Could Tweaking The Atmosphere Help Us Fight Climate Change?

26:36 minutes

earth from space
Credit: NASA/ISS Crew/Johnson Space Center

Last week, world leaders convened in Bonn, Germany to talk about reducing global carbon emissions to fight climate change. Meanwhile, the U.S. House Science Committee held a hearing about a rather controversial method to combating rising temperatures. It’s called geoengineering and it involves manipulating the atmosphere to cool down the earth.

Geoengineering techniques can be broadly classified into two categories: removing excess carbon from the atmosphere and reflecting sunlight back into space. But each of these techniques have their fair share of downsides.  

[The U.S. government has a mustang problem.]

Douglas MacMartin, a senior researcher at Cornell University who also testified in front of Congress at last week’s hearing, joins Ira to talk about the science and politics of solar geoengineering. Plus, Holly Buck, a postdoctoral candidate at UCLA, discusses how geoengineering could influence social ecologies. And, Peter Kelemen of Columbia University’s Lamont-Doherty Earth Observatory talks about his research on carbon sequestration as a way to fight climate change.

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Segment Guests

Douglas MacMartin

Douglas MacMartin is a senior research associate and senior lecturer of mechanical and aerospace engineering, and faculty fellow with the Cornell Atkinson Center for a Sustainable Future at Cornell University. He’s also a visiting associate in computing and mathematical sciences at the California Institute of Technology.

Holly Jean Buck

Holly Jean Buck is a NatureNet postdoctoral fellow with the Institute of the Environment and Sustainability at the University of California, Los Angeles. She’s based in Los Angeles, California.

Peter Kelemen

Peter Kelemen is a professor of earth and environmental sciences at Columbia University’s Lamont-Doherty Earth Observatory. He’s based in Palisades, New York.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow.

For the last three years, global carbon emissions were flat. They weren’t decreasing, but at least they were not going up. But this year, that last bit of consolation may be gone. An international team of scientists announced last week that global carbon emissions are projected to go up by 2% in 2017. We’re dumping much more carbon in the air this year.

So what can be done? Well try to discuss cutting back emissions, and you devolve into an ugly political battle, as you may have heard. But if you don’t get into the discussion about whether climate change is man made, but attacked from the position of how to mitigate it, then it appears that a useful, political free, discussion can be had. By grabbing excess carbon in the atmosphere, storing it somewhere harmlessly? Well that’s a possibility. How about spraying sulfur into the atmosphere, creating a chemical layer to reflect some sunlight back into space and cooling the earth down? All these techniques fall under something called geoengineering, a controversial set of tools that, nonetheless, has caught the attention of Congress, where one of Congress’s greatest skeptics about climate change convened a hearing, where they discussed the science of geoengineering.

LAMAR SMITH: As the climate continues to change, geoengineering could become a tool to curb resulting impacts. Instead of forcing unworkable and costly government mandates on the American people, we should look to technology and innovation to lead the way to address climate change.

IRA FLATOW: That’s Lamar Smith, the Republican who heads the House Science committee, at a hearing on geoengineering last week. And that’s what we’re going to be talking about this hour, if you want to talk about it with us, our number is 844-724-8255. You can also tweet us @scifri, S-C-I-F-R-I.

Let me introduce my guests. Douglas MacMartin is Senior Researcher of Mechanical and Aerospace Engineering at Cornell University in Ithaca, New York. And he testified at the House Science committee hearing last week. Welcome to Science Friday.

DOUGLAS MACMARTIN: Hi, Ira. Thank you, glad to be here.

IRA FLATOW: Holly Buck is a post-doctoral fellow at the Institute of Environment and Sustainability at UCLA. Welcome to Science Friday.

HOLLY BUCK: Hey, good to be with you.

IRA FLATOW: You’re welcome. Peter Kelemen is a professor of Earth and Environmental Sciences at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York. Please, welcome to Science Friday to you.

PETER KELEMEN: Great, thanks. Happy to talk with you.

IRA FLATOW: It’s nice to have you. Douglas, can you quickly explain geoengineering? How would you describe it to someone who’s never heard of it?

DOUGLAS MACMARTIN: Carefully. Usually, the problem is that you need to start with a few sentences of caveats. So none of these– and the first caveat is simply to just be really clear up front. This shouldn’t be thought of as a substitute for cutting our carbon emissions, it really should be thought of as a couple of options that we might consider to add on top of that. It basically falls into two broad categories. One is basically pulling carbon dioxide out of the atmosphere, so CDR, for carbon dioxide removal. And the other is basically ideas that would reflect some sunlight away from the planet. SO CO2 warms the planet, if I reflect a little bit of sunlight away, that’s going to cool the planet and keep the changes from getting worse.

