excluding alternatives. For example, going back to the solar cycle, we have good measurements of the solar cycle over many decades, and in recent decades, satellite-based measurements. So we have a pretty good understanding of the incoming radiation. These sorts of mechanisms—you can go through all possible alternatives that you could possibly think of, including the ones that skeptics think we haven’t considered—and you can exclude them.

But yes, in glacial cycles, when humans sort of didn’t exist, temperature was leading. Today, we know it’s not the case.

5. We often discuss climate tipping points one at a time. If several interact nonlinearly, are we underestimating the danger by focusing on single thresholds rather than cascading effects?

I think the thing that we’ve underestimated is these interactions. The interactions may happen in the model, but some of them are outside of the model space. Coming back to an Australian example—I’m originally from Australia, which is why I keep using Australian examples—through the fires two or three years ago, the fires were outside of the cities. But most of the impact was in the city because of the ash, the air quality, and so on. This is not necessarily directly climate-related; it’s more a health-climate interaction. It’s this sort of interaction between climate and health consequences, which is not included in the model.

Some of the most obvious interactions are, for example, periods of drought. Low precipitation followed by hot weather can lead to high fire conditions. You could also have various other events not necessarily occurring at the same time, but one after another. You might get a drought, then hot weather, then fires, and the next year, perhaps floods. The surface is more exposed because the vegetation’s gone, so those floods can be worse, not because of climate directly, but because previous climate impacts have changed the land surface.

These sorts of things are very hard to incorporate into models. But I think these interactions are probably what is going to surprise us: when two extreme events come one after another, the consequences will be much, much more severe.

6. Integrated assessment models usually treat political failure as something external. What would change if political backlash, loss of trust, or social tipping points were built directly into the models?

Yeah, it’s pretty hard to do. It would probably require a different modeling framework. But it’s also something we see playing out in the real world at the moment.

If you think of it, we’re modeling this in real time, with the US and Trump and so on. He’s withdrawing from various climate initiatives, trying to put the brakes on anything he can in climate, etc. But that doesn’t stop the deployment of electric vehicles or solar elsewhere, even in the US, because the technology curve has moved so far now that you can’t stop it.

We also see examples of this in Venezuela, where Trump says, oh, all the oil guys are going to come over and start digging the oil, whereas all the oil guys are saying, hang on a minute, we’re not that stupid. We’re not going to risk our capital. Also in the US, you’re not going to see a big build-out of coal power plants, for example, because no investor is stupid enough to invest billions of dollars given that Trump will probably be gone in three years and the whole political narrative may change.

So in a sense, there’s various inertia in the system. You really want to look at long-term changes. If, for example, the US political system changed and became a dictatorship, with many decades of a Trump-like president, then sure, that would have a pretty dramatic effect on the world generally. But at the same time, other parts of the world may move along. For instance, there was a headline story the other day where China had its biggest ever trade surplus, so despite all the tariffs, China is still increasing its trade at a breakneck speed.

So it’s very hard to see a situation where everything goes bad simultaneously across all countries. Thinking over time and space, there are various elections and political leadership changes. We’re heading in a direction, and there will be changes along that direction, but I still think we’ll head in roughly the same direction. It’s just a question of how fast we go.

Modeling these things is very hard and would probably require more of an agent-based modeling approach—a model that explicitly models behavior and political issues. But we’ve gone far enough down the technology curve as a world that it’s very hard to reverse. For example, I’m sure you’ve got a mobile phone or a computer—you’re just not going to throw those away. People are not going to burn all their solar panels and stop using them. Progress is very hard to reverse on a broad scale.

7. You’ve shown that carbon intensity is falling while global energy demand keeps rising. If efficiency gains are consistently offset by more energy use, is “green growth” still scientifically defensible?

Yeah. So to answer that question, we really need to think about the country level—what happens in individual countries. If you think of a developed country, let’s say Europe or the US, energy consumption is quite flat. They have old coal power fleets, so building solar and wind displaces coal, and emissions go down. In that context, green growth might look like a thing, but it’s more a consequence of the stage of development.

If you go to a developing country where energy consumption is growing, lifting people out of poverty, they need to use more energy and improve energy services. It’s very hard to displace coal. A classic example here is China. Even though they’re doing huge amounts in terms of renewable technology, emissions are still going up because of the sheer increase in energy use each year. They build mind-boggling amounts of solar and wind every year, but energy consumption is growing even faster. This is true in most developing countries, although we’ll start to see a shift where it becomes so cost-effective to build solar that countries will just do it as the quickest way to get energy or electricity.

Another factor is electrification. There’s a lot of talk about electrification. Electricity use is increasing through heating, cooling, air conditioners, electric vehicles, and industrial processes shifting to electricity. So I’d expect a very rapid increase in electricity demand, which makes it even harder for solar and wind to keep up.

So what does that mean for green growth? I’m not much of a fan of the concept. If you take a country like Nepal, efficiency is improving over time and the economy is growing, but the economy is growing faster than the improvement. By some definitions, Nepal would be successfully achieving green growth; by others, it wouldn’t. We should focus on things like energy and emissions and getting them down, and the economy will do what it does. We should not rely on the narrative that the economy will grow and emissions will automatically go down, because I don’t think that mechanism works.

Put another way, if we reach our climate goals, you could say we did it by green growth, even though that may not necessarily be the case. As a consequence of meeting climate goals, you might have green growth. I don’t think it’s that useful a concept, although it might be a nice political narrative for some.

8. Your recent work on the global hydrogen budget shows that hydrogen leaks can extend methane’s lifetime in the atmosphere by depleting OH radicals. If we scale up a hydrogen economy without fixing methane leaks from existing gas infrastructure, could we inadvertently lock in a warming plateau—even after fossil CO₂ emissions hit zero?

So absolutely, CO₂ emissions have to go down. But absolutely, methane emissions have to go down as well. If hydrogen becomes an important part of the energy system, we can debate whether it does. But if it does, then it’s even better if methane goes down—but methane needs to go down anyway.

So if you want to achieve your climate goals, methane has to go down. In a sense, irrespective of hydrogen, we still need to reduce methane. It’s not that I’d say, oh, we’re going to use hydrogen, therefore reduce methane. I’d say we have to reduce methane, and maybe hydrogen is a useful part of the energy system. So we have to do all of the above, essentially.

9. Your work on consumption-based emissions showed how much carbon the West effectively outsourced to the East. Now that countries like China and India lead in green-technology manufacturing, are we moving toward a kind of “green trade war,” where tools like carbon border taxes are used less to cut emissions and more to protect domestic industries—potentially slowing adaptation in the Global South?

Yeah, this is another quite interesting one. Part of the irony of carbon border adjustments, particularly in the case of China, is that China exports so much clean technology, and you don’t want to tax clean technology—you want to encourage China to build more clean technology, and other countries as well. So I’m not much of a fan of carbon border adjustments. I don’t think other countries are better.

Overall, free trade, particularly in clean technology, is an advantage for everyone. What we need to do is ensure that China, or help China, or other countries—whatever that country may be—reduce their emissions whilst also developing their industries.

You also see, maybe even as a consequence of protection via carbon border adjustments, that European and US car manufacturers are certainly lagging behind China when it comes to clean technology. In a sense, border adjustments might protect them a little bit, give them a few more years, but they’ll eventually lose. I don’t think it’s good industry policy to protect industries. There needs to be some support—maybe protection is not the right word—but even if Nepal wants to get a new industry going, there will be some government support. There might be bad years, good years, etc. The role of the government is to chip in, help, ensure the industry is stable, grows, and becomes cost-competitive. Over time, that will ensure the country brings in lots of export revenue.

You could argue that Europe and the US have not had their eye on the ball and are starting to lose in the clean tech race. The narrative around border adjustments is part of that. Even in areas like steel, outside of clean tech, there’s a delicate balance. Maybe a European steel plant is cleaner than a Chinese steel plant—not in all cases, but on average, that’s the case. Over time, the European steel plant also needs to improve efficiency and reduce emissions. I’m not sure a carbon adjustment helps them do that.

I’d rather see a policy that pushes or encourages, for example, steel facilities to improve their technology so that they become even cleaner over time. Likewise, I would hope other countries—China, India, whoever—do the same, pushing to reduce emissions in a competitive sense. Some government support I would not have a problem with. We already do it across many industries, including fossil industries. But doing it via border adjustments, in my mind, doesn’t reach the objectives we’d want to reach.

I think it’s hard to deny that there are protectionist elements in border adjustments. There’s also a lot of literature on the unfairness associated with border adjustments. For example, if there’s a border adjustment related to carbon in Nepal, you would expect the economy in Nepal to be slightly weaker. I don’t think that should be the game Europe plays at all.

10. You’ve proposed a concept of “Geological Net Zero,” requiring one ton of carbon to be put back underground for every ton extracted. If this became the international standard, it would effectively invalidate much of today’s forestry-based offset market. Is the scientific community ready to tell the corporate world that their trillion-dollar investment in biological offsets is, from a physics perspective, a category error?

Yes. That’s the short answer. But there needs to be a bit of nuance. A more nuanced way of putting it is that we should separate the fossil and the land components and not mix them together.

Yes, it’s important to protect forests and grow more forests. That does not mean you should offset your fossil emissions with them. If you’re going to emit 10 billion tonnes of fossil emissions, and say, oh, we’re protecting forests, no—that’s not how it works in a physics sense. You need to separate those components.

Whatever incentives are used to protect or enhance forests, no problem with that. But they should not be used to offset fossil emissions and allow continued use of fossil fuels. The whole point of climate action, under pretty much any scenario, is to get to zero fossil fuel use or zero carbon emissions. Offsetting that with forest offsets will not help achieve that objective.

11. You’ve warned about countries double-counting land sinks to meet Net Zero targets. If we strictly separated geological carbon removal from biological sinks, would any major G20 country still be on track for 2030—or does most of today’s progress vanish once the accounting is cleaned up?

To date, I don’t think it’s too problematic. The potential is there, and there are some new ones. But if I take Europe, for example, and the US—Australia maybe is a bit more complex—but let’s say the EU and the US, pretty much all their emission reductions have come from reductions in fossil emissions or agricultural emissions. Their sinks have, in fact, gone in the wrong direction. In Europe, the sink is getting weaker. In the US, I think it’s also getting slightly weaker. So at the moment, that’s not a problem, but if you go to individual countries, it’s potentially a problem.

For example, Sweden—their land uptake is about the same size as their emissions, so they’re already net zero by that definition. But that does not mean they should not reduce emissions. They should get their emissions down to zero, in addition to having the sink.

Some large forested countries are already net zero or net negative because of forest uptake. These are generally countries that are covered in forest and don’t have much emissions. But if they use that to claim they are net zero, that would be inconsistent with the science.

There are countries like Australia that have had accounting rules for the forest system that have been beneficial to them. A lot of the reductions in Australia, for example, have come from “tricky” accounting, which is allowed under the rules but perhaps shouldn’t be. Most of Australia’s reductions have happened through the forest sector in a dubious way. This is internationally known as the “Australia clause”—a rule change that only suited Australia. This sort of thing should be avoided.

Generally speaking, most of the emissions reductions that have happened at the country level are in fossil emissions, at least in the rich world. Although examples keep coming up, and it’s getting worse. As we move towards net zero, potentially in Europe and elsewhere, the way land is included becomes more and more problematic.

Another element is the national pledges—the NDCs. When you go out to 2030, a large, disproportionate share of the reductions that countries have planned relates to the land sector, and some of this is a little dubious. So there are problems brewing.

12. Looking back over your career, what belief about mitigation pathways did you hold 10 or 15 years ago that you now think was structurally wrong?

You could think about high emission pathways, where we thought emissions were heading on a higher path than they actually were. Having said that, I have gone back and looked at various things I wrote many years ago. Maybe it wasn’t as bad as I thought. Perhaps we weren’t communicating the uncertainties sufficiently. Maybe that’s not the issue I was thinking of—that’s just the one that naturally came to mind.

An area we talked about a little is consumption-based emissions and border adjustments. Going back 15–20 years, when I worked a lot on consumption-based emissions and border adjustments, I thought there was a range of policy instruments we could implement on the consumption side, including border carbon adjustments, that would be beneficial.

Now, I’ve very much moved into a more traditionalist approach, where I focus on where the emissions are coming from—the production side, etc. That’s not to say consumption isn’t important, but politically, it’s far easier to control or regulate emissions at the source than to go through complex systems that try to capture emissions at the end point and indirectly influence the source.

For example, emissions come from a coal power plant. We need to stop burning coal and start generating electricity by other means. That’s a far more effective strategy than saying, Europe is consuming this much, so if we apply some taxation on consumption or border carbon adjustments, coal power plants will shut down. That’s too indirect and too far from the source of the emissions.

So that’s one area where my thinking has changed over my career. I now focus policy much more on direct emissions at the source and look much less at indirect policies that try to reduce emissions indirectly. Not to say I wouldn’t use some of the indirect approaches, but the primary focus should be on the source of the emissions.

“If you are good at something, never do it for free,” says the Joker—and I love Joker. But I believe educational content should be free for everyone. Hence, this newsletter doesn’t restrict any content behind paywalls; everything is accessible to everyone for free.

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Trenberth’s research focuses on the Earth’s energy balance, particularly the movement of heat through the planet. He is known for identifying that much of the “missing heat” from global warming is absorbed by the deep oceans, and for examining how natural climate patterns like El Niño are affected by human-driven climate change.

He has also pioneered studies of the global water cycle and extreme weather, showing that a warmer atmosphere holds more moisture, driving heavier rainfall and more severe droughts. Trenberth has argued that modern storms unfold in a climate already altered by human activity, shifting how we understand extreme events.

He has been a lead author on multiple Intergovernmental Panel on Climate Change (IPCC) assessment reports, including the Fourth, which contributed to the 2007 Nobel Peace Prize. His work has earned numerous honors, including the Jule G. Charney Award and the Prince Sultan Bin Abdulaziz International Prize for Water.

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Why did you move back to New Zealand?

Oh, I’m from New Zealand. I originally grew up in New Zealand. My family are here. I had the opportunity, through a research fellowship with the New Zealand government, to go overseas to do a PhD degree after I had finished my undergraduate degree. I went to MIT and I graduated with a doctoral degree. Then I was obligated to go back to New Zealand. I did so, but I married an American when I was at MIT. And so she came with me. After about six or seven years of working for the New Zealand government, I took a position at the University of Illinois and I became a professor there. Then after about six and a half years, when I was due for a sabbatical, I took the opportunity to go to NCAR and took a job there. I was there for over 36 years. During that process, I became a U.S. citizen. But I’m still a New Zealand citizen, so I have joint citizenship now. My wife is American, so we have American connections. But we also have New Zealand connections. My grown-up daughter is here. My grandchildren are here. They’re not very far away. So that’s the main incentive to come back.

Define the terms climate change and global warming.

Global warming was a term that was originally invented by Wally Broecker (Wallace Broecker). It’s often used to refer to the global mean surface temperature increases. I think that’s misleading. Heating is a word that is a synonym for warming. So, if you think of it as global heating, then it actually makes a little more sense. And that’s the thing which causes the increases in temperature, the melting of glaciers, the expansion of the ocean, the speed up of the water cycle, increased drying. So it’s the heating which is the real cause of everything. But the general public tends to think of it more as global warming, and it can be a bit confusing at times. After a period of time, I believe for political reasons, it started to get referred to more as a more general term as climate change. “Climate change” builds in the natural variability. So if there’s a large natural component, then that would be manifested as well and it’s not just the human component of climate change, which is really perhaps more the global warming aspect. So it’s a more general term, but it’s also a more neutral term. Some politicians like that because it doesn’t mean warming. It could also mean cooling. And the weather still happens. So we still have cold outbreaks. There are still cool periods, especially locally or regionally, not so much on a continental scale or globally. But that’s where these two terms arose from.

You have frequently pointed out that heating and warming are not the same thing in climate science. Given that a planet can be heating up internally even while surface temperature appears to stall, as seen during the ‘hiatus debate’, do you believe our obsession with surface temperature targets like 1.5 degrees is scientifically misleading? And should we instead be using Earth’s energy imbalance ( EEI) as our primary danger metric for the public?

I’m glad you mentioned EEI. Unfortunately, we only have really good measurements of the Earth’s Energy Imbalance since about March of 2000. That’s when two satellites have been up, looking at radiation coming into and flowing out of the Earth’s atmosphere and so we have actual measurements of the energy imbalance; it’s still somewhat imperfect because there’s quite strong variability during the day and also quite a pronounced diurnal cycle. And as the satellites drift a little bit in orbit and then one satellite gets replaced with another, corrections have to be made. But nevertheless, we have a reasonable record of EEI, the Earth’s energy imbalance, since 2000.

Now, the global mean surface temperature, we can go back to about maybe the 1850s. It’s not as reliable before 1958. 1958 was the International Geophysical Year. That was a major international project which opened up Antarctica in particular, and the main observations over Antarctica and over the Southern Oceans have only occurred since 1958. There were not that many measurements in the Pacific before about then, but especially before World War II. Before about 1942, there were very few measurements in the Pacific at all. So to say we have a global record is perhaps an overstatement slightly, because there are pieces of the Earth that have not been well observed over time. Some of the oceans have not been well observed, especially the Southern Oceans, which are quite extensive, and Antarctica. So we have the best estimate of what has happened over time.

The oceanic heat content, which I mentioned before, can only go back reliably to about 1958. The only way we can do that even is by using the recent record, where, since about 2005, we have a really good global record of oceanic heat content. By taking advantage of that and the relationships with everything else that’s going on, we can extend that back to 1958, but before the IGY, there’s not enough data to have a reliable record to go back in time. So it depends a little on what you want to do.

