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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Changing Climate Report of the Carbon Dioxide Assessment Committee Board on Atmospheric Sciences and Climate Commission on Physical Sciences, Mathematics, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1983 hAS-NAE LIBRARY

National Academy Press • 2101 Constitution Avenue NW • Washington DC 20418 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. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Research Council was established by the National Academy of Sciences in l9l6 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and of advising the federal government. The Council operates in accordance with general policies determined by the Academy under the authority of its congressional charter of l863, which establishes the Academy as a private, nonprofit, self-governing membership corporation. The Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in the conduct of their services to the government, the public, and the scientific and engineering communities. It is administered jointly by both Academies and the Institute of Medicine. The National Academy of Engineering and the Institute of Medicine were established in l964 and l970, respectively, under the charter of the National Academy of Sciences. Library of Congress Catalog Card Number 83-62680 International Standard Book Number 0-309-03425-6 Copyright® l983 by the National Academy of Sciences No part of this book may be reproduced by any mechanical, photographic, or electronic process, or in the form of a phonographic recording, nor may it be stored in a retrieval system, transmitted, or otherwise copied for public or private use, without written permission from the publisher, except for the purposes of official use by the United States Government. Printed in the United States of America

Carbon Dioxide Assessment Committee William A. Nierenberg, Scripps Institution of Oceanography, Chairman Peter G. Brewer, Woods Hole Oceanographic Institution (on leave with the National Science Foundation) Lester Machta, Air Resources Laboratory, National Oceanic and Atmospheric Administration William D. Nordhaus, Yale University Roger R. Revelle, University of California, San Diego Thomas C. Schelling, Harvard University Joseph Smagorinsky, Princeton University Paul E. Waggoner, Connecticut Agricultural Experiment Station George M. Woodwell, Marine Biological Laboratory, Woods Hole, Massachusetts Consultants David A. Katcher, Chevy Chase, Maryland Gary W. Yohe, Wesleyan University Staff John S. Perry, Executive Secretary Jesse H. Ausubel, Staff Officer James A. Tavares Adele King Malone (to 5/82) iii

Detection and Monitoring Working Group Gunter Weller, University of Alaska, Chairman D. James Baker, Jr., University of Washington W. Lawrence Gates, Oregon State University Michael C. MacCracken, Lawrence Livermore Laboratory, Syukuro Manabe, Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration Thomas H. Vonder Haar, Colorado State University John S. Perry, Executive Secretary iv

Climate Research Committee Joseph Smagorinsky, Princeton University, Chairman Tim P. Barnett, Scripps Institution of Oceanography Harry L. Bryden, Woods Hole Oceanographic Institution Isaac Held, Geophysical Fluid Dynamics Laboratory, National Oceanic and Atmospheric Administration Frederick T. Mackenzie, Northwestern University James C. McHilliams, National Center for Atmospheric Research Norman Phillips, National Oceanic and Atmospheric Administration Veerabhadran Ramanathan, National Center for Atmospheric Research Jagadish Shukla, Goddard Space Flight Center, National Aeronautics and Space Administration Thomas H. Vonder Haar, Colorado State University John M. Wallace, University of Washington Ferris Webster, University of Delaware Gunter E. Weller, University of Alaska

Board on Atmospheric Sciences and Climate Thomas F. Malone, Butler University, Chairman Ferdinand Baer, University of Maryland Louis J. Battan, University of Arizona Werner A. Baum, Florida State University Robert A. Duce, University of Rhode Island John A. Eddy, National Center for Atmospheric Research Peter V. Hobbs, University of Washington Francis S. Johnson, University of Texas, Dallas Robert W. Kates, Clark University Michael B. McElroy, Harvard University James C. McWilliams, National Center for Atmospheric Research Volker A. Mohnen, State University of New York, Albany Andrew F. Nagy, University of Michigan William A. Nierenberg, Scripps Institution of Oceanography Roger R. Revelle, University of California, San Diego Juan G. Roederer, University of Alaska Norman J. Rosenberg, University of Nebraska Stephen H. Schneider, National Center for Atmospheric Research Joseph Smagorinsky, Princeton university John W. Townsend, Fairchild Space 6 Electronics Company Thomas H. Vonder Haar, Colorado State University vi

