Over the past several years the issue of global warming has become a national political priority and will likely remain one of the United States' and the world's most pressing and unresolved policy issues for many years. The U.S. Supreme Court's decision in Massachusetts v. EPA makes possible a national program to address climate change under the Clean Air Act (CAA). Even before Massachusetts v. EPA, the congressional shift in power had produced a flurry of bills coalescing around the need for strong national goals and mandatory GHG emissions reductions. While many of the bills before Congress in past sessions moved toward stronger emissions reduction goals and potentially broader and more inclusive policy approaches, they were relatively silent or short on details for the specific pathways necessary to achieve climate stabilization goals.