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Ongoing climate change is happening at a rate 100 times faster than at any time in Earth’s geological history But on a human level, at this early stage climate impacts such as the rise seas, endemic forest fires and intensifying storms, the pace of change was seen as slow In this episode, Professor Hooper of Geology and Professor of Environmental Science and Engineering Daniel Schrag, and Professor Gordon McKay of Applied Physics David Keith discuss the nature of the climate change crisis, choices, and tradeoffs. in the transition to a carbon-free economy, and the risks associated with comprehensive approaches developed to control the earth’s thermostat

Interview transcript (the following has been prepared by a computer algorithm, and may not accurately reflect the audio file of the interview):

Jonathan Shaw: Climate change is perhaps the most difficult problem the human race has ever faced In a century, humans have set off events that will unfold on a geological timescale, ultimately reshaping coastlines from around the world as ice caps melt and sea levels rise What to do in the face of global warming is dominated by uncertainties Can humanity accept to meet its energy needs with renewable energies such as wind and solar power to run global economies on carbon-free energy? If so, how quickly could the transition be done? Is there a threshold beyond which the effects of greenhouse gases will become irreversible? Can solar geoengineering, smoothing reflective particles in the stratosphere help stop this runaway train? Welcome to the Harvard Magazine podcast, « Ask a Harvard Professor » Today we join two guest experts on these issues Daniel Schrag is Director of the Harvard University Center for the Environment, Sturgis Hooper Professor of Geology and Professor of Science and Engineering. environmental engineering and an authority on what ancient climates can tell us about the future of our earth He is the recipient of a MacArthur Fellowship and the James B Macelwane Medal from the American Geophysical Union From 2009 to 2017 , he served on President Obama’s Council of Advisors on Science and Technology At Harvard Kennedy School, he is Co-Director of the Science, Technology and Public Policy program David Keith is Gordon McKay Professor of Applied Physics at the School of Engineering and Applied Science, and Professor of Public Policy at Harvard Kennedy School He is faculty director of Harvard’s Solar Geoengineering Research Program and founder of Carbon Engineering, a company developing technology to capture carbon directly from ambient air. For more than two decades, he has been a leading thinker on how to improve the efficiency of solar geoengineering and reduce its risks. Welcome to both of you

Jonathan Shaw: Dan, my first question is for you What do the paleoclimatic data that awaits us suggest at current CO2 concentrations, which reached a seasonal peak of 417 parts per million in May 2020?

Daniel Schrag: Well I think there are a lot of lessons to be learned from the paleoclimate But I think it is important that everyone understands the difference between what we see in the geological past with climates hotter and higher CO2 levels and what we are experiencing today In the past when we had times with higher carbon dioxide levels and warmer temperatures the changes were very slow This meant that ecological communities have had time to migrate, to adapt And the slow timescale means that what we see in the geological past is a kind of equilibrium climate, when things have adjusted on scales slow times to reach some kind of steady state What we are doing is about 100 times faster than the natural rate of climate change over the, say, a few hundred thousand years The Ice Age cycles that you nt and come over tens of thousands of years, we do it at the scale of a century And so what that means is that we have some idea of ​​the direction of the change, but there is a lot of ‘uncertain how quickly things will change A good example would be the Greenland and Antarctic ice caps We’re pretty sure at this point every summer the Greenland ice sheet is melting a lot, a lot more that new forms of snow in winter So it loses mass every summer And the net over the year raises the sea level by about one millimeter of sea level rise per year

It’s already very likely that he’s passed the point of no return That is, if we go to even higher CO2 levels, 450, 500, 550, basically we’re going to melt the entire ice cap of Greenland It’s something like seven meters of global sea level rise, that’s a huge sum But what we don’t know is how fast it’s going to happen When we look at the geological past , we can see times when the CO2 was a bit higher and there was no ice in Greenland And that tells us that the Greenland ice sheet is fundamentally unstable But that doesn’t tell us how long it takes to melt it, given the experience we have with the climate today

And so, without intervention, things look very bad We have launched a series of changes in the system, and the challenge is that these changes all have very long time scales, ranging from centuries to thousands of years And figuring out how to control these systems which are so massive and have such long time scales is a huge challenge

Jonathan Shaw: That’s a question for both of you First, David, how difficult would it be, from a purely technological standpoint, to meet all of the world’s energy needs with renewables? And how long would this conversion take?