Commission on Physical Sciences, Mathematics, and Resources Herbert Friedman, National Research Council, Chairman Elkan R. Blout, Harvard Medical School William Browder, Princeton University Bernard F. Burke, Massachusetts Institute of Technology Herman Chernoff, Massachusetts Institute of Technology Mildred S. Dresselhaus, Massachusetts Institute of Technology Walter R. Eckelmann, Sohio Petroleum Company, Dallas, Texas Joseph L. Fisher, Secretary of Human Resources, Office of the Governor, Richmond, Virginia James C. Fletcher, Burroughs Corporation, McLean, Virginia William A. Fowler, California Institute of Technology Gerhart Friedlander, Brookhaven National Laboratory Edward A. Frieman, Science Applications, Inc., La Jolla, California Edward D. Goldberg, Scripps Institution of Oceanography Charles L. Hosier, Jr., Pennsylvania State University Konrad B. Krauskopf, Stanford University Charles J. Mankin, Oklahoma Geological Survey Walter H. Munk, University of California, San Diego George E. Pake, Xerox Research Center, Palo Alto, California Robert E. Sievers, University of Colorado, Boulder Howard E. Simmons, Jr., E.I. du Pont de Nemours & Co., Inc. John D. Spengler, Harvard School of Public Health Hatten S. Yoder, Carnegie Institution of Washington Raphael G. Kasper, Executive Director vii

Foreword The Energy Security Act of l980, while focused on the development of synthetic fuels, also called for examination of some of the environ- mental consequences of their development. One such consequence perceived by the Congress was the buildup of carbon dioxide (CO2) in the atmosphere, and the National Academy of Sciences (MAS) and the Office of Science and Technology Policy (OSTP) of the Executive Office of the President were requested to prepare an assessment of its implications. Concern about the atmosphere's carbon dioxide and its influence on climate dates back to the last century. In the l970s, however, with recognition of a growing world population and increasing per capita use of energy, attention markedly heightened. In l977 the National Research Council issued a report, Energy and Climate,1 prepared by a panel chaired by Roger Revelle, calling for an intensified program of research on CO2. At around this time, the federal government began expanding its concern with CO2, primarily through a research and assessment program in the Department of Energy. In a congressional symposium on CO2 and energy policy in l979 some scientists expressed the fear that atmospheric CO2 could double by the first decade of the twenty-first century if coal and fossil-based synthetic fuels were vigorously exploited. Such concerns and the increasing volume of research results led the Congress and the Executive to ask the NAS to consider anew various aspects of the issue. In July l979, a brief preliminary statement about CO2 and energy policy was released by the Academy, and later in that same summer a Panel of the Climate Research Board chaired by the late Jule Charney undertook an evaluation of the models being used to estimate likely effects of CO2 on climate.2 In the following winter and spring, a committee chaired by Thomas C. Schelling and including several other members of the current Committee considered 1 Geophysics Study Committee (l977). Energy and Climate. National Academy Press, Washington, D.C. 2 National Research Council (l979). Carbon Dioxide and Climate: A Scientific Assessment. National Academy Press, Washington, D.C. ix

some of the economic and social aspects of increase in CO2.S At the same time, in April l980, the Senate Committee on Energy and Natural Resources convened a hearing on the issue. In this climate of concern, the Energy Security Act of l980 was passed, calling upon OSTP to request a study by the Academy that would deal with, among others, the following issues: • A comprehensive assessment of CO2 release and impacts of CO2 increase; • Development of an international research and assessment program and definition of the U.S. role; • Analysis of domestic resource requirements for international and domestic programs; Evaluation of the U.S. government CO2 program; and Assessment of the need for periodic reports and a long-term assessment program. Annex 3 of this report contains the relevant subtitle of the legislation. As congressional interest was mounting, the Climate Research Board requested one of its members, William A. Nierenberg, to monitor developments and to advise the Board on appropriate actions. In response to the congressional mandate, the Carbon Dioxide Assessment Committee (CDAC) was formed under his leadership to develop a plan to accomplish the requested study. With support from OSTP, the Committee developed a preliminary plan, which was provided to OSTP for comment in January l98l. The change of administration at that time slowed the discussions of the study's scope and objectives. However, in the summer of l98l a plan of action was agreed on by which the NAS and OSTP could respond to the congressional request for an independent and comprehensive assessment. The report would comprise two major parts: (l) an overview or synthesis repre- senting the views of the Committee as a whole on the issue and (2) a group of papers each addressing a specific topic or problem area and prepared by an individual committee member or a specialist group. The Committee began its work in September l98l. Over the next 2 years, the Committee members met four times (September 28-29, l98l, Washington, D.C.; March 25-26, l982, La Jolla, California; September 20-2l, Berkeley Springs, West Virginia; January l3-l4, l983, Washington, D.C.) to monitor progress on their specific topics and to develop their collective views. A number of considerations went into the design of the Committee and the selection of additional experts to contribute to its work. Com- petence was sought in each of the major subject areas of the question, 3 Letter report of the Ad Hoc Study Panel on Economic and Social Aspects of Carbon Dioxide Increase, T. C. Schelling, Chairman. April l8, l980. Climate Research Board, National Academy of Sciences, Washington, D.C.

