David Keith is a professor of applied physics at Harvard University and a leading thinker on energy and geoengineering. In this episode, Keith explains why we should be thinking seriously about injecting sulfur or other materials into the atmosphere to reduce the amount of solar radiation that hits the surface of the Earth, why the science of geoengineering needs more funding, and some of the issues that will have to be resolved to allow more robust experimentation with the technology. (Recorded September 28, 2022.) 

Episode Transcript

Robert Bryce  0:04  
Everyone, welcome to the power hungry Podcast. I’m Robert Bryce. On this podcast we talk about energy, power, innovation and politics. And I’m pleased to welcome David Keith. He is a professor of applied physics at Harvard University. David, welcome to the power hungry podcast.

David Keith  0:18  
Thank you very much good to be here.

Robert Bryce  0:19  
So we’re going to talk about geoengineering today. I didn’t warn you. But guests on this podcast introduce themselves. So you have a long CV, I’m not gonna go into that. Imagine you’ve arrived somewhere and you have about a minute to introduce yourself, please do. So.

David Keith  0:32  
I worked on climate kind of forever. Since 1980s, I wandered around a bunch of different topics from real climate science to energy technology. I’ve started a company called carbon engineering. And I’ve worked on this topic of solar geoengineering for on and off for the whole time. Gotcha.

Robert Bryce  0:49  
Well, so I wanted to I don’t have a particularly strong opinion on geoengineering. To me, what makes it appealing is that I don’t see pathways for large scale. Mitigation I just don’t see right now, particularly in the wake of the Russia, Ukraine war, any international agreements on reducing co2 emissions or carbon hydrocarbon consumption? But

David Keith  1:09  
international agreements aren’t often the way we accomplish things. Are you saying you don’t think it’s possible to cut emissions?

Robert Bryce  1:15  
I think it’s possible to cut emissions, I just don’t see right now that there’s a lot of traction on that just given the return to coal, what’s happening within Europe, China and India, etc. But that that’s a different discussion. But I think

David Keith  1:27  
it’s a very lengthy discussion. So I spoke differently. Okay. So from my perspective, as I said, I’ve been working on climate forever, I see much more action, and reasons to believe there will be action than I have for a long time. You know, in the end, political rhetoric is cheap, what really matters is the flow of capital. In the end, we’re replacing all the heavy industrial infrastructure of the planet, replacing high emissions infrastructure with low emissions infrastructure. And that flow of capital, you know, rose in the early 2000s, up to around 2010, plateauing around 300 billion a year. And then it’s risen again to somewhere of where six 700 billion a year. And that’s real. And you can see that in the flows into battery electric vehicles into wind and solar power. So that feels in a way that material that wasn’t before and I think the level of political focus is higher than it was before.

Robert Bryce  2:20  
Okay, sure, I’ll grant all those things. But let’s jump into solar geoengineering because you’ve made the argument and I’ve read several of the papers you’ve you’ve written and listened to your YouTube lecture that was from 2019. You wrote this piece in The New York Times last year, you said, this is what it comes down to carbon removal, or solar engineering, or both, at least one of them is required to cool the planet this century, there are no other options. So tell us just briefly, solar geoengineering, you’re talking about injecting particulate into the atmosphere that would reduce the forcing from solar radiation onto the earth. And that that’s the you believe this is you’ve made the point this is going to be one of the key tools we have to use to make to reduce the risk of catastrophic climate change is that it’s fair. So

David Keith  3:06  
what’s your different statement? I’m not saying what we have to do, that’s I’m not in charge of anything. So I can say what I think solar geoengineering is. And to me, it’s a range of different methods. But it’s basically deliberate human action to alter the radiative balance of the earth by reflecting sunlight away most obviously. So that might be done in principle by a giant solar shield in between Earth and sound. I don’t think that’s that likely to happen this half century, but I think it’s not implausible later on. Putting aerosols in the stratosphere sort of twice as high as regular airplane flies is the thing we understand the best, the thing that most easily can be even, I think, probably think it has the best ratio of of reduced risks to the new risks it brings. But there’s a bunch of other ideas of things cirrus clouds are making marine boundary layer clouds wider or making land surface wider. There’s a bunch of ideas, all those ideas, I lumped together as solar geoengineering or sunlight reflection methods or you know, people, that’s a disputed topic. So that’s broadly what it is. And what I said that York Times op ed, which I think is just a correct statement, is that that if you want at any time to make the temperatures cooler than they are at that time, you have to either take carbon out or do selvaggio. Because warming is worse for the cumulative emissions. So even if you bring emissions to zero, you don’t cool the planet down. And so you have to do one of those two things, if you want to cool it down on a policy relevant timescale.

Robert Bryce  4:35  
Well, you also made a forceful yet affordable line in that New York Times piece you said, pretending that climate change can be solved with emission cuts alone is a dangerous fantasy. If you want to reduce risk from the emissions already in the atmosphere, you must look to carbon removal, solar, geoengineering, and local adaptation. I’m also not bullish, bullish on carbon removal just because of the scale scale issue which I’ve written some about, but you focus on some of your work on in particular on sulfuric acid, why sulfuric acid? And how much would it take? You make the case that it was a relatively small number of airplanes 100 or so that could be based in the tropics? What is it about that sulfuric acid that makes it so attractive as the the type of material that you use to put in an aerosol into the atmosphere?