David Keith: First of all I want to pick up on something you said in the introduction, which is that this is the most difficult problem humanity has ever faced I forget your words precise As someone who – I’ve worked on climate my whole career now, 30 years old, but I’ve paid attention to other public policy issues, and I don’t think that’s true I think than the problem of managing nuclear weapons in a divided world, I think the problem of managing biological weapons, maybe there are other problems that are probably more acute in terms of the consequences for the world. humanity and somehow the intense difficulty of reaching agreements So I consider the climate to be the most important environmental problem on a global scale But not all problems have to be the most important problems All buttons do don’t need to be turned on r 11 to make things worth resolving

Daniel Schrag: Let me make a comment on that, because again, that is part of the fun What I say, David, sometimes, and you may disagree with that, but I say that a lot people say climate change is the most pressing problem we face And to me it’s backwards, in fact Climate change is one of the most difficult problems we face precisely because ‘it is never the most urgent problem There is always something more urgent, which makes climate change so difficult Dealing with an issue that is inherently long is painful and very, very difficult

David Keith: Because of that central fact to know about climate, that climate change is somehow proportional to cumulative emissions, it has all these profound consequences Among them, the fact that even among them the fact that even after we got the emissions down to zero we in no way solved the problem, we just kept the problem from getting worse.But the other aspect of this cumulative nature is that it is is rationally true that in a given year, the nature of our emissions does not really make a difference It is these cumulative emissions And that means that even if we want to make it a crisis to force political action, in an objective sense, no year will be a crisis, even if overall it has this terrible environmental impact

Daniel Schrag: That’s right What is, again, I think some people Environmental groups definitely want to make this an urgent issue And what’s frustrating about this issue is that it is important It is always easy to worry about something that is right in front of you that is going to be answered in a short period of time

David Keith: Actually, the question of how quickly we could reduce emissions, I think you said, what’s the technical possibility of reducing emissions? Is that essentially how you put it?

Jonathan Shaw: Yes From a technological point of view, how long would it take to meet all of the world’s energy needs with renewables?

David Keith: So I think this problem is just badly put I mean, the short ugly answer is you can do it in 10 minutes with a big war where you stop it all So probably what you want to say is to do it in a way that makes something happen But then you have to define what services are needed Unless you do, the question is wrongly asked If you mean do it without no impact on the economy, no economic downturn, then the answer could be infinity The transition is extremely difficult So this answer does not have a closed form technocratic answer These are intrinsic compromises

So I think it is possible for us to decarbonize in just a few decades, technically possible to do so while maintaining the fundamentals of modern civilization Always keep transportation and communication networks active, always keep people fed But if you want to do that in a few decades you need a wartime level of command and control where you just nationalize a bunch of industries shut down a bunch of things you don’t want not Take charge of a bunch of location decisions in a very different way from what we know in democracies

And I think with decisions like that I think you can do it in just a few decades, but with huge social consequences and in fact other environmental consequences. So ultimately the answer to this question depends entirely on the political assumptions and questions about secondary impacts, both social and economic, that you are willing to tolerate

Jonathan Shaw: And Dan, why has decarbonizing economies around the world proved so politically difficult?