There is a global surface temperature record, especially on land in Eurasia and North America, not so much on Africa or South America, that goes back, I would say, to about the 1850s maybe. You can get a record which has some credibility. And so if you want a really long-term perspective, then you would likely do that. Of course, with our climate models, we can sample the climate model record in places where only the observations exist, so in the Northern Hemisphere or over the land and so on, and do comparisons, and we can use our climate models, even though they’re not perfect, to interpolate and extrapolate further back in time, and it gives us a more complete picture as to just what has happened and also why it has happened. So we can do tests with the climate models, and we can prove that it’s mainly the carbon dioxide and the other increasing greenhouse gases in the atmosphere that are responsible for the temperature increases in the ocean and in the atmosphere.

If NCAR is broken up, which specific “capabilities” do you believe will disappear entirely?

Well, the main focus has been on attacking the division that I was a part of which is the Climate and Global Dynamics Division. There are a number of other divisions, one of them deals with the so-called High Altitude Observatory. It deals with the sun and the upper atmosphere, the thin upper atmosphere. It doesn’t deal very much with climate. There’s a division called MMM, the Mesoscale, Microscale Meteorology Division, which is focused entirely on weather and severe weather and thunderstorms, and so on, and they’ve done a lot of work to help improve weather prediction. I suspect that all of that activity would remain. There is a special research arm, which has been focused on especially aviation and airports and the safety of flights coming in and out of airports, but they also have a number of other special projects. One of them is on hydrology and creating a global hydrology synthesis of data and also modeling. A lot of this work is based upon what we call soft money. It’s not so much base funded, which is why it is sort of a separate unit. There’s also a unit called Atmospheric Chemistry, which deals entirely with the composition of the atmosphere and air pollution. Then there are some base units called the Scientific Computing Division that deals with all of the supercomputers that are shared with universities, and there’s a major supercomputing center up in Wyoming that is used all around the country. There is also an instrument division that deals with two or three aircraft, (one of them is a Gulf-stream aircraft), that are heavily instrumented, and can fly around and take special measurements. They’re involved in a lot of field programs. There’s also a number of surface instruments, radars, and other portable instruments that can be moved around and deployed with high resolution to make measurements based upon university community proposals that have been evaluated and put into action in order to make these special measurements. So it’s mainly the Climate and Global Dynamics Division that deals with developing an earth system model, previously called a climate system model, but it really deals with all aspects. It deals with the atmospheric composition and the land surface and the ocean, and the cryosphere, what’s happening with the ice in Greenland, and so on. It’s a community tool that is used by people all around North America, and in fact all around the world. You can use it from Australia or New Zealand, where I am, or other places. So even there, it’s not a good case that you should get rid of it. But out of the current political situation in the United States with Donald Trump saying climate change is a hoax, then it’s far from clear just what will happen.

The current administration’s plan seeks to prioritize “severe weather” while cutting “climate science.” As someone who studies the Earth’s energy and water cycles, is it scientifically possible to accurately forecast severe weather (like hurricanes or floods) while ignoring the underlying climate research NCAR currently conducts?

Yeah, so NCAR deals with research. It’s designed to make all of the products, whether they’re analysis products based upon data or satellites, and so on better and the models more predictable for longer. That’s the focus of what goes on at NCAR.

Yes, it relates to privatization. The question is, who does this? If it’s a government agency, then it’s funded by the government. But, you know, NOAA and NASA and DOE, the Department of Energy, have been badly hit by this current administration. So if research is left to the private sector, the question that accompanies your question is, how do they make a profit out of this? And so they have made their own tools or ways of processing data, especially these days with artificial intelligence and so on, that they can gather stuff together and they can develop a product and they can try to sell it. If they can sell it, then they can maybe improve their products and carry it forward. But it very much depends upon sellability. It depends upon marketability. How well these things can actually sell. It completely ignores the public good. It completely ignores the national interests and the international interests.

The thing about weather and climate is that they’re global in scope. And so a private company is less likely to be concerned with what goes on out in the middle of the Pacific Ocean, even though that’s where a lot of influences from the El Niño phenomenon come from, for instance. Or they might not care about the southern hemisphere at all, because their main customers are in Europe or North America or something like that. So privatization and the private sector and how well they respond to things like this is a big issue. And, of course, that’s exactly what the Trump administration is promoting. But it doesn’t work well for the general knowledge and availability of information to the general public.

Without NCAR’s foundational research, how many years do we have before the accuracy of the weather models used by the public and the military begins to noticeably degrade?

Well, the models are useful as they are. There’s a new version that is about to be released by NCAR. It has undergone extensive testing and it will be run, no doubt, many, many times and used for all kinds of experiments, including making projections as to what the best estimate of what is happening in the future and why. They do tests as to how much pollution is influencing things or what happens if the atmospheric composition changes in certain ways. So maybe if we stop increasing methane, for instance, or if we can slow down the increases in carbon dioxide, what happens? And where does it happen and how does it happen? And where should we be making measurements to see if that happens? And so these are the sorts of things that are done with the models. And so we certainly have models. And there are older models that can be used now, but the computers keep getting faster. The knowledge base keeps improving. And so a new generation of models is typically generated about every six to 10 years or something like that. And so that’s sort of the lifetime of a model before it becomes, in some sense, obsolete. It’s replaced by a bigger and better model.

How would the loss of NCAR-developed tools, such as the WRF model, specifically impact the response to local disasters like the Colorado wildfires or flash flooding?

Yes, so that’s a specific example. The WRF model, is a regional weather model. It’s a high resolution model. It’s used for local prediction by many people all around the world. And one branch of that is to do fire research and look at the vulnerability for fire. Then if fires begin, predictions are actually made using a special version of that model as to how the fire is most likely to develop, and it depends critically on how the winds develop, where the dry air is, where the moisture areas are located. A lot of that is already done and fed to firefighters wherever they’re in operation. And some of it is done, I think, by the private sector, maybe a little bit. You know, those models are also used for things like yacht races, the America’s Cup. And one team will have their own predictions as to what’s going to happen to the wind, what kind of sails to use, all kinds of special uses for the information in order to give your project an edge over others. Some people are using them to make predictions and then they try to sell those predictions to the private sector. And they have a lot of special customers. The most obvious special customers are all of the airlines who are doing flights all around the world every day. But usually they’re mostly concerned about what’s going to happen in the next few hours or for international flights, maybe the next 12 hours or something like that. They’re not really interested in maybe even one day ahead or seven days ahead. And so they’re very focused on what’s happening with the aircraft flying in the 5 to 15 kilometer elevation region in particular. They’re trying to optimize the tracks of where the aircraft flies as a particular example. NCAR has played a major role in that kind of thing.

With the current moves to restructure NCAR toward a narrow ‘severe weather’ focus, how does the scientific community maintain the long-term climate datasets you spent your career building?

Well, this is very worrying. I mean, a major part of the computing center is a big sector that deals with special datasets. And NCAR has some of the biggest archives of various kinds of datasets, including what we call reanalysis datasets, which may have been generated, for instance, by the European Center for Medium Range Weather Forecasts. There are tens of terabytes of data associated with these datasets. They’re huge. So this is indeed very worrying as to how all of those datasets will be looked after and whether they will still be accessible or not. There are some groups that are trying to copy some of these datasets that they think are most important. But the volumes are so big, we’re talking about terabytes of data. It requires a pretty big computer system to be able to handle that. This has been indeed one of the roles of NCAR, one which I used a lot in my own research.

If the U.S. retreats from foundational climate research at the center where you spent decades, which nation or institution is best positioned to take over as the ‘global mothership’ of climate science?

I suppose that’s a good question, let me just make a few comments. The Copernicus activity is centered in Europe. I think it’s mainly centered in France, but it has components throughout the European Union and a major component of it is ECMWF, European Center for Medium-Range Weather Forecasts. Their focus has always been on 5 to 15-day weather forecasts, not 0 to 5 days, not the short-term weather forecasts. But they’ve done more and more in terms of trying to keep track on aspects of climate. And under the Copernicus banner, they are issuing reports every month or every year. So they will be coming out with their view as to what happened in 2025 and whether the year 2025 was the second or third warmest year on record. They’re already talking about aspects of that. There are components of that in Germany and the U.K. and France and all the European Union countries. So that is certainly one activity. The timescale matters a lot here because the country which is going ahead probably fastest at the moment is China, I think. But their history on doing this is not long. I have been to China several times and they started putting an enormous amount of effort into building up the universities. And young students were supported to go to universities and get degrees.

You have called for “modernizing” rather than “dismantling” the center. What would a “modernized” NCAR look like to you that satisfies both scientific rigor and current national priorities?

Yes, well, NCAR put out a 10-year plan earlier this year. I was a bit disgusted with it in some ways because not once did it mention climate, not once. And I understand why, because they’re sort of keeping their head down, trying not to be visible to the Congress and to the critics in Congress and in the Trump administration. But the strengths of NCAR have been the fact that it has all these different groups that actually interact more and more, and also it’s a national center for atmospheric research. So it’s actually a center for all of the universities around the country. There’s now 129 member universities in UCAR, the University Corporation for Atmospheric Research, which runs NCAR. And so to the extent that all of these people are focusing on using a single model like WRF or the NCAR community earth system model, then that brings enormous strength and diversity, because so many people are looking at it and using the models, scrutinizing it, and helping to improve it. This is a tremendous resource. So this is something which I think there will be a lot of arguments about. Is there any real pressure to shut down or cut off this part of NCAR? Because many of the other parts of NCAR are dependent upon the climate and global dynamics division in terms of the modeling, including the division that deals with the sun, for instance.

If you were forced to save only one section or tool from NCAR to ensure the survival of climate science, what would it be?

I don’t think I can answer that question. I mean, the whole thing about climate science, in fact, now Earth system science, is that it deals with all aspects of the Earth system. It deals not just with the atmosphere but NCAR also deals with ocean research. There’s a section that deals with glaciers and ice sheets and Greenland and Antarctica and how those are changing and how you can better model those, and how you can fit those in with the ocean and the atmosphere. There’s another section which deals entirely with what happens on land and all of the complexity of the vegetation and how they interact with one another. What happens when a wildfire comes along and how well it recovers. And all of these are interacting through the atmosphere. The atmosphere is global and connects all of these things. So, in order to deal with a system science, you need all these parts.

In fact, over time, the whole way in which it’s been organized and the groups that exist have expanded to embrace all aspects of Earth system science. So, if you cut off one piece or just keep one piece, that one piece would tend to wither away because it loses all the other things that go into it and interact with it. There are annual meetings that last for a week where people come together from all over the world, actually, in order to find out what’s going on in these different areas and what the latest developments are. There can be no doubt some changes that can make that better and more efficient and maybe mandated; some aspects could become more focused. But the NCAR effort in climate has been focused mostly on Earth system modeling. It has not been focused as much on what’s happening in the real world and why, which is what my work was. Since I left, I think that’s an area of weakness. So, they’re very dependent upon other groups to do that, typically NOAA, to say what’s happening. That’s one of the weaknesses, in my view.

Your work shows that for every degree of warming, the atmosphere holds 7% more moisture. At what point does this ‘intensification of the water cycle’ make our current city engineering—our dams, sewers, and levees—fundamentally incapable of protecting us?

Well, I personally think this is one of the things which is most important, and I have spent quite a lot of time documenting aspects of this; I have written about it quite extensively. So, as you say, as the atmosphere warms by 1 degree Celsius, it can hold 7% more moisture. But the moisture is very unevenly distributed. There is a lot more moisture in the tropics because the tropics are warmer than in middle latitudes. And in high latitudes, there’s not very much moisture in the air at all. You don’t hear of a big flooding occurring in high latitudes unless it’s because of melting of glaciers and some rain maybe falling on it to help it melt. The main heavy rains and floods occur either in the tropics or in these things called atmospheric rivers, where a strong flow of the moisture that originated in the tropics is moving into higher latitudes. And it’s essentially brought together as a part of what we used to call cold fronts, and it all gets focused onto a particular area. Nowadays, you can easily get well over 100, even over 200 millimeters in a day and get flooding out of it. But it’s often relatively local. This is where good modeling of just where those areas are most vulnerable is important.

The weather systems have a tremendous amount of natural variability. If it doesn’t catch you this time, maybe it’ll catch you next time. Certainly, there’s a lot of merit in being prepared. A particular form of this of course are tropical storms, hurricanes, typhoons. There are some regions like the southeastern parts of the eastern coast of the United States that are most exposed and vulnerable to those. But also Southeast Asia, from India through to Thailand and southern parts of China and also Japan that have been hit this past year and have experienced severe flooding with tremendous amounts of damage in places where it hadn’t happened before. So there’s huge losses, hundreds of millions of U.S. dollars in damage that are occurring as a part of this, and also the loss of life and the disruption of many people’s livelihoods and so on that have occurred in association with these. Understanding these better and predicting where they’re likely to occur, both on short-term timescales as a part of a weather forecast, but also in a longer-term perspective from the standpoint of the climate variability and the climate change is important.

All of this also depends a lot on things like the El Niño phenomenon. At the moment, we’re in a relatively weak La Niña, but that determines which areas are most vulnerable. In La Niñas, there is often a lot more rain on land and more flooding occurs. Whereas in El Niño, a lot more of the rain action occurs over the ocean in the tropical Pacific, for instance.

You’ve argued forcefully that while we can’t blame climate change for a specific storm happening, we can say it’s responsible for the storm’s intensity (e.g., Hurricane Harvey’s rainfall). Is the scientific community being too timid by not more directly attributing the loss of life and property to human-caused changes?

I think so, and I still think that’s true. The whole science of attribution as to what was the cause or contributors to a particular flooding event or any kind of event has improved over time. But a lot of it is dependent upon a weather model being able to replicate what happened and then take it apart and see how much of that was due to the sea surface temperatures or the land temperatures. There have been improvements in that, but typically, many of these models don’t replicate just what happened in the storm well enough, in my view.

And so a different kind of statement which I have encouraged is that you recognize that the environment where all these storms are occurring has changed. The sea temperatures are different. The land is warmer. The extent of water on the land is different because of where all the storms have occurred over the past winter and so on. The conditions where all of these storms are occurring is different, and therefore, the climate change has played a role. Now, putting down exactly what that role is a bit more difficult. As you said before, 7% increase in water holding capacity occurs with 1 degree Celsius, but because the moisture is coming typically from the tropics, it’s quite easy to get three or four times that amount in the extratropics. You can easily get up to about 30% increases in rainfall events and the total rainfall in the middle latitudes as a consequence of a storm because all of the moisture is coming from lower latitudes.

There are several factors involved in that. One of them is 7% comes from the increases in moisture in the atmosphere, but then the increased moisture in the atmosphere leads to more vigorous storms, stronger storms. So that’s the second factor. Then the third factor is these storms can last longer. This is especially true with tropical storms and hurricanes. So that’s another factor. And then the next factor, is the size of the storms. So the storms actually get bigger. So each one of these can give you about 7%, and so you end up with 28% or something like that. What is not so clear is the track of the storms. The track is mostly controlled by the jet stream and the winds and the local weather situation and not so much the conditions at the sea surface and the environment. But there are these four factors, which are not often adequately appreciated, that can lead, as I say, quite commonly to 20% increases and, in several cases that have been analyzed, 30% increases in rainfall because of the changes in the environment and the sea temperatures that exist.

You’ve criticized the IPCC as being ‘overly conservative.’ In your view, has the pursuit of international consensus actually become a barrier to telling the full, alarming truth about the pace of climate change?

Yes, well, the IPCC has done very well, but there are a number of issues with the IPCC. I think initially the IPCC brought together the most experienced and best scientists, but they were only allowed to participate in maybe three IPCC reports. And then the pressure was to bring in more and more people, and also to bring in more and more people from, let me refer to them as developing countries. And so I was a coordinating lead author in the fourth assessment report, for instance, and about half of my team of 12 were very accomplished and had published extensively. But the others had not published very much. They had done a little bit. So I don’t mean to pick on this person, but there was a guy from Kenya, and he had written papers about changes in rain in Kenya and changes in temperatures in Kenya. But he didn’t know anything about the country next door or the country to the north or the country to the south. He only had a very local knowledge of climate change, and there’s quite a number of people in that category. So they have some background. One part of the IPCC process has been to educate these people and send them back to their countries and help to bring these other countries along. I don’t know that this process is fully appreciated by everyone, but the rules have become stronger, saying that they are going to have a completely new cast. If you lose the experience and the more experienced scientists, then I think the process becomes weaker. You have to build a consensus in the United Nations, certainly in the policymaker’s summary: you have to reach a unanimous consensus. Then if people don’t understand aspects or if there are politics involved, then things get watered down. This is typically what happens in the United Nations. So the final document ends up being a bit weaker than it otherwise would be because of the politics and because of this kind of a process. I worry a bit about this. I think it’s important to have enough experience and strong scientists involved in order to help the newcomers not have to learn how to do things all over again. It’s not an easy process to deal with, and these reports take about three years to put together. Partly as a consequence of that, but also because it’s so all-encompassing. I mean, there are comments and information coming from all over the world. There’s a huge amount of information now.

If the IPCC is indeed lagging behind reality, what are the most dangerous ‘blind spots’ in the latest reports that you believe will surprise us in the next five years?

Yes, so I argued in a couple of reports that the IPCC process was obsolete. It should have been terminated after about 2009 and changed. And it needs to have a more operational arm. And maybe you can argue that there are operational arms in some countries like the Copernicus activity and the UK Met Office.

