Grist: Despite the antics of technofixers, policy wonks, and mad billionaires everywhere, geoengineering persists as an appealing-if-wacky solution to all our climate ills. The basic logic is seductive: If weve messed up the climate by pumping bad stuff into the atmosphere, maybe we can undo some damage by pumping some other stuff up there, too. Of course, a minefield of potential blunders awaits the intrepid geoengineer, including wreaking havoc on rainfall or depleting polar ozone. And then there is...