Is It Time to Consider Dimming the Sun?



Harvard’s Solar Geoengineering Research Program studies a climate intervention strategy that sounds straight out of a science fiction novel. In the past, scientists and politicians have written off solar geoengineering as too risky to even study. But as the planet approaches dangerous levels of warming, that calculus may be just about to change.



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Walking past Oxford Street’s nondescript, brick laboratories, you’d never suspect that inside one, Harvard scientists are researching a technology that could radically alter the climate in our lifetime: solar geoengineering, the effort to dim the sun.

Harvard’s Solar Geoengineering Research Program (SGRP) studies a climate change strategy to cool the earth which sounds straight out of a science fiction novel. If ever implemented, it would entail flying a suite of aircraft 30-odd miles above earth’s surface to inject millions of tons of sulfate particles into the air. High up in the stratosphere, these particles would shroud the globe in a chemical mirror, reflecting away some of the sun’s radiation before it could be trapped by greenhouse gases.

The chemistry is powerful: just a few grams of sulfates in the stratosphere can offset warming from one ton of carbon dioxide, a ratio of nearly 1 million to one.

For all its potency, solar geoengineering cannot serve as a replacement for cutting CO2 emissions. Instead, researchers imagine it could buy time for the transition away from fossil fuels or, assuming this transition comes easily, further minimize the human suffering caused by warming.

The scientists working on it sometimes liken it to engineering a giant, continuous volcanic eruption. In 1815, the eruption of Indonesia’s Mt. Tambora, the largest in human history, released a cloud of ash and sulfates into the stratosphere, blocking out the sun and cooling the planet by an average of 2 to 3 degrees Celsius for over a year. The more recent eruption of the Philippines’ Mt. Pinatubo in 1991 caused nearly 1 degree Celsius of global cooling, often cited as proof that solar geoengineering would work remarkably well.

But volcanic eruptions, evidence of solar geoengineering’s promise, are also evidence of its potential devastation. Pinatubo, by blocking the sun, disrupted the water cycle and thwarted that year’s Indian monsoon, usually crucial to the region’s agriculture. The ozone layer that year also saw an abnormal dip. The year after Tambora, 1816, was dubbed the “year without a summer” for its heavy snow and frost through the summer months; its doom and gloom is said to have inspired Mary Shelley’s “Frankenstein.”

Pinatubo and Tambora are not perfect analogies: solar geoengineering would rely on a different chemical composition of aerosols, and would need to be deployed continuously, unlike a one-time eruption. It would be a climate intervention with no natural precedent at a similar scale — and, in meddling with complex climate systems, would entail complex risks.

Scientists can predict some potential risks from climate models and small lab tests, like an increased chance of acid rain and higher air pollution (sulfates fall back to the earth as pollutants after a couple years). A white, starless sky above our heads. But some risks we may not know, or be able to know, until we deploy the technology itself — and then it may be too late to fix them.

And in addition to the physical risks, both the research and deployment of solar geoengineering give rise to thorny questions about ethics and governance. Among the most contested, the so-called “moral hazard” question: if we seriously considered solar geoengineering, could it decentivize us from cutting emissions or deflate climate justice movements? Given its global implications, who would deploy solar geoengineering, and when? Who would decide what temperature to set the globe to, or when to stop? If something went wrong, who would bear the burden?

The technology is not a new idea — it was proposed as early as 1965, in a memo to President Lyndon B. Johnson — and a few scientific papers delved into the topic in the ’80s and ’90s. But until recently, solar geoengineering hasn’t been studied seriously in the scientific community, let alone considered as a policy option. SGRP, founded in 2017, was one of the first dedicated research centers in the field; a few others, including at Cornell and Stanford, have followed suit.

Though overall funding is still minimal, momentum is building: a recent report from the National Academies of Science, Engineering, and Medicine recommended the U.S. invest $100 to 200 million in a coordinated federal research program on the subject. Solar geoengineering was once a fringe idea, too risky to consider studying — now, the calculus might be changing.

