Four environmental experts weigh in on the peril and promise of a 'geoengineered' Earth

1816 was dubbed “the year without summer.” In 1815, Indonesia’s Mount Tambora erupted; the largest volcanic eruption in recorded history, it left a wake of catastrophic aftermath. “There were still on the roadside the remains of several corpses, and the marks of where many others had been interred: the villages almost entirely deserted and the houses fallen down, the surviving inhabitants having dispersed in search of food,” Sir Stamford Raffles, a British colonial officer, observed. In addition to lava and an eight-inch blanket of ash, the volcano belched out millions of tons of aerosol, effectively blocking large swaths of sun rays from reaching Earth’s surface, cooling the planet by three degrees celsius.

In 1992, in a province in the neighboring Philippines, there was another cataclysmic explosion. The eruption of Mount Pinatubo released 20 million tons of sulfur dioxide into the stratosphere, creating an expansive chemical cloud spanning 200 miles long, again blocking the sun’s rays, lowering Earth’s temperature by 0.5 degrees celsius over the next two years.

These naturally occurring cooling phenomena have today’s climate scientists wondering whether we, in service of combatting man-made climate warming, can use science and technology to simulate organic methods of lowering Earth’s temperature. Can we cool the planet? And, if we can, should we? Once considered the stuff of science fiction, geoengineering—the umbrella term for large-scale, intentional climate intervention—is now a radical solution for an ever-warming world.

Much in the same way that social distancing, masks, and ultimately a vaccine help flatten the Covid curve, climate intervention proponents believe engineering techniques—chiefly, solar radiation management—might “shave the peak” of average global temperatures by using different technologies to re-radiate sunlight out of the atmosphere. Shaving the peak may avert runaway climate scenarios or hothouse effects—feedback loops triggered in Earth’s climatological regime. One runaway scenario involves Greenland’s thawing permafrost: if it indeed melts away, it will reveal heat-absorbing earth, and possibly release methane deposits, the magnitudes of which will severely accelerate warming.

With 40 gigatons of carbon being pumped into the atmosphere each year, it seems unlikely that mankind will reach the two-degrees celsius reduction target of the Paris Climate Accord. As we edge towards climate midnight, radical solutions are looking more and more appealing. In our failure to change our habits, we now consider changing our habitat. So, geoengineering, once fringe science, has entered into the debate over what is scientifically possible and perhaps even necessary in the battle to preserve the planet.

“If there is to be an answer to the problem of control, it’s going to be more control,” writes author Elizabeth Kolbert. Kolbert, a staff writer at The New Yorker, is the author of several books, including the Pulitzer Prize-winning, The Sixth Extinction: An Unnatural History. For two decades Kolbert has traversed our blue planet investigating and communicating nature’s chief environmental stressor: humans. Her latest book, Under A White Sky: The Nature of the Future (out today!), is a study of man’s interventions in nature, including electrifying rivers and lab-grown super coral. “What could possibly go wrong?” Kolbert writes of these solutions, later asking, “What’s the alternative? Rejecting such technologies as unnatural isn’t going to bring back nature. The choice is not between what is, but between what is and what will be, which often enough, is nothing.”

Kolbert joins Document to moderate a roundtable discussion with David Keith, Kelly Wanser, and Holly Jean Buck, as they discuss—for all of its peril and promise—the future of climate intervention.

For decades, Harvard professor David Keith has led research on stratospheric aerosol injection, a solar radiation management technique, which involves uniformly spraying aerosols into Earth’s upper atmosphere to reflect sunlight away from the Earth, thereby cooling the planet. Keith, with a team of Harvard University scientists and researchers will undertake their first field experiment in June.

Kelly Wanser is Executive Director of SilverLining, an NGO working with stakeholders to advance research of large-scale technological innovations, namely Marine Cloud Brightening. MCB, as it’s known, involves seeding clouds with trillions of salt particles per second in an effort to make them brighter, re-radiating the sun’s heat away from Earth.

Holly Jean Buck is a professor of environment and sustainability at the University at Buffalo. Her 2019 book, After Geoengineering: Climate Tragedy, Repair and Restoration is a cogitation on power and equity and adds an edge of stark moral conscience to intervention discourse. Buck worries large-scale interventions will exacerbate inequity as we near deployment scenarios. A best case scenario, Buck writes, involves not writing these expansive programs or deploying these technologies at all.

Elizabeth Kolbert in Williamstown, MA. Photo by Alex Hodor-Lee.

