Decade-to-Century-Scale Climate Variability and Change

A Science Strategy

Panel on Climate Variability on Decade-to-Century Time Scales
Board on Atmospheric Sciences and Climate
Commission on Geosciences, Environment, and Resources
National Research Council

NATIONAL ACADEMY PRESS
Washington, D.C. 1998



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Decade-to-Century-Scale Climate Variability and Change A Science Strategy Panel on Climate Variability on Decade-to-Century Time Scales Board on Atmospheric Sciences and Climate Commission on Geosciences, Environment, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1998

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Page ii 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 competencies and with regard for appropriate balance. Support for this project was provided by the National Oceanic and Atmospheric Administration under Contract No. 50-DKNA-5-00015. 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 above-mentioned agency. Library of Congress Catalog Card Number 98-88439 International Standard Book Number 0-309-06098-2 Additional copies of this report are available from: National Academy Press 2101 Constitution Avenue, NW Box 285 Washington, DC 20055 800-624-6242 202-334-3313 (in the Washington Metropolitan Area) http://www.nap.edu COVER: The Day It Happened, the oil painting reproduced on the cover of this book, is the work of Ilana Cernat of Bat-Yam, Israel. Dr. Cernat is linked to the world of intermediate-scale climate change through her son Michael Ghil, a member of the panel on Climate Variability on Decade-to-Century Time Scales. The Day It Happened (1988) is one of several of her paintings that express her concern for the future, particularly what sort of world we will be leaving to the generations to come. A lawyer by training and profession, Dr. Cernat began studying painting in her teens. Her work has been exhibited in Romania, Hungary, Israel, and the United States, and hangs in collections in other countries as well. Her 1989 painting The Eye of the Storm appeared on the cover of the 1995 NRC report on natural climate variability on decade-to-century time scales. Copyright 1998 by the National Academy of Sciences. All rights reserved. Printed in the United States of America

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Page iii PANEL ON CLIMATE VARIABILITY ON DECADE-TO-CENTURY TIME SCALES DOUGLAS G. MARTINSON (Chair), Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York DAVID S. BATTISTI, University of Washington, Seattle RAYMOND S. BRADLEY, University of Massachusetts, Amherst JULIA E. COLE, University of Colorado, Boulder RANA A. FINE, University of Miami, Florida MICHAEL GHIL, University of California, Los Angeles YOCHANAN KUSHNIR, Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York SYUKURO MANABE, Earth Frontier Research System, Tokyo, Japan MICHAEL S. McCARTNEY, Woods Hole Oceanographic Institution, Massachusetts M. PATRICK McCORMICK, Hampton University, Virginia MICHAEL J. PRATHER, University of California, Irvine EDWARD S. SARACHIK, University of Washington, Seattle PIETER TANS, National Oceanic and Atmospheric Administration, Boulder, Colorado LONNIE G. THOMPSON, Ohio State University, Columbus MICHAEL WINTON, Princeton University, New Jersey Staff ELLEN F. RICE, Program Officer (ending September 1, 1998) PETER A. SCHULTZ, Program Officer DIANE L. GUSTAFSON, Administrative Assistant

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Page iv CLIMATE RESEARCH COMMITTEE THOMAS R. KARL (Chair), National Climatic Data Center, Asheville, North Carolina ROBERT E. DICKINSON (Vice Chair), University of Arizona, Tucson MAURICE BLACKMON, National Center for Atmospheric Research, Boulder, Colorado BERT BOLIN, Osterskar, Sweden JEFF DOZIER, University of California, Santa Barbara JAMES GIRAYTYS, Consultant, Winchester, Virginia JAMES E. HANSEN, Goddard Institute for Space Studies, NASA, New York, New York PHILIP E. MERILEES, Naval Research Laboratory, Monterey, California ROBERTA BALSTAD MILLER, Consortium for International Earth Science Information Network, Palisades, New York S. ICHTIAQUE RASOOL, University of New Hampshire, Durham STEVEN W. RUNNING, University of Montana, Missoula EDWARD S. SARACHIK, University of Washington, Seattle WILLIAM H. SCHLESINGER, Duke University, Durham, North Carolina KARL E. TAYLOR, Lawrence Livermore National Laboratory, Livermore, California ANNE M. THOMPSON, NASA Goddard Space Flight Center, Greenbelt, Maryland Ex Officio Members DOUGLAS G. MARTINS ON, Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York W. LAWRENCE GATES, Lawrence Livermore National Laboratory, Livermore, California SOROOSH SOROOSHIAN, University of Arizona, Tucson PETER J. WEBSTER, University of Colorado, Boulder Staff PETER A. SCHULTZ, Program Officer LOWELL SMITH, Senior Program Officer (IPA) (ending September 30, 1998) TENECIA A. BROWN, Senior Program Assistant