David Keith  5:20  
Well, I think it’s the thing we know the most about it, it senses the devil, you know. So there’s lots of other compounds you could consume for us in the stratosphere. The sulfuric acid is really just there to keep the water there, if you like is one way to think about it in the sense that a water drop in the troposphere were great, but the stratosphere is so dry, it would evaporate instantly. So the sulfuric acid is intense there to keep it from evaporating. And it’s what nature does. So there is sulfur in the stratosphere that does cool the planet with volcanic eruptions. And we have giant and terrible materials with sulfuric acid air pollution and lower atmosphere, we put sort of 50 million tonnes a year of sulfur from fossil fuel combustion in the lower atmosphere, which kills sort of order 5 million people a year. So that also means that we know a lot about it. And so it means that we can have some confidence about unknown unknowns, I think.

Robert Bryce  6:09  
So you said that it was in your 2019 presentation. It’s called the peril and promise of solar geoengineering, which is on YouTube. You said it would require a new design of airplanes an aeroplane, you need about 100 of them, and they’d fly 120,000 flights per year? What would these planes look like? Do any of them exist? What was there a prototype? Or where is there any? I know you make a particular point about the ratio of funding for geoengineering relative to the broader issues around climate science. But where are we on the actual things that would make this happen? Are any of them in existence? Well, no,

David Keith  6:45  
nobody has developed a specialized airplanes that might be used, but you don’t need those to start. So that number, I mean, it’s a human choice how much solar geoengineering to do, and I think it would be crazy to start it suddenly turn it on. So that number you’re quoting of 100, aircraft, all that stuff, that was for something that was doing what we call two watts per square meter, offsetting roughly half of double co2, I could see an argument that we gradually turn that on over sort of half a century, or something, gradually ramping up from zero. But I’m certainly I would strongly oppose somebody just wanting to do that right away. Sure. And so you wouldn’t start with these 100 airplanes and start with some much smaller number of airplanes. And you could start with existing airplanes, because you don’t need to go quite, quite up to the highest altitude.

Robert Bryce  7:32  
So would these be like, like KC 130 fives, like straight to the straight or tankers, like a Boeing 737 type of airplanes, the smaller,

David Keith  7:41  
I think, if you wanted to start you start with something has a slightly higher ceiling for payload. So like, your business jets that have a Gulfstream p 650, carries five tons to 51,000 feet, for example. So that would be something that you could just barely use to get started. Right.

Robert Bryce  7:58  
So that’s the you also talked about the possibility of using calcium carbonate. There are other there are other types of compounds that you could use, but sulfuric acid, you’re saying that’s the one that right now, you say has the most, there’s the most experience with this, this would be the one that is off the shelf, and people kind of understand it right, that

David Keith  8:17  
it’s the thing we know the most about. And and I think that it’s unlikely that it would make sense to do that at really large scale later in the century, I think it’s likely you’d replace if if the world decided to do solar geoengineering, that after a few decades, you’ve stopped using self aid and use something else. But I think starting with sulfate makes a lot of sense, because we have so much knowledge.

Robert Bryce  8:40  
So talk about the you mentioned the amount of money that is going into climate research climate science in general, and that the geoengineering slice of that is still relatively small. Now, I think your numbers are from three years ago. Can you give us an idea about that? What is the total number of mouth is going to climate research? And then how much what fraction of that? Is it related to geoengineering?

David Keith  8:59  
Well, fractional geoengineering is really tiny. It’s an order, it’s hard to measure exactly. But if you have order, you know, 10 million a year globally kind of numbers. And, and climate science is hard to know. But the US Global Change Research budget is of order two and a half 3 billion and maybe Europe’s is kind of similar. So that would make as a guess, global research and climate sciences, including the satellite assets, is maybe of order of 10 billion.

Robert Bryce  9:33  
So 1% or less, but this is what already met a lot of criticism. I just there was one quote from Raymond Pierre Umberto from the University of Chicago who called this idea, just like this phrase, wildly, utterly howlingly barking mad Al Gore

David Keith  9:51  
when they don’t have an argument, fair, fair enough. But if Ray if Ray had a clear argument, if he had a clear way to say that what the The scientific community is was wrong he’d given if Ray had a reason to believe that something that we’ve said that the side of it community has said, there’s there’s a fair amount of science on this now that we got it wrong. He published a paper showing we were wrong. You say something’s barking mad when you’re just really pissed off, but you don’t actually have an argument?

Robert Bryce  10:20  
Well, so I guess the it seems to me from the outside and looking at this without someone on a strong opinion, one way or the other, that the idea, though, of geoengineering has been kind of pushed out of the mainstream, because the mitigation argument has been the one that’s been front and center. But your argument is that, if I’m understanding you, right, this has to be something that is much embraced much more by mainstream climate scientists, because that, in your view, this is something we’re going to have one of the tools we’re going to ultimately have to use, is that a fair set of careful

David Keith  10:49  
never to say to have to work, okay, my job is to form public policy. My job is to communicate the environmental risks in science as best I can. And that’s not I think we often I think scientists often have screwed up in the climate debate by folding in their own values too much. And by dictating what should happen, science can make if then statements, science can say if we keep emitting fossil fuels without doing anything, we’ll have gigantic climate change of certain size. And but science can’t tell you what’s the right pace to cut emissions. And science can’t tell you whether we should do solar, geoengineering, it just can’t.

