We describe three essential elements of an effective post-2012 international global climate policy architecture: a means to ensure that key industrialized and developing nations are involved in differentiated but meaningful ways; an emphasis on an extended time path of targets; and inclusion of flexible market-based policy instruments to keep costs down and facilitate international equity. This architecture is consistent with fundamental aspects of the science, economics, and politics of global climate change; addresses specific shortcomings of the Kyoto Protocol; and builds upon the foundation of the United Nations Framework Convention on Climate Change.