The report summarizes the science and the impacts of climate change on the United States, now and in the future. It focuses on climate change impacts in different regions of the U.S. and on various aspects of society and the economy such as energy, water, agriculture, and health. It's also a report written in plain language, with the goal of better informing public and private decision making at all levels. In addition to discussing the impacts of climate change in the U.S., the report also highlights the choices we face in response to human-induced climate change. It is clear that impacts in the United States are already occurring and are projected to increase in the future, particularly if the concentration of heat-trapping greenhouse gases in the atmosphere continues to rise. So, choices about how we manage greenhouse gas emissions will have far-reaching consequences for climate change impacts. Similarly, there are choices to be made about adaptation strategies than can help to reduce or avoid some of the undesirable impacts of climate change. This report provides many of the scientific underpinnings for effective decisions to be made--at the national and at the regional level.