Revisiting the Geoengineering QuestionPosted on 29 September 2025 by Zeke HausfatherThis is a re-post from The Climate BrinkI have a new guest essay in the New York Times with David Keith that builds off my earlier Climate Brink post The Geoengineering Question. Sulfur emissions are declining sharply as countries started cleaning up air pollution. This is the same mechanism (more or less) through which sulfur emitted as air pollution currently cools the planet. This means that the real risk of geoengineering is not some Hollywood-style catastrophe, but complacency. To that end, we propose that replacing the cooling from current air pollution be used as a clear, enforceable upper limit.