IRA FLATOW: Now you were present at the House Science committee hearing, you were an expert witness. What was it like being there?

DOUGLAS MACMARTIN: It’s a fun experience. I think the thing that’s most surprising to me was, I was sort of going in trying to practice all of my– how do I respond to climate skeptics? And there wasn’t any of that. So it was actually remarkably bipartisan and remarkably positive, in the sense that the questions were generally pretty good. Everybody was very curious and just trying to actually understand the science and how are we supposed to think about this.

IRA FLATOW: So you were able to talk about mitigating climate change without having to have them admit there was climate change.

DOUGLAS MACMARTIN: I think they did actually, effectively, admit that there was climate change. And I think the key thing is that, as soon as you– if you talk about regulating carbon dioxide, regulating fossil fuels, and cutting our emissions, then you immediately get into practically political warfare. This has been highly politicized. But if you take that part out, and you just talk about the science, then you get a remarkably bipartisan discussion. So actually, that quote that you gave from Lamar Smith, he did use the word instead. Which is a word that I would clearly disagree with. I don’t think that you can use these techniques as an alternative to cutting your emissions. But more that it’s unclear that cutting emissions is going to be good enough.

IRA FLATOW: I hear you. Holly, you’ve been following the hearings. What did you think of them?

HOLLY BUCK: I agree with Doug’s assessment that it was generally more positive than, at least I, expected. I think hearings can be a funny kind of theater. I think you need to take this one in the context of other hearings that have been on this topic. The messages were rather similar, but the context is so different now, with an administration that wants to pull out of the Paris agreement.

IRA FLATOW: Did you find it ironic that it was happening at the same time as the Bonn meeting, the international meeting in Bonn was going on?

HOLLY BUCK: Yeah, I suspect that was somewhat intentional. I also think that it’s interesting that geoengineering is something that you don’t have to talk about the human side of the problem. As Senator Inhofe, you might remember, from the famous snowball incident, asked at a hearing back in 2007, when geoengineering came up, he said, his question was, does geoengineering make sense, even if global warming is a natural phenomenon? So they were kind of framing it as a way to escape that part of the discussion.

IRA FLATOW: Peter Kelemen, let’s get into a little bit of the nitty-gritty of some of the science and technology, here. I know that you study carbon capture, one method that could be used for geoengineering. Tell us what that is and what do you make of congressional attention to this now?

PETER KELEMEN: Well, let’s take that in two parts. In a nutshell, I’m studying the weathering process of rocks from the Earth’s interior, the mantle. And there are some places where the mantle is pushed up toward the surface by plate tectonics, and then exposed by faults and erosion. And the mantle is very far from equilibrium with the atmosphere and the ocean. And so that creates a huge chemical potential, kind of like a big battery, that drives carbon dioxide uptake from air to form solid carbonate minerals. And so this natural process is very widespread and it’s possible that we could come up with ways to accelerate it considerably, in order to remove CO2 from air, at a level that would matter, compared to human emissions. So that’s the science side, in brief.

How do I feel about it? I feel that it’s a big mistake to view this kind of thing as a get out of jail free card. It would be immensely less expensive and more practical to switch to a low carbon energy economy, via renewable energy sources. So just to give you an idea of the scale. To remove– let’s say we overshoot a sustainable carbon dioxide concentration in the atmosphere by 100 PPM, so 20% of the current carbon content. That, to get back, to withdraw 100 PPM from the atmosphere, requires removal of 1.8 trillion tons of carbon dioxide. Because you have to take it, not only from the air, but also from the surface ocean. And that’s just an enormous amount. So at $50.00 a ton, that corresponds to $90 trillion to remove it. If we did that over 30 years, it would be 3% to 4% of global GDP. So it’s just an enormous task. And it would be far better to avoid that.

IRA FLATOW: And Douglas MacMartin, I know, instead– you look at the sky, do engineering involving particles in the atmosphere and clouds, and that was something that had been suggested, or at least talked about, at the committee hearings, correct? As a way to reflect the sunlight?