as well as experience with assessment of long-range issues. A balance of viewpoints about environmental issues was sought. Finally, con- tinuity was maintained with previous, related NRC efforts (Energy and Climate, Energy in Transition," the Schelling report). Additional experience and skills were provided by consultants to the Committee and by ad hoc workshops and groups convened with the assistance of other NRC units. Before the reader turns to the contents of this report, the question might be raised: Why another CO2 report, apart from the legislative request? The CO2 issue has been probingly addressed by many indi- viduals and groups in recent years. One could mention, for example, Carbon Dioxide Review: l982,8 Carbon Dioxide from Coal Utilization,* On the Assessment of the Role of CO? on Climate Variations and Their Impact,7 The C(^-Climate Connection,' The Long-Term Impacts of Increasing Atmospheric Carbon Dioxide Levels,9 Interactions of Energy and Climate,"as well as the NRC's own Energy and Climate, Charney report, and Schelling report. There are at least two reasons to con- tribute to the growing volume of literature on the CO2 issue. One is that research developments are occurring at a rapid rate, as we see in many sections of the report that follows. A second reason is that the focus and perspectives of the reports on the CO2 issue differ. A major distinguishing feature of Changing Climate is that it represents a sustained attempt by a group with a wide range of expertise to achieve a comprehensive and internally consistent assessment. On behalf of the Board and the Academy, I wish to express our appre- ciation to Professor Nierenberg, the members of the Committee, and the many other participants in this study for their individual and collec- tive contributions to this report. As described in the Historical Note (Annex 2), the carbon dioxide issue has been with us for a long time, " National Research Council (l979). Energy in Transition l985-20l0. Final Report of the Committee on Nuclear and Alternative Energy Systems (CONAES). W. H. Freeman, San Francisco. SW. C. Clark, ed. (l982). Carbon Dioxide Review: l982. Oxford U. Press, New York, 469 pp. *I. M. Smith (l982). Carbon Dioxide from Coal Utilization. Technical Information Service, International Energy Agency, Paris. 7WMO/ICSU/UNEP (l98l). On the assessment of the role of CO2 on climate variations and their impact. (Based on meeting of experts, Villach, Austria, November l980.) World Meteorological Organization, Geneva, January l98l. *G. B. Tucker (l98l). The CO?-Climate Connection. Australian Academy of Science, Canberra. 9G. J. MacDonald, ed. (l982). The Long-Term Impacts of Increasing Atmospheric Carbon Dioxide Levels. Ballinger, Cambridge, Mass., 263 pp. 10W. Bach, J. Pankrath, and J. Williams, eds. (l980). Interactions of Energy and Climate. Reidel, Dordrecht, The Netherlands. xi

and it will undoubtedly maintain a prominent place on our agenda for a long time to come. We continue to need well-coordinated programs of research, productively interdisciplinary in character and broadly international in scope. As Professor Nierenberg indicates in his Preface, this report is best viewed as one stepping-stone on a long pathway into the future. We are confident, however, that it will prove to be a solid step on that pathway toward more complete understanding of this complex issue. Thomas F. Malone, Chairman Board on Atmospheric Sciences and Climate xii