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Page v BOARD ON ATMOSPHERIC SCIENCES AND CLIMATE ERIC J. BARRON (Co-Chair), Pennsylvania State University, University Park JAMES R. MAHONEY (Co-Chair), International Technology Corporation, Washington, D.C. SUSAN K. AVERY, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder LANCE F. BOSART, State University of New York, Albany MARVIN A. GELLER, State University of New York, Stony Brook DONALD M. HUNTEN, University of Arizona, Tucson JOHN IMBRIE, Brown University, Providence, Rhode Island CHARLES E. KOLB, Aerodyne Research, Inc., Billerica, Massachusetts THOMAS J. LENNON, Sonalysts, Inc., Alexandria, Virginia MARK R. SCHOEBERL, NASA Goddard Space Flight Center, Greenbelt, Maryland JOANNE SIMPSON, NASA Goddard Space Flight Center, Greenbelt, Maryland NIEN DAK SZE, Atmospheric and Environmental Research, Inc., Cambridge, Massachusetts Staff ELBERT W. (JOE) FRIDAY, Jr., Director H. FRANK EDEN, Senior Program Officer LAURIE S. GELLER, Program Officer ELLEN F. RICE, Program Officer/Reports Officer (ending September 1, 1998) PETER A. SCHULTZ, Program Officer DAVID H. SLADE, Senior Program Officer LOWELL SMITH, Senior Program Officer (IPA) (ending September 30, 1998) TENECIA A. BROWN, Senior Program Assistant DIANE L. GUSTAFSON, Administrative Assistant ROBIN MORRIS, Administrative Associate

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Page vi COMMISSION ON GEOSCIENCES, ENVIRONMENT, AND RESOURCES GEORGE M. HORNBERGER (Chair), University of Virginia, Charlottesville PATRICK R. ATKINS, Aluminum Company of America, Pittsburgh, Pennsylvania JERRY F. FRANKLIN, University of Washington, Seattle B. JOHN GARRICK, PLG, Inc., St. George, Utah THOMAS E. GRAEDEL, Yale University, New Haven, Connecticut DEBRA KNOPMAN, Progressive Foundation, Washington, D.C. KAI N. LEE, Williams College, Williamstown, Massachusetts JUDITH E. MCDOWELL, Woods Hole Oceanographic Institution, Massachusetts RICHARD A. MESERVE, Covington & Burling, Washington, D.C. HUGH C. MORRIS, Canadian Global Change Program, Delta, British Columbia RAYMOND A. PRICE, Queen's University at Kingston, Ontario H. RONALD PULLIAM, University of Georgia, Athens THOMAS C. SCHELLING, University of Maryland, College Park VICTORIA J. TSCHINKEL, Landers and Parsons, Tallahassee, Florida E-AN ZEN, University of Maryland, College Park MARY LOU ZOBACK, U.S. Geological Survey, Menlo Park, California Staff ROBERT HAMILTON, Executive Director GREGORY SYMMES, Assistant Executive Director JEANETTE SPOON, Administrative Officer SANDI FITZPATRICK, Administrative Associate MARQUITA SMITH, Administrative Assistant/Technology Analyst

