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.