Robert Bryce  11:30  
Right. But you’re arguing that you’re but this should be more carefully considered? I mean, I’m arguing

David Keith  11:34  
that that’s a different statement. And I think, yes, I think we should do substantially more research and begin the international deliberations about what the rules would be for governing these technologies.

Robert Bryce  11:47  
But then let’s start there that are let’s follow up on that, then. Because the international law on this or that and how this would work in an international framework to me is dauntingly complex. Has it been discussed in in international forums about how this might work? And where where where does that lie these days?

David Keith  12:06  
Yes, it’s certainly been discussed. I mean, it’s been discussed up to heads of state in some cases. It’s complicated to say we’re allies. There’s no formal process. But there’s lots of conversation, some at quite a high level, there’s a thing that I’m an advisor to called the Global overshoot commission. And people can look that up and look at the commissioners. But that’s probably the highest level group of political people who’ve ever dealt with these topics broadly with carbon removal and solar geoengineering allocation, basically, with all the things beyond emissions costs, and that has Forex has estate on it? So it’s a pretty high level panel.

Robert Bryce  12:49  
And is that based? Is that is that? Is that a formal organization? Is it a panel in general does it have it doesn’t one of these

David Keith  12:55  
things that that? No, we set it up. So so this is there’s there’s definitely a prototype for this. It’s a free standing commission. So it has no power and it wasn’t asked for. But this is a bit of a template, it’s been used in other cases where the UN system I hardly tell you is pretty bureaucratic. And sometimes there’s things that a lot of people would know need to be talked about the US system itself has trouble doing it. But a commission like this, who’s got a lot of people who are tightly connected to that system, but who were speaking on their own behalf asked, can articulate points of view that can then get taken up by the international system in a more organized way?

Robert Bryce  13:34  
Sure. One of the things I’ve heard you say as well, was that it was likely that this type of experiment would be done by a smaller country, not necessarily the US or China first, that it would be some other country, particularly when perhaps in the tropics or another one that was had serious risks from climate change, that they would embark on this, perhaps on their own. Tell me why that’s the case. Why do you how do you why do you see that as the that these countries would look out and say, Well, we have to do this, we have to start this experiment, and then would the possibility somebody

David Keith  14:09  
experiment this is about deployment, I think it’s about interests, and checks and balances. So the I mean, a basic thing we know about climate is that it warms up the world and and the temperature increases are worse for places that are hotter. So temperature increases, both kill people and reduce productivity. And they do that more for hotter countries to an added degree temperature is much worse for Indonesia, or India or the Philippines than it is for Sweden or Canada. And so that’s the basic kind of inequality of climate change. It’s also true when it comes to extreme storms. And so kind of flipping that around. Those countries have the most to benefit from stopping or reversing climate change. And also Yep, Go ahead. Well, that’s the big one.

Robert Bryce  15:02  
Okay, well game this out for me because it’s it’s possible, then one of these countries would begin this experimentation. And then another country would say, hey, you know, we don’t want this. I mean, is this potential? What’s the potential for conflict over even experimenting around this? Because the modeling here and the uncertainties are quite large, aren’t they?

David Keith  15:22  
Well, you’ve got a lot of different questions packed up there. So from the political side. I mean, yeah, we can, we’ve gained lots and lots of scenarios, but I don’t know how much those games are worth, it’s very hard to foresee the way things will go. I think you keep talking about experiments, like there’s a giant Gulf literally a factor of a million gulf between the kinds of experiments people are talking about, and actually deployment at a scale that would be climate relevant. Sure. So there is controversy about experiments, because there are groups that really believe that there should be that we shouldn’t be talking about this. So they will oppose even small experiments. But I think that my view is that is gradually going away. And that the main the fundamental underlying conflict, I mean, even the groups that oppose small experiments that are clear, they’re not actually worried about the experiment. They’re worried about the idea. And so my, I think the big, the big dispute, it’ll actually be disputes about deployment. And yes, it’s certainly possible that if one country just started to deploy other countries would oppose. But countries have self interests, and they can think a move ahead of the chessboard. So they probably wouldn’t just start unilateral deployment. They develop some coalition of countries that want to do deployment. And then you got to think about how these coalition’s fit together and how they play out.

Robert Bryce  16:40  
Sure. But you said worried about the idea. I think that’s an interesting concept in that the there’s been so much focus on mitigation, right, that we have to make these drastic cuts in co2, and we can disagree on how much those cuts might actually happen. I’m just looking at the numbers and see the co2 continuing to rise, particularly in the developing world. But the worried about the idea that somehow we

David Keith  17:01  
actually co2 emissions are going down in the US and Europe. So that’s a lot of the developing world. Sure, you’ve got your facts, right. And I don’t think there’s room for us to disagree that if you want a stable climate, you’d have to bring emissions to zero. And you agree with that?

Robert Bryce  17:19  
Well, look, I mean, we can go far into the wet, you know, what emissions are and where they’re going? I see the trend lines going up, particularly in the developers, I’m

David Keith  17:27  
not talking about visions. But if you want a stable climate, you got to bring down emissions to zero. Do you agree with that?

Robert Bryce  17:32  
Well, I mean, yes. If we’re hoping to reduce any climate impact, those emissions are going to have to fall dramatically. But I know that’s

David Keith  17:38  
a different statement. You can’t No, no, that gets it fundamentally wrong. This is the key mistake. Okay. That’s a mistake. That turns out a lot of people make even like, there’s a survey of people that are like, keep making some state. Climate change depends on cumulative emissions. Sure. So even if you eliminate emissions, you don’t actually eliminate climate impacts, you just stop making them worse. Okay, but because it depends on cumulative emissions, it is pretty much a fact as simple as like, gravity is a simple equation, that if you do not, if you don’t bring that emissions to zero, then climate risks will grow without bound. That is literally true.

