FrontMatter -- Preface -- Acknowledgments -- Contents -- Executive Summary -- 1 Introduction -- 2 State of Scientific Understanding -- 3 Radiative Forcing Over Earth's History -- 4 Rethinking the Global Radiative Forcing Concept -- 5 Uncertainties Associated with Future Climate Forcings -- 6 Research Approaches to Furthering Understanding -- 7 Recommendations -- References -- APPENDIXES -- A Biographical Sketches of Committee Members and Staff -- B Statement of Task -- C Glossary and Acronyms.