There is actually a group of people that have sort of undertaken to do this. They’ve been publishing reports on some of the core results of the IPCC. One group has been led by Piers Forster, and I can find the publication for you, if you like. So the last one was called Indicators of Global Climate Change 2024 Annual Update of Key Indicators of the State of the Climate System and Human Influence. And it has quite a large number of contributors. It’s published in Earth System Science Data, which is not the most commonly known publication. But it does undergo a review and it is published and it updates some of the science in IPCC. There is another group that has dealt with the composition of the atmosphere. They just published a major report in Nature led by a scientist called Friedlingstein. It deals with carbon dioxide and methane and the composition of the atmosphere. And whether you can, what we call, close the budget: whether you can get the actual concentrations that are measured in the atmosphere from the estimates of all of the different sources of these gases and blend that in with all of the chemistry and the atmospheric dynamics and understand why the concentrations are going up. The difficulty has been, of course, that the estimates of the sources of pollution are often incomplete. Some countries and some organizations don’t report honestly, because these countries may have made a commitment to cut emissions and if the emissions are still continuing in violation of what they said they would do under the Paris Agreement in 2017 then there is a reason for them to, you know, hide the truth, if you like to think of it that way. So it’s not, to me, altogether surprising that there has been differences between the actual observed concentration increases and the ability to fully explain what that is and where the main contributions are coming from, for instance, and how much of them is coming from burning of fossil fuels, or how much, in the case of the Methane in particular, might be associated with changes in land use and deforestation and changes in vegetation and things which are more complicated. So, anyway, those are the two groups, the carbon budget and the physical climate system that are continuing, and I support those.

How can the scientific community bridge this gap to better alert the public to the Earth’s accelerating energy imbalance, and what specific architectural changes are needed to build a continuous climate information system that delivers real-time, actionable data to local decision-makers?

Yeah, that’s a good question, because some of this involves aspects of social science. Most physical scientists, like myself, are not good at answering that question, but I delved into it and I wrote a paper that was published in Nature a little while ago that dealt with that particular topic. It was actually the time when Trump was first elected, 2015-2016. Ah, let’s see. There’s an article by Trenberth, Marquis and Zibiak in 2016. It was called The Vital Need for a Climate Information System, and it was published in Nature Climate Change, pages 1057-1059. It’s not a long article, but it dealt with exactly the kind of question you’re asking about how to better deal with the knowledge that exists for the general public, and also how best to make the latest information, for instance from the IPCC, available to the general public, and perhaps the role of the private sector, because that’s where the private sector can indeed begin to play a role. There’s often specialized scientists who work on a particular area and advise electricity companies, for instance, on where the best information is to get solar power or wind power or both, and how to deal with wind warnings or storm warnings, and how to cope with them. A number of government agencies have people who specialize in that kind of thing. So a lot of that, I think, is a growth area. But a lot of it is happening much more, at least in the United States, in the private sector. I don’t know what is happening in many other countries around the world. Some may be happening in government departments, but I think that’s an area which will continue to increase.

Have you lost confidence in the world’s ability to hit net-zero targets in time to avoid catastrophe?

It’s a good question. I wrote an article which was certainly suggesting that kind of thing, but it was intended to be somewhat provocative, and it was very much reflective of the current situation with regard to the Trump administration and the fact that the Trump administration has stepped away from any commitments in this regard in the United States. But it seems as though that is mirrored in many other countries around the world. There’s a shift to the right. Agreements and commitments were made in Paris in 2017 by many countries, but they didn’t really develop plans to match those commitments. Very few countries, only one or two, that are on target to match those. Many countries, including my own country here, New Zealand, have backed away from many actions. But there have been some really positive developments, especially in China, in the development of renewables and electric vehicles and solar panels and renewable energy. I think there’s some very encouraging signs there, but there are also these counter signs led by the United States that are going in the other direction. So my own view is that we’re very unlikely to meet any of the targets that were originally set up. Originally, we were on target for passing two degrees in terms of the global mean surface temperatures in about the mid-2050s. And I never thought the 1.5 degree C target that was mentioned by the Paris Agreement was viable. Actually, when we look back, we will say, oh, well, we’re actually already past that, about now. And I think we’re on target that we will double the amount of carbon dioxide in the atmosphere, probably about 2060 or something like that. It depends a bit on some of these other developments. But the population keeps growing. The demand for electricity is going up, especially with artificial intelligence. And a lot of the methods that are being talked about to cut down on emissions, I think, are severely flawed. They’re too expensive. Unless somebody pays for them and I don’t see who that somebody is, then they’re not going to happen. Some governments might do that. Some private sectors, especially with regard to AI, may do that. So Google supposedly is doing that a little bit. But I’m not optimistic. So I don’t expect that we will come close to net zero this century, quite frankly. I hope we will get very close to it. And any progress in that direction is very beneficial. But if we can push the doubling of carbon dioxide out to 2080 or 2090 instead of the 2050s, then even that is quite beneficial. And I expect there to be some progress, but I also expect that climate change is going to continue, I’m afraid.

Federal officials have labeled NCAR a source of “climate alarmism.” How do you reconcile your data-driven work on the Earth’s energy imbalance with this political characterization?

That’s a political statement and the ignorance of Trump and many of his cronies in government. The thing which is very disturbing about the United States, is that he has populated all of the government departments with cronies who have no credentials. I think in every case I would say that. I think the system in the United States has failed. It will be interesting to see what happens next year when the so-called midterm elections occur. I would expect that Trump will lose control of the Congress at least, and maybe the Congress will begin to step forward and challenge some of his often, I think, illegal claims. The trouble is the legal system has not been able to keep up. There are so many cases in the wind, but they take months to go through the system. So Trump keeps doing things and taking advantage of things and doing illegal things that should not be happening. I’m very sad to see it.

Critics of NCAR’s funding model suggest that the center has prioritized high salaries and an ‘alarmist’ approach over practical weather services. How do you respond to the characterization that NCAR has been a poor steward of taxpayer money, and how would you justify the return on investment the public has received from the funding allocated to your sections?

I think that statement is, again, false, completely false. You know, I was one of the highest-paid scientists at NCAR. If I reviewed proposals, I can see the salaries of people who I maybe were comparable or I regarded as inferior to me. And their salaries were three times what mine was. Our salaries were not high by standards of what went on in the universities and in the private sector at all. And so that statement is just completely nonsense.

During the so-called ‘Climategate’ controversy, hacked emails—including some of yours—were weaponized by climate deniers. Looking back, should the scientific community have engaged differently to protect public trust in science, and what lessons remain unlearned today?

Well, there’s certainly some naivety about that. I was quite involved when I was at NCAR in dealing with the media and talking to them, many of my colleagues were not. There was some naivety there. When the so-called climategate happened, there were statements that were made that were not well advised, should I say. But I think there are some actions now at NCAR and other organizations to try to limit the damage in this regard and educate scientists on how to respond to queries and to deal with the public. I think NCAR strongly encourages involvement of other people who are dealing with this on a daily basis to make sure that things are not stated that can be distorted or used out of context. So that’s one of the developments, but it’s much more difficult these days. When I really got into this, there were healthy newspapers everywhere in the United States. And they often had a number of reporters, and they often had a science reporter. Now, most of the smaller newspapers don’t have any reporters. They certainly don’t have a science reporter. And so if somebody does contact you, it’s more likely they’re from the private sector, and they’re writing a column or a commentary. Maybe they’ve been asked or requested to do it. But their background is that they don’t do this on a daily basis. They’re often not very well-informed. They often don’t do enough research like you’ve done, obviously, to find out what has happened before. And so the whole of the media and the developments of social media and misinformation and disinformation is very worrying. I don’t think it’s at all under control. There’s a tremendous amount of disinformation out there.

You were a central figure in explaining the ‘global warming hiatus’ by pointing to deep ocean heat absorption. Critics used this period to claim warming had stopped. Was the scientific messaging around the hiatus a communications failure that gave deniers an unnecessary talking point?

Yes, well, I wrote a couple of papers about that. Indeed, there are reasons why that occurred. And also it turned out there was some incomplete information in regard to the ocean heat content and later we found out the oceans were, indeed, continuing to warm through that period. And so it relates very much to natural variability and El Niños and La Niñas and understanding that. And so if you’re just as focused on the global mean surface temperature you can be quite misled. A much more comprehensive view is essential. I think that’s one of the lessons from that.

With groups like CLINTEL and the 2025 DOE Working Group gaining political traction by claiming there is ‘no climate emergency,’ how do you distinguish scientific skepticism from what you’ve termed ‘rogue misinformation’?

Well, it is misinformation. There are a number of groups that have vested interests and that are quite ignorant and have not done research and don’t understand basic physics. It’s not easy to deal with. There’s a lot of misinformation and disinformation in social media in particular. I don’t have the answer.

There is a persistent public perception that specific, catastrophic environmental predictions made since the 1960s—ranging from imminent ice ages to coastal cities being submerged by the year 2000—have failed to materialize. Given that these past warnings of ‘doom’ often didn’t match the observed timeline, how do you distinguish between those early sensationalized claims and the physics-based models you use today, and why should the public still believe in current predictions of doom and gloom?

Well, you can verify these things. Those statements that are referred to about cooling were made by one or two people. There was no consensus about that at all. They were off-the-cuff remarks by individuals who had a particular perspective generally related to air pollution, worrying about air pollution. Air pollution is certainly an issue. But globally the increase in greenhouse gases overwhelm those in actual fact. And so all you have to do is to look at the past record of what has happened, especially since the 1995 IPCC report, and the predictions and how well they have verified, and bearing in mind the assumptions that went into those products, because the models were often only dealing with carbon dioxide, they weren’t dealing with pollution, the particulates of the atmosphere and other things. The projection record is actually really extremely good. So it depends on where you’re coming from. If you’re interested in this, you can find out what is going on and why, and where you should have confidence in the outcomes.

“If you are good at something, never do it for free,” says the Joker—and I love Joker. But I believe educational content should be free for everyone. Hence, this newsletter doesn’t restrict any content behind paywalls; everything is accessible to everyone for free.

Regardless, if you want me to keep doing what I do here, you can still choose to become a paid member of this newsletter by hitting the subscribe button above and choosing the membership that’s right for you. You can also subscribe for free to regularly receive new posts.

If you do not want to acquire a recurring paid membership, you can also choose to contribute a one-time donation by clicking on the link attached below: https://link.payoneer.com/Token?t=1A1EA995DF1F4471B35100F6C5CCE134&src=dpl

Dr. Mayewski is a pioneer in the use of ice cores from polar and high-altitude regions to reconstruct past climate conditions and atmospheric chemistry. He made major contributions to the discovery and interpretation of abrupt climate change events, showing that Earth’s climate can shift rapidly through sudden changes in atmospheric circulation, rather than evolving only gradually as once believed.

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1. Your recent study on the South Col Glacier found the loss of 2,000 years of ice and unprecedented thinning. What does the loss of this ultra-high elevation archive mean for understanding the Himalayas past climate and how does this extreme sensitivity define models for long-term water security in Asia?

We were quite surprised by the amount of ice lost, which shows that even the highest parts of the planet are being affected by climate change. Research already shows that lower sections are melting, but finding significant ice loss at very high elevations—over 8,000 meters—is striking. The implication is that South Col Glacier could disappear within a few decades, along with much high-elevation ice. Does this mean the Himalayas will lose all their ice? No. But it’s another indicator that change is happening faster than expected.

2. You say the Himalayas will not lose their ice altogether. How long do you think the Himalayas will contain ice?

It’s hard to say exactly, but I think there will be significant losses in the next few decades. Other researchers are doing more sophisticated studies than our program, but major changes are likely within the next few to 50 years. As we’ve discussed, climbers on Everest will encounter a very different environment, particularly near the final camp before the summit cap from which they may be walking mostly on rock and debris.

More importantly for the people living in the Himalayas, this loss of ice is significant. Glaciers are a major water storage source, critical for agriculture, hydroelectric power, water quality, and overall life. As ice volume decreases, steep slopes where people live become less stable, increasing the risk of landslides and glacial outbursts. None of this is good for local communities.

3. You developed and led major programs at the three poles (Greenland, Antarctica, and Mount Everest). What are the unique challenges for extracting ice cores from high-altitude glaciers, like the South Col, compared to the massive polar ice sheets, and what distinct climate information does the Everest core reveal?

Working in the polar regions has its own challenges, quite different from the Himalayas. Elevations are lower, typically not above 3,000 to 3,500 meters, but it is much colder and very remote. Some parts of the Himalayas are remote too, but places like Everest Base Camp and a few higher camps are far more accessible than they used to be.

The big challenges in the Himalayas are moving equipment. Helicopters are valuable but usually only reach 6,200 to 6,400 meters. Sherpas are essential for guiding, safety and moving loads, but they can only carry so much. Heavy drills needed to go deeper than our 2019 work would make drilling, for example, 50 to 100 meters into South Col Glacier very complicated. South Col is interesting, but it’s missing the upper 2,000 years of ice.

I’ve worked with the Chinese on Everest’s north side, recovering cores from the Rongbuk region that go back several thousand years, giving a good understanding of past climate and air quality there. But the Himalayas are vast, and there is much more to learn beyond Everest.

This past month, we worked in the Langtang Valley with a team from Utrecht University in the Netherlands, led by Walter Immerzeel (Utrecht University). They plan to extend their work into other parts of Nepal. Their program includes automatic weather stations, climate modeling, and stream runoff studies. We recovered a shallow 11-meter core to better understand annual accumulation in that region. Many others are also active in the Himalayas, including Tribhuvan University, a primary partner with Immerzeel’s program, and ICIMOD.

4. Could you elaborate on the pioneering methods you developed for ultra-high-resolution ice core analysis? How have these methods, like Continuous Flow Analysis (CFA), changed the field by allowing for storm-by-storm precision?

The measurements done in recent years using continuous flow analysis are very valuable, with a resolution of about 1 to 2 centimeters, or 50 to 100 samples per meter. For a meter of accumulation per year, that provides plenty of detail to study seasons and storms.

We’ve developed a laser technology sampling system that allows fewer types of measurements than continuous flow, but has much higher resolution, over 8,000 samples per meter. This lets us study not just year-to-year or season-to-season variations but even individual storm events. Understanding the timing, frequency, and magnitude of these storms is critical for knowing how much snow enters the Himalayas, when, where and from which moisture source.

As the climate warms, monsoon patterns may change, leading to years with very heavy rainfall and possibly dryer years. Climate change does not just mean warmer or wetter conditions; it also brings increased variability. For example, in North America, temperatures were mild a couple of weeks ago, well above freezing, and then recently dropped far below freezing. There is no reason to assume future conditions will be any less variable.

5. Your work with GISP2 and ITASE used glaciochemistry (e.g., sea-salt/dust ratios) to reconstruct atmospheric circulation. How does the chemistry preserved in ice cores act as a proxy for past circulation patterns, such as the North Atlantic Oscillation or the Antarctic Oscillation?

The chemistry we study covers a broad range, typically 50 to 60 chemical species, sometimes more. Sodium and chloride, for example, come primarily from the ocean and can indicate the amount of monsoonal air reaching a site. From regions like the Tibetan Plateau, which is cold and dusty, we detect both cold signals and high dust content.

We can also examine rarer chemistries to see how human activity has altered the chemistry of the atmosphere, introducing more toxic substances. Different chemical signatures help us track air mass pathways—not just from the Tibetan Plateau or the monsoon to the south, but also from local sources, the Mediterranean, or eastern Asia. In this way, ice cores act like automatic weather stations, but providing data that extend back hundreds or even thousands of years.

6. Your research was pivotal in the discovery of abrupt climate change events, which saw temperature increases in less than five years. What is the currently accepted understanding of the forcings and mechanisms that trigger these rapid reorganizations, and how relevant are these past events to our current climate trajectory?

Those are very good questions. In the early 1990s, we discovered that climate could change faster than a political cycle—faster than five years—and sometimes very dramatically. These changes could also persist for decades or even centuries. The causes of these changes are the same forces that drive climate overall: variations in solar energy and greenhouse gases, volcanic events, changes in ocean circulation, and other factors. Finding abrupt climate change events in the pre-anthropogenic record shows that abrupt climate change can occur naturally.

However, what has changed now is the rapid increase in greenhouse gases. CO2 has risen by about 150 percent, at a rate 100 times faster than anything seen in the last 800,000 years, with a similar story for methane. While past abrupt events likely arose from multiple natural factors coinciding, today we face a unique situation driven by greenhouse gases, creating an abrupt climate change event.

A clear example is the dramatic Arctic sea ice decline between roughly 2007 and 2012, especially in summer. Reduced sea ice impacts how easily cold air moves south and warm air moves north, altering atmospheric circulation patterns across the Northern Hemisphere. This can trigger droughts, intensify storms, increase forest fires, and cause a range of other impacts that we are already experiencing.

For the Himalayas, declining Arctic sea ice opens new ocean moisture sources from the north, potentially increasing precipitation on both the north and south sides of the range. Warmer oceans allow monsoon air to carry more moisture, which can increase snow accumulation. The key question is timing. Most monsoon moisture arrives during warmer months as rain, not snow, which does not contribute to glacier growth. Understanding the timing, type, and temperature of precipitation, as Walter Immerzeel and colleagues are doing at Utrecht University, is critical.

Other abrupt climate changes include the recent drying of the Sahara, the Horn of Africa, and the Middle East. These changes have major consequences for agriculture, food availability, and geopolitics, as traditional farming becomes increasingly difficult.

7. Your work on ice cores from the Southern Hemisphere touches on paleo-sensitivity. Specifically, what does the extreme rapidity of past atmospheric shifts and the past orbital forcing sensitivity of the East Antarctic Ice Sheet (EAIS) tell us about the stability of Antarctica under current anthropogenic warming?