Daniel Schrag: Well, I actually think until recently decarbonization was relatively expensive You either had to forgo cheap fossil fuels or replace them with technologies that were pretty much all much more expensive. And it’s really just over the last 5-10 years that we’ve seen, for example, solar and wind emerge as one of the cheapest, at least, low-penetration forms of power generation. where you don’t have to worry a lot about the storage or intermittence of electricity It’s amazing It’s like a new world all of a sudden

My prediction is that in the next decade or two we will build solar and wind power like crazy This year in the US, 75% of new power generation capacity was wind and solar That is very good news Now the bad news is that the total amount we are building is in the range of 20 gigawatts And 20 gigawatts is not fast enough To put it simply in round numbers the total electricity consumption in the United States is about 500 gigawatts per year And if we were to electrify transportation, electrify home heating, and electrify industry, we would probably double or even triple that demand for electricity. But suppose we are very, very committed to conservation and only double our demand for electricity.This means that we would need some 1000 gigawatt-years of electricity in the near future

A thousand gigawatts years if we had to do everything with wind and solar, and forget about the intermittency problem Let’s imagine that it fits perfectly and we could just ignore the times when there is no wind or no of sun This is a minimum of around 4000 gigawatts of wind and solar power, because the capacity factor between wind and solar average will be around 25% So you just need to make 20 gigawatts per year, 4000 gigawatts And that’s the minimum required You probably need several times You’re talking at current rates of some 200 years

Now I’m not saying it’s going to take 200 years I think David is absolutely right It is certainly possible to speed it up But which is not only technically feasible but predictable I think it will probably last much more than a few decades, unfortunately I would love to be wrong about this I just don’t see people going to be willing to make the kind of sacrifices WWII demanded We’re talking about real sacrifices, financial sacrifices, d ‘dropping out of healthcare, dropping out of education, things that people care about And not only do we have to do it here in the US, but it has to be done globally And so when I look that, I say: « Boy, I would love to imagine that it could happen in 20 or 30 years But it does not seem very likely to me »

David Keith: Yeah To be clear I think it’s extremely unlikely that this will happen in 20 years and I don’t think I would vote for it I don’t think it would be ethical To do it that fast, c ‘is a compromise on the benefits for future generations of drastically reducing CO2 emissions, which are huge compared to the other environmental damage caused by doing it too quickly and the social damage You can’t do this 20 or 30 years from now in a way that keeps the things we care about, from healthcare to human rights If you want to do it that fast you’re going to tear up a bunch of rights and stop doing a bunch of other things we care about

David Keith: So I don’t personally think this compromise would be ethical, but I don’t think it’s technologically impossible I think we have to be very careful in saying this and defining carefully I think the key point that I’m trying to argue is that these are human choices, political choices, and we shouldn’t imagine there is a technocratic response, cranking the worthless crank There is no worthless answer to haste with which we should reduce emissions There is no threshold without a value and what is the maximum amount

Daniel Schrag: I think maybe that’s a way to frame it, because I think David said it’s really important to be careful when you think about wind and solar power and to building something so fast Forget the Green New Deal, we’re talking 10 years, let’s talk about 20 or 30 years What David said is absolutely correct, that doing something on this timescale means forgetting to allow you will just build things And people don’t like that

David Keith: Let’s see how it would actually work Yeah How it would actually work So let’s say you want to do it on wind and solar power So in the short term in the US you do a lot of solar energy because the factors of solar capacity are much higher, and you are doing that coupled with a huge amount of long distance transmission At present the time taken to allow large long distance transmission lines is basically infinite, we cannot do that So you have to start this, if you imagine Congress really wants to do this in 15, 20 years, your first law is the national law allowing clean energy And that says local people can complain, they can argue, but they have about three weeks to do so And then there’s a final binding decision and it’s backed by the troops Good farmers don’t like it, they are sidelined It must be so if you go this fast If you allow every local person to fight every facility throughout the court system, you never will

Daniel Schrag: Another good example for people who live in the northeast: why don’t we have a fast train? Thanks to French TGV technology from the 1970s, we should be able to get from New York to Boston in about 45 minutes Why does it take three and a half hours? And it’s on the fast train And the answer is actually very simple The answer is called Connecticut The tracks through Connecticut on the New London coast, the trains go 20 miles an hour So what would it take to have a high speed train to get rid of planes that fly short distances between New York, Boston and Washington DC?

