Climate Change 2001:
Working Group I: The Scientific Basis
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12. Detection of Climate Change and Attribution of Causes


Executive Summary

12.1 Introduction

12.1.1 The Meaning of Detection and Attribution
12.1.2 Summary of the First and Second Assessment Reports
12.1.3 Developments since the Second Assessment Report

12.2 The Elements of Detection and Attribution

12.2.1 Observed Data
12.2.2 Internal Climate Variability
12.2.3 Climate Forcings and Responses Natural climate forcing Climatic response to natural forcing Anthropogenic forcing Climatic response to anthropogenic forcing
12.2.4 Some Important Statistical Considerations

12.3 Qualitative Comparison of Observed and Modelled Climate Change

12.3.1 Introduction
12.3.2 Thermal Indicators
12.3.3 Hydrological Indicators
12.3.4 Circulation
12.3.5 Combined Evidence

12.4 Quantitative Comparison of Observed and Modelled Climate Change

12.4.1 Simple Indices and Time-series Methods
12.4.2 Pattern Correlation Methods Horizontal patterns Vertical patterns
12.4.3 Optimal Fingerprint Methods Single pattern studies Optimal detection studies that use multiple fixed signal patterns Space-time studies Summary of optimal fingerprinting studies

12.5 Remaining Uncertainties

12.6 Concluding Remarks

Appendix 12.1: Optimal Detection is Regression
Appendix 12.2: Three Approaches to Optimal Detection
Appendix 12.3: Pattern Correlation Methods
Appendix 12.4: Dimension Reduction
Appendix 12.5: Determining the Likelihood of Outcomes (p-values)


Co-ordinating Lead Authors
J.F.B. Mitchell, D.J. Karoly

Lead Authors
G.C. Hegerl, F.W. Zwiers, M.R. Allen, J. Marengo

Contributing Authors
V. Barros, M. Berliner, G. Boer, T. Crowley, C. Folland, M. Free, N. Gillett, P. Groisman, J. Haigh, K. Hasselmann, P. Jones, M. Kandlikar, V. Kharin, H. Kheshgi, T. Knutson, M. MacCracken, M. Mann, G. North, J. Risbey, A. Robock, B. Santer, R. Schnur, C. Schönwiese, D. Sexton, P. Stott, S. Tett, K. Vinnikov, T. Wigley

Review Editors
F. Semazzi, J. Zillman

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