The Ranking Member, Senate Committee on Environment and Public Works, requested that we determine whether the U.S. Environmental Protection Agency (EPA) followed key federal and Agency regulations and policies in developing and reviewing the technical data used to make and support its greenhouse gases endangerment finding. On December 15, 2009, EPA published its Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act. As the primary scientific basis for EPA's finding, the Agency relied upon assessments conducted by other organizations. EPA summarized the results of these and other scientific assessments in a technical support document (TSD).