As the alarm over global warming spreads, radical ideas are taking hold: if cuts in greenhouse gas emissions are insufficient, let's use reflective nanoparticles to bounce sunlight directly into space or launch mirrors into orbit around the earth. We could make clouds thicker and brighter or surround Arctic sea ice with a huge plastic flotilla. Yet while these proposals seem edgy and exciting, they often test the limits of scientific possibility and overlook the political, ethical, and social consequences of climate management. Revisiting over a century of efforts at weather and climat.