WG I The Scientific Basis - Technical Summary

Climate Change 2001: The Scientific Basis

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WG1 - Technical Summary


A. Introduction

A.1 The IPCC and its Working Groups
A.2 The First and Second Assessment Reports of Working Group I
A.3 The Third Assessment Report: This Technical Summary

B. The Observed Changes in the Climate System

B.1 Observed Changes in Temperature
Temperatures in the instrumental record for land and oceans
Temperatures above the surface layer from satellite and weather balloon records
Surface temperatures during the pre-instrumental period from the proxy record
B.2 Observed Changes in Precipitation and Atmospheric Moisture
B.3 Observed Changes in Snow Cover and Land- and Sea-Ice Extent
B.4 Observed Changes in Sea Level
Changes during the instrumental record
Changes during the pre-instrumental record
B.5 Observed Changes in Atmospheric and Oceanic Circulation Patterns
B.6 Observed Changes in Climate Variability and Extreme Weather and Climate Events
B.7 The Collective Picture: A Warming World and Other Changes in the Climate System
Taken together, these trends illustrate a collective picture of a warming world
Some important aspects of climate appear not to have changed

C. The Forcing Agents That Cause Climate Change

C.1 Observed Changes in Globally Well-Mixed Greenhouse Gas Concentrations and Radiative Forcing
Carbon dioxide (CO2)
Methane (CH4)
Nitrous oxide (N2O)
Halocarbons and related compounds
C.2 Observed Changes in Other Radiatively Important Gases
Atmospheric ozone (O3)
Gases with only indirect radiative influences
C.3 Observed and Modelled Changes in Aerosols
C.4 Observed Changes in Other Anthropogenic Forcing Agents Land-use (albedo) change
C.5 Observed and Modelled Changes in Solar and Volcanic Activity
C.6 Global Warming Potentials

D. The Simulation of the Climate System and its Changes

D.1 Climate Processes and Feedbacks
Water vapour
Land surface
Carbon cycle
D.2 The Coupled Systems
Modes of natural variability
The thermohaline circulation (THC)
Non-linear events and rapid climate change
D.3 Regionalisation Techniques
D.4 Overall Assessment of Abilities
Flux adjustment
Climate of the 20th century
Extreme events
Interannual variability
Model intercomparisons

E. The Identification of a Human Influence on Climate Change

E.1 The Meaning of Detection and Attribution
E.2 A Longer and More Closely Scrutinised Observational Record
E.3 New Model Estimates of Internal Variability
E.4 New Estimates of Responses to Natural Forcing
E.5 Sensitivity to Estimates of Climate Change Signals
E.6 A Wider Range of Detection Techniques
Sea level
E.7 Remaining Uncertainties in Detection and Attribution
E.8 Synopsis

F. The Projections of the Earth's Future Climate

F.1 The IPCC Special Report on Emissions Scenarios (SRES)
F.2 Projections of Future Changes in Greenhouse Gases and Aerosols
F.3 Projections of Future Changes in Temperature
AOGCM results
Simple climate model results
F.4 Projections of Future Changes in Precipitation
F.5 Projections of Future Changes in Extreme Events
F.6 Projections of Future Changes in Thermohaline Circulation
F.7 Projections of Future Changes in Modes of Natural Variability
F.8 Projections of Future Changes in Land Ice (Glaciers, Ice Caps and Ice Sheets), Sea Ice and Snow Cover
F.9 Projections of Future Changes in Sea Level
F.10 Projections of Future Changes in Response to CO2 Concentration Stabilisation Profiles
Greenhouse gases and aerosols
Sea level

G. Advancing Understanding

G.1 Data
G.2 Climate Processes and Modelling
G.3 Human Aspects
G.4 International Framework

Source Information: Technical Summary

A report accepted by Working Group I of the IPCC but not approved in detail

"Acceptance" of IPCC Reports at a Session of the Working Group or Panel signifies that the material has not been subject to line by line discussion and agreement, but nevertheless presents a comprehensive, objective and balanced view of the subject matter.

Co-ordinating Lead Authors
D.L. Albritton (USA), L.G. Meira Filho (Brazil)

Lead Authors
U. Cubasch (Germany), X. Dai (China), Y. Ding (China), D.J. Griggs (UK), B. Hewitson (South Africa), J.T. Houghton (UK), I. Isaksen (Norway), T. Karl (USA), M. McFarland (USA), V.P. Meleshko (Russia), J.F.B. Mitchell (UK), M. Noguer (UK), B.S. Nyenzi (Tanzania), M. Oppenheimer (USA), J.E. Penner (USA), S. Pollonais (Trinidad and Tobago), T. Stocker (Switzerland), K.E. Trenberth (USA)

Contributing Authors
M.R. Allen, (UK), A.P.M. Baede (Netherlands), J.A. Church (Australia), D.H. Ehhalt (Germany), C.K. Folland (UK), F. Giorgi (Italy), J.M. Gregory (UK), J.M. Haywood (UK), J.I. House (Germany), M. Hulme (UK), V.J. Jaramillo (Mexico), A. Jayaraman (India), C.A. Johnson (UK), S. Joussaume (France), D.J. Karoly (Australia), H. Kheshgi (USA), C. Le Qu�r� (France), L.J. Mata (Germany), B.J. McAvaney (Australia), L.O. Mearns (USA), G.A. Meehl (USA), B. Moore III (USA), R.K. Mugara (Zambia), M. Prather (USA), C. Prentice (Germany), V. Ramaswamy (USA), S.C.B. Raper (UK), M.J. Salinger (New Zealand), R. Scholes (S. Africa), S. Solomon (USA), R. Stouffer (USA), M-X. Wang (China), R.T. Watson (USA), K-S. Yap (Malaysia)

Review Editors
F. Joos (Switzerland), A. Ramirez-Rojas (Venzuela), J.M.R. Stone (Canada), J. Zillman (Australia)

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