Robert Bryce  18:12  
So therefore, we need carbon, and therefore we need carbon emissions to zero. So then we have to either have carbon removal or geoengineering, as you’ve said, that

David Keith  18:23  
isn’t about emission doesn’t solve the problem. No, it’s really that you must bring net emissions, that is actual emissions, net of carbon removals have to get to zero if you want a stable climate. I think that’s pretty close to a hard fact. Okay. I think that political dispute is how fast to do it.

Robert Bryce  18:38  
Fair enough. But your your point about the worried about the idea that somehow that any focus on the geoengineering would take focus away from mitigation. Is that what you construct? Yes. Okay. Because then I think is the key here that I see is that there these ideas around mitigation, particularly around large scale renewables, which I’ve been very critical of, because of the land use issues, the material inputs, transmission, etc, once

David Keith  19:00  
the problem for solar?

Robert Bryce  19:03  
Well, solar has power density, 10x wind, so it has higher power density, and I think that’s one of the reasons why it’s it’s gaining more traction, but I’ve seen and documented over and over. In fact, over 300 examples of wind energy, rejections and restrictions in the US you’ve done similar work on this, you didn’t

David Keith  19:18  
answer my question. I said, What’s the big energy density problem for solar? I don’t think I see one when this different wind has real constraints. But solar you can imagine running the world up to many terawatts of solar if you actually build it in sunny places and move it around with a pretty small land footprint, a land footprint is less than 1% of land area.

Robert Bryce  19:39  
Fair enough and I’ll concede the power density of solar is 10x that of wind but I also see all across the US in fact, a local community saying we don’t want these solar projects in our in our

David Keith  19:50  
in our county generally people don’t want anything that doesn’t

Robert Bryce  19:53  
and that’s fair enough, but these are these are these are still

David Keith  19:56  
seem to want the power and they want to drive around so

Robert Bryce  19:59  
that I will agree. I will agree with that. But the power density issue is I see that but I also see the land use conduct constraints and the transmission siting constraints are very real. And I think they get ignored in all of these models being put out by a lot of elite academics that ignore this land use issue as the fundamental the I mean, this is the first first priority issue first first principles. But

David Keith  20:25  
I agree, it’s a really important issue. I’ve worked on it a lot myself, but I think you’re overstating it. And that’s why I’m calling you on it. I think it’s different for solar and wind. So the way I think about it is if you want to decarbonize industrial society with pretty low environmental impact and low land footprint, you’re either doing it with solar, or nuclear or some combination. There’s nothing else you can do it at large scale without being environmental impacts. But But solar is definitely possible. It has an energy density that works. And yes, transmission siting is hard, especially in America, for sure. It’s hard to build. And that’s a true statement. Absolutely true. And yes, it’s ignored and models a lot. Yes.

Robert Bryce  21:05  
And that’s why I’m so pro nuclear that the footprint is so much smaller, we can use the existing transmission network, and we’re not going to have to build a lot more. So solar has other supply chain issues that we can talk about poly silicon and the rest of it. But nevertheless, I’m much more bullish on nuclear in the long term than I am on solar for the reasons we’ve discussed. But so what how much research is going on? What is the budget need to be right? You’ve talked about the disparity and research and what are the next steps that were going to be needed in terms of bringing more focus on this because you’ve been involved in in pushing out the ideas around geoengineering in the Public Media, which in big forums, what else has to happen to get this more traction in the in the public debate?

David Keith  21:48  
So I think it’d be appropriate to have a budget that is, you know, of order 5%, or more of the budget for climate science, that is that 5% or more of total climate science be spent on this topic. And that’s consistent with what the US National Academies said. That’s obviously there’s lots of people in the kind of mainstream environmental climate community who don’t agree with that. And just to be clear, the fundamental issue here is dispute about this, what’s often called the moral hazard. The idea of this will distract for emissions cuts, I guess, the underlying concern, most of all, but I think the research of that scale would be what would be required to really substantially reduce uncertainties about these about solar geoengineering. But I think it’s really important that it be kind of globalized, this is something that inherently is global, there’s no there’s only one planet, you change things in one place you affecting somewhere else. So unlike lots of other things, where the issue is about driving down cost, solar geoengineering is cheap enough to make it cheaper really is the issue. The issue is building up trust. And I think trust gets built out by to me by having no single actor in charge of research, but having a diffuse research community that’s diffuse, really around the world.

Robert Bryce  23:00  
I like that idea about the building up trust. So then you would need the leading academic institutions from Europe, Asia, the us all working together on this, then. So you’re thinking about some kind of consortium of academic lots

David Keith  23:13  
of them working on it, you don’t need that. I think actually, you don’t want everybody working together? Because then they come to come to one answer. I think diversity of opinion is really important. But yeah, you want more institutions working on it seriously. And and to be clear, that is gradually happening. There’s much more research and acceptance of research, and there was even five years ago, and they’re now you know, I think it’s changing, but it hasn’t changed enough.

Robert Bryce  23:35  
Fair enough. So where would those experiments mean? Because you’d have to do some experiments at some kind of scale. Where would they occur? What is there a way that you mentioned that if this were going to be deployed at scale, it could be done, it would likely be done from an airstrip or a country in the tropics? But where would the first experiments for this kind of injection of sulfuric acid in the atmosphere? Where would those happen?

