An Introduction to Simple Climate Models used in the IPCC

0,57

MB

Second Assessment Report

59

stron

4409

ID

Intergovernmental Panel on Climate Change

1999

rok

Contents

Preface v

Summary . 3

1. Introduction 7

1.1 Aims . 7

1.2. Climate Models as Tools for Scientific and Policy Analysis 7

2. Climate and the Climate System 9

2.1 Human Perturbations to the Composition of the Atmosphere . 10

2.2 Cloud, Surface and Dynamical Interactions 10

2.2.1 Clouds . 10

2.2.2 Land surface . 11

2.2.3 Oceans . 11

2.2.4 Atmospheric Motions 11

2.3 Radiative Forcing, Feedbacks and Climate Sensitivity 11

2.3.1 Radiative Forcing . 11

2.3.2 Fast and Slow Feedbacks . 12

2.3.3 Climate Sensitivity: Definition . 12

2.3.4 Climate Sensitivity: Constancy and Independence 12

2.3.5 Regional Climate Response . 13

3. Simulating Climatic Change 15

3.1 A Hierarchy of Atmosphere and Ocean Climate Models . 15

3.2 Models of the Carbon Cycle 16

3.3 Models of Atmospheric Chemistry and Aerosols 17

3.4 Models of Ice Sheets . 19

3.5 Computation of Sea Level Rise . 19

3.6 Utilization of Simple and Complex Models 19

3.6.1 Comparison of Simple and Complex Models 21

3.6.2 Data Limitations of Biosphere Models . 22

3.6.3 Policy Development . 22

4. Simple Climate Models used in the IPCC Second Assessment Report . 25

4.1 The Biogeochemical Component of a Simple Climate Model: Turning Emissions into Radiative

Forcing 25

4.1.1 Treatment of Well-Mixed Gases with Well-Defined Lifetimes . 25

4.1.2 Treatment of Carbon Dioxide 25

4.1.3 Treatment of Gases not Directly Emitted . 26

4.1.4 Treatment of Aerosols . 27

4.1.5 Calculating Radiative Forcing From Concentrations . 27

4.2 Translating Radiative Forcing into Global Mean Temperature Change 28

4.3 Calculating Sea Level Change 30

4.3.1 Calculations Starting From the One-Dimensional Upwelling-Diffusion Model . 31

4.3.2 Calculations Starting From the Two-Dimensional Upwelling-Diffusion Model . 32

4.3.3 Uncertainties in Sea Level Projections . 33

5. Comparison of Surface Temperature Changes and Ocean Thermal Expansion as Simulated by

AOGCMs and SCMs 35

References . 37

Appendices . 41

Appendix 1 Summary of methods used to compute concentrations of greenhouse gases in the SAR

WGI (Chapter 2 and Section 6.3) and the IPCC Technical Paper on Stabilization of Atmospheric

Greenhouse Gases (IPCC TP STAB, 1997)41

Appendix 2 Functional dependence of forcing on greenhouse gases and aerosols used in the SAR

WGI (Section 6.3) and in IPCC TP STAB (1997). 42

Appendix 3 Parameter values for the ice-melt module described in the text, and used to obtain the

low, medium and high sea level rise estimates for this Technical Paper and IPCC TP STAB (1997)43

Appendix 4 Glossary of terms . 44

Appendix 5 Acronyms and abbreviations . 48

Appendix 6 Units . 49

Appendix 7 Lead Authors’ Affiliations 50

Appendix 8 List of IPCC outputs 51