This year has already brought a litany of climate change impacts. In June, temperatures reached 121 degrees Fahrenheit in Canada. In China, subway riders were up to their necks in water, inundated by a year’s worth of rain in a single day. In California, the Dixie Fire burned nearly an unfathomable million acres of land. If that’s not evidence enough, the Intergovernmental Panel on Climate Change’s most recent report confirmed that climate change is “widespread, rapid, and intensifying.” UN Secretary-General Antonio Gutteres called the report a “code red for humanity” and the evidence “irrefutable.”

And we’ve only warmed the world 1.1 degrees Celsius — or around 2 degrees Fahrenheit. The IPCC recommends we keep warming to 1.5 degrees Celsius, 2 at most. Currently, we’re on track for 3 or 4 — a benchmark which would bring catastrophic, exponentially worse impacts. The COP26, the UN environmental summit convening world leaders, may well decide which target the world reaches, and how quickly.

Lives, current and future, are at stake — lending a new sense of urgency to climate strategies, and justifying a second look at the options at hand. As the planet reaches an inflection point, debates around solar geoengineering research function as a sort of litmus test. How bad do you think the current state of the climate is? And what risks are you willing to stomach to reverse directions?

A Planetary Painkiller

Harvard professor David W. Keith has been urging people to take solar geoengineering seriously for over a decade, and has been researching it for even longer. Now, as the co-founder and leader of SGRP, Keith is one of the most prominent faces in the small but growing field.

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Keith teaches Applied Physics at SEAS and Public Policy at HKS, leads SGRP, and runs a carbon capture company, Carbon Engineering, on the side. With his free time, he likes to go on multi-week wildlife trips — hiking, backcountry skiing, even ice climbing — to remote destinations. He has the look of a mountaineer: wiry and rugged, a little severe. He debates like one too, anticipating rebuttals, challenging vague questions, and navigating through arguments with frightening ease. By the end of our interview, he manages to make solar geoengineering, an intuitively terrifying prospect, seem inescapably logical — if not to deploy, at least to research aggressively.

In a 2007 Ted Talk, viewed 84,000 times to date, Keith paces the stage, advocating for more research on solar geoengineering. He stresses that rapid warming will inevitably push future leaders to consider deploying the technology; although little-studied, it stands out amongst other climate interventions as particularly cheap and feasible to employ. “We should move this out of the shadows and talk about it seriously,” he says, leaning forward to look the audience dead in the eyes. “Because sooner or later, we’ll be confronted with decisions about this, and it’s better if we think hard about it.”

Though Keith’s delivery has changed since then, his core argument for solar geoengineering research has stayed consistent: solar geoengineering is an imperfect technology with myriad risks, but has serious potential to save lives, especially for those in vulnerable regions of the globe. Keith counts on his fingers a spate of climate hazards the technology could mitigate: peak temperatures, disruptions to regular precipitation patterns, typhoons, and hurricanes.

Keith was first “sucked into” researching the subject as an MIT graduate student in the late 80s. At the time, it “was one of the topics that nobody was dealing with,” he says. He recalls that he and his fellow graduate students working on various climate interventions were “ahead of our professors in a way,” and the effort was “very much bottom up.”

Since then, he’s tried to bring solar geoengineering out of the shadows and into the public eye. He’s published a book, written op-eds, given multiple Ted Talks, and even made an appearance on The Colbert Report, all with the goal of bringing solar geoengineering research into the mainstream. It hasn’t been easy — people used to “inch away” from him at conferences when he brought up solar geoengineering, Keith told the New York Times in 2017. But he’s continued his efforts because he is convinced that solar geoengineering is not a sci-fi fantasy to be dismissed; it is a powerful, though dangerous, tool that does what other climate strategies cannot: cool the planet quickly and cheaply.

Keith is careful to state that solar geoengineering is not a substitute for cutting emissions — “nobody who has a brain” is saying that, he quips. But he also differentiates between the two. Decarbonization, or cutting emissions, stops the flow of new carbon dioxide into the atmosphere, preventing any additional warming. But even if we cut emissions today, the climate would continue warming. Historical emissions stay in the atmosphere as long as 1,000 years, locking the planet into a certain amount of warming. “With emissions cuts, the underlying thing is all we can do is stop making the world worse,” Keith says.