Another good question. The Antarctic Ice Sheet has varied in size over time, sometimes larger and sometimes smaller than today. The last time it may have been smaller was about 120,000 years ago, due to the Earth’s orbital relationship with the Sun and resulting changes in solar energy. Warming causes ice loss.

Antarctica is divided into East and West. East Antarctica, the largest part, rests on a continental landmass, while West Antarctica sits on islands, making it much more vulnerable to warming. As West Antarctica thins, parts begin to float, and research suggests large sections could be lost in the next few decades or certainly within 200 to 300 years. Past records show this is possible, and today it is happening because of the unprecedented rise in greenhouse gases.

8. Your paper establishes an association between U.S. Northeast precipitation trends and Greenland Blocking (GB). What does the behavior of this circulation feature imply about the predictability and modeling of mid-latitude extreme weather events under accelerating Arctic warming?

It’s true. As I mentioned earlier, Arctic warming allows cold air masses to migrate farther south and warm air to move farther north. One dramatic example is that in midwinter at the North Pole, in complete darkness, temperatures can rise above freezing. At the same time, cold air that sits over Greenland, can create a blocking effect that prevents warm air from moving in. In places like Maine, this blocking increases moisture along the coast.

For the Himalayas, much farther east, these changes create irregular jet stream patterns, with cold air plunging south and warm air moving north. This contributes to rapid day-to-day or week-to-week weather changes. For example, in the Langtang Valley, we recently experienced large snowstorms after the normal monsoon ended. How long that snow remains depends on local temperatures, and much of it has already melted at lower elevations.

Changes in the jet stream are critical because air masses carry heat, cold, moisture, and pollutants, redistributing them to regions where we haven’t typically seen them in recent decades.

9. You documented human impacts on the chemistry of the atmosphere, including pollutants like lead and black carbon. What is the most compelling example from the ice core records that clearly differentiates anthropogenically derived pollutants from natural variability over the last few centuries?

The main concerns are increases in pollutants, including toxic metals like lead, cadmium, and mercury, as well as human-made substances like microplastics and PFAS. In a Greenland study a few summers ago, we found PFAS on the top of the ice sheet. PFAS was also detected in our 2019 Mount Everest snow samples. These are substances that didn’t exist previously and they are being widely distributed with consequent health impacts for humans and the ecosystem.

Lead which is very hazardous to our health, which in the natural environment be at very low levels, but human activity has dramatically increased lead in the atmosphere. What is particularly concerning is that these pollutants are stored in ice. As glaciers melt, these substances are released, directly impacting water quality for humans and ecosystems downstream, and increasing toxicity in drinking water.

10. As the author of The Ice Chronicles, how do you manage the responsibility of communicating complex, fact-based climate science to a public audience, and what are the most significant “lessons learned” from your paleoclimate-societal studies that you apply to modern policy and planning?

It’s very important for scientists to explain their findings in ways that are relevant to people. That’s what we’ve tried to do in The Ice Chronicles, on our Climate Change Institute website, and through movies and interviews like yours that I have been involved in. The relevance of climate change varies by location. For example, sea level rise is not a major concern for people in Nepal, but changes in water availability, glaciers, and storm patterns are critically important.

The most important lesson we’ve learned is that climate can change much faster than previously thought. If climate changed as slowly as believed before the early 1990s, adding CO2 or methane to the atmosphere might take centuries to have an effect. But responses can be rapid. Changes in Arctic or Antarctic sea ice, or in the Himalayas, can immediately affect atmospheric circulation patterns. Over time, these changes become embedded in the ocean, altering ocean circulation and heat transport. For example, if the Gulf Stream slows, regions of Northern Europe, including Scandinavia and the northern UK, which are currently relatively warm for their latitude, could become colder.

11. Given the current rate of climate change, what remains the most critical unanswered question in glaciology or paleoclimatology that you plan to address next, and what is the next frontier for ice core drilling and analysis technology?

Good questions, as always. I think the most important goal is to improve our predictions of climate—not globally, but region by region, for the Himalayas, dry areas, different latitudes, and so on. We have a lot of data, but high-quality records really only go back to about 1940. To understand how much, how fast, and where climate can change, we need longer records from other parts of the world, and ice cores turn out to be the best resource.

Improving predictability requires not just climate models but also analogs of past climate change, which ice cores provide. We also need to recover more ice cores. Programs like Ice Memory focus on collecting cores from glaciers that are melting rapidly, then storing them in places like Antarctica for preservation. As ice core technologies improve over the next few decades, we’ll be able to learn even more about past climate.

Once glaciers melt, the archive is lost, so preservation is critical. One innovation we’re proud of is our laser sampling technology. It uses very little ice, leaving only a microscopic scratch, so the ice core appears unchanged. Technologies like this need further development to allow more types of measurements, but they are a major step forward in studying past climate.

12. If we extrapolate current trends and findings, what is the ultimate, long-term scientific and societal scenario if all the ice in the world were to melt?

Not all the ice will melt, but a lot will. A recent report from the University of Edinburgh is particularly important. It looks not just at 2100, but also at 2200, 2300, and 2400. Cities will still exist, and today’s planning will heavily influence the future. The expectation is that within the next 200 to 300 years, sea levels could rise at least 4 meters, possibly 8 or 9 meters. Considering the large proportion of the global population living in coastal areas, this will have major impacts on how people live and the resources our coastlines provide.

Food production is another critical issue. As climate changes, we need to carefully plan where and how to grow food. The ocean is a major food source, but it is warming, acidifying, and accumulating plastics and toxins. Mitigating greenhouse gases and other pollutants is essential to maintain a world at least as good as the one we live in now. Ideally, it could be even better, though not for everyone. Rising seas will affect Pacific Islands and other coastal regions, but if we act wisely, we can improve air and water quality, manage energy more efficiently, and grow food more sustainably.

13. How has your long tenure as the director of the Climate Change Institute at UMaine been? What has been your most memorable experience while working there, and how do you feel now that you’re finally stepping down from the role?

Yes, I stepped down a couple of months ago after serving as director for 24 years. Our institute is 53 years old, so I had the opportunity to guide some important changes. As the Climate Change Institute, change is in our name, and climate change itself is always evolving. It’s been vital for the institute to adapt as our understanding of climate change grows and as its impacts—from catastrophes to ecosystem health to geopolitics—become clearer. We’ve responded by bringing in more disciplines and people, and I’m very proud of how we’ve evolved.

Unfortunately, under the current U.S. administration, climate change is not considered a priority, while the rest of the world sees it as important. This will make our work more challenging, but our dedicated team will continue to pursue what they believe matters.

Being director was a great privilege. The last few years were complicated, and I’m excited to pass leadership to someone else. We have an interim director now and will search nationally and internationally for a new director. I will gradually step back from the institute, but that doesn’t mean I’ll be less involved in climate change communication. I expect to work even more with collaborators in Nepal, Europe, Australia, and New Zealand. It’s a great opportunity, and I’m proud to have helped shape the institute’s vision.

14. Following on your last answer, President Trump recently denoted climate change as a “hoax”. How do you feel about that, and what would you like to tell him?

Well, it’s a very interesting thing to say, based on absolutely no facts whatsoever. We’ve known for more than 100 years that greenhouse gases trap air and heat. We’ve known for the last 30 to 40 years that glaciers have been melting, and glaciers don’t care about politics. If glaciers melt, it means it’s getting warmer. There are many other indicators as well.

Twenty or thirty years ago, when climate change was not as well understood or accepted, there were many skeptics, and interactions with them were often positive because they found holes in what we were doing, and we would go to work on those suggestions. As the years went by, there were fewer skeptics, and their comments became less valuable. They began taking information from existing peer‑reviewed papers, pulling it out of context, and using it as an argument.

In the last few years, there have been no rational arguments from skeptics at all. So if climate change is a hoax, why is there no data showing it’s a hoax? There is none. And avoiding the issue won’t be healthy for any country because, whether we like it or not, whether people believe it or not, it’s happening.

15. You do advocate for the phase-out of fossil fuels, right?

Yes. Fossil fuels will remain essential for a long time. They have gotten us where we are, but they have a negative side because they produce warming and pollutants. Renewable energy is becoming increasingly important worldwide. It makes sense because it creates jobs, does not cause pollution, and does not contribute to warming. As time goes on, its use will grow, and opposing it does not make sense.

We are also constrained by fossil fuel use because access varies by country and markets can be manipulated. Geoengineering to reduce greenhouse gases is a worthwhile area of research, but so far nothing has proven very effective. As long as we continue emitting these gases, we will live in a world that is more polluted, warmer, wetter, and in some regions drier and stormier than we would like. Ignoring this reality makes no sense.

16. What is your message to the group of scientists who recently prepared DOE’s new report on the impact of GHGs Emission on the U.S. Climate? To scientists like Dr. Judith Curry and also Dr. Richard Lindzen. I guess you know them.

I do. They have been skeptics for a long time, but that doesn’t mean they were not good researchers at one time. Dr. Curry, for example, believes solar variability is very important, and she’s right. Solar variability was a major control on climate until greenhouse gas emissions became significant. If greenhouse gases had not risen, we likely would have remained in a much cooler climate.

I debated Lindzen some years ago in Sweden. He has his own agenda and interests. Skeptics in science are valuable, but not when they push a biased agenda instead of focusing on the facts. The IPCC (Intergovernmental Panel on Climate Change)is based on thousands of peer-reviewed papers. When they state something is happening and caused by humans, it is generally moderate and conservative. One or two skeptics presenting limited or insignificant information do not outweigh the evidence.

The fact that this is coming out of the US DOE (Department of Energy) reflects the current administration’s priorities, which want papers saying climate change is unimportant. But it doesn’t matter. Climate change is real, and it will not disappear because someone presents an unfounded opinion.

“If you are good at something, never do it for free,” says the Joker—and I love Joker. But I believe educational content should be free for everyone. Hence, this newsletter doesn’t restrict any content behind paywalls; everything is accessible to everyone for free.

Regardless, if you want me to keep doing what I do here, you can still choose to become a paid member of this newsletter by hitting the subscribe button above and choosing the membership that’s right for you. You can also subscribe for free to regularly receive new posts.

If you do not want to acquire a recurring paid membership, you can also choose to contribute a one-time donation by clicking on the link attached below: https://link.payoneer.com/Token?t=1A1EA995DF1F4471B35100F6C5CCE134&src=dpl

Dr. Riahi is the Director of the Energy, Climate, and Environment (ECE) Program at the International Institute for Applied Systems Analysis (IIASA) in Austria. He is a prominent researcher studying global energy systems and sustainable development, who has spent decades analyzing the long-term evolution of the global energy system and has published hundreds of peer-reviewed research papers. In addition to his role at IIASA, Dr. Riahi has contributed to several IPCC assessments since 1998, is part of the UN Secretary-General’s Group of Ten High-level Representatives, the European Scientific Advisory Board on Climate Change, a member of the Integrated Assessment Modeling Consortium (IAMC), and more. In 2021, Reuters listed Dr. Riahi as the world’s top climate scientist.

In this post, I and my colleague Niroj Subedi, a graduate student of BiogeoSciences in Germany, interview Dr. Riahi about various aspects of the global energy system, the basis for formulating models to understand future climate, the necessary steps to restrict global warming below the Paris Agreement target, and what really keeps Dr. Riahi awake at night after years of studying the global energy system. “What keeps me up at night is that, at the moment, climate and environmental issues are not a top concern for many politicians,” stressed Dr. Riahi.

(This interview has been edited for length and clarity.)

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1. Your work has shaped the scenarios that policymakers and the IPCC rely on to plan for climate futures. Looking back, has any projection you made surprised even you?

Perhaps “surprise” is not the word I would use, but there are scenarios that we’ve learned more from than others. What we learn through using these scenarios is essentially how to represent the whole human system and the biosphere within our models. We try to understand what the future evolution could look like. The main thing we aim to learn is: if we introduce certain boundaries—say, constraints to limit climate change—how would our socio-economic systems respond?

For a long time, we saw that it’s possible to limit climate change to what are considered “non-dangerous” levels. The Paris Agreement defines this as around 1.5°C, and definitely well below 2°C. But every decade that we delay introducing climate policies—because of various reasons—we see emissions continue to rise. At some point, we cross the line and start to overshoot those targets. That’s when models began applying so-called “negative emissions technologies.” Essentially, if we put too much CO₂ into the atmosphere, later generations will have to remove some of it to repair the imbalance.

Another important learning was realizing that to stop climate change, anthropogenic emissions must reach net zero. But “net zero” doesn’t mean that every single activity must have zero emissions. Some sectors are much harder to abate. About ninety percent of the work can be done by reducing emissions, but the remaining ten percent involves finding ways to offset the residual emissions from sectors that are very difficult to decarbonize—such as aviation, chemical production, and industries requiring high temperatures.

It’s not that there are no alternatives for these sectors, but that current alternatives are not yet viable for industrial-scale deployment. We’ve also learned that different assumptions about innovation, structural change in the economy, and the role of negative emissions all influence how we can achieve the net-zero objective.

So, I wouldn’t call it “surprises,” but rather that we’ve learned quite a lot along the way.

2. Your models deal in numbers, probabilities, and pathways — yet the effects of climate change are profoundly human. How do you bridge that distance between the abstract and the immediate, the data and the lives it represents?

Modeling is essentially an attempt to represent the real world in an abstract way. If you are a modeler, your main aim is to design a model that can capture as many real-world dynamics as possible. This is generally easier in systems that are purely physics-based—what we call the natural science models.

When describing climate change itself, once we know the emissions, we can estimate how much climate change will occur. Then the task is to represent the climate system accurately. In this regard, we’re getting better and better at simulating both historical and future climate change, and we understand the uncertainties quite well—though, of course, uncertainties always exist.

When we move to human systems, the challenge becomes greater. Humans are ingenious; they make different decisions. The implementation of policies doesn’t depend only on available technologies or the “best” solutions—it also depends on the social acceptability of those solutions and the capacity of different countries and societies to implement complex new systems. This is where social and behavioral sciences play a major role.

In modeling, we increasingly try to incorporate those social constraints and opportunities—such as innovations and behavioral factors—into our frameworks. The ongoing challenge is that we can’t represent every individual human being, so we have to simplify and aggregate. Determining the right level of resolution and granularity is key to capturing human responses, including the irrational behaviors that also shape outcomes.

That’s really the frontier of research right now: moving one step further from the purely technical and economic aspects toward understanding human decisions within their cultural and social contexts.

3. Over the years, your models have incorporated new technologies, social trends, and economic shifts. Which emerging trend do you think is most underappreciated—and could radically alter the global energy outlook?

At the moment, the energy sector is changing very rapidly. We’ve seen massive drops in the cost of renewables—particularly solar PV—and in the cost of batteries. These declines have made battery-plus-PV systems an economically viable solution compared to fossil fuels in many contexts.

What is currently underappreciated, I think, is the vast potential of seasonal storage. As we move toward a system without fossil fuels, we need to ensure that electricity generation can meet demand year-round. In regions without winter, we’re already in a relatively good position, but in places that experience winter, we must find ways to provide electricity when solar power diminishes. This means developing solutions that can store energy from the summer and release it during the winter months.

Many people think about pumped hydro as an option—and that’s an excellent solution for countries like Nepal, for example. But not everyone lives near the Himalayas or the Alps. In flatter regions, we need other forms of storage, and that’s an area where technological breakthroughs are still needed. There are many emerging ideas, such as various types of gravity storage, where energy is stored by elevating mass and released when it drops. There are also innovative concepts involving ocean-based storage: for instance, pressing large volumes underwater, which naturally try to rise back up, can be used to generate energy. It’s like inverting the pumped-hydro principle—rather than moving water up a mountain, you move pressure underwater and recover energy when it’s released.

We need much more experimentation with small, distributed storage systems and to design new energy infrastructures where storage is a built-in component. At the moment, we are building a lot of PV and wind capacity, but we’re running into constraints because the infrastructure and grid systems in many parts of the world are not up to date. The next crucial step is to focus more on integrating storage solutions.

Another area of innovation we must think about concerns removing CO₂ from the atmosphere. The later we act to radically change our systems and reduce emissions, the more CO₂ we’ll need to remove in the future. There are several ways to do this. The simplest is through trees and forests, which naturally absorb CO₂; managing them sustainably is essential. But there are also technical solutions—for example, direct air capture technologies that remove CO₂ from the atmosphere using industrial processes. Some of these projects face challenges, but they remain an important area of exploration.

Then there are hybrid approaches, combining natural and technological solutions. For instance, bioenergy with carbon capture and storage (BECCS): when bioenergy crops grow, they absorb CO₂, and when they’re used for energy, if the resulting CO₂ is captured and stored underground rather than released, the process can yield negative emissions.

Other promising methods include mineralization, where certain rocks—like basalt—naturally bind CO₂ through chemical reactions. By crushing these rocks and increasing their surface area, we can enhance this “weathering” process and accelerate CO₂ uptake.

There are many possibilities, and honestly, we could spend an entire hour just discussing these emerging options.

4. Energy transitions are happening unevenly around the world. Which countries or regions are surprising you—either in a positive or negative way—in terms of aligning with climate goals?

Who would have thought that the solar PV auction systems in Germany—where Germany invested heavily in upscaling renewable technologies—would eventually help create a massive industry on the other side of the planet? As a result of that dynamic, China has become a global leader in the green technology revolution, including solar PV, electric vehicles, and battery production.

That’s a very positive and encouraging development, because we all want renewable energy to become as affordable as possible. However, we also don’t want it all concentrated in just a few countries. The dependency and vulnerability we experienced in the fossil fuel system should not be repeated in the renewable energy system.

