The Keystone Dialogue on Global Climate Change brought together approximately 30 representatives from environmental non-governmental organizations (ENGOs), industry, and the research and technical communities. The purposes of the dialogue were (1) to review the magnitude and timing of carbon dioxide (CO2) reductions required globally and by the United States to achieve four concentration ceilings under alternative international allocations of these reductio ns; and (2) to review policies for their ability to achieve the U.S. reductions from three key emitting sectors and from biologic sequestration. This dialogue was predicated upon the long-term goal of stabilizing atmospheric CO2 concentrations embedded in the United Nations Framework Convention on Climate Change (UNFCCC), an international agreement that has entered into force. The project's focus on long-term stabilization of CO2 concentrations is consistent with the UNFCCC and distinguishes it from many other studies. The analysis concludes that significant CO2 emission reductions are required on a global basis and by the United States from the reference case in order to achieve the range of concentration ceilings (450-750 parts per million volume) (ppmv)) under discussion by the international community. Significant technological advances are incorporated into the reference case. Achieving the "business as usual" levels of technological progress and associated emission reductions will require a major effort. The U.S. share of global emission reductions required for stabilization were developed as a benchmark for this analysis, given a specific set of assumptions regarding international participation in a global program designed to reduce greenhouse gas emissions and modeling framework. The selection of the cases used for analysis does not constitute an endorsement or prediction by the Dialogue group. The second part of the study focuses on potential sources of emission reductions and explores the impacts of policy, timing and carbon prices on private firms' investment decisions during the timeframe from 2010 to 2030.