David Keith  23:58  
So so the experiments are there fundamentally, to improve our knowledge of how the atmosphere works, what we call our process, understanding that we incorporate into global models. And so in some sense, those experiments in a way have been done for 100 years, because they’re all the set of atmospheric science experiments. There are specific things that are worth doing to help us specifically go after things that we that we don’t know, that are really relevant to solar Geo, and there have been some already done. So there was a thing called the EPS experiment that was done by men. Russell was the pi a bunch of years ago. There’s an experiment in Australia that’s been done making a certain kind of cloud scattering. We’ve been proposing experiment this is transparent experiment. That was we tried to do it in Sweden, because that’s where a balloon operator was wanting to work with was around a balloon operators and we were prevented from doing that. But we expect we will be able to

Robert Bryce  24:52  
do it somewhere else and prevented how

David Keith  24:56  
the Swedish government basically responded to critics and told the little company that that we couldn’t they couldn’t fly us.

Robert Bryce  25:03  
Well, that’s not a good indicator. Right? You would think that in Sweden,

David Keith  25:06  
but things are changing and yeah.

Robert Bryce  25:09  
Well, I mean, I’d say that because Sweden is, I mean, a developed country, a lot of very smart people there. But the there would be some pressure that would prevent even this kind of relatively small scale experiment.

David Keith  25:20  
Experiment was tiny, it was like releasing kilogram materials. So even the strongest critics didn’t say the experiment was dangerous. But as I said, they oppose the idea of doing it, which is their right to do. I don’t actually fault the critics at all, I felt the Swedish government for not having a serious debate and making an informed science and risk based decision.

Robert Bryce  25:41  
Yeah. But it goes back to this idea about the moral hazard idea that even and I just want to focus on this a little bit more, because it seems to me that the there the focus on mitigation, and we can disagree on what you know, how much mitigation is going to be effective, right? And, yes, it’s true emissions in the US and Europe have plateaued. But that the idea of the argument being, oh, well, if we’re not focused on mitigation, we’re going to lose the fight. And this would be somehow surrendering to more co2 emissions, is that if I get my finger on it, is that that that’s the moral hazard here? Yes, the

David Keith  26:15  
concern, the concern is that by having a sort of a tech fix, get out of jail free card that Get Out of Jail Free card that people will will not do the thing they should do. And this another way to think about this is a risk compensation that we know for lots of personal behavior, that if you give people a potentially risk reducing technology, like airbags or whatever, that they’ll actually end up taking more risk. And that’s actually not necessarily irrational, individual level, if you take pleasure from the things that are risky. So I think that’s the underlying concern of many people. And I think it’s a valid concern, absolutely a valid concern. But given the fact that climate change is proportionately cubed of emissions, so even if we eliminate emissions, the climate change is still there. And given the risks, the huge risks, especially the people that are many of the poorest people in the world, my view is that that argument is not a basis for saying we, we shouldn’t do research.

Robert Bryce  27:09  
Sure. And fair enough. But let me let me ask you about models. Because, you know, a friend of mine, Chuck Spinney, worked in the Pentagon for many years helped build fighter planes and warn me many years ago about models. And there’s a lot of talk about this. And I’m just going to put it to, you know, in a way that I think Chuck would say, is, are these atmospheric models? Are they robust enough to even to be reliable when it comes to the many variables already existing? And then you’re adding another variable with these with with geoengineering with reflective particles in the atmosphere? Are the models that good? I guess it’d be the shortest question.

David Keith  27:43  
Yeah, the answer is the models are amazing. And you can see that because we use them every day. And and people trade big money on the models have a funny tale that I had friends who were involved in some of the first science, it was able to do a beginning of a job on Alenia forecasts. And they knew that they were getting it right when grain traders started to pay attention. And, and weather forecasts, I know people like to complain, but they’re actually stunningly good. And they’re much better than they were half a century ago, there’s been a steady improvement. These are fundamentally the same models. That represents his deep improved knowledge of the way the atmosphere works. There are just lots of examples that show how well models do. So mean, to give you some examples. Pinatubo was at the volcano and I do that put a lot of cell phones stratosphere in the climate cooled, people predicted the amount of cooling before it was observed. So it’s easy to predict exactly the fact that they predicted it before it was observed. And how much was there’s actually a lot of a lot of basis to believe those models, right? And what was

Robert Bryce  28:51  
the how much material did Pinatubo release? What was that of the scale of that in terms of the overall mass of stuff that came out of the earth on that eruption?

David Keith  29:00  
was about 8 million tons of sulfur that gone into the stratosphere? And

Robert Bryce  29:05  
is that what would be required? I know I have the your flight numbers here and some of the other numbers what what what are you proposing or what do you think? What are what are some of the indicators would would we require something on the same order of magnitude, 8 million tons to achieve that same kind of cooling that Pinatubo did

David Keith  29:21  
no, you can do better because you can get the size distribution of particles better and until those are two different pieces of pulse. I think, you know back to that number you’re citing from that talk again, if you want to do you know cool temperatures by a degree or so you’re talking something of order 2 million times a year round numbers.