The answer is we could do it with existing technology It would just take people’s homes and build straight tracks And the Governor of Connecticut is the only person with the power to do it Why the Governor of Connecticut s take over the homes of Connecticut people so people can get from Boston to New York very quickly? Very hard to imagine in our current political system

David Keith: Maybe it’s a useful back-and-forth I mean, I don’t think it’s going to happen in 20, 30 years But I also think that to get substantial progress, fast enough to satisfy me or satisfy me, we will need a new political reality And the answer is that at the end of the day the Connecticut governor can be overruled at the federal level, just to take this example.I think we will come to some level of federal consensus and power around decarbonization that will be slower. that kind of 20 year old pace I said but faster than 200 year old pace Dan says but it will take some political discontinuity in between every now and then I don’t mean a revolution But I mean , something that really shifts this to the center of the political agenda And I think it’s actually quite possible, but it’s very hard to guess when that will happen

Daniel Schrag: I think that’s a useful way to think about it, and I agree, David, and I wasn’t trying to say that we were going to do it in 200 years, I was just saying that the current rhythm if you just need to sort of scale it, it’s on a timescale of several hundred years and it’s an important number to know I’d kind of see two paths of end members and the reality of the world is likely to be somewhere in between One would be some kind of free market timescale where wind and solar are cheap and so they are built And gradually they replace the old one coal and natural gas thereafter Batteries are getting cheaper the more we install them

It’s kind of a technological advancement and transition, maybe with a little bit of advice from the government, but mostly letting the market and letting the technology do the work And people are buying electric cars because this are better choices, not because the government tells you, or because the government heavily subsidizes them The other member is more what David was talking about, that kind of command control Kind of what London did with electric taxis There will be no more diesel taxis in London in the next few years They are all being phased out This is one way to go And you can imagine the problem with that being finally in a democracy people are revolting

Imagine if you told New York that in the next 10 years we are going to eliminate all gasoline taxis, and that the price of taxis will increase by a factor of three, but you are all going to have electric vehicles I suspect that many New Yorkers would break out And whoever made this law, whether it was the governor of New York or the mayor of New York, would be fired from office That’s the challenge But I think somewhere in that range is there ‘place we are likely to see And my hope is that technology may be the wind in our sails That is, right now some of the new technology seems to be making this problem a lot easier But there is still some big obstacles ahead

Jonathan Shaw: Awesome Thanks to both of you David, what is solar geoengineering? And how could this be used to mitigate global warming?

David Keith: Solar geoengineering is the idea that humans could deliberately change the amount of heat the earth absorbs from the sun This could be done by putting in reflective aerosols – these are just tiny little particles of dust – in the upper atmosphere, the stratosphere, maybe 20 kilometers above our heads But this could in principle also be done by shields in outer space or by clearing up some cirrus clouds or making some low level clouds a little lighter, or maybe even painting the roofs or changing the way crops are planted There are a number of ways humans can deliberately alter what we call radiative forcing, the amount of imbalance in Earth’s energy that is out of balance by the CO2 we put into the atmosphere. And this would have the net effect of reducing somewhat the climate changes – changes in precipitation, changes in temperature – which come from the accumulated amount of long-lived greenhouse gases like carbon dioxide. The goal would therefore be to reduce the climate risk for a given amount of carbon dioxide in the atmosphere

Jonathan Shaw: And David, do you imagine solar geoengineering being used as part of a larger decarbonization project?

David Keith: I have no idea what’s going to happen And I think the ability of people to predict what’s going to happen is just terrible But personally I think it would make sense and I don’t would argue that the use of solar geoengineering in combination with deep emission reductions and the possibility of removing CO2 from the atmosphere in a mode where it is used to reduce the peak, climate damage during the peak CO2 concentrations

Jonathan Shaw: Dan, what kind of global governance structures would this kind of geoengineering project need?

