Solar geoengineering would not just be cheap, relatively speaking; it would also be speedy. Pretty much as soon as the fleet of SAILs went into operation, cooling would begin. (A year and a half after Tambora erupted, the cucumbers in New England were frozen.) As Keutsch told me, it’s the only way to “do something fast” about climate change. But if a fleet of SAILs looks like a quick, cut-rate
