National Academies Press: OpenBook
Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
×

RADIATIVE FORCING OF CLIMATE CHANGE

EXPANDING THE CONCEPT AND ADDRESSING UNCERTAINTIES

Committee on Radiative Forcing Effects on Climate

Climate Research Committee

Board on Atmospheric Sciences and Climate

Division on Earth and Life Studies

NATIONAL RESEARCH COUNCIL OF THE NATIONAL ACADEMIES

THE NATIONAL ACADEMIES PRESS
Washington, D.C.
www.nap.edu

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
×

THE NATIONAL ACADEMIES PRESS
500 Fifth Street, NW Washington, DC 20001

NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

Support for this project was provided by the National Oceanic and Atmospheric Administration under Contract No. NASW-01008. Any opinions, findings, and conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.

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International Standard Book Number 0-309-54688-5 (PDF)

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Additional copies of this report are available from the
National Academies Press,
500 Fifth Street, N.W., Lockbox 285, Washington, DC 20055; (800) 624-6242 or (202) 334-3313 (in the Washington metropolitan area); Internet, http://www.nap.edu.

Cover: Images obtained from the Clouds and Earth’s Radiant Energy System (CERES) instrument on board NASA’s Aqua satellite on June 22, 2002. The image on the front cover shows the amount of infrared energy, or heat, emitted by the Earth and its atmosphere to space. Clear, warm land regions (shown in yellow) emit the most heat. High, cold clouds (shown in blue and white) emit less heat to space. The image on the back cover shows the amount of sunlight reflected back to space. Clear ocean areas (shown in dark blue) reflect the least amount of sunlight back to space, and clouds and snow-covered surfaces (shown in white and green) reflect the most sunlight back to space. SOURCE: National Aeronautics and Space Administration (NASA) Goddard Space Flight Center.

Copyright 2005 by the National Academy of Sciences. All rights reserved.

Printed in the United States of America

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
×

THE NATIONAL ACADEMIES

Advisers to the Nation on Science, Engineering, and Medicine

The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences.

The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Wm. A. Wulf is president of the National Academy of Engineering.

The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine.

The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. Wm. A. Wulf are chair and vice chair, respectively, of the National Research Council.

www.national-academies.org

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
×

COMMITTEE ON RADIATIVE FORCING EFFECTS ON CLIMATE

DANIEL J. JACOB (Chair),

Harvard University, Cambridge, Massachusetts

RONI AVISSAR,

Duke University, Durham, North Carolina

GERARD C. BOND,

Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York

STUART GAFFIN,

Columbia University, New York, New York

JEFFREY T. KIEHL,

National Center for Atmospheric Research, Boulder, Colorado

JUDITH L. LEAN,

Naval Research Laboratory, Washington, D.C.

ULRIKE LOHMANN,

ETH Zurich, Switzerland

MICHAEL E. MANN,

University of Virginia, Charlottesville

ROGER A. PIELKE, SR.,

Colorado State University, Fort Collins

VEERABHADRAN RAMANATHAN,

Scripps Institution of Oceanography, University of California, San Diego

LYNN M. RUSSELL,

Scripps Institution of Oceanography, University of California, San Diego

NRC Staff

AMANDA STAUDT, Study Director

PARIKHIT SINHA, Program Officer

GERALDEAN H. LANTIER,

Christine Mirzayan Science and Technology Policy Intern

ELIZABETH A. GALINIS, Senior Program Assistant

ROB GREENWAY, Senior Program Assistant

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
×

CLIMATE RESEARCH COMMITTEE

ANTONIO J. BUSALACCHI, JR. (Chair),

University of Maryland, College Park

LEE E. BRANSCOME,

Environmental Dynamics Research, Inc., Palm Beach, Florida

JAMES A. COAKLEY, JR.,

Oregon State University, Corvallis

JULIA E. COLE,

University of Arizona, Tucson

JUDITH A. CURRY,

Georgia Institute of Technology, Atlanta

CLARA DESER,

National Center for Atmospheric Research, Boulder, Colorado

DAVID KAROLY,

University of Oklahoma, Norman

ROBERT J. LEMPERT,

RAND Corporation, Santa Monica, California

LINDA O. MEARNS,

National Center for Atmospheric Research, Boulder, Colorado

GERALD A. MEEHL,

National Center for Atmospheric Research, Boulder, Colorado

PETER B. RHINES,

University of Washington, Seattle

W. JAMES SHUTTLEWORTH,

University of Arizona, Tucson

LYNNE D. TALLEY,

Scripps Institution of Oceanography, La Jolla, California

HASSAN VIRJI,

International START Secretariat, Washington, D.C.

