The insistence on complete certainty about the full details of global warming-the most serious threat we have ever faced-is actually an effort to avoid facing the awful, uncomfortable truth: that we must act boldly, decisively, comprehensively, and quickly, even before we know every last detail about the crisis. Those who continue to argue that the appropriate response is merely additional research are simply seeking to camouflage timidity or protect their vested interest in the status quo.