I was also quite surprised by the rapid adoption of electric vehicles in countries like Norway, where around 90 percent of all new cars are now electric. They’ve practically completed the transition—almost no one in Norway buys gasoline-powered cars anymore. That’s an important signal to the world: it shows that such a transformation is not a distant dream, but something practical and achievable.

Bangladesh also surprised me—with millions of solar PV rooftops paired with small-scale batteries that provide decentralized, community-based electricity generation. I thought that was a very clever move. In many developing countries, including perhaps Nepal and other rural regions, the key question is whether to build a nationwide centralized grid or to pursue decentralized, small-scale community grids powered by renewables. Renewables provide a valuable entry point—perhaps not sufficient for every need or for achieving a “good life” alone—but once you have a local grid, it becomes much easier to expand and connect. That, to me, is a very interesting and pragmatic development.

And I must say, I’m genuinely excited that Texas, in the United States—traditionally known as the oil powerhouse—is now actually the largest solar PV producer in the country. Everyone associates Texas with oil, yet today it is installing more solar PV capacity than even California. That’s a fascinating and inspiring turnaround.

5. In your view, where are the biggest gaps between what your models predict and what governments are actually doing?

That’s a very difficult question to answer, because what we try to do in modeling is to understand how systems respond under different levels of policy ambition. As modeling scientists, we can explore the implications of certain choices, but we cannot determine what the political ambition actually is.

Political realities tend to focus on the very near term—on what is happening right now. They often don’t give enough consideration to the risks associated with the changing frequency and intensity of extreme events, or to the exposure of the most vulnerable populations.

I think that’s where the biggest difference lies: where short-term economic interests and political priorities drive decisions that diverge from what scientific studies and models indicate would be beneficial, both in the near term and the long term. Models show that viable investments and economic restructuring toward sustainability can bring broad benefits to society, yet these insights are often overlooked when immediate interests take precedence.

This gap isn’t universal, but in many developments I observe, particularly now that climate has slipped somewhat lower on the global political agenda, there’s a high risk that decisions will continue to be made based on other, more short-term priorities.

6. Technologies like direct air capture and advanced storage are often touted as silver bullets. How realistic is it to rely on these solutions, and how do they factor into your scenarios for the next decade?

It’s clear from most scientific analyses that about ninety percent of the work to address climate change must come from reducing emissions, not from removing CO₂ from the atmosphere. But the remaining ten percent—removing CO₂—is also crucial. If we can scale these technologies quickly, we can accelerate the reduction of CO₂ emissions, achieve net zero earlier, and lower the peak warming that society will experience.

Some CO₂ removal will be necessary because there will always be residual emissions in sectors where alternatives to fossil fuels are limited, such as aviation or parts of the food system. In the long term, it may even become a preventive strategy to pursue negative emissions more broadly, in order to repair and reduce atmospheric CO₂ concentrations.

We are already exceeding the 1.5°C target, destabilizing the climate, and seeing massive consequences around the world—impacts that will continue to increase. It’s sensible to recognize that we now live in an overshoot world. Managing this overshoot requires not only emissions reductions, but also removing CO₂ from the atmosphere.

Whether this happens through direct air capture (DAC) is uncertain. I’m somewhat skeptical that DAC can be deployed at the massive scale needed. Its main disadvantage is that it consumes energy rather than produces it. Many DAC processes also require significant water, and they demand large land areas—essentially huge industrial zones to remove gigatons of CO₂. Another challenge is monitoring and verification: CO₂ stored underground must be continuously monitored for centuries to ensure it remains safely sequestered.

Because of these constraints, I think DAC’s potential is limited. In contrast, nature-based solutions—such as enhanced weathering, biochar, and other approaches—may be more viable, safer, and scalable for large-scale CO₂ removal.

7. Policymakers often face the tension between short-term economic pressures and long-term climate imperatives. Based on your research, what is the most compelling argument for acting decisively now?

Any fossil fuel that you do not burn represents an immediate benefit. The combination of measures needed to respond to climate change generally includes efficiency improvements and demand-side management—essentially, providing the same services using fewer resources. These measures bring a range of co-benefits.

For example, they reduce pollution, enhance energy security, and decrease reliance on imports, which protects countries from price volatility and supply disruptions. In countries where infrastructure is still being developed, renewable solutions are often cheaper than building a society based on fossil fuels. They also provide significant near-term economic benefits.

It’s no longer accurate to say that there are only near-term costs for long-term gains. While new technologies can be capital-intensive, investments in them are not just costs—they are investments that pay off. For instance, installing a solar PV panel on your roof reduces or eliminates your electricity bill over time.

The main paradigm shift needed is to rethink how we mobilize finance for these solutions. Ironically, in many countries without sufficient liquidity, governments are often forced to rely on polluting, uneconomic solutions simply because they lack the funds to invest in alternatives that would actually be profitable in the long term.

So the argument is clear: the near-term economic cost of acting is not really a cost—it is an investment with long-term economic and societal benefits.

8. As COP30 approaches, negotiators will be grappling with emissions pledges that are still far short of what the science demands. From your perspective, what is the single most misunderstood or overlooked aspect of climate modeling in these negotiations?

I cannot speculate on that. I think the negotiators are actually well aware of the science; they know many of the details. It’s not that they haven’t heard the science—they have—but they may have other priorities.

9. Much of COP30 will focus on dollars as much as on degrees. In your view, what’s the single most persistent obstacle to mobilizing climate finance, especially for countries already facing the brunt of climate impacts?

That’s going to be an important discussion in Belém at the next COP. Climate finance will again be a central topic. There are plans to scale up international climate finance, with targets of around $300 billion per year by 2035, and more than $1.3 trillion of that expected to support developing countries, which face the greatest challenges in both mitigation and adaptation.

The main challenge is trust and cooperation between countries. Industrialized nations, which have historically benefited from emissions-intensive development, need to recognize their responsibility to support countries with lower capacities or higher vulnerability. Scientific studies grounded in climate justice show that current financial support is far from sufficient.

However, the required support is still not materializing, and I am somewhat skeptical about progress in international negotiations, given the current fragmented and polarized global context. Distrust across geopolitical blocs—sometimes framed as Western economies versus BRICS nations—makes coordinated action difficult.

The key is to regain trust, with the understanding that climate change can only be solved through cooperation. Scientists can contribute by providing evidence-based scenarios that show the benefits of different forms of collaboration. While the evidence cannot dictate exactly how countries should work together, it can clarify which types of cooperation lead to which benefits, and for whom. This transparency can open doors that might otherwise remain closed in political negotiations.

Institutions like ours—the International Institute for Applied Systems Analysis, with a long tradition in science diplomacy—can play a critical role by delivering solid analytical frameworks and scenarios that inform dialogue and build mutual understanding.

10. How do you assess the Paris Agreement’s successes and shortcomings so far? Are the current NDCs sufficient to keep warming below 2°C?

I think the Paris Agreement has been a huge success. Without it, we would not have seen the major drop in renewable energy costs, nor the mainstreaming of climate policies globally. Every country has at least considered its Nationally Determined Contributions (NDCs) and thought seriously about how emissions could be reduced. The Agreement has made it possible for the entire world to engage with the problem of climate change.

That said, progress has been very uneven, and the current NDCs are not sufficient to limit warming to below 2°C. Given current policies, we are likely headed toward warming above 3°C. If the NDCs were fully implemented, we could limit warming to somewhere between 2 and 2.5°C—but that assumes strong follow-through. There is a significant implementation gap: countries often put forward ambitious NDCs but do not fully follow through with the necessary legislation and actions.

There is also the risk that instead of increasing ambition, some countries may reduce it. For instance, many countries have not yet submitted their updated NDCs ahead of COP30 in Belém, including major economies like the European Union, India, and China. This lack of updated submissions is a major concern.

Overall, while the Paris Agreement remains the most important international instrument to meet climate objectives, countries need to follow up on their commitments. Signing the Agreement alone is not enough—implementation is critical. My hope is that COP30 will see some progress, but at the moment, I remain somewhat skeptical.

11. How would you describe the world under each of the main RCP scenarios — 2.6, 4.5, 6.0, and 8.5? What would life on the planet actually look like under each pathway?

In each of these worlds, there are many possible pathways to reach them. Perhaps the easiest to describe are the very high and the very low scenarios.

In the very high scenario—RCP 8.5 as it was originally framed—our current understanding of climate impacts suggests a world where large parts of the planet would experience severe climate-related disruptions. Economically and socially, a prosperous life would be very difficult in many regions. However, high-end scenarios like RCP 8.5 have become less likely due to global climate action and technological innovation. The Paris Agreement has effectively reduced the probability of such an extreme future. Current updates to the RCPs suggest that the highest plausible scenario is now closer to RCP 7.0, reflecting that a world where all remaining coal and fossil fuels are burned is increasingly unlikely.

Even so, high-impact scenarios would still produce extreme harm, particularly for vulnerable populations where adaptation options are limited. The cost and difficulty of adapting to such a climate would be massive, and the social and economic consequences would be severe.

12. Looking ahead, if COP30 could deliver one concrete outcome that would make the biggest difference in keeping the world on track for 1.5°C, what would it be?

This is a very good question. At COP30 in Belém, there will be discussions on the implications of adaptation, including how to measure progress across different sectors. There will also be discussions about ratcheting up the ambition of countries’ NDCs, as well as ongoing conversations about climate finance.

For me, the absolute game-changer would be if countries increased their ambition to meet the long-term targets of the Paris Agreement. If the major players—China, India, and Europe—jointly agreed to raise their ambition to that level, it would set a strong example and encourage others to follow. The European Union may be closest to this, although political developments there risk making climate a lower priority. My hope is that the EU will maintain its commitment and put forward a very ambitious NDC, which could help drive global progress.

13. In a recent interview on a climate podcast, the CEO of COP30, Ana Toni, commented that the COPs only constitute a ‘moment in the year.’ She said what matters most is what governments, businesses, and citizens do during the rest of the time. Do you agree with her statement?

(Giggles) Of course. The COPs exist to help sharpen our objectives, but I agree with her statement.

14. Given the rise of unexpected disruptions (e.g., pandemics, geopolitical fragmentation), how are your modelling frameworks adapting to “shock”-type events, and how might those alter mitigation pathways you previously considered unlikely?

What we do is develop different types of scenarios to account for disruptions, such as supply interruptions of critical materials or fossil fuels. For example, we create scenarios with perfect foresight, where no disruptions occur, and compare them to scenarios that include defined disruptive events. By examining the differences, we can assess the value of information, the importance of long-term planning, and the potential risks to society and the economy.

If there is a specific disruption, like the impact of the Ukraine War on Europe’s energy system, we can simulate it by running scenarios with and without that disruption. However, the model itself does not generate disruptions; it is designed to find solutions. To test resilience, we need to define the disruptive event and tell the model, “This event is happening, and here is the disruption.”

15. Artificial intelligence is transforming almost every field. Do you see Al changing the way we build or interpret climate models in the coming years

I think AI has massive implications for climate modeling as well as for climate solutions. In terms of solutions, AI can accelerate change, help us respond more effectively, improve mitigation, and make systems more efficient. At the same time, it has potential downsides. It could drive excessive resource use, destabilize the planet, reduce political agency, or even be used to manipulate people. On the positive side, it could increase democratic access to information and services. Overall, AI’s role in this transition will be huge; I don’t see any other single factor that could have as much influence on the solution space for climate.

AI is also an additional tool for modeling. Machine learning, physics-constrained AI algorithms, and digital twins can improve both the efficiency of models and the types of questions we can address. For example, AI makes it easier to explore how different solutions align with the preferences and needs of people, allowing us to design climate models that are closer to real human needs than we can achieve today.

16. Finally, after decades of modeling the future, what gives you hope? And conversely, what keeps you up at night?

I can tell you a bit about my other roles. I’m a scientist at IIASA, but I’m also part of the European Advisory Report on Climate Change, the Viennese Advisory Report on Climate Change, and I have the opportunity to serve on the Science, Technology, and Innovation Board of the UN.

What keeps me up at night is that, at the moment, climate and environmental issues are not a top concern for many politicians. I see a shift in perception that I think is a misperception—people may not fully realize that solving some of the issues politicians worry about depends on addressing climate change. Across the advisory boards I’m part of, I see genuine willingness from political leaders to do something beneficial for society. But their focus has shifted in a way that risks delaying the actions we need to limit climate change.

On the positive side, I am generally very optimistic. If you read my papers, you’ll see they are full of different solutions to address the climate problem. There is not just one way to do it—there are hundreds of possible approaches. We need to choose and implement one or more of these options. I remain hopeful that we can succeed, but this requires making climate a higher priority as a society, because ultimately, politicians follow public priorities.

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Dr. MacCracken is a prominent climate scientist who worked on the earliest climate models and has been studying global climate change for decades. A scientist who is thoroughly committed to understanding the narrowing paths for responsibly addressing climate change and moderating its impacts, Dr. MacCracken has held positions such as the first executive director of the Office of the U.S. Global Change Research Program, where he supervised federal research on global environmental change. In addition, Dr. MacCracken has also worked at the Lawrence Livermore National Laboratory (LLNL), where he coordinated efforts in climate and atmospheric modeling and spent much of his career there. He has also contributed to the IPCC’s several climate assessment reports and has served as Al Gore’s climate science advisor. After retiring from his government career, Dr. MacCracken has been working on a pro bono basis as Chief Scientist for Climate Change Programs at the Climate Institute.

In this interview, Dr. MacCracken discusses what stumbles the US government from taking effective actions to tackle climate change, his opinion on solar geoengineering, how the developed nations might approach climate finance, his suggestions to the world leaders meeting in the upcoming COP, and his advice to the U.S. government’s climate and research policy for the next decade.

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Dr. Michael C. MacCracken, veteran climate scientist and former executive director of the U.S. Global Change Research Program.

1. You’ve watched US climate policy evolve for half a century. Why does science keep getting clearer, but political actions always lag behind?

So, as a bit of history, Swedish scientist Arrhenius in 1896 suggested CO2 could warm the atmosphere and even did the math to show it was possible. There were scientific objections that weren’t resolved until around 1960. One objection was how the atmosphere could warm from CO2, given that more CO2 seemed redundant because it was already absorbing all the radiation in the CO2 bands. It turns out this has to do with the height at which the radiation in CO2 wavelengths is emitted and absorbed, which is a topic we could explore further.

The second objection was that the ocean contains 40 to 50 times as much CO2 as the atmosphere. So, how could the atmospheric concentration build up if most of the CO2 would mix into the oceans? It took measurements from after nuclear weapons testing to realize that the ocean is layered and can’t take up CO2 as efficiently as had previously been thought.

In 1965, the President’s Science Advisory Council released a report explaining the problem. The report reached Congress and President Johnson, who were clearly informed of it as an issue. If you read that report, you would see that the science was—and still is—quite solid. Unfortunately, subsequent administrations largely ignored the issue until late in the 20th century. There is actually a book by James Gustave Speth, an environmental advisor to President Carter, titled They Knew: The US Federal Government’s Fifty-Year Role in Causing the Climate Crisis, which reviews the issue administration by administration, showing that the problem was understood but largely ignored. This continued until 1992 and agreement to the UN Framework Convention on Climate Change, which formally recognized the global nature of the problem and led to the Kyoto Protocol. That protocol called for voluntary measures by developed nations. President Clinton and Vice President Gore proposed to implement changes, but Congress would not approve them without a detailed plan for implementation. Even then, the plan fell short, and I don’t think any countries fully achieved the voluntary emission targets set in the original draft of the Kyoto Protocol.

Since then, U.S. policy has swung back and forth depending on the administration, often influenced by fossil fuel companies, and there has been this troubling denial of climate science by many in the Republican Party. Still, many states are making progress. President Trump’s idea of returning to coal, for example, is economically unfeasible. Coal is far too expensive—electricity from coal costs around 8–9 cents per kilowatt-hour, while solar is about 3 cents per kilowatt-hour and dropping. Business leaders aren’t going to pay three times as much for electricity; that’s not how capitalist systems operate.

There are challenges: the U.S. has abundant solar and wind resources, but they aren’t always near where energy is needed. We need a better transmission network, which is a side project I’m involved in promoting. This is true in most countries: renewable resources aren’t necessarily located where demand is highest. Transmission networks are key, and countries like China and those in Europe are starting to implement them. The U.S., however, is lagging, and several of us are trying to push for improvement.

U.S. emissions are slowly decreasing, but not fast enough. Globally, emissions are still slightly rising, far from the zero level of emissions that we need to halt further warming. Given where we are, additional warming will, in my view, be “dangerous” given the phrasing of the UN Framework Convention.

Scientists continue to respond by providing clear information as best we can. One project I’m currently working on has a few-day deadline for responding to questions from members of Congress that were posed following a hearing I testified at a month ago. We scientists are trying, but it’s very sad that this has become such a politically divisive issue in the United States.

2. You worked on some of the earliest climate models. With all the new data and computing power we have today, are we still missing something important about how fast or how far the climate is changing?

Well, yes, I worked on an early climate model, though not the earliest. And in fact, the earliest one was published by Manabe in 1965 while I was still in graduate school; it was the one that showed this was an issue. The newer models, which I wish I could work with, take advantage of millions of times the computer power that we had back when we were doing modeling. And so, they can include more and more regional detail and detail about the weather. I mean, the really strange thing is we talk all about climate, but climate is not really something that one experiences directly. One experiences the weather directly, and it’s the extreme impacts that happen. Society has tried hard to be reasonably resilient to the weather, to some range of weather conditions. Farmers figure out somehow to grow productively for a range of conditions. So, it isn’t so much the climate that is the problem, but it is the weather. It’s the extreme drenching rains that come and flood everything out. You can say, Oh well, we get about the right amount of precipitation over the year, but if it mostly comes in very drenching rains that wash crops away and flood valleys, that’s a problem. So, we should really be talking about what’s happening to the weather. Scientists are only starting in recent decades to really analyze the weather that the models are putting out, how it is changing, and what’s happening. Minimum temperatures are going up, for example, at night, so you’re having warmer temperatures, and those have different effects.