YUK YUNG,

California Institute of Technology, Pasadena

NRC Staff

AMANDA STAUDT, Senior Program Officer

ROB GREENWAY, Senior Program Assistant

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
×

BOARD ON ATMOSPHERIC SCIENCES AND CLIMATE

ROBERT J. SERAFIN (Chair),

National Center for Atmospheric Research, Boulder, Colorado

FREDERICK R. ANDERSON,

McKenna Long & Aldridge LLP, Washington, D.C.

ROBERT C. BEARDSLEY,

Woods Hole Oceanographic Institution, Massachusetts

MICHAEL L. BENDER,

Princeton University, New Jersey

ROSINA M. BIERBAUM,

University of Michigan, Ann Arbor

RAFAEL L. BRAS,

Massachusetts Institute of Technology, Cambridge

MARY ANNE CARROLL,

University of Michigan, Ann Arbor

WALTER DABBERDT,

Vaisala Inc., Boulder, Colorado

KERRY A. EMANUEL,

Massachusetts Institute of Technology, Cambridge

CASSANDRA G. FESEN,

Dartmouth College, Hanover, New Hampshire

JENNIFER A. LOGAN,

Harvard University, Cambridge, Massachusetts

VERNON R. MORRIS,

Howard University, Washington, D.C.

WILLIAM J. RANDEL,

National Center for Atmospheric Research, Boulder, Colorado

ROGER M. WAKIMOTO,

University of California, Los Angeles

JOHN C. WYNGAARD,

Pennsylvania State University, University Park

Ex Officio Members

ANTONIO J. BUSALACCHI, JR.,

University of Maryland, College Park

ERIC F. WOOD,

Princeton University, New Jersey

NRC Staff

CHRIS ELFRING, Director

PAUL CUTLER, Senior Program Officer

AMANDA STAUDT, Senior Program Officer

JULIE DEMUTH, Program Officer

PARIKHIT SINHA, Program Officer

ELIZABETH A. GALINIS, Senior Program Assistant

ROB GREENWAY, Senior Program Assistant

DIANE GUSTAFSON, Administrative Coordinator

ANDREAS SOHRE, Financial Associate

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
×

Preface

Radiative forcing is a way to quantify an energy imbalance imposed on the climate system either externally (e.g., solar energy output or volcanic emissions) or by human activities (e.g., deliberate land modification or emissions of greenhouse gases, aerosols, and their precursors). The concept of radiative forcing has been central for guiding climate research and policy over the past two decades. There are several reasons for this. It provides a simple yet fundamental index that allows us to look at how climate change is driven by the energy imbalance of the Earth system. It is successful in predicting change in global mean surface temperature as computed from climate models and it, thus, allows quantitative comparison of the contributions of different agents to climate change. It is easy to compute and is reproducible across models and therefore offers a convenient common metric on which policy research and recommendations can be based.

New studies on climate forcing agents not conventionally considered have, however, raised doubts as to the continued viability of the radiative forcing concept. For example, the climatic effects from light-absorbing aerosols or land-use changes do not lend themselves to quantification using the traditional radiative forcing concept. Aerosol effects on clouds are difficult to describe in terms of simple radiative forcing. These challenges have raised the question of whether the radiative forcing concept has outlived its usefulness and, if so, what new climate change metrics should be used.

To address these issues, the U.S. Climate Change Science Program (CCSP) asked the National Academies to undertake a study to evaluate the current state of knowledge on radiative forcings and to identify relevant

Page viii Cite
Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
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BOX P-1
Statement of Task for the Committee on Radiative Forcing Effects on Climate

This study will examine the current state of knowledge regarding the direct and indirect radiative forcing effects of gases, aerosols, land use, and solar variability on the climate of the Earth’s surface and atmosphere and it will identify research needed to improve our understanding of these effects. Specifically, this study will:

  1. Summarize what is known about the direct and indirect radiative effects caused by individual forcing agents, including the spatial and temporal scales over which specific forcing agents may be important;

  2. Evaluate techniques (e.g., modeling, laboratory, observations, and field experiments) used to estimate direct and indirect radiative effects of specific forcing agents;

  3. Identify key gaps in the understanding of radiative forcing effects on climate;

  4. Identify key uncertainties in projections of future radiative forcing effects on climate;

  5. Recommend near- and longer-term research priorities for improving our understanding and projections of radiative forcing effects on climate.

research needs. In response, the Committee on Radiative Forcing Effects on Climate was formed. The committee was charged to examine the current state of knowledge of how gases, aerosols, land use, and solar variability force the climate system, identify key gaps in understanding, and recommend research priorities (see Box P-1 for the full statement of task). This report presents the committee’s findings and recommendations.

