From About this Report:
[T]he U.S. Global Change Research Program (USGCRP) oversaw the production of this stand-alone report of the state of science relating to climate change and its physical impacts. …
The USGCRP is made up of 13 Federal departments and agencies that carry out research and support the Nation’s response to global change. The USGCRP is overseen by the Subcommittee on Global Change Research (SGCR) of the National Science and Technology Council’s Committee on Environment, Natural Resources, and Sustainability (CENRS), which in turn is overseen by the White House Office of Science and Technology Policy (OSTP). The agencies within USGCRP are 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.
From the Executive Summary:
… 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. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence. …
The magnitude of climate change beyond the next few decades will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally. Without major reductions in emissions, the increase in annual average global temperature relative to preindustrial times could reach 9°F (5°C) or more by the end of this century. With significant reductions in emissions, the increase in annual average global temperature could be limited to 3.6°F (2°C) or less.
In the New York Times, Lisa Friedman and Glenn Thrush write that the report contradicts positions of the Trump administration on climate change.
While there were pockets of resistance to the report in the Trump administration, according to climate scientists involved in drafting the report, there was little appetite for a knockdown fight over climate change among Mr. Trump’s top advisers …
The White House put out a statement Friday that seemed to undercut the high level of confidence of the report’s findings. …
Responsibility for approving the report fell to Gary D. Cohn, director of the National Economic Council, who generally believes in the validity of climate science and thought the issue would have been a distraction from the tax push, according to an administration official with knowledge of the situation.