Instead, Keith envisions using solar geoengineering in conjunction with decarbonization and carbon capture to keep temperatures low while we cut emissions. Though he admits the climate models have their uncertainties, he’s pretty certain solar geoengineering would work to cool temperatures: “I know solar geoengineering could keep temperatures to 1.5 or 2,” he states.

Frank N. Keutsch, his colleague and a professor of Engineering and Atmospheric Science at Harvard, compares solar geoengineering to a “really strong painkiller” for the planet: like an opioid, solar geoengineering comes with side effects and the potential for abuse, but also may be instrumental in taking the edge off a painful transition to a net-zero world.

Though Keith is careful to specify that he is an advocate for research, and not deployment, he has envisioned what deployment could look like: ten jets could fly around the stratosphere, 70,000 feet above the earth’s surface, spraying reflective particles that could provide global cooling — all for around $1 billion a year, he told the New York Times in 2017.

Not everyone is convinced by this scheme.

The risks, physical and social, still outweigh the potential benefits of cooling, skeptics argue. Of particular prominence is moral hazard: what if solar geoengineering diminishes how important the public, or policymakers, perceive cutting emissions to be? Another is “termination shock,” the painful consequence of stopping the technology once deployed.

According to Raymond T. Pierrehumbert ’76, a physics professor at the University of Oxford, the cooling effects of aerosol injection last only one to two years, meaning that solar geoengineering would require continuous upkeep. If we were to deploy the technology and then suddenly stop, we’d pay a steep price — in the compressed span of five to ten years, the climate would warm back up to its previous temperature. Pierrehumbert fears that moral hazard could exacerbate the situation — if we fail to rapidly cut emissions and instead choose to pump more and more tons of sulfur into the stratosphere, this backlash would balloon.

Keith is ready with rebuttals: moral hazard, he says, is a serious concern but could also go the other direction. If people know scientists are taking something as radical as solar geoengineering seriously, they might be doubly incentivized to cut emissions, recent papers suggest. Keith also imagines we could avoid termination shock by slowly phasing out solar geoengineering over the span of 100 to 200 years, all the while using carbon capture technologies to remove the CO2 already in the atmosphere.

Pierrehumbert maintains that society is too disorderly to ethically maintain solar geoengineering efforts through potential wars, famines, and other disruptions, and that carbon capture technology is as of yet expensive and difficult to scale. To him, counting on CO2 removal as an exit strategy is a form of techno-optimism: “It’s like jumping out of an airplane and hoping someone invents the parachute before you hit the ground,” he says.

For Keith, assuming the worst is “close-minded,” and not good science. “In academia it’s our job not to be dismissing things just because they sound bad,” he argues. To dismiss a potential tool for good, as he frames it, would be nothing short of immoral, especially considering that governments may be highly tempted to deploy it to mitigate climate suffering.

“My view is that, in general, it’s very hard to be confident about how the future will unwind, but knowledge is better than ignorance,” Keith says.

In 2017, Keith crystallized his interests into a formal research program, co-founding SGRP along with Gernot Wagner, now a professor at New York University. Finding funding was difficult at first, says Keith, but later funders began to “knock on the door” to give him money. With over $16 million in funding from private foundations and philanthropists, including Bill Gates, SGRP is one of the best-funded programs of its kind in the world. It strives to take an interdisciplinary approach, providing research grants not just to physical scientists, but also social scientists and ethicists.

SGRP is still one of the most prominent research efforts in solar geoengineering, though others have sprouted up since its founding. There’s evidence to suggest solar geoengineering might finally be emerging from the shadows: Congress has allocated modest funding for solar geoengineering research — $9 million out of the National Oceanic and Atmospheric Administration’s $182 million climate research budget is earmarked for studies of “stratospheric conditions and the Earth’s radiation budget.”

Pierrehumbert, who has tracked the field for over a decade, attributes the growing political appetite for research in part to Keith’s advocacy for it, advocacy he fears is only bolstered by the credibility of the Harvard brand name. “Anything that's done at Harvard just is stamped in the public eye as something that has a lot of legitimacy,” he explains.

