The scientific community has been studying the question of how human-caused emissions of greenhouse gases are affecting the climate for well over a century. Much is known today, drawing on decades of direct observations of the Earth system and detailed research. This report summarizes the latest evidence on whether greenhouse gas emissions threaten public health and welfare in the United States.The impetus for this report was a notice of proposed rulemaking issued in August 2025 by the U.S. Environmental Protection Agency (EPA) indicating its intention to rescind the 2009 Finding of Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act. Recognizing that significantly more evidence is available today, the National Academies of Sciences, Engineering, and Medicine launched this study to review newly available scientific evidence on the topics included in a Technical Support Document that EPA prepared to inform its decision-making on the finding.The report's authoring committee found that EPA's 2009 finding that human-caused emissions of greenhouse gases adversely affect human health and welfare was accurate, has stood the test of time, and is now reinforced by even stronger evidence. Today, many of EPA's conclusions are further supported by longer observational records and multiple new lines of evidence. Moreover, research has uncovered additional risks that were not apparent in 2009.
