This article surveys the issues involved in slowing the climate change induced by global emissions of greenhouse gases, especially carbon dioxide. It addresses the possible social and economic impacts of global warming, the elements involved in evaluating the pros and cons of steps to reduce those impacts, and the issues involved in engaging most of the worlds states in a cooperative endeavor to reduce greenhouse gas emissions. It expresses doubts about the efficacy of a global approach based on national emission targets, such as those set by the 1997 Kyoto Protocol, and favors instead mutually agreed actions focused on a common emission tax. It also discusses issues of compliance with an international agreement to reduce emissions, actions states can take in the absence of international agreement, and contingency actions that might be considered if the problem proves to be more serious than now seems to be the case.