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But for Keith, the cultural shift was bound to happen — and still remains slow-going. Whether solar geoengineering research is still taboo or not is “in the eye of the beholder,” Keith says, noting it was not included in the most recent IPCC report. The NASEM report is “thrilling,” Keith told Science in March, but he still wants to see more funding. “There is essentially no research going on,” he said in a 2019 talk at the Harvard Museum of Natural History. According to Keith, the current global budget for climate research is around $10 billion — he’d like to see 5 to 10 percent of it, or at least $500 million, spent on solar geoengineering.

Still, Keith believes thinking around solar geoengineering is moving in the right direction. “The direction is clearly that people are willing to talk about it more,” he says. And as funding scales up, albeit slowly, research is also moving out of the lab and into the field, bringing debates about solar geoengineering onto a new stage with higher stakes. Earlier this year, SGRP planned to launch a field test called the Stratospheric Controlled Perturbation Experiment, or SCoPEx, under the guidance of Keith and Keutsch.

Originally planned for June 2021, SCoPEx would have marked one of the first field tests contributing to solar geoengineering research — if not for the public backlash that caused its cancellation. Researchers planned the tests to occur in Sweden, coincidentally over indigenous land, but did not reach out to the resident Saami people four months before the first test flight. “The essence of solar geoengineering technology is composed of unknown risks we cannot take as a global community, for the sake of our future generations to come,” wrote the Saami Council in one of two open letters protesting the experiment. In response, SCoPEx was postponed, and now stands at a bitter impasse.

Though the scope of the experiment was small, its symbolic significance looms large, as does the backlash it inspired. Academics like Keith and Pierrehumbert have been talking in circles about solar geoengineering for decades, but through field tests, the public encounters the idea for the first time. And as solar geoengineering teeters on the edge of the mainstream consciousness, SCoPEx might push it one way or the other.

Both advocates and skeptics of research acknowledge that solar geoengineering is more than just a scientific intervention: it is a social and political one, too. Yet the story of SCoPEx suggests that current models to bridge the scientific and the socio-political are insufficient: structural barriers make it difficult for members of the public to express their concerns about the research. How to adequately govern these field experiments — nevermind deployment — remains unclear. But as the research proceeds in an ever-worsening climate, the implications of these questions grow ever larger – and it’s not clear who is equipped to answer them.

‘No Part in Our Plan For the Future’

The scientists hadn’t expected SCoPEx to go so poorly, so quickly.

The plan had been to launch a specialized balloon 20 kilometers above Kiruna, Sweden, a small mining town in the Arctic Circle. If the apparatus — a balloon fitted with propellers and a hanging gondola — passed an initial test flight, it would then complete a second pass through a thin band of the stratosphere, this time releasing a small plume of calcium carbonate into the air.

The project aimed to answer two basic questions: if one kilogram of aerosols would scatter uniformly over a kilometer distance, and how calcium carbonate aerosols would react with the stratosphere. (The team is exploring the idea that calcium carbonate could serve as a less damaging alternative to sulfate, which is a pollutant.)

Keutsch, who serves as Principal Investigator, says the experiment was designed to “fill a critical knowledge gap” in research while managing to remain narrow in impact. The SCoPEx webpage states that the flight would have released such a trivial amount of calcium carbonate that it would have posed “no significant hazard to people or the environment.”

And the project intended to do more than advance research: the researchers hoped to develop good governance practices that future field experiments could use as a template. As a private experiment, SCoPEx does not fall under the purview of federal regulation. Instead, at the team’s request, it received guidance on decision-making from an external Harvard-appointed task force which shares its reviews and recommendations with the public: the SCoPEx Advisory Committee.

Kiruna, Sweden, though on its face odd, was also an intentional choice. According to Keutsch, the researchers entertained various U.S. sites first, but many presented logistical or technical challenges. Moreover, the team began planning SCoPEx when Trump was still president; it was wary of conducting an experiment that could be perceived as a “technological cheap way out” in a country actively rolling back climate regulations. In Sweden, the experiment seemed to have the best chance of causing minimal harm. Plus, says Keutsch, the Swedish Space Corporation, which runs the test site, was “technically just amazing” and gave helpful feedback on the experiment.

But for all the prior planning, these efforts to preempt political and social concerns still failed.

