A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate Climate Working Group United States Department of Energy July 23, 2025 ii iii A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate Report to U.S. Energy Secretary Christopher Wright July 23, 2025 Climate Working Group: John Christy, Ph.D. Judith Curry, Ph.D. Steven Koonin, Ph.D. Ross McKitrick, Ph.D. Roy Spencer, Ph.D. This report is being disseminated by the Department of Energy. As such, this document was prepared in compliance with Section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Public Law 106-554) and information quality guidelines issued by the Department of Energy. Copyright © 2025 United States Suggested citation: Climate Working Group (2025) A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate. Washington DC: Department of Energy, July 23, 2025 iv v Table of Contents SECRETARY’S FOREWORD ....................................................................................................................... VIII EXECUTIVE SUMMARY .............................................................................................................................. IX PREFACE ................................................................................................................................................... X PART I: DIRECT HUMAN INFLUENCE ON ECOSYSTEMS AND THE CLIMATE .................................................... 1 1 CARBON DIOXIDE AS A POLLUTANT .................................................................................................. 2 2 DIRECT IMPACTS OF CO2 ON THE ENVIRONMENT .............................................................................. 3 2.1 CO2 AS A CONTRIB...