Elizabeth Kolbert: Geoengineering is a term that’s often used and seldom defined. Can you define what you mean by ‘geoengineering’? If it’s a term you eschew, can you give us a better one?

Holly Jean Buck: I define geoengineering as climate interventions that are intentional and large scale. I see those as the two defining characteristics. I titled my book After Geoengineering in part because I think we need to move past this term and onto other ones.

David Keith: I don’t really have a strong opinion. The only thing that matters is that these two really quite different sets of things, carbon dioxide removal and solar geoengineering, are really distinct in policy and in technology. There’s nothing that relates them particularly, other than they’re all part of what we’re going to do about climate.

Kelly Wanser: I agree with both Holly and David. I actually like the term that Holly used when she described it, which is intentional large-scale interventions in the climate. That’s the term that the National Academies of Science adopted in 2015. [At] SilverLining we engage a lot with non-scientists and non-experts. We’ve found the term ‘climate intervention’ to be useful, in terms of its more accurate and intuitive understanding and a little bit less reactive in terms of how people see it.

Elizabeth: Can I ask you all what got you interested in this topic and should people everywhere be interested in it? If so, why?

Kelly: SilverLining’s mission focus is actually near-term risk—looking up what scientific assessments suggest might be the most prominent approaches to countering or arresting climate warming quickly. If you want to reduce warming quickly, these atmospheric climate intervention techniques appear to be the most promising way to do it. And so that’s what brought me into the equation.

David: I got involved in ‘89. I was part of a wonderful bottom-up group of graduate students at Harvard and MIT who were interested in lots of climate policy and science—and this was an odd topic nobody was working on.

Holly: I wanted to write a cyberpunk story about geoengineering. I saw a talk advertised in the Washington City paper about it. I thought I’d go to the talk and get some realistic details. This was in 2009 and the talk was at the American Enterprise Institute. The room was full of very well-credentialed, serious people talking about this as if it was going to possibly happen, so that was an alarm bell. Somebody asked the panelists what people in other countries think about this. And nobody could answer. And I thought, ‘Well, that’s something that needs more serious consideration.’ I just wanted to keep following it.

Elizabeth: Can I ask you all to briefly describe, once again, what specific aspect of geoengineering, as we’re defining it in this context, you’re working on these days? David?

David: A really broad range, from public policy to detailed technical stuff like a paper showing how you could do some science fiction-y tweak to the color of sunlight that’s reflected in a way that would allow you to bring both temperature and global precipitation back together.

Kelly: SilverLining’s primary mission is to advance research in this field so that society has an ability to assess options for responding to warming, primarily in the service of public safety. We work fairly extensively with a U.S. government system so we can see how we can move research forward. And we also work in the arena of communications and engagement with the public.

Holly: My work is focused on scaling carbon removal in ways that can benefit communities, as well as policy for managing the decline of fossil fuels. I think we need more basic science on geoengineering and then there will be more roles for social science after a few more well-funded years of science research. That said, I do maintain an interest on how solar geoengineering research programs can be more international and inclusive.

“Everybody’s first reaction upon hearing this is that it’s crazy. That’s an entirely healthy reaction.”

Elizabeth: This question is aimed at David and Kelly: can you talk a little bit about the state of the science right now? Are we looking at something that we need big technological breakthroughs even to have the possibility of deploying?

David: We certainly don’t need technological breakthroughs to allow people to deploy some of these things in a crude way. It’s possible that deployment would be ill-advised or destructive, but the basic technological ability to do these things is here from preexisting technology. The technologies have been around for decades. While there are a big range of methods—space-based, stratospheric, cirrus clouds, cloud brightening, and surface—they’re all possible.

Elizabeth: I’m wondering if you’re seeing any changes as the odds of meeting some of these targets—that are set by the UN, the UNFCCC—seem increasingly unlikely to be met. Do we see a change in the conversation in the scientific community? In the policy community?

David: Things really feel different. I was invited to an important meeting in Bangladesh this spring, a part of the developing world that’s most engaged in climate risk. They wanted me to speak because they want some ownership and understanding of this topic. I think that’s a really healthy thing and a maturation on this topic that would not have happened two years ago.

Kelly: We’re a little over two years old as an organization, and I’ve seen changes since we’ve started. [Especially at] the international level. We work directly with policymakers too. That seems to have shifted and continues to shift year after year.

Elizabeth: To what do you attribute that?