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Åsa Larsson-Blind, vice president of the Saami Council, first learned about the flights slated to pass over her land in February, from a concerned friend’s email.

The friend, a leader of a grassroots environmental justice group called the Indigenous Environmental Network, warned that he had just become aware of a Harvard-led effort to test a technology so disruptive and unpredictable that even its advocates compared it to a forceful volcanic eruption. He worried the flights could threaten the traditional land-based livelihood of the Saami, which is centered around reindeer hunting, fishing, and foraging. And most startling of all, he noted, they were set to begin soon: in just four months, at the start of June.

The Saami Council had heard vaguely about the concept of solar geoengineering before, but the SCoPEx experiment put its members onto a “steep learning curve,” Larsson-Blind admits. But as soon as the Council got a hold on the idea, its position was clear and unanimous: solar geoengineering had “no part” in their plan for the future of their environment.

The Council quickly realized SCoPEx would not cause any direct major environmental harm, but still saw it as dangerous in the long-term. In their eyes, SCoPEx was the first step in developing and legitimizing a technology that would not only detract from the necessary work of cutting emissions, but introduce a slate of new environmental risks.

In a February 24 letter, the Council called on the SCoPEx Advisory Committee to cancel the scheduled test flight. It criticized the experiment for failing to consult the Saami and other key stakeholders, arguing that the oversight was especially egregious given the technology’s “risk of catastrophic consequences.” It portrayed the project’s governance mechanism as inherently flawed due to its “homogenous” and “far from representative” advisory board, and seemed to suggest that remedy was impossible. The scale of solar geoengineering made its risks unquantifiable and unmanageable: “There are therefore no acceptable reasons for allowing the SCoPEx project to be conducted either in Sweden or elsewhere,” the letter read.

Larrson-Blind says the Council would have never voluntarily entertained solar geoengineering as an option — the concept runs counter to the Saami’s philosophy of living sustainably within nature, rather than of it. She argues that the logic behind it only perpetuates the problem at hand. “The idea that mankind is above nature and can control everything has led us into the climate crisis in the first place,” she says. “It’s like chewing off the branch you’re sitting on.”

But the subject “fell into [the Saami’s] lap,” Larsson-Blind says, forcing the Council to share its perspective. Had she not received that email from a friend, she fears she would have never been informed of the experiment.

In March, the Swedish Space Corporation — the organization hosting the flights — and the SCoPEx Advisory Committee both released statements announcing the postponement of the test flight. The Committee said it would need to first conduct a “listening-based engagement activity in Sweden” and complete a “societal review” on the ethical and moral complexities surrounding the flight before another launch.

In June, the Council released a petition calling on Harvard to shut down the experiment altogether. Speaking as “representatives of Indigenous Peoples,” the Council frames solar geoengineering as antithetical to Indigenous environmental thought. The bolded head of the letter reads: “Climate manipulation strongly contradicts our understanding and experience of how to respect and live in harmony with Mother Nature.”

***

When we ask Keith about the Saami Council’s letters, he sighs in exasperation.

In his telling, the researchers were long aware that Kiruna was home to the Saami and planned on reaching out to the Council after the SCoPEx Advisory Committee approved plans for the second flight: the particle-releasing flight. The letter preempted this effort. In its wake, Keith and Keutsch reached out to members of the Council to privately discuss their positions, but never received a response — a move Keith calls “ethically inconsistent.”

“I don’t see how you can call for engagement and refuse to engage yourself,” he says, shaking his head.

Keith disputes the Saami’s claim that SCoPEx tests or advances the use of a technology. He says the team intentionally designed the experiment to use a delivery platform that would be “useless for deployment.” In fact, it imagined the field test would provide much-needed insight into why we shouldn’t deploy solar geoengineering, uncovering risks computer models and lab-based studies might have missed.

Keith argues the Council takes too narrow and settled a view of the risks of the technology to begin with. “They’re basically saying they know all the answers, which the UN doesn’t agree with, which the CBD [the Convention on Biological Diversity] doesn’t agree with, which most scientists don’t agree with,” he says of the Council’s letter.

Keith believes that rather than dominate nature, solar geoengineering has the potential to restore it — and better human lives at the same time. Coming from a family of environmentalists, he sees the technology as an intervention which could “protect the environment.”

