Fourth National Climate Assessment special report

The Trump administration has released an updated assessment of the science of climate change, concluding "based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century."

The report by the U.S. Global Change Research Program, 2017: Climate Science Special Report: Fourth National Climate Assessment, Volume I, represents the first of two volumes of the Fourth National Climate Assessment, mandated by the Global Change Research Act of 1990. It builds on previous assessments while covering new information developed since the May 2014 publication of the Third U.S. National Climate Assessment. The program is composed of 13 Federal departments and agencies that carry out research and support the Nation’s response to global change, including the Department of Agriculture, the Department of Commerce (NOAA), the Department of Defense, the Department of Energy, the Department of Health and Human Services, the Department of the Interior, the Department of State, the Department of Transportation, the Environmental Protection Agency, the National Aeronautics and Space Administration, the National Science Foundation, the Smithsonian Institution, and the U.S. Agency for International Development.

According to the Fourth National Climate Assessment special report, "Recent data add to the weight of evidence for rapid global-scale warming, the dominance of human causes, and the expected continuation of increasing temperatures, including more record-setting extremes." The report cites temperature data, global average sea level rise, and changes in the characteristics of extreme weather events as evidence.

While the report does not provide much detail on potential policies that could be adopted to address climate change, it does link the magnitude of climate change beyond the next few decades to the amount of carbon dioxide and other greenhouse gases emitted globally.