Daniel Schrag: Well I think it’s a bigger question than that, Jon I think climate change itself is ultimately going to push us towards new forms of global governance The top-down Kyoto-style treaty n ‘was not very effective So we moved on to a very loose Paris deal where countries offer their own commitments and set their own goals with maybe a little bit of peer pressure, but no one is telling anyone what to do. there are no negotiations per se, as there was part of the Kyoto process

Ultimately, as climate change worsens and I speak 20, 30, 40 years from now, I think managing the impacts and managing the decarbonization process are going to require innovations in the form of interactions between countries in a way that’s hard to imagine right now, but I think they are inevitable And I think solar geoengineering is a big part of it I wouldn’t see it in isolation, I would see it as part of a larger framework for dealing with a global problem In the same way the world invented, in some ways, with the rise of terrorism, after 9/11 the world reinvented a variety of structures that have helped manage terrorism I think the same is going to be true with the threat of climate change

I think some sort of innovation in how countries are handling this will be essential.I can’t imagine that one or two superpowers are implementing a solar geoengineering system that affects all living things in the world. the planet without any kind of consultation or membership I don’t think it’s very stable and just wouldn’t be very smart I guess I can imagine a few countries still doing it But I think it wouldn’t be a very good result because in the long run I suspect it’s not very stable And we’re talking about, even if you were to do it in concert with removing the carbon which would end up reversing the problem, you still have to do it for a very long time no matter the scale political time David, what do you think?

David Keith: I agree I mean new technologies and new interconnections require different kinds of global governance And it happens I mean we have imperfect global governance that imperfectly manages infectious diseases and weapons nuclear, internet and commerce And these things actually work, have enforcement powers We have an Outer Space Treaty, to take a really interesting example, which in principle applies to solar geoengineering because that he is very general, who had the power to make Russia reimburse Canada by literally dropping a nuclear reactor on Canada in the early 1980s

So I think there are many examples like this where global governance has developed It’s not just one top-down thing, it’s definitely not just what lies in a comprehensive treaty like the Kyoto Protocol There are many underlying governance mechanisms, and we need and need to develop them faster in order to deal with all kinds of issues of which the climate is only one For the solar geoengineering, I see kind of two tracks So one track is the, you could call it the UN system process, the IPCC, all these meetings, all this conversation about something that indicates a global consensus

I think the conversation is actually very important, because it’s a way for people to share information and for nations to start to see what their interests and competing interests are. has virtually no chance that such a thing would produce a clear answer to implement or not to implement, although, I think it could produce some interesting enabling treaties or frameworks that could reduce the risk of one-sided really badly. thoughtful and thoughtless action

But I think if solar geoengineering is on the international agenda for its implementation, it will be because a small group of countries, probably not one, will be putting it on the agenda. by pushing mainly towards deployment Essentially saying that it is in our fundamental right to protect ourselves against environmental risks, that we will move towards this technology, which will precipitate the debate on what is really going on. I’m not saying it’s good or bad, but I think that’s probably the way it is

Daniel Schrag: I think that’s really interesting There’s a quote from H g Wells that I love from The Time Machine where he wrote: “We’re always on the lookout for pain and pain. necessity « And that sounds a bit harsh, but I honestly think we are in the early stages of experiencing the impacts of climate change And I think the real question that we don’t understand is how the political will to do something thing against climate change will change as people become more and more afraid of the impacts I think the fires in California, Australia and Greece are just a little wake-up call I mean, it’s just to use a bad phrase, the tip of the iceberg

I think it is really difficult for us today to imagine the political context of the international debate on climate change 30 years from now When, literally, several weeks in summer it can be too hot to go out in India to do any kind of physical labor or just walk the streets It’s hard to imagine the kind of empowering ability that gives to political discussions And I think our perception of world politics will change completely But again, maybe it will be wrong, but I think it is possible

David Keith: No I think it’s very likely I think there are ways that we’re still in a bit of a bogus war on the climate, where there’s a lot of talk about how it is ‘is a top priority.And many national leaders find it important to keep part of their political constituency happy to express how important the climate is.But when you measure it by real actions, it’s clear that it really isn’t. not at the top of the political agenda, basically everywhere But it will reach the top of the political agenda, and it will get there as these impacts become sharper And it will be later than it should be, but I think this is how it will play out

Daniel Schrag: That’s right That’s exactly it I mean, now imagine when the G7 will meet and come out with a climate statement, which I guess President Trump didn’t want to come out of. join, but imagine they all made a climate statement It’s a posture right now But when they get together to talk about a terrorist attack in Paris, or New York, or whatever, they’re actually talking with their top military advisers. And they are serious, what are they going to implement? How are they going to coordinate to actually solve this problem? And you can imagine at some point that the climate change talks among world leaders will have that sense of urgency, the same you might imagine after 9/11, that’s when we’re going to see real change.