The committee began its discussions with a good dose of skepticism about the continued viability of the radiative forcing concept. In the end, however, one of our major findings is that the concept retains considerable value. It needs to be expanded to account for the vertical and regional structure of radiative forcing and also for nonradiative climate forcings. We propose several new research avenues that should be pursued to accomplish this expansion. We present an agenda for addressing uncertainties in forcings and climate effects from conventional and nonconventional agents. We make specific recommendations for using past climate records to improve our understanding of the relationship of radiative forcing to climate change and for developing an observational strategy aimed at continuous monitoring of climate forcing variables for the indefinite future. Finally, we examine ways to improve the application of radiative and nonradiative forcing metrics in policy analyses directed at climate change.

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
×

The committee met four times over the course of a year to gather information and to deliberate over findings and recommendations. We thank the following speakers who shared their knowledge with the committee: James Anderson, Harvard University; Theodore L. Anderson, University of Washington; Gordon Bonan, National Center for Atmospheric Research; Thomas Crowley, Duke University; Kea Duckenfield, National Oceanic and Atmospheric Administration (NOAA); Jerry Elwood, Department of Energy; David Fahey, NOAA Aeronomy Laboratory; Jay Fein, National Science Foundation; Peter Gent, National Center for Atmospheric Research; James Hansen, National Aeronautics and Space Administration (NASA) Goddard Institute for Space Studies; Dennis Hartmann, University of Washington; Eugenia Kalnay, University of Maryland; Yoram Kaufman, NASA Goddard Space Flight Center; James Mahoney, U.S. Climate Change Science Program; Kenneth Mooney, NOAA; Richard Moss, U.S. Climate Change Science Program; V. Ramaswamy, NOAA Geophysical Fluid Dynamics Laboratory; Daniel Rosenfeld, Hebrew University; Susan Solomon, NOAA Aeronomy Laboratory; Graeme Stephens, Colorado State University; Lucia Tsaoussi, NASA; and Josh Willis, Scripps Institution of Oceanography.

The committee hopes that this report will be useful to the U.S. Climate Change Science Program in mapping future research directions to improve our knowledge of radiative and other climate forcings, their variability, and their impacts on climate.

Daniel J. Jacob

Chair

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
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Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
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Acknowledgments

This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report:

Tami C. Bond, University of Illinois

James A. Coakley, Jr., Oregon State University

Robert E. Dickinson, Georgia Institute of Technology

James A. Edmonds, Pacific Northwest National Laboratory

Jonathan A. Foley, University of Wisconsin

Peter R. Gent, National Center for Atmospheric Research

Richard Goody, Harvard University

Venkatachalam Ramaswamy, Geophysical Fluid Dynamics Laboratory

William J. Randel, National Center for Atmospheric Research

Stephen E. Schwartz, Brookhaven National Laboratory

Although the reviewers listed above have provided constructive comments and suggestions, they were not asked to endorse the report’s conclusions or recommendations, nor did they see the final draft of the report

Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
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before its release. The review of this report was overseen by John H. Seinfeld, California Institute of Technology. Appointed by the National Research Council, he was responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution.

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Suggested Citation:"Front Matter." National Research Council. 2005. Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties. Washington, DC: The National Academies Press. doi: 10.17226/11175.
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Changes in climate are driven by natural and human-induced perturbations of the Earth’s energy balance. These climate drivers or "forcings" include variations in greenhouse gases, aerosols, land use, and the amount of energy Earth receives from the Sun. Although climate throughout Earth’s history has varied from "snowball" conditions with global ice cover to "hothouse" conditions when glaciers all but disappeared, the climate over the past 10,000 years has been remarkably stable and favorable to human civilization. Increasing evidence points to a large human impact on global climate over the past century. The report reviews current knowledge of climate forcings and recommends critical research needed to improve understanding. Whereas emphasis to date has been on how these climate forcings affect global mean temperature, the report finds that regional variation and climate impacts other than temperature deserve increased attention.

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