One of the really long-term trends on all continents is that a larger fraction of the precipitation is coming in these drenching rain events and big storms. Warmer weather leads to more water vapor in the atmosphere, and so there is more energy stored in the atmosphere. Then, when condensation happens, it is not just that there’s more energy released because there is more water vapor giving off heat as condensation occurs. Because more energy is released by that additional water vapor, the additional heat makes the storm stronger. This pulls in more moist air, which leads to more precipitation and more heat. Instead of rainfall going up roughly seven percent with each degree Celsius of warming, the actual response in a storm is about three times that much because the stronger storm pulls in the additional moisture, releases the additional heat, and drives more precipitation. So, we’re getting more of these drenching rains and fewer of the moderate rains.

For agriculture, that can be really problematic. A lot of rain on already moisture-soaked slopes increases runoff, causing havoc downstream, and it doesn’t really supply farmers with the soil moisture they need for a whole growing season. Growing seasons are hotter too, so there’s more evaporation. Agricultural production is becoming more challenging. Global warming is also becoming problematic for forests, which are a vital resource. Forests don’t just move in response to the climate. They have to reseed and regrow in new locations, which takes time. Ecosystems become stressed, wildfires occur, or pests attack. That’s a continuing problem for forests, for water resources, and for food production.

Along coastlines, sea level rise occurs because of thermal expansion and melting of land ice. Nepal doesn’t face sea level rise directly, but it is affected by melting glaciers and changes in snow cover. The resulting sea level rise affects countries globally. What’s unfortunate is that people often ask, for example, in Virginia, where I will be giving a talk in two weeks, what climate change will do there. That somewhat misses a key point because we are now in a global economy. What happens elsewhere affects us. Coffee isn’t grown in the U.S., but it is important. As conditions in Central America and Brazil change, coffee production suffers.

If vital crop production fails, it affects everyone. Major food crops like wheat, corn, and soybeans are mainly grown in five or six countries. About 90 percent of each crop that is exported comes from just a few countries. We’ve seen what happens, for example, when Russia had a drought and crop failures — they stopped exporting, and bread prices went up worldwide. With more warming, failures in two or more regions at once become more likely. That will affect the global economy. People will spend more on food, leaving less for spending on other goods. Business leaders need to think about more than the impacts of climate change on their own factory. They must consider impacts on workers getting to the factory, on supply chains, on transportation, and whether people can afford their products during crises. Most business leaders have not thought that far ahead. Climate change can disrupt supply chains just like COVID did. Extreme events, like the Category 5 hurricane hitting Jamaica, can have horrific consequences.

I was an informal advisor to the World Bank for some of their reports. They’ve seen extreme storms wipe out ten years of development work. In Central America, people face impossible choices about where to live. Coastal plains flood, mountains have landslides, valleys also flood. These events create environmental refugees; the scale of future displacements could reach tens or hundreds of millions, creating international security issues.

In India, the wet-bulb temperature during heat waves is approaching 30 degrees Celsius, almost the limit for surviving outdoors without air conditioning. In a region a colleague is from, about 70 percent of people work outdoors in agriculture, construction, and transport. Extreme heat will force emigration, creating social and economic stress. Local impacts are thus linked to global challenges. Even in the U.S., national climate assessments focus on local effects, but we must consider global interconnections for economic, humanitarian, and ethical reasons. Just because some regions can afford air conditioning doesn’t excuse ignoring the problems facing others.

3. You’ve said we shouldn’t completely rule out solar geo-engineering. At what point does studying or even using such technology become necessary—and what risks worry you most?

I’ve been suggesting that climate intervention, or solar geoengineering, is going to be necessary. It’s sometimes hard to think that a temperature increase of one or two degrees Celsius really matters, but if you go back 20,000 years to the Last Glacial Maximum, global sea level was about 120 meters lower than it is today. I often open talks with the public by asking people if they’ve ever been on an ocean cruise or seen how large the ocean is. Can you imagine it being 120 meters, or about 400 feet, lower than it is today? That was because ice was piled on land. From 20,000 years ago to 8,000 years ago, two-thirds of the ice on land melted as the global average temperature rose about six degrees Celsius, roughly 20 meters of sea level rise per degree of global warming.

We have already gone up about one and a half degrees Celsius and are headed toward two or even three. There are still 60 meters of sea level equivalent tied up in the Antarctic and Greenland Ice Sheets, enough to inundate most of the major cities on coastlines. I was recently on a cruise with my wife in the Baltic Sea and was amazed at how low the elevation is in many of those countries. If Greenland had melted following the Last Glacial Maximum, northern Europe’s coastline would be very different. Most of Denmark would be gone. Huge areas of the Baltic States, St. Petersburg, and parts of Russia would be submerged. Levees might help as future sea level rises, but they will not withstand the six or seven meters of sea level rise if Greenland or West Antarctica melts. The coastlines would simply be completely different.

The large change in sea level shows that climate and sea level can change a lot. In the past, these changes were driven mainly by variations in Earth’s orbital shape and axis tilt, then also amplified by changes in the CO2 concentration. Using the IPCC approach to calculate global average radiative forcing, these orbital changes don’t change the total annual global forcing—they just redistribute incoming solar radiation by season and latitude. Yet this redistribution changed global average temperature by six degrees Celsius, with 120 meters of sea level change. Such large changes should really help people understand that the climate can change by large amounts.

People doubting that the human influence will be significant often say that the climate has always changed, but past changes were not random. They occurred for reasons that affected the global energy balance. Adding CO2 to the atmosphere changes the global energy balance, and in the past, such large changes caused large changes in climate. So, paleoclimatic and geologic evidence make it clear that it should be expected that climate will change significantly, which is what models project and what we are beginning to observe.

International negotiations are still difficult. Emissions are rising, and getting them to zero will take decades, not just because of inaction by political leaders, but because of all the vehicles, airplanes, ships, buildings, and energy systems that must be changed. We are already at about one and a half degrees Celsius of warming, which is too much given past climatic conditions and sea level rise.

In my view, climate intervention, such as the injection of stratospheric aerosols that would mimic volcanic cooling, should be considered. My view is that given the sea level risk, very high wet-bulb temperatures in low latitudes, and the potential for unlivable heat waves, it’s something we ought to research and start carefully. The goal would not be to return to preindustrial temperatures, but to prevent further warming and give countries more time to adapt and reduce their emissions. No country wants more warming.

I recall a decade or two ago, a Climate Institute board member from Florida whose center studied coastlines and ports. About a third of his research team was from China, because China has low-lying ports like Shanghai and Hong Kong that could be devastated by typhoons and storm surges. Due to its vulnerability, Japan developed one of the fastest computers at the time to simulate typhoons and storms with high resolution. Countries understand the risks and are preparing scientifically.

Would solar intervention be worth considering? Some people are concerned about blocking incoming sunlight, but offsetting the equivalent of half of a CO2 doubling would require reflecting only about 1 percent of solar radiation—almost unnoticeable. Keeping the global average temperature about level over the next few decades would require reflecting only about 0.2 percent of solar radiation for each decade that emissions continue as high as they are. The changes would be almost impossible to notice for people, though they would be noticed by instruments. It seems to me that researching and learning gradually as we go makes sense rather than facing increasing impacts. This is not a substitute for cutting emissions. We must decarbonize, transition from fossil fuels, and increase forest carbon uptake. Solar geoengineering is a complement, not a replacement.

I sometimes compare what is being proposed to coming across a seriously bleeding accident victim. Ideally, you would get them full treatment at a hospital. But if they are bleeding severely, using a tourniquet to stop the situation from getting worse while help arrives would be what to do. That’s our situation with climate. We need to stop things from getting worse while reducing emissions and restoring natural systems.

Currently, I am working on answering a follow-up question after a Congressional hearing: how should policymakers consider solar geoengineering? If the goal is a world that does not get dangerously warmer and allows countries to achieve Sustainable Development Goals, then solar intervention is part of what would need to be done. Politicians would be the ones to weigh economic, environmental, social, and ethical considerations.

The only way to pull back further warming over the next decade or two is to deploy solar engineering alongside emissions reductions. Other interventions, like reducing methane in the atmosphere, could also help. We must act on multiple fronts. It is unfortunate that solar intervention is needed, as it is seen as a “last resort,” but the reality is that emissions reduction alone cannot prevent dangerous warming quickly enough.

4. Have we already crossed the 1.5 degrees target?

Well, we’re right about at 1.5. It’s inevitable we’re going to overshoot. One of my pet objections is using the global average temperature as a metric for the increasing damage and its importance. The global average temperature is about the most innocuous metric negotiators could use. People live on land, not in the ocean. The ocean has a greater heat capacity, so it takes longer to warm. Warming on land, especially at high latitudes, can be one and a half, two, three, or even four times the global average warming.

The official global average temperature is also calculated by averaging over the past 10 or 20 years, not projecting into the future. That approach understates where we are when temperatures are rising. Scientists chose this metric in the 1970s and 80s to provide a definitive measure that humans are really affecting the climate. The idea was to take the largest average possible as proof and to smooth out variability. A colleague of mine at Livermore, Ben Santer, helped undertake that first detection effort and continues to work on it. It was a great measure for showing humans were definitely changing the climate, but it is not a good measure of impacts.

Impacts matter a lot locally. Climate change is global, but the effects on people and the environment are local and often short-term. For example, a severe storm can devastate a community. Civil infrastructure is traditionally designed to withstand the worst flood in 100 years. That standard originated in a Pennsylvania community that had had its bridges washed out every 20 or 30 years. Recovery is slow when a main street is destroyed, so civil engineers created a safety factor—build to withstand the worst storm in 100 years.

Buildings also matter. After World War II, Europe rebuilt with buildings designed to cool naturally in the summer with airflow. But now, with more extreme heat waves, those buildings get too hot in summer without air conditioning, creating the need for expensive retrofits. What matters for people in India and Southeast Asia is how severe the worst heat waves will be, because that is what people must survive. Global average temperature is a terrible metric for understanding this.

If you look at what happens in low latitudes, much of the trapped energy from warming goes into evaporating moisture, not heating. That moisture returns as intense rain. For a tropical island or a place like Jamaica, saying the global average temperature goes up 1.5 degrees is not really helpful information about local impacts. Scientists find it useful to note that global averages are increasing, but that doesn’t tell the public how much conditions like heat waves, storms, and flooding will change locally. Yes, we have exceeded 1.5 degrees globally, and it’s serious, but global average temperature is not a good measure of how bad things really are for local cities and communities.

5. The US has been cautious about funding climate aid for vulnerable countries. From your point of view, what would a fair and responsible US approach to global climate justice look like?

Well, I think the first thing for the US Administration is to acknowledge that climate change is an issue, and a global issue, and that because we have air conditioning and enough wealth for protective structures, we are a bit better off in terms of direct impacts than others—even though the US does have a lot of vulnerable coastal areas. For example, if you go to the San Francisco Bay area, the whole inland area, all the way to Sacramento, is below sea level. If saltwater intrudes into the Sacramento-San Joaquin delta, given how the State’s water system is set up and managed—namely, by keeping the salt water in San Francisco Bay and out of the agricultural San Joaquin Valley—much of California’s economy could collapse. The distribution system depends on getting fresh water from Northern California to the agricultural areas in the southern parts of the Central Valley, and the delta lies right in between. There’s a very insightful book by an environmental writer, Marc Riesner, describing how dangerous things could be [A Dangerous Place: California’s Unsettling Fate].

The United States has vulnerabilities as well as other nations. We’re a little better off than others, but we must understand that it is a global economy that we depend on, so what is happening elsewhere matters. COVID, with its international breakdowns and trade disruptions, made clear how vulnerable the United States is.

The solution the world needs is essentially full electrification. Some electricity may go to producing hydrogen for aircraft or other fuels, but everything has to be electrified. I think the main path forward is not going to be through regulations alone, but by encouraging technologies that can achieve and facilitate renewable electricity deployment in the U.S.

One step needed is a better transmission grid. We know how to do that: high-voltage direct current lines instead of high-voltage alternating current, to transport energy from solar and wind resources in the southwestern and central U.S. to the rest of the country. Similar approaches are needed elsewhere.

Current international negotiations, such as at the Conference of the Parties, focus on loss and damage provisions. These are facing resistance because they envision developed countries giving large sums of money to developing countries essentially indefinitely. My sense is that what is really needed is to provide money and technology so that countries can become self-sustaining. For example, Africa has huge solar energy potential in the Sahara and other regions. What they need is a strong long-distance transmission network. With inexpensive electricity widely available, people could work, develop businesses, and grow their economy. It’s like the old parable: do you keep giving fish to a poor fisherman, or do you give them equipment to catch fish and develop a life of their own?

Expanding foreign aid in a way that helps countries become self-sufficient is, in my view, practical and politically more sellable. Simply giving money repeatedly is a hard sell. Many countries would ask why they are giving away money when they have people in need at home. Expecting a billion people in the developed world to indefinitely pay for damages affecting seven billion elsewhere is not viable, in my view. Instead, we need approaches that help countries help themselves. China is starting to do this by building solar panels and providing them to other countries. Ideally, this would be aid rather than loans that create debt. Donations and foreign assistance are necessary, but providing tools that enable countries to be self-sufficient is a way to build global capacity and opportunities.

6. Yes, but wasn’t it the U.S., the U.K., or Europe that started the Industrial Revolution, and not the Global South?

Yes, that’s true. These nations also developed medicines and other technologies that have allowed populations to grow as they have. That’s certainly the kind of debate and discussion that needs to happen. There are responsibilities that go back in time, for example, the U.S., and now China, being the largest emitter, so what are they responsible for? Figuring out this responsibility issue is going to be a real challenge, but there is no question that some responsibilities exist.

It’s not just a matter of responsibility; it’s also in the U.S. interest to help solve this issue. If we don’t address the issue adequately, it will also harm our country and our economy. So, it’s both in developed countries’ self-interest and their ethical responsibility to take action. That needs to be understood and communicated.

We have to find ways to help everyone get through this. One of my main arguments for solar intervention is that without it, the Sustainable Development Goals become unachievable. It simply becomes too hot, with too much flooding and other problems, for these goals to be met if climate change continues. The main push for solar intervention should be to ensure the Sustainable Development Goals remain plausible and are advancing. Otherwise, we risk a collapse of international civilization, which nobody benefits from.

Reducing methane emissions is a good approach, but not progressing fast enough. Chemical methods to reduce methane could help, though it’s almost an unimaginable task. Some people say it could be done, though it’s not yet proven. We should do everything we can, but that doesn’t mean we stop pursuing other options. Fortunately, the cost of climate intervention is relatively low compared to other measures. It wouldn’t replace other necessary efforts but would be a helpful additional investment.

Any intervention should be governed in a way that ensures it supports the Sustainable Development Goals and gives control to those most impacted.

7. As the next COP approaches, what key breakthroughs do you think are most needed to turn global climate promises into real progress?

Well, there are a couple of things they can do. One, they need to focus much more on reducing methane emissions. Methane only lasts in the atmosphere for a couple of decades, so if you can get emissions down, that will reduce its warming influence in the near term.

It would also really help Brazil and others to end deforestation and reverse it. Cutting forests not only releases CO2 into the atmosphere, but forests are also what naturally take up CO2. If you cut the trees down, a larger fraction of emitted CO2 stays in the atmosphere, which is something we don’t want.

A number of us are also arguing that solar intervention needs to become part of the discussion.

One more point I should have mentioned first: as China and others reduce coal combustion and emit less SO2 into the atmosphere—which is important locally for health—we need to do something to balance the cooling effect of SO2 and sulfates. One approach is to reduce black carbon emissions. Black carbon comes from sources like 2-stroke motorcycles, diesel engines, and coal-fired power plants. It’s unburned fuel and inefficient, so improving efficiency and reducing black carbon emissions is important. Black carbon gets into the air, lands on snow and ice, darkens the surface, and leads to faster melting.

All of these are specific measures that could have a near-term influence. The focus should be on limiting near-term warming while we address longer-term solutions. Those are the main items I would highlight.

8. If you were advising Washington today, what top priorities would you set for U.S. Climate research and policy for the next decade?

The one that a number of us are working on that could really make a difference in the United States is putting in a transmission network that can move renewable energy—solar and wind—across the country. Right now, the transmission network can’t do that. There’s a lot of potential investment in solar energy helping California, but without the transmission lines, that energy can’t get to where it’s needed.

California invested two or three billion dollars in a transmission line to connect a desert area with high solar radiation to the main power network. Private investors then put in sixty billion dollars of solar panels. On that desert land, they can harvest solar radiation and sell electricity at a low price while still making about ten times what farmers make on irrigated land because the sun is so reliable there.

This is a capitalist system approach to solving a problem. The government needs to make investments that facilitate what the private sector can then execute on a large scale. A group of us is looking at other places around the country where transmission investment could make a big difference [see https://areday.net/hvdc-supergrid/]. If it happens, the U.S. would be getting the lowest-cost energy purely on economic grounds. That’s essential for remaining competitive in the global economy in the 21st century.

If other countries like China invest heavily in renewables and produce cheap electricity, the U.S. won’t be economically competitive. It doesn’t matter whether you’re a Republican or Democrat—this is about getting the lowest-cost energy for the country. Otherwise, other countries will outcompete us.

Investing in the grid itself isn’t all that expensive compared to the broader investment in energy. It’s not just about putting in solar panels—the private sector will do that if the transmission lines exist. The government’s role is to facilitate electrification. That would help our country, our continent, and beyond.