Jonathan Shaw: You may have already answered my next question, but I’ll ask it anyway and see what you say What is the risk that the fruits of solar geoengineering research will be used to lower the temperature of the Earth without addressing the underlying cause of warming? In other words, what is the risk that the fossil fuel industry or even individuals who are invested in combustion engines, in everything from cars to household appliances to lawn mowers, will use the potential technology as a cover to continue pumping CO2 into the atmosphere?

David Keith: You’ve asked two completely different questions First, what’s the risk that some people will try to exploit this as a cover? I think the answer is that the risk is 100% I think it is certain that, I mean, it is a deep truth that humans act most of the time in their own self-interest So it’s obvious that some countries, oil companies or whatever, are going to be over-demanding at some point how solar geoengineering could work as a way to avoid emission reductions I’m sure of it

But another question you asked was, what is the likelihood that this means that there is somehow no action to reduce emissions? I think the likelihood of this happening is also zero since we are, after all, already taking action to reduce emissions We’re currently spending some $ 300 billion a year around the world on clean energy, which is really fundamentally driven by CO2, above all, and so we’re not as fast as I want or Dan wants, we’re cutting emissions So for me, reality is between these two rails

The question is, to what extent will geo-solar lead to somewhat slower emission reductions than what would have happened in a world without geo-solar? And the even sharper question is to what extent will this lead to slower emission reductions than it should have been in a world without geo-solar that was doing the right thing under certain ethical compromises? Because of course it is in fact rational and ethical to compromise between risks

So if solar geoengineering really does reduce some of the risks, the long-term risks of CO2, and if your choice of how fast to cut emissions is a trade-off between the current costs of reducing emissions and the risk long-term CO2, if Solar geoengineering reduces this risk a bit, then it is actually rational and ethical to reduce a bit more slowly, even if you still have to reduce these emissions in the end.

Daniel Schrag: I’m moving away from it I agree with what David is saying I think in the real world, again, as the impacts of climate change become more and more apparent to people, as their sufferings worsen, I expect the political will to increase And it doesn’t usually develop in a linear fashion, it develops as a kind of tipping point But as, all of a sudden, the political leaders of the whole world are called to act because people are afraid And when people are afraid the political demand for action is intense But here is the problem, again the timescale of the climate system is such that, like the John Holdren said many years ago [professor of environmental policy at Heinz], « We drive a super-tanker, we don’t drive a sports car » And so you just can’t turn around, you just can’t you ar reopen very quickly And so, the short timeframe of solar geoengineering is one aspect of it that I suspect makes it incredibly appealing to a political leader in the future. When the political will that demands action is so strong it is actually something that can happen in the short term And I think it will make it very attractive This is my suspicion I wonder what David thinks about it

David Keith: I think it will probably be very appealing at some point But I think it’s really hard to see Many interviewers have asked me if I think solar geoengineering is inevitable, and the answer is definitely not I can easily imagine situations where this is avoided I think it is extremely difficult to guess how this will turn out

Jonathan Shaw: David, what are some of the scientific risks of solar geoengineering that you have thought about over the past two decades? And how to minimize them?

David Keith: So first of all, the risks are It’s not like talking about the risks of something that is a given, whether it is the risk of a volcano or the risks of something that humans, because solar geoengineering is basically an engineering choice There are many ways to do it And there are definitely ways to do it that would have very high risks that would just be crazy, destructive for free. So is there no way to separate the discussion of risks from the discussion of engineering choices made when implementing solar geoengineering?