Robert Bryce  29:43  
And you would have to be continually apply them. That’s correct. Yeah, I was. So

David Keith  29:48  
so the point is that in your first reaction when somebody says we’re going to put 2 million doses of uric acid in the sky should be that that’s completely insane. But but we do put 50 million tonnes a year in the lower EMIS We’re now so that’s only 4%. And and and so it’s it’s not as big a change to the way the world is than you might think.

Robert Bryce  30:09  
So as I’ve thought about this, I was in Arkansas a few weeks ago speaking to a Rural Electric Co Op and I saw a crop duster. And I’m only I can only think in his terms that you’re going to have ge 5g six airplanes crop dusting these the stratosphere is that is that a fair way to think about how that would be a

David Keith  30:26  
reason why it’s so much more effective to put in the stratosphere. So is that material stays in the stratosphere for about two years round numbers. And soy and things mixed in the slow cycle and stratosphere it’s very different than the atmosphere we’re used to, we’re the kind of mixing time in the atmosphere is more like a week. So it’s a really different thing. But But yes, you’d have to have a continuous set of aircraft moving material up to, to the stratosphere, for sure.

Robert Bryce  30:57  
And that aerosolization would be somewhat similar to then to crop dusting. I mean, I’m just it’s the only thing I in my head, I don’t know,

David Keith  31:03  
well, or not obviously know it, lots of the ways that we think about doing it, you put if you’re dealing with sulfur, you’d want to put a sulfur vapor and co2 in or h2 s or something. And that’s a vapor that you can’t see. And it takes it actually a month or so to oxidize to end up making the aerosols. Gotcha. Okay, so you wouldn’t actually see any wouldn’t actually be aerosolized in the same way at all. Good.

Robert Bryce  31:29  
Well, let’s, let’s return to I know you’ve, you’re on a schedule here. So I want to cut to a couple of other things. You’ve done some good analysis on land use and renewables. And I’ve often cited the paper you did with Lee Miller in 2018. On wind energy’s land use that you came up with, if we were to attempt to generate enough electricity in the US. With wind alone, it would require roughly 900,000 square kilometers. That’s roughly the same number that Vaclav Smil came up with. In his book. What was it? Energy realities in 2010? I thought it was, again, the it’s one of the constraints on the system. But what’s interesting to me, I guess I’ll get to the point, this question. What’s interesting to me about the what we’re talking about here with geoengineering and mitigation is that you’re not going to have a big land use footprint. It’s not even the energy inputs for this kind of system. You use the word leverage around geoengineering, I thought that that was an interesting term, and that you get a lot of bang for your buck, I guess. Is that how you were talking about it?

David Keith  32:27  
Yes, certainly, it takes pretty small amounts of money and materials. But that’s, that just means that money is not the decisive factor, the decisive factor is risk versus risk. There’s risks of doing it, and there’s risks of not doing it. And the issue is to weigh in compare those risks. That’s really the essence of the question. There are lots of other things in our society where it’s not primarily about money, it’s about risk balancing. That’s true of lots of things. So So I think, I think the issue is solar. Yeah, the bottom line is energy is going to be cheap enough by certainly for stratospheric aerosols, that it’s not really going to be constrained by money. And there’s no reason to make it cheaper. It’s just that we need to really understand better how the risks are. And in order for there to be a kind of stable deployment. You know, obviously, you never have a world where everybody agrees, but you need a enough level of trust between enough people in countries that the thing is basically going to work for it to keep working without people really disagreeing or wanting to shut it down.

Robert Bryce  33:28  
And are you doing much more work on the land use part of this? You did research it was a forgotten the name of the title of the paper that you published back then and four years ago? Are you doing any more work in that area? Or you’ve moved on to other fair

David Keith  33:39  
No, really? No, I did not wind power work over and starting in 204, or something like that, starting early and about 20 years ago, and I’m not really doing much more now. It’s I kind of like to go back and write an overview paper because I agree with you. I think I feel like you were overstating it about solar. But I agree that people undercount the land use undercount the importance of the land use footprint of some renewables, particularly of of of, of wind. And I think the there really are impacts of wind that aren’t zero and that people need to think about more. And to me, that means we should sort of it doesn’t mean we should not build any wind, but it means we should tip the balance to focus more on solar. In fact, I think this is going to kind of sort out anyway, because solar is just going to get cheaper. I think the big issue is really as you say about building transmission lines. Yeah.

Robert Bryce  34:26  
Well, and the mentioned Schumer bill, well, the mentions infrastructure bill was pulled from the continuing resolution budget bill just yesterday, which I had a piece in the Hill about that yesterday, because but anyway, let me ask you just a couple of other quick questions here. So you were at Calgary University of Calgary now at Harvard. That’s big changes in

David Keith  34:47  
Yeah, I I bounced around a few times at Carnegie Mellon before that,

Robert Bryce  34:53  
and so well, and then you’re a citizen of the looked at Wikipedia. You’re a citizen of the US, Canada and the US. Okay, you have three passports.

David Keith  35:02  
I don’t actually have three passports now or not three up to date ones. I don’t have an up to date UK passport, but I did have one at one point.

Robert Bryce  35:08  
And this is why your father Your father was a brother with

David Keith  35:10  
some complicated day. I guess I was born in the US, but we moved to Canada. I was two years old. So I really feel more Canadian. If you asked me more culturally Canadian. I really that’s my kind of core allegiance, I guess. And my father was a Brit, though, so

Robert Bryce  35:24  
yeah. So is this mean? You’re a hockey fan? Then? I’m guessing.