The person, Alexander “Sandy” MacDonald, proposing this approach, even has a book in preparation, arguing that every continent needs to do something similar. India, for example, has very sunny regions that could generate a lot of solar energy, but you also need to be able to transport that electricity to other areas. China and Europe are already ahead of the U.S. on this, which is concerning because cheaper energy gives them a competitive advantage.

The U.S. needs to catch up while also helping other countries become self-sufficient so they can generate income and build their economy. At the same time, the US and other nations must continue to provide humanitarian aid for losses caused by climate impacts. The main goal, however, I think, needs to be to help countries become more self-sufficient and capable of building and powering their own economies.

“If you are good at something, never do it for free,” says the Joker—and I love Joker. But I believe educational content should be free for everyone. Hence, this newsletter doesn’t restrict any content behind paywalls; everything is accessible to everyone for free.

Regardless, if you want me to keep doing what I do here, you can still choose to become a paid member of this newsletter by hitting the subscribe button above and choosing the membership that’s right for you. You can also subscribe for free to regularly receive new posts.

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In partnership with the Yale Program on Climate Change Communication, Dr. Maibach co-directs the “Climate Change in the American Mind” polling project, which conducts surveys twice a year in the United States to investigate the public’s climate change knowledge. In addition, Dr. Maibach also leads the Climate Matters institute, which aids TV weathercasters and journalists in the United States in effectively conveying climate change stories to local audiences through data-driven approaches.

In this interview, Dr. Maibach answers what surprises him the most as a climate change professional, what mistakes he sees experts making while communicating climate change, his message to the world leaders gearing up for the next COP in Belem, Brazil, and more.

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Dr. Edward W. Maibach, Distinguished University Professor and Director of the Center for Climate Change Communication at George Mason University.

1. Over the years, what’s been the most surprising thing you’ve learned about how people respond to climate science?

I continue to be most surprised by how many people—including government officials and even political parties—are misled by the fossil fuel industry into believing that climate change is not a serious problem, and that clean energy is not a better product.

Conversely, I continue to be amazed by how many of the poorest people in the world who have never heard about climate change per se, nevertheless know that the environmental conditions in their community—including the weather and the kinds of illness that afflict their community—are getting worse, which is making it harder for them to survive, much less thrive.

2. When communicating climate change, what’s one mistake you see experts making that you wish they would avoid?

Climate communicators should focus more on the present than on the future, and more on people than polar bears. Most people see climate change as a distant problem—in time, in space, and in species—which is true, but it is also a present problem: today, in our community, and harming us. Climate communicators should emphasize that. Climate communicators should also be stressing the immediate, local, human benefits of climate solutions, like switching from dirty fossil fuels to clean renewable energy. By emphasizing the immediate, the local, and the human sides of climate impacts and climate solutions, communicators can help make the issue more concrete (and less abstract), which will help build public and political will to implement solutions.

3. Across the world, climate change is experienced differently—how can communicators make the science feel relevant to people whose daily lives aren’t yet visibly affected?

Nearly every community worldwide is already being affected, although people may not know that the burning of fossil fuels and forests is the cause. Journalists and other climate communicators can help people understand that what they are experiencing is part of a larger global problem that requires immediate global solutions, but that also requires local actions to protect people in their community.

4. In regions where climate impacts are most immediate, how can scientists effectively engage communities without appearing alarmist?

The Ancient Greek myth of Cassandra—the Trojan princess, cursed with prophecies that no one believed—strikes me as relevant to the challenge we face in climate communication.

The projections of climate scientists have been essentially correct—if not underestimating the impacts—since the earliest days of climate science in the 1960s, and they are getting more accurate with each passing year. But economically motivated actors, especially the fossil fuel industry, have dismissed those projections as “alarmist.” The public trusts scientists more than they trust the fossil fuel industry, but the fossil fuel industry has an almost unlimited amount of money to deceive the public through their advertising and public relations.

Climate science has a Cassandra problem largely because the loudest voices talking about climate change are the fossil fuel companies and the public officials whose loyalty they rent through lobbying and campaign donations. The scientific community, civil society, and news organizations need to find ways of speaking more frequently, and clearly, to make the case that the projects of climate science have consistently been correct, not alarmist.

5. How do you see social media shaping global perceptions of climate science, and are there ways it can be harnessed to unite rather than divide on this issue?

Social media is both a boon and a bane of climate communication. It’s a boon in the sense that people can share the truth—and their concerns about the truth, and what they would like to see done about the truth—with members of their social networks, which are often quite large. This is important because most people place most trust in their own friends and family members, rather than in people they don’t personally know. Social media is a bane, however, in the sense that disinformation can be easily and rapidly spread through social media—including by bots that are easily created by petro-dictators and other economically motivated actors—and that people tend to spread disinformation unknowingly.

Some communication research—and many communication practitioners—suggest the best way to unite people around the truth is to shine a light on the economically motivated actors who are deceiving us, perhaps especially fossil fuel CEOs, their lobbyists, and their advertising and PR companies who help them deceive. No one likes being lied to, and no one likes someone else profiting at the expense of our health and well-being.

6. What message would you send to the world leaders gathering at the upcoming COP in Belem, Brazil?

The continued burning of fossil fuels and the world’s forests—and the climate change it is causing—is already the leading preventable cause of death and illness in the world today, and it is getting worse. By rapidly bringing the fossil fuel era to a close and instead powering the world with clean renewable energy, we can minimize the damage caused by climate heating and usher in a new era of good health and prosperity.

I believe educational content should be free for everyone. Hence, this newsletter doesn’t restrict any content behind paywalls; everything is accessible to everyone for free.

Regardless, if you want me to keep doing what I do here, you can still choose to become a paid member of this newsletter by hitting the subscribe button above and choosing the membership that’s right for you. You can also subscribe for free to regularly receive new posts.

If you do not want to acquire a recurring paid membership, you can also choose to contribute a one-time donation by clicking on the link attached below: https://link.payoneer.com/Token?t=1A1EA995DF1F4471B35100F6C5CCE134&src=dpl

#EdwardWileMaibach #CenterforClimateChangeCommunication #GeorgeMasonUniversity #Sciencecommunication #climatechangecommunication #ClimateChangeintheAmerican Mind #ClimateChangeintheAmericanMind #climatechangeprofessional #EdMaibach

A much-debated graph, The Hockey Stick, was collectively constructed by the scientists and published in a research paper in 1999. It showed that the planet’s temperature had remained relatively stable for a millennium before suddenly rising in the 1980s. The Hockey Stick attributed this recent temperature rise to anthropogenic greenhouse gas emissions that had accumulated since the advent of the Industrial Revolution. The graph gained prominence in subsequent IPCC reports, received widespread attention, and ended up becoming a totem of anthropogenic global warming.

In 2009, just two weeks before COP 15—a pivotal meeting of world leaders set to agree on curbing fossil fuel emissions—an anonymous source hacked the University of East Anglia’s server in the U.K. and released thousands of private email correspondences between the institution’s climate scientists and their colleagues from the United States and China. The leaks revealed that the embattled climate scientists and their adversaries had been engaged in a heated debate for nearly a decade by that time.

The climate scientists were pressured to disclose all the climate data they had gathered during their tenure as researchers at their respective institutions. This included data obtained through contracts with foreign governments, as well as the statistical techniques, computer codes, and other methods they used to reconstruct the planet’s temperature record spanning the past millennium. Their critics remained steadfast in their efforts to disprove both the scientists and their findings. As a result, the conflict between the two sides continued both before and after the hacks emerged.

Among the co-authors of The Hockey Stick graph is Dr. Raymond S. Bradley, a paleoclimatologist and Distinguished Professor at the University of Massachusetts Amherst (UMass). Along with Dr. Michael Mann, who was then his postdoc at UMass and is now at the University of Pennsylvania, and Dr. Malcolm Hughes at the University of Arizona, the trio constructed The Hockey Stick graph.

As a result, Dr. Bradley was among a group of seventeen scientists—from various academic institutions—who were condemned by the U.S. government for producing data that attributed recent global warming to anthropogenic causes. These climate scientists have been fighting the climate war ever since their first confrontation with their opponents—and they continue to do so to this day.

Dr. Bradley has been a working climatologist for almost five decades now. He has published hundreds of research papers and multiple books on climate science. To address the whole issue of Climategate from his lens, he published a book in 2011 titled Global Warming and Political Intimidation: How Politicians Cracked Down on Scientists as the Earth Heated Up.

In that book, which he told me he wrote to get all the things relating to Climategate off of his chest, Bradley mentions that before the Industrial Revolution, the level of carbon dioxide in the atmosphere “were about 275 parts per million by volume (ppmv).” By the time he joined graduate school in 1969, CO2 levels had risen to “320 ppmv,” he reminisced in his book’s seventh chapter, and to about “390 ppmv” in 2010, a year before the book was published.

He goes on to blame the “wealthy, more developed countries of the world” partly for increasing the CO2 in the air by the “burning of fossil fuels” and reprimands the other half of the gas increase to the “Third World” countries that were, at that moment, dramatically spanning in terms of population and economic growth. Thus, Bradley no longer regarded them as “The Third World” by then.

In a conversation that my colleague Niroj Subedi, an environmental science graduate, and I had with Dr. Raymond Bradley on March 6, 2025, Bradley once again explained to us the details of the Climategate incident, along with the relationship between climate science and politics, and various other interesting facets of his research field. This interview has been edited for clarity and accuracy:

1. Can you explain the Climategate event in detail? How do you see it from your perspective?

I would say that you have to remember that ClimateGate was about the time of these COP meetings in Copenhagen. Obama was president and went to Copenhagen to sign an agreement about reducing greenhouse gases. Remember that ClimateGate occurred just around the time of the COP meeting in Copenhagen when Obama was president. There was a lot of effort to prevent or defuse the possibility that Obama would sign an agreement. It turned out that the hack of the server at the University of East Anglia was designed, I think, to deflect attention away from that possibility and to focus attention on emails and correspondence, a lot of it private correspondence, between climate scientists. So, it was a deliberate attempt to—and actually a very successful attempt—to interfere with the possibility of reducing greenhouse gases or signing an agreement at the COP meeting in Copenhagen.

I think the prospect of limiting temperatures to 1.5 degrees C globally is already past. I think we'll be fortunate if we can limit temperatures to below plus 2 degrees over pre-industrial levels.

2. You mentioned that even with CO2 removal, we could still end up with 550 ppm of CO2. What effects would this level have on the planet, and how can we mitigate them?

Well, we're already at, what is it, 425, and we're producing 40 billion gigatons of carbon dioxide a year in emissions. It's almost impossible to limit the level of CO2 unless we drastically reduce emissions, and I don't see that happening any time soon. I think we'd be very fortunate if we were able to limit CO2 levels to less than 500 ppm. I mean, there is only one solution—well, two solutions, really. One is to reduce emissions, the other is to extract carbon dioxide directly from the atmosphere and sequester it into some permanent archive in the ocean or in rocks. Those technologies don't exist at scale yet, so I think the prospect of limiting temperatures to 1.5 degrees C globally is already past. I think we'll be fortunate if we can limit temperatures to below plus 2 degrees over pre-industrial levels. That's the reality of it, I'm afraid. And, of course, the election of Trump didn't help.

3. Who did you vote for, Harris or Trump?

Trump is a disaster, unfortunately. Although I must say, despite his rhetoric, despite what he says, there is still a lot happening at the state level, at the local level, and at the industrial level. And that is a very hard thing to stop. I mean, it's much cheaper to produce energy with renewables than it is with coal or oil. So, the economics of the situation are against him, and he can’t change that. He may slow the pace of CO2 removal, emissions, and reductions, but he won’t be able to stop it. The train has left the station, and all he can do is try to slow it up a little bit."

4. Why do you think Trump and his administration are taking these steps to stall renewables? The U.S. represents a major force in the world of science, and we, here in Nepal, are dumbfounded by his recent decisions regarding science, his reluctance to promote renewables, and his preference for coal and oil.

To be honest, it's exactly the same feeling we have here in Massachusetts. Massachusetts is a liberal-democratic state that has no common values with Trump. We didn’t vote for Trump. In my little town here, 85 percent of people voted against Trump. And so, he is a puppet of the oil and gas industry. He is supported by very powerful interests. Those are the people who helped him get elected. But there are very curious things happening. I bought a Tesla; I like the car. I haven’t bought gasoline for the last eight years. I produce solar power, and I power my car in my garden using the sun. Doesn’t that make sense if everybody could do that? So, I can’t explain the stupidity of the Trump administration. It is ideological; it is stepping back in time. It’s destroying the U.S.'s technological and scientific base. Why? I can’t explain it. It will take decades to recover.

Trump is a disaster. However I must say, the train has left the station, and all he can do is try to slow it up a little bit.

5. Do you think this path forward could help the U.S. economically? I mean, what is the Trump administration trying to achieve?

You can see many examples around the world where the reduction of carbon dioxide emissions has gone hand in hand with economic growth. Because you are building new industries, saving money on energy, and investing in new technologies. Going back to the early 20th century makes no sense at all. So, I can’t explain the stupidity of it. All I can say is, don’t believe that the majority of Americans are behind this because they are not. Trump won by a bare, I think, it was one and a half percent in the election. So, that means more than fifty percent of the people are not on board with what he is doing. But unfortunately, under the U.S. system, it’s impossible to recall him or change things once he’s been elected. It’s exposed a very weak aspect of the constitution: once you elect somebody like that, they have extreme power, and it’s very difficult to change. Anyway, let’s not talk about Trump; let’s go back to your questions.

6. Besides CO2 and methane, what other greenhouse gases should be considered?

Well, there are a number of non-carbon dioxide greenhouse gases. The most important are methane, nitrous oxide (N2O), and various industrial gases: chlorofluorocarbons, which have also been responsible for damaging the ozone in the stratosphere. The quickest and cheapest way to reduce greenhouse gases, in fact, is to control methane, because it’s a very powerful greenhouse gas and it's relatively cheap to take care of. Legislation was introduced in the U.S. by Biden to basically charge companies for releasing methane. The idea was that the cost of reducing methane was less than the fines they would be charged if they kept emitting, but Trump has done away with that already. So, stupid again—another stupid policy. But ultimately, nitrous oxide is used in fertilizers, and another sensible way of reducing that particular product would be to make agricultural use of fertilizers more efficient so that we use less. And that’s not impossible to do; that’s quite feasible to do.

7. You and Dr. Jones from CRU have been colleagues for decades. What’s he like as a person, and how has it been working with him all these years? Can you also share your thoughts on Dr. Mann and Dr. Hughes?

Well, Mike Mann, I have known Mann for almost thirty years. He is a very smart physicist, mathematician, and statistician. When I met him, he had just finished his PhD and came to my university to work with me as a postdoc. He had the statistical tools that I wasn’t familiar with, so we combined our efforts to do an analysis of paleoclimate data.

Malcolm Hughes is an expert on tree growth and tree rings at the University of Arizona. I have known Malcolm for many decades. Malcolm Hughes and I combined our efforts to assemble a dataset that would be useful to reconstruct climate or temperature over the last thousand years or so, and Mike Mann applied his statistical knowledge to analyzing that data.

So, collectively, the three of us put together, well, many papers actually, but the first one was in 1998, published in Nature. That took us back to A.D. 1400. Then we published a longer reconstruction in Geophysical Research Letters in 1999. That went back a thousand years. And that was what became known as “The Hockey Stick.” Mike and I worked over the years on a number of papers, but those are the ones that got the most attention. All very hard-working, honest, and scrupulous in their work. Phil Jones and I worked a long time ago on the global temperature records, the instrumental temperature and precipitation records.

It’s hard to think about this now, but many decades ago, there was no reliable global temperature record for the last hundred years. We were asked by the U.S. Department of Energy to go through all the global data, collect all the data from around the world, and correct it or adjust it as required in order to produce a reliable temperature record.

Let me just give you an example: Many of those records had different recording times. For example, in some countries, the average daily temperature was the maximum plus the minimum divided by two. But in other countries, the temperatures were recorded at 7 am, noon, 4 pm, and so on, so they were not compatible with the other data.

We went through carefully and adjusted all the records to get a common basis for calculating daily and monthly temperatures. Then we put that together and threw out a lot of data that was low quality. Anyway, we came up with, what I think, was the very first reliable global temperature record. It went back to, I think, 1880. That was published, and we did the same with rainfall data. A paper was published in Science.

Phil Jones continued to work on that for many years, and that eventually became the now-famous Hadley Center global temperature records (HadCRUT) that we all use and rely on. So, Phil was the founder of that whole effort to improve the quality of the data. We worked on that together. What came out of that, actually, was the work I did with Mike Mann. Once we got back to 1880, the question was: What happened before? Was the warming that we saw in the last century just a cycle, or was it unusual in some way? So, we wanted to push the record back as far as we could. Of course, that meant relying on paleoclimate data.

Well, I think Biden was very far-sighted. He understood the dangers and threats associated with climate change and also saw the opportunities to boost the economy — not just in the U.S., but elsewhere.

8. How do you combine proxy temperatures with climate simulations to account for incomplete geographic data, and how do you cross-check with independent records like ice cores? What does this process achieve, and what challenges does it present?

That’s a long, complicated question. Let’s focus on one aspect: the distribution of data. If you have a global climate model and calculate a time series of global temperature based on the model simulation, every point on the globe is represented, right? You can then take the model and ask, “What if we only had data from this part of the world, or only half as much data?” Alternatively, you could take the distribution of instrumental records and reproduce that exactly in the model. How would that compare with a complete 100% dataset? This is one way to assess how valid your available data are.