“It’s not clear to me that knowing less is really a strategy which is better for the next generation that will have to make decisions,” he adds. “That’s a perfectly fine position, but it’s not engagement.”

Larsson-Blind rejects this framing. The Saami made their decision clear in the letter, she says, and they worried any discussion would signal their tacit endorsement of the tests. “We perceived that this was an invite to a dialogue on how these tests were supposed to happen,” she says of Keith and Keutsch’s invitation. “That’s not a dialogue about whether or not these tests were going to take place.”

Larsson-Blind says her conviction around solar geoengineering stems from an intimate experience with climate change. As wind and weather patterns in the Arctic have grown more erratic, her family has struggled to care for reindeer as it has in the past. (In the winter, for instance, the animals now sometimes struggle to find food: when precipitation comes as rain, rather than snow, impenetrable layers of ice form over sources of lichen, a seasonal staple.) These challenges, among others, keep her “humble of the forces of nature,” reinforcing her commitment to avoid tinkering with the planet.

She imagines that in a conversation, the researchers would simply condescend to the Council or seek to undermine their position. “They’ll say we don’t understand [the science], but we do.”

Keutsch says he personally wrote to Larsson-Blind, explaining the purpose of a dialogue would have been to gain a “deeper understanding” of the Saami’s perspective and not to convince her of his opinion. “If she had been willing to meet, she would have seen that I would not be dismissive,” Keutsch wrote in an emailed statement.

Keith, who says he also wrote privately to the Council, maintains he takes the Council’s concerns seriously, but believes that they are in no way representative or universal. “It’s what one political organization says,” he stresses.

But later he worries about the extent of the Council’s impact. “They're very powerful,” he adds, shaking his head. “These voices are very powerful in the climate debate now.”

An Uneven Playing Field

As one of Keith’s former postdocs, Jennie C. Stephens ’97 is a rare bridge between SGRP and the Saami, whose petition cites her work. Stephens, the current Director of the School of Public Policy and Urban Affairs at Northeastern University, is one of the most vocal critics of solar geoengineering.

Stephens first met Keith after receiving a fellowship to research carbon capture in the early 2000s, as the topic was just gaining traction. In 2008, the two even authored a paper together calling for more research on the technique, which aims to remove CO2 from the atmosphere and store it underground. Soon after the fellowship ended, however, Stephens started to have doubts about the merits of carbon capture, and technological solutions to climate change more generally — a skepticism that extends to her views on solar geoengineering.

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She began to fear that the technology she helped advance might have the opposite of its intended effect: that it would supplant, rather than supplement, efforts to transition away from fossil fuels. The hope of scalable carbon capture technologies allowed companies to have it both ways: to at once acknowledge the reality of climate change and continue emitting CO2, only to later suck it back up and spit it into the ground. Ultimately, as she recalls, she decided to “quit playing the game,” putting the carbon capture research aside and focusing instead on social and political interventions to climate change.

Today, Stephens finds striking parallels between the field of carbon capture and solar geoengineering. In her mind, solar geoengineering is a “techno-fix” which could allow the powerful to tighten their hold on wealth and status while harming the planet — and disproportionately, the vulnerable people living on it.

She asserts that solar geoengineering research distracts from and actively discourages viable approaches to the climate which center social justice, like those highlighted in the Green New Deal. A popular argument in favor of research is that we will fail to go carbon neutral by 2050; to Stephens, this “constrains our imagination about what’s even possible,” encouraging us to embrace a radical technological intervention over the radical social change — change which has become ever closer to being possible.

She also worries that a narrow demographic funds most of this research, one with a vested interest in appearing philanthropic but maintaining power: rich white men from tech circles in the West.

“A handful of rich folks could get to decide what the temperature is, what the climate is, and play around with everybody’s realities,” she stresses.

She highlights that among the major donors to SGRP is noted philanthropist Bill Gates, to whom Keith serves as a scientific advisor. Stephens says Gates’ most recent book, “How to Avoid a Climate Disaster,” reveals his pro-technology ideology towards climate solutions, one that lends support to solar geoengineering efforts.