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Page vii Preface In 1990, the Intergovernmental Panel on Climate Change (IPCC) released its monumental scientific assessment on climate change. This document presented, for the first time, a broad international scientific perspective on the status of our understanding of global climate change, focusing predominantly on anthropogenic change. While first recognized as a scientific issue nearly 100 years ago and the subject of many reports, this first attempt at producing a comprehensive assessment of the problem was both timely and energizing. It helped focus our collective scientific attention on key issues, by identifying, among other things, critical gaps in our understanding of the fundamental physics, chemistry, and biology of global change. One significant gap involved our meager understanding and documentation of natural variability in the Earth's climate system which provides a context for evaluating the significance of human-induced changes. The climate change and variability that we experience will be a commingling of the ever changing natural climate state with any anthropogenic change. While we are ultimately interested in understanding and predicting how climate will change, regardless of the cause, an ability to differentiate anthropogenic change from natural variability is fundamental to help guide policy decisions, treaty negotiations, and adaptation versus mitigation strategies. Without a clear understanding of how climate has changed naturally in the past, and the mechanisms involved, our ability to interpret any future change will be significantly confounded and our ability to predict future change severely curtailed. Recognizing this gap, the Climate Research Committee of the National Research Council's Board on Atmospheric Sciences and Climate, organized a workshop in 1992 involving the world's most prominent climate researchers, to assess the state of understanding of natural climate variability. The workshop focused on natural climate change that occurs slowly, sometimes remaining almost imperceptible for many years, decades, or even a century. These "decade-to-century" (dec-cen) time scales are the same ones over which anthropogenic climate change is expected to manifest itself, and thus the ones most likely to confound our interpretation and prediction of observed climate change as it relates to anthropogenic change. The results of this workshop, elaborated and published in a peer-reviewed National Academy of Science volume in 1995, showed considerable progress in our understanding of dec-cen climate variability on a broad number of fronts. At the same time the NRC workshop was being organized in the United States, the Joint Scientific Committee, an international scientific oversight body for guiding international climate research under the auspices of the World Climate Research Programme (WCRP), called on a group of experts to consider possible future directions for climate research. The results of their deliberations were published in 1992 in a report entitled CLIVAR—A Study of Climate Variability and Predictability. This document proposed the need for a new internationally-coordinated, interdisciplinary research program on climate variability and predictability, with decade-to-century time scale variability (natural and anthropogenic) playing a central role. As the science plan for the CLIVAR program was being developed, the United States Global Change Research Program (USGCRP), also active in the international process, began formalizing plans to advance the development of a U.S. national science plan for addressing climate variability and change on decade-to-century time scales. The manifestation of these plans would contribute to the international effort while clearly defining and articulating our own particular national scientific interests. This led to the formation of the NRC panel on Climate Variability on Decade-to-Century Time Scales (the Dec-Cen panel). The NRC's Climate Research Committee (CRC) is the U.S. national committee to the WCRP. The Dec-Cen panel, as well as the complementary Global Ocean-Atmosphere-Land System (GOALS) and Global Energy and Water Cycle Experiment (GEWEX) panels (addressing shorter time scales and key processes), were established under the CRC to interface with the WCRP and CLIVAR organizational

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Page viii Decade-to-Century-Scale Climate Variability and Change A Science Strategy

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Page ix Acknowledgment of Reviewers 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 NRC's Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making the 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 participation in the review of this report: Russ E. Davis, University of California, San Diego W. Lawrence Gates, Lawrence Livermore National Laboratory George M. Hornberger, University of Virginia, Charlottesville Upmanu Lall, Utah State University Gerald A. Meehl, National Center for Atmospheric Research Richard S. Stolarski, NASA Goddard Space Flight Center John M. Wallace, University of Washington John E. Walsh, University of Illinois at Urbana-Champaign Warren A. Washington, National Center for Atmospheric Research In addition, we appreciate the post-review material and comments from Russ Davis, Robert Dickinson, Upmanu Lall, and Peter Niiler that helped to provide a more balanced discussion in some key areas. While the individuals listed above have provided constructive comments and suggestions, it must be emphasized that responsibility for the final content of this report rests entirely with the authoring committee and the institution.

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Page x 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. William 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. Kenneth I. Shine 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. William A. Wulf are chairman and vice chairman, respectively, of the National Research Council.

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Page xi Contents Executive Summary 1 1. Introduction 6 Society and a Varying Climate System 6 A U.S. Dec-Cen Science Strategy 7 2. Climate Attributes That Influence Society 9 Precipitation and Water Availability 10 Temperature 11 Solar Radiation 15 Storms 17 Sea Level 20 Ecosystems 22 3. Modes of Climate Variability 25 Climate Patterns in the Atmosphere 26 Other Patterns of Interest 28 Co-variability in the Climate System: Coupled Patterns 28 The Role of Dec-Cen Variability in Global Warming 35 Fundamental Issues and Questions 36 4. Mechanisms and Predictability 39 The Nature of Climate Prediction 39 Short-, Medium-, and Long-Range Climate Prediction 40 Prediction and Mechanisms 41 The Uses of Climate Prediction 43 5. Climate-System Components 48 Atmospheric Composition and Radiative Forcing 49 Atmospheric Circulation 62 Hydrologic Cycle 71 Ocean Circulation 80 Cryosphere 97 Land and Vegetation 106 6. Crosscutting Issues 111 Climate Information 111 Coupled-Model Development and Infrastructure 120

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Page xii Detection, Attribution, and Simulation 122 Linkage Across Time Scales 123 7 Conclusions and Recommendations 124 References 126 Acronyms and Abbreviations 141

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