DOUGLAS MACMARTIN: Yeah, so that’s– the things that Peter just talked about, and there’s a variety of ideas in that category, in some sense, there’s no climate risk. You’re solving the problem directly by taking the CO2 out. And the issues there, as Peter said, they’re basically their cost, their scalability, and then, for some of the ideas that’s discussed, then there’s potentially significant local issues, competition with food crops or things like that.

The ideas for reflecting sunlight, there’s two main ones. One that we know with absolute certainty would work, in the sense of cooling the planet, is just by observing– every time you get a very large volcanic eruption, there’s another one that may be going off soon in Indonesia. A volcanic eruption puts large amounts of sulfate into the stratosphere, and that cools the planet for a year or two. And so the idea would, roughly speaking, be directly put that material in the stratosphere, ourselves, where it would reflect sunlight away, and that would cool the planet. Two– so the stratosphere, just for context, is significantly higher than where aircraft fly. And all of our life, we live in the troposphere, which is well mixed. If you put pollution in the troposphere, it rains out within a week or two. But if you get high enough in the atmosphere, you can put material there and it basically just stays there for a year or two, before it comes down. So you don’t have to put very much in.

The problem, basically, is– well, there’s a number of problems. One is, that if you add CO2 to the atmosphere and warm the planet, and then you cool it by reflecting sunlight away, that doesn’t affect the climate the same way. So if you look at it as, for a given amount of CO2 in the atmosphere, would some amount of solar geoengineering help? The answer is maybe. It would certainly bring the temperatures down, and so that might be important for protecting ice sheets, avoiding heat waves, all of the impacts that you’re used to thinking about in terms of climate change. But if you ask the question, is it better to cut the carbon emissions or to do some sort of solar geoengineering? That answer is pretty easy. That it’s much, much less risk to just cut the carbon emissions.

So I mentioned the stratospheric aerosols. The other suggestion that’s been made is a little bit more uncertain. I guess that made sense. Which is trying to make clouds brighter. So if you go over the ocean, where you have low lying clouds quite often, and you basically spray salt water into the clouds, the water evaporates, you get little tiny droplets of salt, and that forms more condensation nuclei for the clouds, and, in principle, the clouds then are brighter and reflect more sunlight away. So that’s another idea that could potentially work to keep the planet cooler.

IRA FLATOW: But these are, I guess to do these things with the atmosphere, and the reflectivity option, we’re doing a giant experiment on ourselves, aren’t we, Holly? I mean, we have no idea what the outcome of these things are going to be.

HOLLY BUCK: Yeah, I’m concerned that there’s not enough ecological research on this topic. How it would impact biodiversity and non-human life. Because we don’t know if it could help to save species, or worsen the extinction crisis. You have different type of light coming down, more diffuse light. You have new precipitation patterns, and on top of that, high CO2 concentration. So that’s, ecologically, a novel environment.

IRA FLATOW: I’m Ira Flatow, this is Science Friday, from PRI, Public Radio International. Talking about the environment and the hearings and possible mitigation by geoengineering. Coming to you from Louisville Public Media.

Holly, tell us about the social impact of this. I remember years ago, I went to Florida, and I covered cloud seeding. We’re talking a long time ago, over three decades ago. And experiments about whether you could get it to rain by going up and spraying silver iodide by planes through clouds. And they conducted the experiment, but then sort of stopped them. And I asked why, I asked one of the scientists why they stopped them. And they said, well we don’t know what the impact’s going to be. We don’t know if it’s going to rain more here, or more there, who’s going to get gored by this. So is that is that part of what you’re afraid of?

HOLLY BUCK: Well one part of the social side is the impacts on people and human systems. And the other part of the social side is how can citizens be involved upstream in the research and design of these technologies, rather than just getting impacted by them after they’re developed? In terms of public perception, there have been about 30 empirical studies, and I’d say the one thing we know is that most people have no knowledge about this. Probably about 10% of people have heard about it, which is really not enough for a good discussion.

IRA FLATOW: Do you feel like there isn’t enough awareness about geoengineering, is that what you’re saying? We need to talk more about it? Can you give us an example, or do we know what people think about it?

HOLLY BUCK: We know that increased concern about climate change correlates with increased interest in learning more about solar geoengineering. But there’s a big difference between supporting research and supporting actually doing it. A lot of people are supportive of research, just because they think science, in general, is interesting, and that things should be found out about. I’d say that people have remarkably similar concerns, if you look at results from focus group discussions about whether we can control this, what are the side effects, and what are the unknown unknowns.

IRA FLATOW: Let’s see if I can get a call in here before we have to go. Let’s go to Joe in Gainesville, Florida. Hi Joe.

