atmospheric concentrations of greenhouse gases. Both the workshop and the present volume cover a wide range of topics relevant to climate variability; they include the characteristics of the atmosphere and ocean environments as well as the methods used to describe and analyze them, such as proxy data and numerical models. The papers in this volume clearly demonstrate the range, persistence, and magnitude of natural variability as represented by many different climate indicators over the decade-to-century time scale.

This book is not a simple "workshop proceedings". Not only have the 42 papers included been refereed and edited, but each paper is followed by a brief critique by the workshop discussion leader and by a condensed version of the lively discussion that followed each presentation. In addition, each of the major sections is introduced by an essay that provides a perspective for the reader, and completes the picture sketched by the individual papers. Chapter 2 of this volume presents the atmospheric side of natural climate variability. It begins with papers dealing with observational data, and then discusses current atmospheric modeling. Similarly, Chapter 3 presents ocean observations first, and then ocean models. Papers about coupled atmosphere and ocean models appear in Chapter 4, and Chapter 5 introduces a variety of sources of proxy data, from lake beds to ice cores. Chapter 6 contains the conclusions the CRC has drawn from the papers, commentaries, and discussions included. The introductory essays, which outline the significance of the papers included, in conjunction with Chapters 1 and 6 constitute a portrait of our current understanding of many aspects of climate variability on decade-to-century time scales. Chapter 7 presents the committee's recommendations for the direction of future research.

Despite the volume's breadth, it is still not comprehensive. Most of the current research effort has involved the oceans and the atmosphere. Other, less studied components, such as the cryosphere, land-surface processes, and biogeochemical cycles, may also play substantial roles in natural variability. For example, the cryosphere, through snow cover, sea ice, and land ice, can influence climate over sub-seasonal to millennial time scales. It has been implicated in a number of important climate processes, including ice—albedo feedbacks, thermohaline circulation, and abrupt climate change. Land-surface processes influence the hydrological cycle and surface albedo. The biosphere affects climate on a variety of time scales through its influence on surface moisture fluxes, albedo, and the carbon cycle. The roles of these components require considerable attention still; they are under-represented in current studies. The CRC nonetheless feels that this book will serve as a foundation upon which research into climate variation on decade-to-century time scales can build. The ultimate goals—determining the characteristics of natural climate variability, predicting climate changes on decade-to-century scales, and assessing the effects of human activities—will be realized only through the cooperation of scientists and national and international agencies in all the fields represented.

REFERENCE

Marcus, M.G., and S.W. Brazel. 1984. Climate Changes in Arizona's Future. Arizona State Climate Publication No. 1, Office of the State Climatologist, Arizona State University, Tempe.



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