David Keith  35:27  
I’m moderate hockey fan. climber an outdoors person, but I but but yeah, like any Canadian. I’ll watch. I’ll watch hockey.

Robert Bryce  35:36  
Fair enough. I read that you had worked with Paul corkum. I interviewed him in my well actually. He’s featured in my fifth book for his work on attosecond science. Cool. He was a

David Keith  35:49  
very, it’s really cool. That’s me. But you’re interviewed Paul, in his in his

Robert Bryce  35:53  
lab in Ottawa overlooking the Ottawa River, if I remember,

David Keith  35:57  
he was one of the most important mentors for me in my life. He told me about that, because he

Robert Bryce  36:01  
was a lovely guy when I met with him, and I thought, you know, this guy is really, and just taking pictures. What did he mean? I’m trying to I write for a general audience, right? And when I look at his his work, and he’s photographing electrons, right, which is just,

David Keith  36:15  
ya know, he’s had I mean, he’s, yeah, absolutely. I couldn’t win the Nobel Prize, completely top scientist and but he’s like a really low key maritime or he came from Nova Scotia as I remember. And he’s just an extremely calm and good person. And he he ended up I guess, my stepmother had. They were working together for some, I don’t know, providing support for Vietnamese boat people at the time. And, and then she extracted some promise that he would take me another guided tour of his lab when I was in late high school. And I asked a lot of questions. And I guess I didn’t ask asked enough good questions. And he ended up hiring me. And so I worked there for three summers, including like the last two summers of high school, and it was just completely kind of made me in terms of getting me started in physics, it was absolutely wonderful. And it was also kind of lucky, because at that point, he wasn’t so famous, didn’t have such a big lab. So he had a lot of time to spend kind of mentoring me and teaching me physics. And it was just fantastic.

Robert Bryce  37:18  
Well, we’ve talked now about power density, and I wrote him in the book. And because I calculated the power density of the lasers that he’s using, they’re 10 to the 18th. And x a watt of power.

David Keith  37:28  
Worked on the first I worked on building pico second amplifiers for his his, one of the we’re trying to to get up to milliwatts into pico seconds.

Robert Bryce  37:36  
And so are you staying up with corkum these days? Because he also just was awarded another big, big prize, a Canadian prize science prize. I mean, he’s had several.

David Keith  37:45  
Yeah, he’s had a bunch. Yeah. Yeah, I mean, I’ve seen them socially, reasonably often want to go to Ottawa. Yeah.

Robert Bryce  37:55  
And so we’ll on that score, then. So we’ve talked about geoengineering. And I think that’s interesting. But I’m also just kind of curious about you, as in science and how you view science. And let me ask you this question about academics and their relationship to the broader society. Is there is there a sense, because I’ve thought about this lately, in terms of some of the science some of the things that are coming out of academics? And, you know, I’m not one, I’m not going to be one? Is their duty? Do they? Or do they have a duty to the general public? Where’s their allegiance? I guess, would be another way to think about that.

David Keith  38:26  
Yeah, I think they have I mean, it some sense they’re working, or should be working for the public at some level. So yeah, I think they should. And I think that I really, I like what it says on the Einstein statue outside the National Academy, which I’m not gonna get the quote, exactly, right. But it says something like, those who have the privilege to seek after the truth, you know, who gets they get paid the salaries, do all cool science experiments and write books, and whatever the people like, we get to do have a duty to tell all that they know. So I think I think my view is it’s really people’s job to try and as clearly as possible, explain the, the facts as they know them, and they could separately state their political views, and they have every right to do that. But I think it’s important that academics find ways to try and separate what they can say, from their expertise from what they happen to believe, based on politics, which like anybody else, they’re gonna have beliefs.

Robert Bryce  39:24  
So well, that’s interesting. Well, in your case, then to say all that they know. So as I as I proceed, what how we’ve talked about this, what your charge, as you see it on the geoengineering side is to push this forward. And so we have to be seriously getting this more into the mainstream debate. Yeah. And is that a fair summary?

David Keith  39:40  
Yes. And I’m pushing some of my fellow academics who will behind the scenes say, Yes, you guys might be right about the science of this, you know, but essentially, they’re saying, but the public can’t handle it, or the politicians can’t handle it or we should not talk about it because it will be misused

Robert Bryce  39:59  
and And we can only focus on when we can only focus on mitigation because that’s because we have

David Keith  40:05  
a reasonable fear. But I think if you’re really not telling people about something that’s potentially useful, it can save lives because you’re worried about the politics. That’s it’s not your job. We’re not a secret academics aren’t a secret society that makes the final decisions. We’re just supposed to be informing people and producing knowledge. And academics don’t have special knowledge about how politics works. I mean, unless they’re ones who are really expert in politics. And and so I feel that when my colleagues from the sciences do that they’re overstepping. They’re not clearly enough separating their political concerns from from their knowledge

Robert Bryce  40:39  
that the scientists are becoming too political in their in presenting

David Keith  40:43  
on that and that raping Humbert quote you started with Ray is very worried about this. He really believes only misused I actually really respected like him a lot. But I think it’s his duty to separate the fact that Ray is genuinely a monster brain, amazingly good geophysicist. And if he has particular reasons why he thinks me and others are wrong to physically where he’s got expertise, he should say it and use the power of his expertise to say you guys are wrong, or I believe you’re wrong. Here are the reasons. But But I think where people overstep is where effectively they’re getting the credit for being an expert, but they’re talking about something on which they’re really not expert, in this case on, you know, whatever the politics is going to be that the answer is, we just, we’re not very good at predicting the way politics will go.