Preface There is a broad class of problems that have no "solution" in the sense of an agreed course of action that would be expected to make the problem go away. These problems can also be so important that they should not be avoided or ignored until the fog lifts. We simply must learn to deal more effectively with their twists and turns as they unfold. He require sensible regular progress to anticipate what these developments might be with a balanced diversity of approaches. The payoff is that we will have had the chance to consider alternative courses of action with some degree of calm before we may be forced to choose among them in urgency or have them forced on us when other—perhaps better—options have been lost. Increasing atmospheric CO2 and its climatic consequences constitute such a problem. Research developments are taking place rapidly in this area. In the pages that follow we report our understanding of the status of a number of selected, critical aspects and comment on how well we think the overall attack on this complex matter is proceeding. Our stance is conservative: we believe there is reason for caution, not panic. Since understanding and proof of what is happening to climate as a result of practices that load the atmosphere with CO2 may come too late to allow for corrective action, we may not be able to wait to make certain there is a best course. Thus, we must proceed in a manner that keeps open our major options on energy development and use, on water management, agricultural adjustment, and other relevant activities, as we move from one set of uncertainties to another. We make an effort in this report to point the way as we see it today. A range of approaches was employed in developing the Committee's report. For example, in the study of possible future CO2 emissions, a review of earlier research was commissioned and a new model was constructed to remedy some of the shortcomings of previous work. The carbon cycle was addressed through individual reviews of its oceanic, atmospheric, and biotic components, together with model-based sensitiv- ity analyses. In the area of agriculture a survey was undertaken, and several outside experts were convened in a small informal workshop to address the relationship of climatic change to crop yield. A group was also convened, in Athens, Georgia, in May l982, in conjunction with a meeting organized by the American Association for the Advancement of xiii

Science on direct effects of C02 on plants. Small, informal work- shops were also convened in the areas of hydrology and land surface processes (La Jolla, March l6-l7, l982), Antarctic Ice (La Jolla, March l8-l9, l982), and Arctic Ice (Philadelphia, June l-2, l982). Questions of sea-level rise were explored with assistance from experts from the Samenwerkende Instellingen ten Behoeve van beleidsanalytische Studies (SIBAS), Delft, The Netherlands. The general area of scenario construc- tion and evaluation benefited from the participation of three Carbon Dioxide Assessment Committee (CDAC) members in a workshop on this topic at the International Institute for Applied Systems Analysis in Laxenburg, Austria, in July l982. The Committee recognized early that the central issue of CO2 effects on climate would require intensive review. Thus, the Board's Climate Research Committee was asked to re-examine and update the work of the l979 Charney panel. A panel chaired by Joseph Smagorinsky, a member of the CDAC and Chairman of the Climate Research Committee (CRC), undertook this task and issued its report, Carbon Dioxide and Climate: A Second Assessment, in l982. This document should be considered an integral part of the present study; its conclusions are reproduced in this volume together with brief supplementary comments. The CRC was also asked to consider the detection of climatic change induced by CO2 and the monitoring of climatic variables. With the advice of the CRC, a group of experts, including a number of CRC members, was asked to contribute to the report. These experts met several times during l982 under the leadership of Gunter Weller, and the results of their conferring form Chapter 5 of this volume. The scope of the Committee's report is broad, and I believe it meets as fully as a small group could the congressional request for a "compre- hensive" assessment of the C02 issue. A truly complete assessment of the CO2 issue might involve most or all of a very wide range of elements, including identification of various risks and prospective changes; estimation of probabilities of their occurrence; linkage of such events with various environmental and social consequences; and evaluation of the risks by comparison with costs, with other risks, with benefits, with alternative ways of reducing risks, or with risks of substitute activities. In this report the Committee does attempt to shed a little light on all of these aspects of the C02 issue: CO2 emissions and concentrations are projected; possible climatic changes are assessed; implications of increasing CO2 and climatic change for agriculture and water, sea level, and other selected areas are examined, including possible impacts that might have a low probability but a high cost; and possible consequences are evaluated against historical experiences and other current and future problems. However, the report certainly does not exhaust the issue. A number of possibly important problems are left for future investigators. Among such problems are the effects of non-C02 greenhouse gases on climate, effects of altered climate on agriculture and water outside the United States, and the feasibility of alternative nonfossil energy strategies. Furthermore, as interest in synfuels development dimin- ished, the CDAC chose to place less emphasis on this aspect of the xiv

