Effective mitigation of climate change will require deep international cooperation, which is much more difficult to organize than the shallow coordination observed so far. Assessing the prospects for effective joint action on climate change requires an understanding of both the structure of the climate change problem and national preferences for policy action. Preferences have become clearer in light of the United Nations Framework Convention on Climate Change Conference of the Parties in December 2015. Although deep cooperation remains elusive, many partial efforts could build confidence and lead to larger cuts in emissions. This strategy of decentralized policy coordination will not solve the climate problem, but it could lead incrementally to deeper cooperation.