Not researching geoengineering is at least as dangerous as attempting it. Geoengineering is definitely going to be attempted--nay, ordered--long before Manhattan, Mumbai, Shanghai, etc. are under a foot of water. Whatever we've managed to figure out, no matter how stupid a solution it might be, is what's going to get tossed at this problem by the same ignorant politicians that got us into this mess. So we might as well make it a good one.