CO2 issue than would have been the case if the report had been prepared largely during l979 and l980. While the report offers estimates of probabilities in several areas, it is not always possible to do so in a meaningful way. Consistent treatment of uncertainty in each of the aspects of this heterogeneous issue remains elusive, but I believe that this report makes substantial progress in this regard. The CO2 issue is so diverse in its intellectual components that no individual may be considered an expert on the entire problem. For this reason, as noted above, the CDAC prepared or commissioned separately authored and separately peer-reviewed papers in each area, with no attempt to force unanimity of style or of views. For the same reason, the Committee members felt themselves incapable of judging and endors- ing as a group the details of each paper's analysis and findings. Thus, each paper should be viewed primarily as the product of its individual author or authors, having had the review and comment of the Committee members and other reviewers but not enjoying the unanimity of conclu- sions possible in a more homogeneous and less controversial topic. However, the Committee's work did reveal a large core of views, find- ings, conclusions, and recommendations on a more general level, which all members could wholeheartedly and responsibly endorse. These are presented in the Synthesis of the report. Despite the existence of some areas of continuing controversy, such as the carbon cycle, there are no major dissents with respect to the contents of this assessment. There continues to be an outpouring of fact, interpretation, con- jecture, and proposals for research and policy having to do with the effect of increasing carbon dioxide and its consequences. Periodically, it will be well worth taking stock. Where are we? What is most impor- tant or troublesome? What should we be doing now, although treatment of the issue is full of uncertainties, to avoid the haste and waste of being forced to shoulder a burden later, when our best choices may have been foreclosed? What opportunities does the prospect of CO2-induced changes offer societies? Are we doing anything now that will look like a mistake later on? This report is the result of one effort to gain insights into these questions. We hope that others in the United States and other countries will continue to ask them. Such sustained question- ing may be the best insurance we can buy. The support that the CDAC has received from the Congress and the federal government throughout its work has been gratifying. The Office of Science and Technology Policy (OSTP) of the Executive Office of the President, the Department of Energy (DOE), and the National Science Foundation (NSF) provided the necessary means, as well as ready coopera- tion on access to information and expertise. Richard Meserve and Thomas Pestorius of OSTP, David Slade and Frederick Koomanoff of DOE, and Bernard Stein of NSF deserve special mention. I am sure that all the members of the Committee also share my gratitude to the many experts who let us draw upon their knowledge and wisdom through many ad hoc means. Our sister Climate Research Committee deserves many thanks for organizing groups to address the questions of climate modeling, detection of climate changes, and xv

monitoring. Some 30 volunteer reviewers provided trenchant and most helpful comments that greatly strengthened the report. Finally, we appreciate greatly the support provided by the NRC staff: particularly Jesse H. Ausubel and John S. Perry of the Board on Atmospheric Sciences and Climate (BASC); and also Robert S. Chen of BASC's predecessor, the Climate Board; James A. Tavares of the Board on Agriculture; and Gary Yohe and David Katcher, consultants to BASC. William A. Nierenberg, Chairman Carbon Dioxide Assessment Committee xv i

Contents EXECUTIVE SUMMARY l SYNTHESIS 5 Carbon Dioxide Assessment Committee l.l INTRODUCTION, 5 l.2 THE OUTLOOK, 9 l.2.l Future CO2 Emissions, 9 l.2.2 Future Atmospheric CO2 Concentrations, l4 l.2.3 Changing Climate with Changing CO2, 27 l.2.4 Detection of CO2-lnduced Changes, 32 l.2.5 Agricultural Impacts, 36 l.2.6 Water Supplies, 40 l.2.7 Sea Level, Antarctic, and Arctic, 40 l.3 SERIOUSNESS OF PROJECTED CHANGES, 44 l.3.l Specifiable Concerns, 45 l.3.l.l Agriculture and Water Resources, 45 l.3.l.2 Rising Sea Level, 48 l.3.2 More Speculative Concerns, 48 l.3.3 The Problem of Unease about Changes of This Magnitude, 50 l.4 POSSIBLE RESPONSES, 55 l.4.l Defining the Problem, 55 l.4.2 The Organizing Framework, 57 l.4.3 Categories of Response, 57 l.4.4 Reprise, 6l l.5 RECOMMENDATIONS, 6l l.5.l Can CO2 Be Addressed as an Isolated Issue?, 6l l.5.2 Actual and Near-Term Change of Policies, 62 l.5.3 Energy Research and Policy, 64 l.5.4 Synfuels Policy and CO2, 65 l.5.5 Applied Research and Development, 66 l.5.6 Basic Research and Monitoring, 67 l.5.6.l General Research Comments, 68 l.5.6.2 The International Aspect, 70 xvii