JOE: Hi, Ira. Say, if we could sequester the carbon in underground, let’s say, or wherever, what will happen in the future if, by chance, through a seismic event or other natural occurrence– what will happen to the carbon?

IRA FLATOW: Good question.

PETER KELEMEN: Let me respond to that. So if we were to convert CO2 to solid carbonate minerals, that’s essentially permanent. Because you’re making the CO2 into limestone or marble. And on a human time scale, that lasts forever. It wouldn’t be released by earthquakes or any other process.

IRA FLATOW: Is it possible to sequester it in the oceans? We’ve heard talk about you can bring the carbon dioxide down into the oceans, it’ll sort of turn into rock down there.

PETER KELEMEN: There are several options that have been proposed. Probably, the most benign is to add calcium or magnesium to the ocean, and that will draw CO2 from the air and also act to mitigate ocean acidification. Right now, because of the International Convention on Dumping in the Oceans, that is kind of a no-go, but all of these different proposed techniques have regulatory hurdles and environmental downsides. So until people get really concerned about this problem, we’re going to be doing research, but we’re probably not going to implement any of these things at scale.

IRA FLATOW: All right. We’re going to take a break. And when we come back, more on engineering the climate. You can give us a call, you can also tweet us @scifri, S-C-I-F-R-I. We’ll be right back after this break stay with us.

This is Science Friday. I’m Ira Flatow. We’re talking about the geoengineering, and why the House Science committee is interested in this solution as an alternative to cutting greenhouse gas emissions. Talking with my guests, Douglas MacMartin, senior researcher at Cornell University, Holly Buck, post-doctoral fellow at UCLA, Peter Kelemen, Professor of Earth and Environmental Sciences at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York. Also, you can tweet us @scifri, S-C-I-F-R-I, and also, we’re taking your calls at our usual number.

There’s some interesting tweets that are coming in about unintended consequences. Maybe I’ll ask this to you, Douglas. People are saying if you’re going to reflect the sunlight, and cool the earth that way, what about the plants that need sunlight for photosynthesis, is that going to cut down on what they need?

DOUGLAS MACMARTIN: Well the short answer would be yes. But you don’t have to reflect very much sunlight. So if you wanted to– so for context, the Paris Agreement, for instance, said we should make sure we stay below 2 degree global mean temperature rise, above pre-industrial, that’s Celsius. And really try to stay above 1 1/2 degrees, below 1 1/2 degrees, but we’re likely– the promises that were made as part of the Paris Agreement are going to put us, probably, closer to a three degree warming. So you’ve got at least 1, 1 1/2 degree greater temperature than what the general consensus is is safe for the climate. And recognizing that we don’t actually know what’s safe.

If you wanted to reduce the temperature by about 1 1/2 degrees Celsius, you need to reflect about 1% of the sunlight back to space. So the total amount of sunlight you’re reflecting isn’t very much. Holly mentioned this increase in the diffuse light. So it is true that– we talk about doing– that you could do this with sulfate, mainly because that’s what volcanoes do, and so we know that sulfate occurs naturally in the stratosphere from time to time. Sulfate is not actually a very good back-scatterer, so to reflect 1% of the light back to space, you actually scatter a fair amount of light. And so you actually– the sun would be a little bit dimmer, and the rest of the sky would be a little bit brighter. And the short answer is we don’t know what the impact of that would be on plants. I think you could write down, actually, quite a long list of things that we don’t know. [INTERPOSING VOICES] [INAUDIBLE] conducting a giant experiment.

IRA FLATOW: Yeah, are we not doing that?

DOUGLAS MACMARTIN: Yeah, well, we’re doing that right now, that’s the problem.

IRA FLATOW: I see. Just trying to change the experiment. Let’s go to the phones, go to Amy in Manhattan, New York. Hi, Amy, welcome to Science Friday.

AMY: Hi, thank you. I think you maybe touched on this a little before, that this method would come with this temperature, but by itself, it wouldn’t actually reduce carbon emissions. And I’m thinking about the effect that would have on the ocean, someone mentioned acidification. And I’m thinking about what that would do to the coral reefs and all the life that depends on them.

IRA FLATOW: Good question.

AMY: Could they be addressed separately, or how does that work?

IRA FLATOW: Doug, Holly, Peter? The ocean is acidifying.