Robert Bryce  41:27  
The thing that pops in my head, David, is you say that, and again, my guest is David Keith. He’s a Professor of Applied Physics at Harvard University. He’s on Twitter, among other places, D. Keith, climate at D. Keith climate. When you said that about the duty to the public, the part that pops in my head, and you’re talking about geoengineering and the relatively small budget, or massive budgets for mitigation is that part of why this debate is skewed more toward mitigation? Because there’s a whole lot more money there? And I’d say that

David Keith  41:55  
no, that’s that’s cart before horse, we shouldn’t be spending much, much more money on mitigation. Its mitigation is really expensive, and we have to mitigate.

Robert Bryce  42:01  
Right. But there’s a lot of industrial it. A lot of industrials, big industry, big, big business that’s interested has a lot of money at stake and mitigation as well, right?

David Keith  42:10  
Sure. So like any big activity that people do, there’s politics and profits, and what do you know, they interact. But but but that’s always going to be true, I’m not defending it, but we just, you know, that’s the way the world is. But whatever. Mitigation is expensive, actually, cutting emissions at a reasonable pace is going to cost us like 1% of GDP. So we need to have a lot of money for sure. If I was boss, it’d be less gifts going out and more just setting rules about emissions, but those are still really imposing costs and make money flow. The point is, the actual flows of money for mitigation should be much much more than flows of money for Sergio, I don’t think it’s about the money flow equivalency, it’s about the fact that in thinking about managing the risks, we need to think about the full set of things, emissions cuts, carbon removal, solar, Geo and adaptation. And we need to think in four dimensions think about all of them and take seriously what their strengths and weaknesses are and how they fit together to produce a you know, a path through climate the century that is fair, that you know is doesn’t punish people too much for by mitigating so hard that it really crushes people’s jobs, but also doesn’t hurt the poorest people who will suffer most from climate change or doesn’t hurt to hear some less than than otherwise would.

Robert Bryce  43:30  
Sure. So you mentioned carbon removal. Let’s just touch on that real quickly. And then I just have a few more questions. So again, I see this as a scale problem just a massive amount of atmosphere you know, scaled mass of air etc that have to be treated have to be then you have to separate the co2 and then you have to put it somewhere. It sounds to me like you haven’t have you focused much of your work on carbon removal How do you view that as a as a metric as a strategy with regard to climate?

David Keith  43:56  
So I do want to wrap up in just a sec actually. Well, so I’m biased or potentially biased because I started one of the probably two most active companies is doing direct air capture which is one version of carbon removal I definitely I think that carbon removal is the only way to draw down the kind of underlying climate risk this is why these things fit together the underlying co2 I think some of these things appear to be pretty scalable I think adding alkalinity into the ocean and and direct air capture both seem to be scalable in the sense that there’s not obvious kind of land use or materials constraints

Robert Bryce  44:43  
adding adding what to the ocean Did

David Keith  44:44  
you say alkalinity

Robert Bryce  44:45  
alkalinity Okay, yeah. Which is different from because I’ve also heard about iron flakes and so on is another way to for

David Keith  44:51  
Yeah, yeah, iron seemed like a good idea 20 years ago. It’s a high leverage thing potentially but it just short answers. doesn’t work in a meaningful way.

Robert Bryce  45:01  
Okay. So then you said you need to go. So just a three last question. So who would scientists did dead or living do you admire? You mentioned? We’ve talked about corkum? Whose ball? Certainly. Who’s In Who’s in your pantheon?

David Keith  45:16  
Oh, man. Oh, I don’t know. Actually, you get to meet Fineman for a minute once. Some of those old Phil Morrison, some of those Oh, we used to call them the bomb Johnny’s, Phil Morrison.

Robert Bryce  45:31  
That’s the name I don’t know who is he?

David Keith  45:34  
He wasn’t one of the younger people. He he younger people on the weapons project to then help to really become a little politically run radicalized, but in really interesting ways and help to get people working on energy and environmental topics.

Robert Bryce  45:47  
And he was the Manhattan Project. He’s on the Manhattan Project.

David Keith  45:51  
Yeah, he did some beautiful public communications. They he he and his wife, they work very much together, Phil and Phyllis had a series on I guess on PBS called the ring of truth that was just really one of the best things I’ve ever seen in science education. He was an amazing rat.

Robert Bryce  46:08  
And what about Fineman was you have a reaction that you find when he was asked to describe electricity. He said something like, well, a thing moves over here. And then a thing moves over here. And I was like, it was almost like, and he also said something that I thought was really very right on, which is that energy is a very difficult thing for people to understand. And I think that that is absolutely true.

David Keith  46:29  
Yeah, sure. I gotta go by now. But I think those are those are some anyway.

Robert Bryce  46:34  
Okay, what books are you reading?

David Keith  46:37  
Oh, man. I really, I really gotta go. I want to eat some food. Before my next meeting. I said I wanted to go.

Robert Bryce  46:45  
Okay. All right. Fair enough. My guest has been David Keith. He’s a physics professor of applied physics at Harvard University. You can find him on Twitter on the Harvard website, etc. David key thanks for being on the podcast. Appreciate it.

David Keith  46:57  
Thanks very much.

Robert Bryce  46:58  
Thanks for holding all your podcast and tune in for the next episode of power hungry podcast. Until then, see you

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