l.5.6.3 Projecting CO2 Emissions, 72 l.5.6.4 Projecting CO2 Concentrations, 72 l.5.6.5 Climate, 74 l.5.6.6 Detection and Monitoring, 76 l.5.6.7 Impacts, 78 l.6 CONCLUDING REMARKS, 8l REFERENCES, 8l 2 FUTURE CARBON DIOXIDE EMISSIONS FROM FOSSIL FUELS 87 2.l FUTURE PATHS OF ENERGY AND CARBON DIOXIDE EMISSIONS, 87 William D. Nordhaus and Gary W. Yohe 2.l.l Overview, 87 2.l.2 Detailed Description of the Model, Data, and Results, 99 2.l.2.l The Model, l00 2.l.2.2 The Data, lll 2.l.2.3 Results, l30 References, l5l 2.2 A REVIEW OF ESTIMATES OF FUTURE CARBON DIOXIDE EMISSIONS, l53 Jesse H. Ausubel and William D. Nordhaus 2.2.l Introduction, l53 2.2.2 Projections Based on Extrapolations, l55 2.2.3 Energy System Projections, l56 2.2.3.l Perry-Landsberg (NAS), l57 2.2.3.2 IIASA, l57 2.2.3.3 Rotty et al., l59 2.2.3.4 Nordhaus, l60 2.2.3.5 Edmonds and Reilly, l6l 2.2.3.6 Other Projections, l62 2.2.4 Projections with CO2 Feedback to the Energy System, l64 2.2.4.l Nordhaus, l64 2.2.4.2 Edmonds and Reilly, l65 2.2.4.3 CEQ, l66 2.2.4.4 A. M. Perry et al., l67 2.2.4.5 General Comments, l68 2.2.5 A Note on the Biosphere, l69 2.2.6 Projections of Non-CO2 Trace Gases, l70 2.2.7 Findings, l7l 2.2.7.l The State of the Art, l7l 2.2.7.2 Likely Future Outcomes, l73 2.2.8 Conclusion, l8l References, l8l xviii

3 PAST AND FUTURE ATMOSPHERIC CONCENTRATIONS OF CARBON DIOXIDE l86 3.l INTRODUCTION Peter G. Brewer, l86 3.2 CARBON DIOXIDE AND THE OCEANS Peter G. Brewer, l88 3.2.l Introduction, l88 3.2.2 The Cycle of Carbon Dioxide within the Oceans, l89 3.2.3 The Deep Circulation, l89 3.2.4 Biological Activity, l90 3.2.5 Deep Decomposition of Organic Matter, l9l 3.2.6 Calcium Carbonate, l9l 3.2.7 The Chemistry of C02 in Seawater, l94 3.2.8 Measurements of Ocean C02, l99 3.2.9 Models of Ocean CO2 Uptake, 202 3.2.l0 Future Studies and Problems, 209 3.2.ll Summary, 2ll References, 2ll 3.3 BIOTIC EFFECTS ON THE CONCENTRATION OF ATMOSPHERIC CARBON DIOXIDE: A REVIEW AND PROJECTION George M. Woodwell, 2l6 3.3.l Introduction, 2l6 3.3.2 How Much Carbon is Held in the Biota and Soils?, 2l7 3.3.2.l The Biota, 2l7 3.3.2.2 The Soils, 2l7 3.3.2.3 Total Carbon Pool under Biotic Influences, 2l7 3.3.3 Metabolism and the Storage of Carbon in Terrestrial and Aquatic Ecosystems, 2l8 3.3.3.l The Production Equation, 2l8 3.3.3.2 A Basis in the Metabolism of Forests for the Oscillation in Atmospheric CO2 Concentration, 2l9 3.3.3.3 Factors Affecting Global Net Ecosystem Production, 22l 3.3.4 Changes in Area of Forests of the World, 225 3.3.5 The Biota in the Context of the Global Carbon Balance, 229 3.3.6 A Projection of Further Releases from Biotic Pools, 234 3.3.7 Summary and Conclusions, 234 References, 236 3.4 THE ATMOSPHERE Lester Machta, 242 3.4.l Introduction, 242 3.4.2 Changes in Atmospheric CO2 Growth Rate with Time and Space, 243 3.4.2.l Shorter-Term Variation and Its Possible Cause, 243 3.4.2.2 Longer-Term Variations, 246 3.4.2.3 Change in Annual Cycle, 247 3.4.2.4 Spatial Distribution, 248 3.4.2.5 Isotopic Content of Atmospheric C02, 249 3.4.3 Conclusions, 250 References, 250 xix