Even worse, Stephens notes, the harms of deployment could fall especially hard on one side. Solar geoengineering can have variable effects on the climate, particularly in the hydraulic system, and poorer countries might find it more difficult to adapt to sudden developments of drought, for instance, or crop resistance. They are also the least likely to have the technological skill to deploy solar geoengineering or the political sway to inform its use, which as of yet remains unregulated.

In an effort to be transparent with the public, SGRP lists all of its donors on its website and details its decision-making process for accepting donations. The program says it disqualifies prospective donors with ties to the fossil fuel industry unless it is clear, through a “strong track record of supporting efforts to address climate change,” that they do not have a conflict of interest. While Keith would prefer wealth to be more evenly distributed in society, he maintains that all current donors, billionaires or not, meet the program’s standards.

Knowing many of the researchers behind top solar geoengineering efforts does not put Stephens at ease. Although she believes the scientists are well-intentioned, she thinks they lack an understanding of the power dynamics at play in their field and lack humility about the complexity of the climate and the political nature of research. “There’s an arrogance to these scientists that literally think that they can come up with something that will control the climate in a way that will do good for society,” she explains.

Although they hold nearly diametrically opposed views, Keith curiously recommends Stephens as a critic he respects. The two have also had a number of private discussions about the subject, but Stephens claims their approaches to solar geoengineering tend to clash.

“He genuinely tries to understand but, I don’t know, it just doesn’t mesh,” she says.

According to Stephens, Keith has repeatedly offered her funding to conduct social science research on solar geoengineering for SGRP and invited her to join the SCoPEx Advisory Committee, but Stephens has declined. To accept either the funds or the position would be to enable the growth of the field — research could not minimize any of the risks of the technology, she says, only legitimize it.

She argues that the researchers at SGRP “strategically respond” to criticisms she and others raise. They acknowledge the concerns, but either fail to act on their stated principles — she points to the issues with SCoPEx’s implementation) or aim to resolve a tension they feel is inherent to the technology.

But choosing not to accept the money also comes with a cost. Stephens says the gulf in financial support, status, and coordination creates a “stark imbalance of power” between advocates of research and skeptics. One side continues to collect data, write peer-reviewed papers, and refine its points; the other doesn’t have the same luxury.

If this imbalance exists between Stephens and Keith, it becomes magnified with regards to the Saami. The Saami do not write their own scientific papers or conduct studies. To rise to the level of the researchers’ discourse, they must rely on the few peer-reviewed papers by solar geoengineering skeptics and try to interpret them — an uneven playing field.

Compared to the scientists in favor, “the voice of resistance is not as loud, at the end,” says Stephens.

‘Full, Global Consensus’

Though SCoPEx is just one experiment and the Saami just one people, the impasse between the two could have terrifying implications. If there is no channel for communication and criticism between scientists and the public for a small-scale experiment, what hope is there for larger experiments? Solar geoengineering is a technology of immense scale: it has the potential to change the climate for every person on earth, making communication and criticism all the more important — and yet, these channels don’t seem to exist. Currently, discussions about solar geoengineering remain insular and academic, proceeding from the same handful of people.

Keith is one of the few people trying to bridge that gulf between scientists and society — he says public education is a “significant part” of his work. But the results are polarizing. In a 2007 Ted Talk, his best-known talk, Keith stands in front of an image of Archimedes’ lever — of “Give me a place to stand on, and I can move the earth” fame — discussing the cost of solar geoengineering. “You could create an ice age at a cost of 0.001 percent of GDP,” he says gravely. “It’s very cheap. We have a lot of leverage.”

A few audience members laugh; the rest look on with some combination of disbelief and fear. The comments below the video are also split. “EXCELLENT talk. Necessary.” reads one. “Thank you for tackling this serious topic. Here's hoping it will start some more open and honest discussions about what our future holds.” reads another.

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But the majority are negative. Some people worry about the idea of solar geoengineering — “uh...I kinda like the sun, could you give it back please?” reads one. But most mock Keith himself: “Foolish beyond belief; doesn’t care how many people die” one user writes. One user mocks his fast, intense presentation style; another compares him to a “mad scientist.”