Kelly: I attribute it to the evolution of this moving into more legitimacy building arenas. The National Academies of Sciences is currently undertaking a study to develop a research agenda. That sort of legitimacy-building tends to cascade on itself. At the same time, you have these major events in the natural system, which in the United States have been very dramatic and high profile. The fires in the West are at the heart of the communities of power and money, at least in technology.

Holly: In the past decade, we’ve seen moments of climate emergency. We’ve seen net-zero targets and corresponding interest in carbon dioxide removal, but compared to those changes, solar geoengineering seems, to me, actually stuck. If we imagine a world that was serious about researching it, what would that look like? That’s a very different situation than what we see right now. It hasn’t moved as much as I would have expected, frankly, a decade ago.

David: Interesting. I would agree, that we’re nowhere near close to a world that’s researching it seriously, but it feels really different from just a year ago. Suddenly I’m talking to people who are high-level government officials from around the world, U.S. senators and what not. There are now serious scientific meetings.

Elizabeth: Do you have a sense of why that is, David?

David: I don’t think it should be about this issue of the targets—the 1.5 or 2 degree targets. I think partly it’s just that this is naturally a slow thing. Everybody’s first reaction upon hearing this is that it’s crazy. That’s an entirely healthy reaction. In addition, there’s a sensible fear of [fossil fuel] addiction. Many people in the scientific elite and policy community tend to overstate the risks and understate the efficacy because they’re worried about addiction.

“I don’t want to live in a society where a secret scientific elite makes the policy decisions. That’s the job for democracy. Our job is to inform that process as honestly and transparently as we can and to have our own voices speak about what we think politically, but not to confuse the two.”

Elizabeth: There are some pretty prominent climate scientists who say, ‘We should not even be going near this. We should not be touching it.’ What do you say to those folks?

David: It’s crucial to do two things in science. One is to say, as a citizen, what you think should happen—including the risks for political misuse and abuse—and, separately, [to say] what the facts are. So, I think there’s actually a reasonable case you could make that solar geoengineering should be banned forever based on this addiction argument. But that’s not because of its physical risks or lack of efficacy. What I do not respect is fellow scientists who effectively hide the underlying acknowledgment of efficacy or exaggerate risks because of their separate view of the addiction risk.

Over the years of working on this I’ve had senior scientists tell me that we shouldn’t talk about it, though they agree behind closed doors that it can work. But they shouldn’t say we shouldn’t talk about it because it will inevitably get misused. I don’t want to live in a society where a secret scientific elite makes the policy decisions. That’s the job for democracy. Our job is to inform that process as honestly and transparently as we can and to have our own voices speak about what we think politically, but not to confuse the two.

Kelly: Right now we have a certain risk exposure and we lack sufficient tools for responses that can ensure our safety. In this context, we’re looking at the best possibility available to reduce warming quickly. To David’s point, generating information about the possibilities so that we can assess them, and assess them openly and together, is very crucial. Efforts to attempt to block the development of scientific information—we’re seeing what that looks like in today’s world now in public health.

Holly Jean Buck in Buffalo, NY. Photo by Alex Hodor-Lee.

Holly: I think that we have been shown that we kind of suck at following the science. There’s the science that we wish we had—the ideal science that’s producing this empirical objective knowledge—and there’s the science we have, which has been produced, in a world of incentives, by elites—not by diverse publics. I think that people are right to be wary about this. I still believe we need a lot more scientific research on this before we make judgements about whether it’s a good idea. There are particular areas such as impacts on ecosystems that have been understudied. So, what I would like to see is a broad, inclusive, publicly funded international research program that looks comprehensively at all the dimensions.

David: Totally agreed with Holly. I want that program to, most of all, avoid groupthink by focusing on all the ways it could fail. Instead of a single comprehensive program, I’d like to see some programs develop in ways that could work—really clear cut paths to deployment to reduce climate risks—and, separately, efforts that show all the way those things could fail. That’s how you reduce groupthink.

“We can experiment with scenarios and discuss them at a level that we couldn’t 50 years ago. But our models for governing are still what we had 50 years ago.”

Elizabeth: That does bring me to the next question that obviously hangs over this topic. When we define geoengineering as conscious large-scale intervention, that brings a whole new set of questions: who gets to decide and how the hell would you ever decide?

Holly: If you talk to members of the public, like I have for my research, almost everyone imagines there will be a global-level decision process because that’s the model we have right now. That’s what people are familiar with. It’s a challenge because representative democracy doesn’t always represent all of the people. There are regimes that are democratic in name but not in practice. Are there governments that are going to make decisions?