When comparing ice core data with other data, you need to look at the individual records, compare them, and see which ones best reproduce the observed temperatures.

9. What’s the relationship between politics and climate science in the U.S.? Biden waving the green energy flag and Trump opposing it—what is this all about?

Well, I think Biden was very far-sighted. He understood the dangers and threats associated with climate change and also saw the opportunities to boost the economy—not just in the U.S., but elsewhere—by developing new ways of producing energy, saving energy, new battery technology, wind power, and so on. Obviously, if you can produce something with less energy, everything becomes more efficient and cheaper. He saw all that and introduced legislation that leveraged private investments. For every U.S. government dollar, it could generate maybe five dollars in private investment. This started before the election, but unfortunately, it didn’t gain momentum, and he didn’t get credit for it. Now, new factories, new battery and electric car plants are being built, and Trump is trying to stop all of that.

10. You were quoted in Fred Pearce’s book saying you’d like to disassociate from Mike Mann’s views. What did you mean by that? Can you elaborate?

I mean, there were things Mike said that I didn’t agree with. Very often, Mike would react quickly to something without thinking and say or write things he shouldn’t have. At the time, I was his advisor, supervisor, or colleague—he was my postdoc. I wanted to make it clear that those weren’t my views. I told Mike very clearly that he needed to cool it. But, you know, when people are under a lot of pressure, especially if you’re a young scientist, you feel the need to defend yourself and sometimes react quickly without careful thought. That’s all I was saying: I felt Mike often said things he shouldn’t have.

11. How old are you, Dr. Bradley?

How old am I? Seventy-six.

12. Mike Mann mentioned “dirty laundry” in a 2003 email to Tim Osborn. Was this referring to something your group didn’t want to be exposed to? Why couldn’t you release all the data, especially if you were confident about your work?

We did release all the data; we never held back any data. Mike initially refused to release his code, his software, because he said it was his private intellectual property. Eventually, I persuaded him to release it so others could use it. But as for the data we based our hockey stick on, that was all released. I never understood what the issue was with that.

When we were assembling the data, we had to enter agreements with different countries. In many parts of the world, meteorological data is considered national defense—it holds value to them.

The same goes for Phil Jones. When we were collecting instrumental data, we often had to contact other countries. Many times, these countries—China, for example—would only release it for our use. So, we had to buy the data from them. I remember we had to pay for each digit; if the temperature was ten degrees, it cost twice as much as if it was five or six degrees because there were two digits. When we were assembling the data, we had to enter agreements with different countries. In many parts of the world, meteorological data is considered national defense—it holds value to them. So, when people asked Phil, “Give us the data you got from China,” we said, “We can’t,” because that was not the agreement we had with China. The claim that he was trying to hide the data was simply not true.

13. How do you think science should be conducted: as a closed system with gatekeepers or a more open system?

Every study published in journals like Science or Nature, or other journals, requires the data to be made available in a publicly accessible database. For example, if we are funded by the National Science Foundation (NSF), we must deposit the data in a publicly available database. That wasn’t always the case. When Phil Jones and I published the book Climate Since AD 1500, we required every chapter author to provide the data for each figure. It was a hundred percent effort, and we made sure of it. Those data were then deposited in the World Data Center for Paleoclimatology (WDCA). I believe that was the first time anyone had done that in a published book. Since then, it has become standard practice to put all data into public databases.

14. Who do you think hacked the emails? Do you think the audacity of Mr. McIntyre had any influence on the hackers?

I can’t be sure, but one thing I know he did was use the system known as FOIA (Freedom of Information Act). In the U.K., if you get a FOIA request, you have to respond within forty-eight hours or so. He asked all of his followers on his website to bombard Phil Jones with FOIA requests. As a result, Phil received dozens of requests and couldn’t do his research because all his time was spent responding to them. It was a deliberate attack on his scientific productivity.

We also had FOIA requests here under the U.S. system, but the legislation differs by state. In Arizona, where Malcolm Hughes was, they first tried to get all of my emails through FOIA, but Massachusetts law protected me from that. However, in Arizona, there was no protection, so they left me alone and went after Malcolm Hughes. I guess they figured that whatever emails I had, Malcolm Hughes had the same ones, making it easier for them to access. There were a lot of these deliberate attacks and attempts to limit our ability to do research.

15. Journalist Fred Pearce told me that Jones suspected the hackers might have been Russian. Do you agree with this?

Well, they might have used a Russian address, but that doesn’t necessarily mean it came from Russia. I just don’t know.

16. What role did sulfate particles play in mid-century cooling? Do you think Paul Crutzen’s theory about them offsetting warming today holds any truth?

Well, there are two things here: One is sulfate in the upper atmosphere from volcanic eruptions, which definitely cools the atmosphere. In fact, the only thing that could slow global warming at this point would be a series of massive volcanic eruptions. People are also considering geoengineering, such as putting an artificial cloud of sulfate in the atmosphere, which I think would be terrible.

We didn’t leave anything out of The Hockey Stick. We simply used the data we had and let the data speak for itself.

The second is sulfate and other aerosols in the lower atmosphere, in the troposphere, which result from industrial activity and so on. In the mid-twentieth century, part of the slowdown in warming and cooling was related to that. In fact, since we’ve cleaned up the atmosphere in recent decades, warming has increased partly because the atmosphere is now much cleaner than it used to be. Over the last few decades, we’ve been controlling aerosols and improving air quality, but that has actually amplified the warming. So, part of the acceleration in warming is related to cleaning the atmosphere by reducing air pollution.

17. Why did the new leadership at CRU start challenging Hubert Lamb’s theories? What’s your take on the Medieval Warm Period and the Ice Age Lamb warned of? Why did Lamb have opposing views on past carbon levels?

Lamb’s work was entirely focused on Western Europe. When people use the term “Medieval Warm Period,” they often confuse that with global trends. Western Europe is only five percent of the Earth's surface. Some parts of the world were indeed warmer during Medieval times, but when you look at global data, including the oceans, which cover seventy percent of the Earth’s surface, it’s very hard to identify a globally significant warm period.

Now, when you ask, “Why did you leave it out of the ‘Hockey Stick’?”, we didn’t leave anything out. We simply used the data we had and let the data speak for itself. In fact, the warmest thirty-year period in the Hockey Stick before the twentieth century was in the twelfth century, and the coldest period was in the fifteenth century. So, we had a relatively warm late Medieval period followed by a little Ice Age.

18. How accurate are the techniques you and your group use to reconstruct past climates? And what about current climate models?

Climate models are driven by whatever forcing you put into them, such as solar forcing, volcanic forcing, greenhouse gas forcing, and internal variability within the model. They’ve done a pretty good job of reproducing observed temperatures. They may overestimate the effects of volcanic eruptions, but overall, they’ve done a solid job of capturing the temperature record.

As for the accuracy of our reconstructions, I’ve always said that the Hockey Stick was a work in progress. If others come up with more data, different data, or better techniques, great! Let’s see the results. In fact, there have been a dozen or more, maybe twenty, subsequent reconstructions published, and they all look like a hockey stick. They don’t differ much from what we published. So, I’d say we got it right. Maybe it was a fluke, maybe it was chance, but I don’t think you can really shoot down the Hockey Stick.

19. You didn’t downplay the Medieval Warm Period in the Hockey Stick graph, did you?

No, we didn’t manipulate anything. We published what we saw. The Hockey Stick is simply what the data reflects. We didn’t alter anything, we just published what the data showed.

As I mentioned, there were certainly parts of the world that were warm in the Medieval period. I recently published a paper called “Medieval Quiet Period,” where I argued that we focused too much on the period from around 1000 to 1200 AD. I think the period from 700-750 to 1100 is a more interesting reference period because there were few volcanic eruptions, and solar variability was minimal. That period served as a baseline, after which we had more volcanic eruptions and larger changes in solar radiance. I discussed the “Medieval Quiet Period” as the baseline we should be looking at.

20. How do you know that there were less volcanic eruptions during the Medieval Quiet Period?

I don’t know why there were fewer volcanic eruptions; that’s a geological question I can’t answer. But the biggest eruption was in 1257 AD in Indonesia. Before that, there were some eruptions in Iceland, but there weren’t any major tropical eruptions like Samalas, Krakatoa, or Tambora. After 1257 AD, we start to see temperatures decline. That marked the onset of the Little Ice Age, and temperatures continued to get cooler with subsequent volcanic events. There were some significant eruptions in the fifteenth century as well.

Maybe it was a fluke, maybe it was chance, but I don’t think you can really shoot down the Hockey Stick.

21. Why don’t tree ring data align with other datasets from the 1960s onward? Has this been resolved?

Oh, yes, the so-called “divergence issue.” I haven’t followed that literature closely, but Malcolm Hughes has. I think it’s pretty clear that this was not an issue affecting the global temperature record.

22. Why was Dr. Briffa reluctant to give prominence to the Hockey Stick graph in the subsequent IPCC reports?

I think Keith was a great guy, an honest guy, and he believed, like I did, that this was just one work in hypothesis when it came out, as we said. I think Keith felt there needed to be more effort to reproduce it and compare it with other methods. That’s why he thought it was a bit early and immature to focus on the Hockey Stick in that IPCC report. However, I wasn’t involved in writing that report, so I can’t say for sure what was going through his mind in detail.

23. What do you think the skeptics were trying to achieve? Were they being honest in their criticisms, or were they influenced by outside forces? Do you agree with Jones and others that skeptics were trying to obstruct scientific progress?

Yes, I think many of them were ideologically opposed to the issues of global warming. They were also promoting their own visibility on the web – people like McIntyre, for example. I don’t have any problem with criticism, as long as it’s done in a proper scientific manner. If I publish a paper and you disagree with it, you can write a rejoinder, and usually, the journal will send it back to me for a response. That’s fair enough; it’s how progress is made.

What happened with McIntyre in the GRL (GeoPhysical Research letters) was that the editor didn’t send it to us for comments and just published it. That was an unfortunate event. They also sent a paper to Nature criticizing us, and Nature asked us to respond, which we did. After looking at the response and the criticism, the editor said, "Well, there’s nothing here," so he didn’t publish their criticism. But the GRL editor did – which was a mistake.

All editors are expected to send a critique to the author being critiqued, especially if the title of the article explicitly says, “We are criticizing this paper,” as they did. That was just a bad decision on his part.

24. Many researchers in your group, including Jones and Mann, were hesitant to share data with outsiders. How hesitant were you? How has this attitude changed in the scientific community since Climategate?

We responded as best as we could to those requests, but they became very aggressive, I would say, in asking for more data and criticizing the data we sent them. Eventually, it became clear: "If you want to do this work yourself, go get the data, do your own analysis, and publish it. We're not going to do that work for you." I think Phil Jones was attacked more than I was. Of the four of us—myself, Malcolm, Mike, and Phil Jones—I was affected the least. That’s mainly because, being in Massachusetts, I was more protected from those attacks. My university strongly supported me, and the state laws were on my side.

For example, when someone asks me for data or information under Massachusetts law, I can say, “Okay, this will take me 85 hours of my time, and here’s what my time is worth.” So, when you send me a check for $15,000 or whatever, I will provide you with what you're asking. Of course, they didn’t want to pay, so they went after Malcolm Hughes instead. They left me alone. So, of the four of us, I was the one who was a little bit more protected. I was happy about that and didn't have any problem speaking out against these people either.

25. What’s your take on geoengineering and its potential for addressing climate change?

Geoengineering has so many problems. First of all, who is going to control it? Who will manage it? Are we going to allow a billionaire like Elon Musk to decide to put stratospheric aerosols in the atmosphere? There are negative effects to consider. If you look at the impacts of volcanic eruptions, they may reduce monsoon rainfall in certain parts of the world and have beneficial effects elsewhere. So, there will be winners and losers. Who decides which side gets to make the decisions? I don't think there are good solutions to that.

Who is going to control Geoengineering? Are we going to allow billionaires like Elon Musk to decide to put stratospheric aerosols in the atmosphere?

There may be more localized solutions, though. Let's face it, putting carbon dioxide in the atmosphere has been a form of geoengineering, right? We've been doing that for centuries, and we've altered the climate as a result. But there could be more targeted engineering actions that can be taken. For example, in Nepal, there are many dangerous glacier-dammed or moraine-dammed lakes due to the receding glaciers. Engineering solutions exist to address those problems and need to be dealt with urgently. That’s not a global solution, but it’s certainly a regional solution with important benefits for communities downstream.

There are other examples like that where large-scale engineering projects could help. But they’re not global and don’t deal with solar radiation management on a massive scale.

26. What is the current status of our planet’s climate—past, present, and future? What’s the latest research with the most consensus?

We have a good understanding of the current climate dynamics, and we have a fairly clear picture of past climate variability and change. The future, however, is really based on modeling and, to some extent, analogs of what we’ve seen during warm periods in the past. So, I think we know pretty much what will happen if greenhouse gases continue to increase. We can expect certain outcomes. We’re already seeing signs of this around the world, particularly in mountain regions, where glaciers are receding, and snow lines are rising.

Ocean temperatures are increasing, and sea levels are rising. Sea ice is decreasing in both the Arctic Ocean and Antarctica. So, we know what's happening now, and we know what will happen if we continue to pump greenhouse gases into the atmosphere.

27. Has the IPCC ever colluded to mislead the public, even once?

No, that would be impossible. There are too many scientists involved, and to orchestrate a conspiracy of hundreds—if not more—would be unfeasible. It's simply not possible.

All of us who were involved in the Climategate feel like it's old news and it's gone. We have all moved on from that.

28. Why was the IPCC established? Was it created to act as a gatekeeper of scientific consensus?

I don’t think I would describe the IPCC as a gatekeeper. I would say it's a periodic status report, really. So, it began following the Earth Summit, actually about the same time as the Earth Summit in Rio de Janeiro, 1992, I think that was, when there was an agreement to study what was dangerous interference with anthropogenic interference with the climate system. I think the first IPCC report was already in progress at that time, but then, every five or six years, a new report simply reviewed the status of climate research up to that point. So, I would say they are important—or have been very, very important—warnings or reports on what is happening to the climate system. And each time an IPCC report has come out, it has received a lot of media attention, and it's brought to the public concerns about how climate change is affecting the environment. So, it's been very, very important over the years.

29. Can you share some of your current projects? Are you working on something in northernmost Greenland?

Yes, over the last few years, I've been working more and more with archaeologists, looking at the history of how people have been affected by climate change and how people have migrated in relation to climate change. So, for example, in the North Atlantic, we've been working on places in northern Norway where the first farming occurred 2,800 years ago. And then we went to the Faroe Islands in the North Atlantic and looked at the migration of people into the Faroe Islands. And then to the Viking settlements in southern Greenland and what happened there.

Well, I think there is a lot of momentum now towards replacing fossil fuel use with renewables. I think a lot of countries have committed to that, despite what's happening in the U.S. And I don't think the U.S. momentum can be stopped.

We also went to Rapa Nui (Easter Island) in the South Pacific to look at the arrival of people and the changes in the environment on Easter Island. And in northern Greenland, we're working with archaeologists from the National Museum in Greenland to look at the first arrival of people in Greenland, which was about 4,000 years ago. And the question was, what was the environment like 4,000 years ago? They came in 4,000 years ago, and then after a few hundred years, they disappeared. The question was, what was it like when they arrived? Why did they disappear? When the next wave of people came in, what was going on? So we're looking at the relationship between the ability of humans to survive in a very, very severe environment, which was 82 degrees north, and what allowed them to survive and what encouraged them to stay.

30. Dr. Jones declined an interview, calling Climategate old news. Mike Mann is unavailable for interviews, and Mike Hughes is either. Why did you choose to step forward for an interview? What makes you different?

All of us who were involved in that feel like it's old news and it's gone. We have all moved on from that. I encourage people like you; I think it's very important to have scientific journalism. I am happy to talk to people from other parts of the world. So, I'm impressed that you wanted to pursue this story. I would say, yeah, for us this is old news, but there's plenty of good news, modern news that you also should be thinking about. And let me suggest something to you, you're in Kathmandu? You know ICIMOD? There are important activities that they're doing. We're working to some extent with them, and I think the whole question of what's happening to mountain glaciers, to water resources, to hazards in the mountains, these are good stories to write about. And that's where I would say you should put your attention on those issues, because they're all related to climate change.

31. In the prologue of your book Global Warming and Political Intimidation, you express hope that we can overcome the climate crisis if we push back against political pressure and denial. What keeps you hopeful today, and what signs of real progress do you see in the global response to climate change?

Well, I think there is a lot of momentum now towards replacing fossil fuel use with renewables. I think a lot of countries have committed to that, despite what's happening in the U.S. And I don't think the U.S. momentum can be stopped. It can be slowed, but not stopped. And I do think that countries will, especially—I mean, China is taking the lead on this, leading on renewables—and they're going to reap the benefits, the economic benefits of having cheap energy, and other countries like India will probably do the same. So it's just, it's like a waterfall, you can't stop it once it starts, right? And I think that people like Trump are living in the past, and they cannot block progress. They can temporarily halt it or slow it, but eventually, they'll be swept away by the torrent of activity that is already taking place. Economics are against them, quite simply. The cheapest activity will prevail, and the cheapest activity is renewable energy.

32. Like everything else in this world, renewables have their downsides, don't they? How are we going to recycle their components?

You know, that’s exactly what happens. You have a new technology, it raises problems, then new technologies are developed to deal with those problems. So there will be new technologies, new industries that will be developed to recycle solar panels, to reclaim rare earth minerals, and so on. Everything will improve over time. I have a very positive view of that.

If you would like to read my conversation with Fred Pearce—one of the lead journalists who investigated the Climategate scandal from the front, please click on the link attached below:

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