3.5 METHANE HYDRATES IN CONTINENTAL SLOPE SEDIMENTS AND INCREASING ATMOSPHERIC CARBON DIOXIDE Roger R. Revelle, 252 3.5.l Methane in the Atmosphere, 252 3.5.2 Formation of Methane Clathrate in Continental Slope Sediments, 253 3.5.3 Effect of Carbon Dioxide-Induced Warming on Continental Slope Clathrates, 256 3.5.4 Future Rate of Methane Release from Sedimentary Clathrates, 257 References, 260 3.6 SENSITIVITY STUDIES USING CARBON CYCLE MODELS Lester Machta, 262 3.6.l Comparison among Different Models, 262 3.6.2 Comparison of Parameters within a Single Model, 263 3.6.3 Deforestation as a Source of CO2, 264 3.6.4 Conclusion, 265 References, 265 4 EFFECTS ON CLIMATE 266 4.l EFFECTS OF CARBON DIOXIDE Joseph Smagorinsky, 266 4.l.l Excerpts from "Charney" and "Smagorinsky" Reports, 266 4.l.2 Epilogue, 277 References, 282 4.2 EFFECTS OF NON-CO2 GREENHOUSE GASES Lester Machta, 285 References, 29l DETECTION AND MONITORING OF CO2-INDUCED CLIMATE CHANGES 292 Gunter Weller, D. James Baker, Jr., W. Lawrence Gates, Michael C. MacCracken, Syukuro Manabe, and Thomas H. Vonder Haar 5.l SUMMARY, 292 5.2 HAVE CO2-INDUCED SURFACE TEMPERATURE CHANGES ALREADY OCCURRED?, 297 5.2.l Introduction, 297 5.2.2 Requirements for Identifying C02-Induced Climate Change, 30l 5.2.2.l Climatic Data Bases, 303 5.2.2.2 Causal Factors, 306 5.2.2.3 Relating Causal Factors and Climatic Effects, 3ll 5.2.3 Attempts to Identify C02-Induced Climate Change, 3l3 5.2.3.l Carbon Dioxide as a Causal Factor, 3l8 5.2.3.2 Volcanic Aerosol as a Causal Factor, 320 5.2.3.3 Solar Variations as a Causal Factor, 322 5.2.3.4 Combinations of Causal Factors, 324 5.2.4 Steps for Building Confidence, 327 5.3 A STRATEGY FOR MONITORING CO2-INDUCED CLIMATE CHANGE, 330 5.3.l The "Fingerprinting" Concept, 330 XX