PETER KELEMEN: I’ll jump in, here. So it’s a big problem. And in fact, there’s been some modeling studies, again, everything’s very uncertain, but there have been some modeling studies where if you use solar radiation management for a decade or two, and then you stopped for some reason, the chances are that, in addition to the ocean acidification that would accumulate over that time, the temperature would rise very rapidly to the level that it would have had if you hadn’t been reflecting sunlight. And so, at best, I think solar radiation management provides a stopgap, during which time interval, you could try to remove carbon dioxide from air. Otherwise, you’re stuck with doing it forever.

IRA FLATOW: Let me get back to a point that was made at the beginning. The Science committee was trying to concentrate on the costs involved in mitigating or not mitigating. Give us an idea– you touched on it briefly, give us an idea of how expensive doing these things would be, compared to expense of just reducing carbon emissions. Who’d like to tackle that?

PETER KELEMEN: Well I mentioned some dollar amounts for carbon dioxide removal from air, and it’s fairly expensive, as I said. If we amortized removing 100 PPM of CO2 from the atmosphere over 30 years, it would correspond to about 3% of GDP, globally, which is a lot. But you should look at that against the background of– in large metropolitan areas, we currently spend about 2% of GDP just handling human waste. And no one thinks that money is misspent. So when the day arrives, when people think that putting carbon dioxide in the air is like throwing poop in the street, then 3% of GDP might not seem like very much money. Until then, it’ll be viewed as an expensive thing to do.

DOUGLAS MACMARTIN: I can jump in just a little bit, with the costs on the solar geoengineering stuff. Cost is– it’s effectively free, it doesn’t actually matter what the cost is. Because all of the issues with it are the things other than the cost. They’re are all the risks and the impacts and things.

IRA FLATOW: And who’s going to share the costs? How do you split up this, it’s an international, a worldwide, problem.

HOLLY BUCK: Well what I’d like to add is I don’t think that some members of the House Science committee understood that solar geoengineering comes with both carbon removal and mitigation as part of the package. Because, as was just mentioned, unless you do the carbon removal, you’re stuck with solar geoengineering indefinitely, and you risk that termination shock if it gets interrupted. So the costs of carbon removal are going to be probably the biggest part of it. And then carbon removal, in turn, implies large amounts of mitigation. Because all of the ways we know to remove carbon are very energy intensive, so they need to be powered by new renewables in order to actually be negative.

IRA FLATOW: Holly, you were just at the climate engineering conference last month in Berlin, where the world’s top experts in geoengineering were gathering, and one thing the conference has been criticized for is how few women experts were invited. You’ve written about this issue before. Who’s doing the science and who will be affected by it?

HOLLY BUCK: Yeah, I think that in some sense, it faces the problem of STEM science, more generally, and science technologies. How can we get more women involved in the field? But I also think this is a little bit special because there’s kind of a narrative of masculine attempts to control the climate, as a backdrop. And scientists are largely the ones framing this idea, who give voice to it. I did a study some years ago, where I counted the statements in the press made by women, and just 3% of them were by women. So it has been men articulating this concept and what it means. That’s one issue. Then there’s the issue of whom it impacts and benefits. And then there’s an issue about participation in decision making and goal setting.

IRA FLATOW: Now this is not the first time that Congress has talked about geoengineering, Doug, is it?

DOUGLAS MACMARTIN: No, there was a hearing, I think it was almost exactly eight years earlier, to the day. So I think it was 2009. And in fact, if you actually go back, the first time that a president was briefed on climate change was Lyndon Johnson, in 1965. And geoengineering actually was mentioned in that discussion, as well.

IRA FLATOW: Wow So you can’t be accused of not talking about this a while ago, and thinking about it.

DOUGLAS MACMARTIN: To Holly’s point, about using these things in concert, I tried to tell them that in the hearing. I’m not sure they got it.

IRA FLATOW: But you made a major point before, is that the hearing was predicated on the idea that you could geoengineer your way out of the problem. The high tech solution. And what I hear all of you saying today is that you can’t do that, this has to be one part of the solution that goes along with reducing carbon emissions. Would that be a correct summation?

PETER KELEMEN: Absolutely.


IRA FLATOW: All right. I want to thank you all for taking– that’s a good way to end it– time to talk with us. Douglas MacMartin, senior researcher at Cornell University in Ithaca, Holly Buck, post-doctoral fellow UCLA, Peter Kellemen, Professor of Earth and Environmental Sciences at Columbia’s Lamont-Doherty Earth Observatory in Palisades, New York. Thank you all for taking time to be with us.

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