But I think if you ask questions, I think a good question is what would be the risks of solar geoengineering being implemented to try to deliver global benefits and even global modification of that? that we call radiative forcing And I think the risks of that, which seem to go without saying, would be some risk from the aerosols themselves Aerosol air pollution now kills millions of people every year, around the world, and we let’s talk about adding more aerosols to the atmosphere And while there are many reasons why these risks may be low, they won’t be zero And you will definitely disrupt atmospheric chemistry, disrupt the distribution of aerosols from a way that will have consequences

Another risk is the fact that solar geoengineering is not anti-CO2 It changes the climate in a way that in most places reduces most of the climate changes we are interested in, but it will not reduce them everywhere In some places it will certainly increase some climate changes compared to pre-industrial with consequences It’s very general I mean, there is a whole series of individual things, air pollution, ozone, loss of ‘stratospheric ozone, acid rain, changes in the stratospheric circulation that alter the trajectories of storms You can go on and on and on Changes in direct or diffuse radiation, solar radiation, which affect plant growth There is a long list of physical risks like this

Jonathan Shaw: What about the risk of termination shock? Perhaps you see it as a political risk But it could be a scientific risk, if something was discovered about the sulphate aerosols that had been thrown into the atmosphere, there had been a deleterious effect and you wanted to stop the engineering project

David Keith: Personally I don’t see this as a risk in the same categories as the others So first of all it is definitely true that we will discover new surprises and new bad results And it can bring people to change what they’re doing or switch from one type of solar geoengineering to another But I think the risk of large scale solar geoengineering very suddenly stopping is quite low due to the personal interest of each country Even countries that initially opposed the deployment of solar geoengineering have a very strong personal interest in maintaining the ability to start it once deployed due to the risks of sudden shutdown. And the abrupt break does indeed require unanimity, world unanimity among countries of significant size, to close it. And I think this is a very unlikely result

Daniel Schrag: I think David is right about that, that the termination shock, first of all, I think I’m not so convinced that we would ever put aerosols of sulfate up there, at this stage, given what we know But imagine we put something else Suppose we put calcium carbonate up there And then we found out that there were some effects of calcium carbonate that we didn’t like L ‘ timescale, and that’s why I actually think how you do it really matters, some people have been advocating for a low-level cloud change And I’ve always said that was a bad idea because the deadline was too short

Daniel Schrag: What we want to do is power, if we want to do anything it should be on a timescale that gives us a timescale of one year, two years, three years that allows us to adjust without too much fine control Kinda like a steady hand on the helm on a very large ship Imagine putting calcium carbonate in the air, in the stratosphere, and then we find that it ‘was a problem If we were to scramble and find something we needed as an alternative next year, we could probably do it

I think we would definitely do that rather than end geoengineering altogether if it was something that was really urgent to do because the impacts of climate change were intolerable So I think David is right I think the shock of termination is not, for me, one of the biggest fears to come

David Keith: I don’t know if it’s a feature or a bug, you wouldn’t want solar geoengineering technology that you couldn’t turn off You want it to be adjustable with a timescale of probably a few years So it’s very strange I mean there are some people who hypothesize that if we somehow forget how to do this technology? Or what if there is a world war? So it’s important to say that the timeframe for which we need to do this if you’re doing it as part of an emissions reduction and carbon elimination strategy is a century or two. We have now been operating transatlantic telecommunications for over a century, in two world wars We have been operating power systems in the midst of war for decades or, in some cases, centuries I think given its cheapness I think that if people want to maintain it, it will be maintained in anything other than an absolutely apocalyptic world war And under such circumstances the thermal shock resulting from the end will be minimal compared to the effects of this war anyway, so it doesn’t matter.So I actually think there are a lot of terrible things in solar geoengineering, but I don’t see this one really being that important

Jonathan Shaw: My last question, for both of you Since the natural mechanisms of removing CO2 from the atmosphere work slowly, is there a way to remove carbon from the atmosphere on a large scale? ? Or do you imagine that new innovation might be needed to meet this need?

