Just weeks after Hurricane Sandy ravaged the east coast, climate change was on the forefront of everyone's mind at Techonomy 2012 in Tucson, Ariz. In a session about geo-engineering, Harvard physics professor David Keith and Harvard Kennedy School research fellow Andrew Parker talked about the realistic possibility of reflecting sunlight away from the planet to lower the earth's temperature -- and, more pressing, the complicated political implications of this climate change quick-fix. More