Observations show that warming of the climate is clear. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil, and gas), with important contributions from the clearing of forests, agricultural practices, and other activities. This report combines information from a wide variety of scientific assessments and recently published research to summarize what is known about the observed and projected consequences of climate change on the United States. It combines analysis of impacts of various sectors such as energy, water, and transportation at the national level with an assessment of key impacts on specific regions of the United States. This report focuses on observed and projected climate change and its impacts on the United States and identifies a number of areas in which inadequate information or understanding hampers our ability to estimate future climate change and its impacts.