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Co-founder Andrew Song of solar geoengineering startup Make Sunsets holds a weather balloon filled with helium, air and sulfur dioxide at a park in Reno, Nevada, United States on February 12, 2023.
Balazs Gardi for TIME

Stratospheric aerosol injection, the idea of spraying sulfur dioxide into the upper atmosphere to cool the planet, is one of the most controversial topics in climate science, with scientists engaged in a fierce, yearslong debate over whether even researching such techniques poses unacceptable risks. To some people outside of that community, though, it no longer matters much what the academics think. “Can we just disagree and move on?” Andrew Song, the co-founder of controversial geoengineering startup Make Sunsets, said in February, as he and his business partner Luke Iseman drove to the Reno, Nev., site of their first stratospheric aerosol injection (SAI) test on U.S. soil. He described one email chain in which academics argued over how to categorize the technology. “This thread is 50 messages long in this debate,” Song said. “Like, who gives a fuck?”

For many observers, though, the heated petitions and articles on either side of the issue are deadly serious. Supporters of researching solar geoengineering techniques like SAI say it could serve as a critical tool to save lives from some of the worst effects of climate change; opponents say that even researching the subject risks legitimizing a solution with potentially catastrophic risks. Yet to some extent, for better or worse, the argument among researchers may soon be moot: the geoengineering horse might have left the stable. The Make Sunsets experiments in the U.S. and Mexico are just one indicator. Last year, the U.S. Congress mandated that the White House start looking at how the U.S. might research the technology. And the European Union earlier this year called for high-level talks on how to research and govern the practice.

This realignment became yet more clear on Sept. 14, when a group of prominent figures in climate policy published a new report calling for continued research into SAI and another geoengineering technique known as marine cloud brightening (artificially producing extra cloud cover to reflect the sun’s energy back into space) along with supporting further discussion between governments about the rules of the road. The group, dubbed the Climate Overshoot Commission by its organizers at the Paris Peace Forum, a non-profit focused on global governance issues, also calls for a moratorium on large-scale real-world geoengineering experiments.

Perhaps just as notable as its recommendations is the body’s composition: primarily former politicians, government ministers, diplomats, and NGO leaders. This 12-member group doesn’t directly have any policymaking authority, but its recommendations may carry weight for government leaders looking for a sparknotes primer on geoengineering policy.

And the fact that the commission took up the issue at all, much less recommended research despite warnings from a sizable section of the scientific community, may serve as an important signal that—as in last century’s debate over building atomic weapons—the deliberations over whether and how to use geoengineering are shifting out of scientists’ purview, and into the hands of political leadership.

“This discussion will happen, and in my view, the worst case scenario is that every country does what it sees fit,” says Laurence Tubiana, president of the European Climate Foundation and a member of the commission. “You cannot have only a scientific discussion at the moment where there may be a lot of pressure to really test.”

Read more: Inside a Controversial Startup's Risky Attempt to Control Our Climate

In general, opponents of geoengineering research remain skeptical of any attempt to take geoengineering out of scientists’ purview. Some former participants with the Commission have expressed worry that the drafters of the report, some of them politicians with little background in atmospheric science, were being “instrumentalized” by the group’s organizers in order to create a global sense of normalcy around discussion of solar geoengineering, according to Climate Home. The opposition to studying geoengineering among scientists isn’t universal, though. In March 2021, the U.S.’s National Academies of Science, Engineering and Medicine, recommended that scientists “cautiously pursue” solar geoengineering research and establish governance frameworks to protect against risks.

It’s almost undisputed, even among those that want to study it, that solar geoengineering is very scary, and that use of it could potentially be catastrophic for human civilization. Weather pattern changes caused by releasing large amounts of sulfur dioxide into the upper atmosphere, for instance, could cause new natural disasters or global famine. Tinkering with the climate could create new geopolitical risks: what if one nuclear-armed country wants to alter the atmosphere and another does not? And, among policymakers and international businesspeople, the perception that humanity indeed does have another option, however dangerous, could siphon away initiative to pursue the zero-risk climate policy that scientists have been asking for for years: cutting greenhouse gas emissions.

“It’s really dangerous, and I’m very troubled that [solar geoengineering] has gotten mainstreamed to the extent that it has,” Jennie Stephens, a professor of sustainability science and policy at Northeastern University told TIME in March. “There’s only a handful of people who have made it their life’s mission to do this, and they’ve gotten philanthropists and billionaires on their side.”
The risk that a country—or one of those billionaires—might unilaterally employ geoengineering has grown more urgent as the world fails to address climate change at the scale necessary to avoid its worst effects. Geoengineering techniques like SAI are relatively easy and inexpensive to deploy, and could conceivably be done at scale by many different countries. For some of the most vulnerable, geoengineering could seem like a low-cost solution to stave off urgent damages. The Overshoot Commission frames itself as a way to get ahead of those actions and to cut through the scientific debate to offer actionable guidance to policymakers.

The report offers a range of suggestions about how to govern solar geoengineering research. It calls for an expert assessment body housed at an institution like the Intergovernmental Panel on Climate Change to assess current scientific understanding of the research and for U.N.-coordinated engagement between countries. The report calls for the expansion of research partnerships between countries in the Global North and Global South and for regulatory guidelines on where outdoor experiments might be conducted.

Read more: A Controversial Technology Is Creating an Unprecedented Rift Among Climate Scientists

Ultimately, those recommendations will only have weight if the world listens—and lots of politicians, billionaires, and philanthropies may have their own ideas. That’s especially concerning given that researchers have estimated that deploying solar geoengineering could cost only a few billion dollars—a relatively small sum for many countries and even some individuals. Last year, a report from the U.S. intelligence community identified ongoing solar geoengineering research programs in Australia, China, India, Russia, the United Kingdom, and the U.S. It warned that worsening climate change was making it more likely that countries would unilaterally deploy solar geoengineering projects.

Speaking in Nevada in February, Iseman and Song mentioned the possibility of performing their own experiments from international waters if governments banned their work. “I've worked with PhDs before, and I get what they do,” Song said, in the lead up to their experiment. “They're very intelligent. They can look very far into the future. But at the end of the day, when the rubber meets the road, they need someone like me to actually implement it.” Then he and Iseman pulled up to a Reno-area dog park, filled up three balloons with helium and sulfur dioxide, and let them go.

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Write to Alejandro de la Garza at alejandro.delagarza@time.com and Justin Worland at justin.worland@time.com.

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