I think there’s also room for publics to learn and deliberate about this in ways that we’re not taking advantage of. We have the internet; we have this global infrastructure for networking, we can experiment with scenarios and discuss them at a level that we couldn’t 50 years ago. But our models for governing are still what we had 50 years ago. So we really need to update and think about how we use these new capacities to explore scenarios and explore techniques, weigh in, and integrate communities into the process at the research stages rather than afterwards.

David: Scientists’ values shouldn’t count more than anyone else’s. Scientists are part of the elite value group that may not reflect what people want. When you’re talking about the goals of a research program—not what’s inside, but what it’s trying to do—scientists should have no more say than anyone else, maybe less. Part of the way to do that is these citizen-driven systems that maybe aren’t what top-level representative democracy does very well.

“You can have a future with solar geoengineering that is far more equitable than the world we have today. But it could also be far more inequitable.”

Elizabeth: I was in Australia and they were looking at [geoengineering techniques, asking], ‘Could we use this to save the Great Barrier Reef?’ So there are going to be regional efforts. I’m not saying they are going to deploy but there are going to be people thinking, ‘Well, we’re going to do this for our region.’ How could we—how should we—deal with that?

Kelly: If you include the field of weather modification, and hydrology—snowmaking, rainmaking—this is already happening. There’s actually large-scale weather modification efforts in the western United States. Indonesia ran a program to make rainfall off the coast to try to mitigate floods earlier this year. China launched a program in the Tibetan plains to try to increase precipitation in an area they say is the size of Alaska. So these sorts of atmospheric efforts to mitigate impacts, we think are likely to grow as climate continues to warm. There are substantial questions about that in terms of the teleconnection effects and their potential influence on other places.

David: All the modern U.S. investigations of climate started with the Advisory Committee on Weather Control. It began, if I remember correctly, in 1957 as a consequence of unregulated cloud seeding. If each region could set its own climate the way it wanted, there would be no global governance problem. Local regions would [take them on] but that’s fundamentally impossible: the atmosphere is all interconnected by flows, heat, and momentum. So, even if you do apply some kind of geoengineering technology locally, there are necessarily non-local effects—teleconnections, as Kelly said.

Elizabeth: Are we just going to see more and more of that?

Kelly: Moving these things through scientific fora like the IPCC, the Montreal Protocol—places where scientific analysis can help form some of the questions about the risks, pros, cons, how we understand these things—is likely to help the development of the right decision-making structure. Some of these localized techniques fall under what are currently different laws or bodies. Most of them are subject to national jurisdiction. So you can grow things in your own jurisdiction even if they have teleconnection effects.

“The lesson is that technology won’t make the world more or less unequal, we have to fight that battle for justice reasons, but we can separately fight the battle of reducing climate risks—they’re interconnected.”

Elizabeth: One of the fears, which Holly talks about in her book, is that we’ll end up reproducing a lot of the same political and economic inequities that climate change is exacerbating right now. Is that a worry, Holly, with carbon removal—with land, land grab, carbon colonialism? Do you see the same issues arising with different forms of geoengineering?

Holly: The main point I was trying to make in that book is that these techniques can be used in a variety of ways—a variety of policies and effects. They’re not just one thing. They’re what we make them. So that’s a call for everyone to engage in helping to shape what future they want. You can have a future with solar geoengineering that is far more equitable than the world we have today. But it could also be far more inequitable.

David: Solar geoengineering is important but it’s not a big driver one way or the other of inequality. It’s just a truism that people with power have power to shape the outcomes. I would like a world where power is more diffuse. Where economic opportunity and justice was more diffuse. If I think about technologies that are really impacting that, geoengineering would be fiftieth on my list. Climate change overall isn’t that big a driver. The lesson is that technology won’t make the world more or less unequal, we have to fight that battle for justice reasons, but we can separately fight the battle of reducing climate risks—they’re interconnected. But we don’t solve problems when we make everything into one big ball.

Kelly: [I] don’t see this as terribly material to the equality question. But [I] do see it as material to the justice question. The most vulnerable people in society are most vulnerable (in the near term) to the impacts of climate change and one could view solar climate interventions as a form of abatement of mitigation for them. For people to stay in the locations that they’re at versus becoming climate migrants. This is an important debate to have: what we owe the vulnerable people in society, most of whom were not material to the cause of this problem.

