A Startup’s Bid to Dim the Sun

Advocates for geoengineering—or, at a minimum, of pursuing research into geoengineering—say that such risks impose obligations. They note that, since attempts to limit warming have failed, it’s incumbent on humanity to consider all the options. “If sunlight reflection could save lives and protect the environment, it is at least worth discussing,” David Keith and Zeke Hausfather, both climate scientists, wrote in a recent essay for the Times. “I don’t think we have the luxury of saying there are certain options we don’t explore and study,” Yedvab, the co-founder of Stardust, said. “Just as a metaphor, if there is one person in a household who’s in a crisis, you want to make sure that you have all the options in front of you of how to deal with this crisis.”

The gloomy arguments for geoengineering are compelling. So are the even gloomier counter-arguments. Among the technology’s many possible side effects are shifts in regional weather patterns and the disruption of monsoons that hundreds of millions of people depend on. Since solar geoengineering would have global impacts, it would seem to demand that some sort of global agreement be in place before it could be deployed or even tested on a meaningful scale. But it’s hard to see how such an agreement could be reached, as conditions that benefit one region might very well flood or dry out another. Meanwhile, in the absence of such an agreement, there’s nothing to stop a powerful country, or group of countries, from utilizing the technology, except for the fear of disapproval (or that another country will shoot down their planes). A company called Make Sunsets is already selling “cooling credits” for lofting small quantities of sulfur dioxide into the stratosphere via balloons, though it is unclear whether this is having any effect on anything. Stardust says that it is committed to “comprehensive regulation of this emerging field, including governance mechanisms for the stratosphere”; so far, though, it has been moving ahead without these.

Another geoengineering downside—and it is a deep one—is its duration. Were the world, or any subdivision of it, to embark on a campaign of “sunlight reflection,” the scheme would have to be continued more or less indefinitely. After a volcanic eruption, reflective droplets fall out of the stratosphere within a few years. The same, presumably, would hold for any man-made particles, meaning that these would have to constantly be replaced: if they weren’t, temperatures would suddenly shoot up, a prospect that’s become known as “termination shock.” (Stardust says that “termination shock” can be avoided by gradually tapering off the quantity of particles deployed, as decarbonization efforts go into effect.)

Finally, and most important, solar geoengineering is not a solution to climate change. It’s a way—once again, in theory, at least—to depress global temperatures. But the technology does nothing to deal with the underlying problem, which is CO₂ emissions. Using it to counter the effects of warming while carbon emissions continue to rise is a bit like cranking up your thermostat and then turning on the A.C.

In the three decades since the summit in Rio, our technologies have grown ever more powerful, ever more rapidly. ChatGPT, interceptor drones, humanoid robots, mRNA vaccines, quantum computing—one mind-blowing breakthrough follows quickly on another. But our institutions—the United Nations, the U.S. Congress, American higher education—have failed to keep pace. They seem increasingly sclerotic, or perhaps just ineffectual. The net effect is to make ambitious techno-fixes such as geoengineering increasingly attractive. Presumably, this is what prompted Stardust’s investors to hand over sixty million dollars. It is also what should make us wary. Technologies don’t manage themselves. ♦