Congress has, over the past three decades, authorised and funded federal programs to improve understanding of climate changes and their implications. Climate changes have potentially large economic and ecological consequences, both positive and negative, which depend on the rapidity, size, and predictability of change. Some of the impacts of past change are evident in shifting agricultural productivity, forest insect infestations and fires, shifts in water supply, record-breaking summer high temperatures, and coastal erosion and inundation. People and natural systems respond to climate changes regardless of whether the government responds. Over time, the consequences of climate change for the United States and the globe will be influenced by choices made or left to others by the U.S. Congress. Policy proposals take different approaches to setting goals or managing climate change-related risks. This book describes four strategies for setting climate change policies: (1) research and wait-and-see, (2) science-based goal setting, (3) economics-based policies, and (4) incrementalism or adaptive management. Each may take into account the concerns, values, and scepticisms of some constituencies, but each also has limitations. It is unclear whether any single conceptual approach could cover all elements of the policy debate, though hybrid approaches may help to build political consensus over whether and how much policy intervention is appropriate.