David Keith: Well there is no doubt that you can remove CO2 from the atmosphere on a large scale Nor is there any doubt that we don’t have mechanisms to do it now that are really cost effective , have a low environmental impact and can be adapted to what we need But since this is a large-scale industrial project, which would take place over a century, there will of course be innovation, there is no way to do it always with the same technology I should say that I have a personal interest in participating in the creation of a company working on a technology

My personal opinion is that if you are really talking about large scale removal, one of the technologies that is never popular, but I would go to great lengths to add alkalinity to the ocean Essentially CO2 is a weak acid And if you add alkaline to the ocean you tend to bring the pH back from the ocean to the pre-industrial and you tend to remove CO2 permanently so it is dissolved in ocean water in a safe way I think this technology requires real work and may not prove useful But I think there is huge scope for innovation efforts funded by governments in the public interest

Daniel Schrag: I agree that governments should fund research Because if someone developed a way to do it at a much, much lower cost, it would be incredibly big. So it’s worth funding a lot of different ideas at this point because we just don’t know at this point That said, unless there’s a drastic breakthrough in costs, I think there is a growing consensus, of the less on the range of what this is likely to cost Maybe it will be wrong, but I think there is a convergence of views with a certain range, but I think we have a sense of what this is likely to be

I’ll tell you what my concern is about this is that humans are very good at adaptation In the climate community, we often underestimate human ingenuity when it comes to adapting to difficult situations For example, the literature is full of articles on how climate change will reduce agricultural production, as they take a climate model, examine a relationship between crops and temperature, and run the climate model and project on 100 years And what they never do is think about what farmers are going to do in response They do the same with malaria, with all kinds of problems

It sounds a bit like fear at times And again it’s well-meaning scientists who do this But for me, I actually have a lot of confidence in the ability of humans to deal with very difficult situations that are happening to them locally We’re really bad at collective action issues We’re tribal, we’re nationalists, and we’re really bad at long-scale issues But if your house is attacked you’re going to find out Hopefully that doesn’t mean the people will not suffer But it means that people are very good at adapting to difficult circumstances

My concern is that, let’s imagine we stabilize the CO2 in the atmosphere and reduce the emissions to zero, and solar geoengineering is part of the mix The question is, at this point, is the will of the people paying for carbon removal will persist even if they get used to the current climatic circumstances? And that’s a question I’m not familiar with But I’m concerned that the ability of humans to get used to their surroundings will mean their willingness to sacrifice themselves to come back to something that has a lot more carbon dioxide is going to be a challenge I would love to hear what David thinks about it

David Keith: One thing is I think this problem I think the threats to humans are the most important problem, but at least as I see it personally, it is not the only problem I thinks it’s useful to leave the natural world that we’ve evolved, inherited, leaving as much as possible for future generations to love, to anchor their civilizations And I think that’s not only for my mind to manage human risks I think one of the things that really excites me about solar geoengineering is the possibility of really reducing climate risks in places where adaptation is not relevant , in natural systems, in a way that we could not do otherwise

I think Dan’s question of willingness to pay once the type of acute human risk is reduced, I think it’s very real.But it’s an interesting tradeoff, because it’s also true that societies get richer, they are often more willing to pay for things beyond the most necessary and pay to protect the natural world in more idealistic ways And we see this in all kinds of measurable ways And the cost of technology is getting cheaper So when you play that in those simple built-in valuation models that just let you have these knobs, the carbon dollars look really high in 2100 or 2150 in these models But the economy is very important and richer people tend to be willing to pay more to protect the things they love, as you see in nature parks and other natural protections. So I’m actually a little cautiously optimistic that people will pay to do it, because at this point it’s only going to be a tiny fraction of an economy and an economy where people are. care more about the natural world as a sort of fraction of their total utility

Daniel Schrag: Unlike the situation with solar geoengineering, the carbon removal problem has a huge collective action component and a huge free rider component So how willing are people to pay for something if there are a few rogue countries that keep putting CO2 in the atmosphere? It’s gonna be hard I think it’s gonna be really hard

For an in-depth look at the impacts of climate change and a discussion of the research on the geoengineering of solar aerosols, see Harvard Magazine’s feature article, « Controlling the Global Thermostat »

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Climate change, climatic engineering, solar radiation management, Earth, atmosphere