5.3.2 Considerations in Climate Monitoring, 33l 5.3.2.l Statistical Variability and Expectations of Change, 33l 5.3.2.2 Initial Selection of Parameters, 332 5.3.2.3 Revision and Application of a Monitoring Strategy, 332 5.3.3 Candidate Parameters for Monitoring, 333 5.3.3.l Causal Factors, 335 5.3.3.2 Atmospheric Parameters, 35l 5.3.3.3 Cryospheric Parameters, 36l 5.3.3.4 Oceanic Parameters, 367 5.3.4 Conclusions and Recommendations, 370 5.3.4.l Priority of Parameters to be Monitored, 370 5.3.4.2 Measurement Networks, 37l 5.3.4.3 Modeling and Statistical Techniques, 372 5.3.4.4 Objective Evaluation of Evidence, 372 REFERENCES, 373 AGRICULTURE AND A CLIMATE CHANGED BY MORE CARBON DIOXIDE 383 Paul E. Waggoner 6.l INTRODUCTION, 383 6.l.l Concentrating on a Critical, Susceptible, and Exemplary Subject, 383 6.l.2 Agriculture and Past Changes in the Weather, 384 6.l.3 The Range of Change in the Atmosphere, 386 6.2 EFFECTS OF CO2 ON PHOTOSYNTHESIS AND PLANT GROWTH, 388 6.2.l Photosynthesis, 388 6.2.l.l Rate of Photosynthesis, 389 6.2.l.2 Duration of Photosynthesis, 390 6.2.l.3 Fate and Partitioning of Photosynthate, 390 6.2.2 Drought, 39l 6.2.3 Nutrients, 39l 6.2.3.l Nitrogen Metabolism, 392 6.2.3.2 Organic Matter and Rhizosphere Association, 392 6.2.4 Phenology, 393 6.2.5 Weeds, 393 6.2.6 Direct Effects of CO2 on Yield, 394 6.3 PREDICTING THE CHANGES IN YIELD THAT WILL FOLLOW A CHANGE TO A WARMER, DRIER CLIMATE, 396 6.3.l History, 396 6.3.2 Simulation, 403 6.3.3 Summary, 405 6.4 PATHOGENS AND INSECT PESTS, 405 6.5 IRRIGATION IN A WARMER AND DRIER CLIMATE, 407 6.6 ADAPTING TO THE CHANGE TO A WARMER, DRIER CLIMATE, 409 6.6.l Breeding New Varieties, 409 6.6.2 Adapting to Less Water, 4ll 6.7 CONCLUSION, 4l3 REFERENCES, 4l3 xxi

EFFECTS OF A CARBON' DIOXIDE-INDUCED CLIMATIC CHANGE ON WATER SUPPLIES IN THE WESTERN UNITED STATES 4l9 Roger R. Revelle and Paul E. Waggoner 7.l EMPIRICAL RELATIONSHIPS AMONG PRECIPITATION, TEMPERATURE, AND STREAM RUNOFF, 4l9 7.2 EFFECTS OF CLIMATE CHANGE IN SEVEN WESTERN U.S. WATER REGIONS, 42l 7.3 THE COLORADO RIVER, 425 7.4 CLIMATE CHANGE AND WATER-RESOURCE SYSTEMS, 43l REFERENCES, 432 PROBABLE FUTURE CHANGES IN SEA LEVEL RESULTING FROM INCREASED ATMOSPHERIC CARBON DIOXIDE 433 Roger R. Revelle 8.l THE OBSERVED RISE IN SEA LEVEL DURING PAST DECADES, 433 8.2 THE FUTURE RISE IN SEA LEVEL, 435 8.2.l Melting of Greenland Ice Cap and Alpine Glaciers, 436 8.2.2 Heating of the Upper Oceans, 437 8.2.3 Possible Disintegration of the West Antarctic Ice Sheet, 44l REFERENCES, 447 CLIMATIC CHANGE: IMPLICATIONS FOR WELFARE AND POLICY 449 Thomas C. Schelling 9.l INTRODUCTION, 449 9.l.l Uncertainties, 45l 9.l.2 The Time Dimension, 45l 9.l.3 Discounting, Positive or Negative, 452 9.l.4 Perspective on Change, 453 9.l.5 Prudential Considerations, 454 9.l.6 Variation in Human Environments, 455 9.2 A SCHEMA FOR ASSESSMENT AND CHOICE, 456 9.2.l Five Categories, 463 9.2.2 Background Climate and Trends, 465 9.2.3 Production of C02, 466 9.2.4 Removal of CO2, 467 9.2.5 Modification of Climate and Weather, 468 9.2.6 Adaptation, 470 9.2.7 Breathing CO2, 47l 9.2.8 Change in Sea Level, 472 9.2.9 Defenses against Rising Sea Level, 472 9.2.l0 Food and Agriculture, 474 9.2.ll Global Warming and Energy Consumption, 476 9.2.l2 Distributional Impact, 477 9.3 SUMMING UP, 477 xxii

Annex l: Report of Informal Meeting on C02 and the Arctic Ocean 483 Roger R. Revelle Annex 2: Historical Note 488 Jesse H. Ausubel Annex 3: Energy Security Act of l980 492 Annex 4: Background Information on Committee Members 494 xxiii

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