"Uncertainty regarding global warming appears to be a legitimate basis for postponing action, which is usually identified as 'costly.' But this idea is almost unique to climate change. In other areas of public safety, such as terrorism, nuclear proliferation, inflation, or vaccination, an 'insurance' principle seems to prevail: if there is sufficient likelihood of significant damage, we take some measured anticipatory action."
-- Thomas Schelling, Nobel Laureate in Economics
(from Eli Kintisch's Hack the Planet)