In his 2013 appearance on the Colbert Report, Keith acknowledges the risks of solar geoengineering; he calls it “horrifying,” “a totally imperfect technical fix,” and says he “wake[s] up sweating” about its risks. Colbert responds: “Well, it’s your goddamn idea!” and the studio audience laughs.

It isn’t Keith’s idea, but in the eyes of the public, it might as well be. In the absence of third parties, scientists like Keith become the de facto communicators for the strategy — and they don’t always succeed. Armed with statistics and counter arguments, Keith sometimes comes across as condescending, or worse, as pushing a dangerous and unethical technology forward, even as he attempts to distance himself from it.

Keith’s public education efforts don’t translate into opportunities for public dialogue or debate, as exemplified by SCoPEx. Keith speaks in Ted Talks and peer-reviewed papers; the Saami speak in open letters posted online. The two don’t speak to each other.

Keith says he’d stop research if enough people wanted him to. “I would change my mind, almost completely, if I saw consistent data from these surveys we have on public judgement that said people opposed it,” Keith says. “I mean, I don’t want to do something people don't want.”

The Saami certainly don’t want solar geoengineering research — at least not until there’s “full, global consensus on its acceptability,” as they write in their letter — an impossibly high standard.

But what about everyone else between these two extremes? Keith references several small studies that he says demonstrated reasonable support for solar geoengineering research among the public. The short answer may be that we just don’t know yet. But when we do, it’s not clear how the public will voice their support or dissent — and if it will make a difference.

Another barrier to the “global consensus” the Saami want may be the structure of the technology itself. Solar geoengineering is dangerously easy and uniquely powerful: just a few airplanes, deployed from just one country or even one city, could change the climate of the entire globe. Is there any way such a technology could be used democratically?

‘You Only Have One World’

Despite the current barriers to public feedback, research is nonetheless proceeding, and could be scaling up soon.

If Congress adheres to the NASEM report’s recommendations, direct funding for solar geoengineering — and not just the basic science underlying it — could increase substantially.

The push to expand research has also moved beyond the bubble of academia. At least one advocacy group, the nonprofit SilverLining, has emerged to lobby U.S. policymakers on climate intervention options and it takes an extreme stance: that solar geoengineering experiments should be subject to even less regulation. (Executive director Kelly Wanser argues that concerns about governance and societal impact are irrelevant in basic science research; current models like the SCoPEx experiment’s “politicize things too early on.”)

SCoPEx currently remains postponed, pending review from its Advisory Committee. A final recommendation on whether or not the scientists should run the experiment in Kiruna is expected to come as soon as 2022. In April, Keith told the Times that the team was considering moving the test stateside, but a new location has yet to be confirmed. If the project launches again, Keutsch says it would likely include several particle-releasing flights.

Keith is largely undeterred by the pushback to the experiment. Driving his commitment to the research is a solemn, if not grim, assessment of the climate.

Atmospheric CO2 concentrations have now passed 400 parts per million — their highest concentration in at least 2 million years. In essence, we’ve been conducting an experiment of our own for the past few centuries: pumping carbon dioxide into the atmosphere with no abandon — 2.6 million pounds of it each second — and waiting to see what happens.

Keith speculates that some of the opposition to solar geoengineering, then, stems from “ignorance.” He believes that many people who dismiss the concept outright simply haven’t taken the time to read the scientific literature and therefore assume the risks greatly outweigh the potential benefit to the planet.

In his mind, the worsening climate has created a sick new calculus, where every decision, even indecision, comes with a dangerous consequence. If we were “sitting around a campfire a thousand years ago,” he imagines, we could simply pit the benefits of cooling against the risks of deploying solar geoengineering. But at the current precarious moment, he claims we are tasked with making a difficult risk-risk calculation: weighing the potential risks of deploying solar geoengineering against the risks of not doing so.

For Keith, the inescapable uncertainty brings clarity.

“You only have one world,” he states. “You’ve got to make a choice.”

— Associate Editor Maliya V. Ellis can be reached at maliya.ellis@thecrimson.com. Follow her on Twitter @EllisMaliya.

— Associate Editor Saima S. Iqbal can be reached at saima.iqbal@thecrimson.com. Follow her on Twitter @siqbal839.