Elizabeth: What’s your best hope for geoengineering and what’s your worst fear?

David: My best hope is that it is used imperfectly and with mistakes, with side effects, in a way that reduces climate risk for some of the most vulnerable ecosystems by a lot—like, half over the next century. My worst fear is the addictive response—that it’s used in a way that takes political will out of the need to cut emissions, that we end up driving emissions higher, which is the underlying climate risk driver.

Holly: My hope is that a rapid shift of social norms can push policies [to] scale up carbon drawdown so that we don’t need solar geoengineering. My worst fear is that there is continued delay on climate mitigation and solar geoengineering is introduced without adequate research, coupled with a politics of authoritarianism or xenophobia—that [geoengineering is] introduced as a way to stop climate migrants or packaged with toxic politics; that those forces feed each other. I hope we can avoid that.

Kelly Wanser in Boulder, CO. Photo by Alex Hodor-Lee.

Kelly: One of my biggest concerns is the state of what we don’t know. I would include in that both solar climate intervention and carbon dioxide removal at scale. My biggest hope is that in the next five years we can make major investments in climate research—in observations, in models, in impact assessment—that give us the ability to then assess the interventions, in something like a five-year time scale, to determine what would be relevant and safe to scale.

David: Holly, I think said, you can correct me, that you really hope that carbon removal goes so quickly that we don’t need solar geoengineering. All the evidence I know suggests that carbon removal will have much larger environmental side effects. As somebody who really cares about the footprint on the environmental world, I think there is a monsterous over-hype on carbon removal that will come back to bite the environmental community hard. People are just not being realistic or honest about the environmental or social consequences it entails.

Holly: I think phase-down has primacy, I think carbon removal is an important complement especially over the course of the century.

Kelly: From SilverLining’s perspective we’re really uncomfortable with the level of uncertainty we have now. That is the problem. We need to push knowledge very quickly in these things in order to make the right kind of decisions about them.

David: Really quick progress could be made on knowledge of solar geoengineering because it’s not some magic new technology. It’s a new application of [existing technology], of environmental science, of aerosol science, aircraft engineering of sprayers—a whole bunch of things that are already out there in the world. It’s possible to know much more about its risk and efficacy quite quickly because of that underlying body of knowledge.

“This is an important debate to have: what we owe the vulnerable people in society, most of whom were not material to the cause of this problem.”

Elizabeth: How has Covid changed how you think about your work?

Kelly: From our anecdotal point of view, in talking to different types of people around these issues, the COVID crisis has actually raised the profile of the relevance of science-based decision making [and] the problem with politicizing science or interfering with science. What we’ve seen at the public policy level and the general public level is an appreciation for why objective scientific information is important and why decisions based on science may be really critical to public safety.

David: I think the same underlying thing but the almost exact opposite of what Kelly said. I think that science itself can’t help us make better decisions. In fact, what [Covid] has shown us very sharply is the weakening structure of the U.S. I don’t think it’s just Trump. I think [Covid has] shown [us] a real gradual decay of the way the U.S. works as an advanced industrial society. The fact that the U.S. had some of the best science shows you really sharply that this isn’t about the quantity of science, it’s about the ability to make sensible social decisions about science. The U.S. is failing at [that] at a really extraordinary level. [When] you compare the deaths in a place like Seoul, Korea, a densely-packed innovative amazing city compared to New York City—that’s not about science, that’s about government. People in [the] solar geoengineering [community] overemphasize the U.S. But I think the U.S. gets less important, relatively every year. This COVID crisis is to me a breakpoint in accelerating the sense at which the U.S. is just less important than it thinks it is. I’m personally worried about U.S. stability. Watching this in Canada there’s ways in which it just looks like a train wreck.

Elizabeth: Watching it from the U.S. it still looks like a train wreck!

Holly: [Covid has] made me more concerned about groupthink in science and the need for safeguards against that, as David has discussed. It’s shown that we need more research on how the relationship between science and policy is mediatized by new platforms, such as Twitter and Facebook, both here and in other countries. Covid has highlighted how there might be problems that arise not from intervention itself, but with it being implemented poorly or undemocratically in an emergency context.

Alex: Elizabeth, do you want to answer the question also?

David: Yeah, weigh in!

Elizabeth: Obviously, anyone who looks at what’s happened with Covid, particularly in the U.S., as David alludes to, has to rethink a lot of what one thinks about humanity’s capacity for rationale. I’ll leave it at that.