Many economic models exist to estimate the cost and effectiveness of different policies for reducing greenhouse gas (GHG) emissions. Some approaches incorporate rich technological detail, others emphasize the aggregate behavior of the economy and energy system, and some focus on impacts for specific sectors. Understandably, different approaches may be better positioned to provide particular types of information and may yield differing results, at times rendering decisions on future climate change emissions and research and development (R&D) policy difficult. Reliable estimates of the costs and benefits to the U.S. economy for various emissions reduction and adaptation strategies are critical to federal climate change R&D portfolio planning and investment decisions. At the request of the U.S. Department of Energy (DOE), the National Academies organized a workshop to consider these issues. The workshop, summarized in this volume, comprised three dimensions: policy, analysis, and economics. Discussions along these dimensions were meant to lead to constructive identification of gaps and opportunities. The workshop focused on (1) policymakers' informational needs; (2) models and other analytic approaches to meet these needs; (3) important economic considerations, including equity and discounting; and (4) opportunities to enhance analytical capabilities and better inform policy.