IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group I: The Physical Science Basis

Chapter 9: Understanding and Attributing Climate Change

Executive Summary

9.1 Introduction

9.1.1 What are Climate Change and Climate Variability?

9.1.2 What are Climate Change Detection and Attribution?

9.1.3 The Basis from which We Begin

9.2 Radiative Forcing and Climate Response

9.2.1 Radiative Forcing Estimates Used to Simulate Climate Change

9.2.2 Spatial and Temporal Patterns of the Response to Different Forcings and their Uncertainties

9.2.3 Implications for Understanding 20th-Century Climate Change

9.2.4 Summary

9.3 Understanding Pre-Industrial Climate Change

9.3.1 Why Consider Pre-Industrial Climate Change?

9.3.2 What Can be Learned from the Last Glacial Maximum and the Mid-Holocene?

9.3.3 What Can be Learned from the Past 1,000 Years?

9.3.4 Summary

9.4 Understanding of Air Temperature Change During the Industrial Era

9.4.1 Global-Scale Surface Temperature Change

9.4.2 Continental and Sub-continental Surface Temperature Change

FAQ 9.1 Can Individual Extreme Events be Explained by Greenhouse Warming?

9.4.3 Surface Temperature Extremes

9.4.4 Free Atmosphere Temperature

FAQ 9.2 Can the Warming of the 20th Century be Explained by Natural Variability?

9.4.5 Summary

9.5 Understanding of Change in Other Variables during the Industrial Era

9.5.1 Ocean Climate Change

9.5.2 Sea Level

9.5.3 Atmospheric Circulation Changes

9.5.4 Precipitation

9.5.5 Cryosphere Changes

9.5.6 Summary

9.6 Observational Constraints on Climate Sensitivity

9.6.1 Methods to Estimate Climate Sensitivity

9.6.2 Estimates of Climate Sensitivity Based on Instrumental Observations

9.6.3 Estimates of Climate Sensitivity Based on Palaeoclimatic Data

9.6.4 Summary of Observational Constraints for Climate Sensitivity

9.7 Combining Evidence of Anthropogenic Climate Change


Appendix 9.A: Methods Used to Detect Externally Forced Signals

9.A.1 Optimal Fingerprinting

9.A.2 Methods of Inference

Coordinating Lead Authors:

Gabriele C. Hegerl (USA, Germany), Francis W. Zwiers (Canada)

Lead Authors:

Pascale Braconnot (France), Nathan P. Gillett (UK), Yong Luo (China), Jose A. Marengo Orsini (Brazil, Peru), Neville Nicholls (Australia), Joyce E. Penner (USA), Peter A. Stott (UK)

Contributing Authors:

M. Allen (UK), C. Ammann (USA), N. Andronova (USA), R.A. Betts (UK), A. Clement (USA), W.D. Collins (USA), S. Crooks (UK), T.L. Delworth (USA), C. Forest (USA), P. Forster (UK), H. Goosse (Belgium), J.M. Gregory (UK), D. Harvey (Canada), G.S. Jones (UK), F. Joos (Switzerland), J. Kenyon (USA), J. Kettleborough (UK), V. Kharin (Canada), R. Knutti (Switzerland), F.H. Lambert (UK), M. Lavine (USA), T.C.K. Lee (Canada), D. Levinson (USA), V. Masson-Delmotte (France), T. Nozawa (Japan), B. Otto-Bliesner (USA), D. Pierce (USA), S. Power (Australia), D. Rind (USA), L. Rotstayn (Australia), B. D. Santer (USA), C. Senior (UK), D. Sexton (UK), S. Stark (UK), D.A. Stone (UK), S. Tett (UK), P. Thorne (UK), R. van Dorland (The Netherlands), M. Wang (USA), B. Wielicki (USA), T. Wong (USA), L. Xu (USA, China), X. Zhang (Canada), E. Zorita (Germany, Spain)

Review Editors:

David J. Karoly (USA, Australia), Laban Ogallo (Kenya), Serge Planton (France)

This chapter should be cited as:

Hegerl, G.C., F. W. Zwiers, P. Braconnot, N.P. Gillett, Y. Luo, J.A. Marengo Orsini, N. Nicholls, J.E. Penner and P.A. Stott, 2007: Understanding and Attributing Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.