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Global Warming

The Complete Brie¬ng
Third Edition

Global warming and the resulting climate change are among the most
serious environmental problems facing the world community. Global
Warming: The Complete Brie¬ng is the most comprehensive guide avail-
able to the subject. A world-renowned expert, Sir John Houghton ex-
plores the scienti¬c basis of global warming and the likely impacts of
climate change on human society, before addressing the action that could
be taken by governments, by industry and by individuals to mitigate the
effects. The ¬rst two editions received excellent reviews, and this com-
pletely updated new edition will prove to be the best brie¬ng the student
or interested general reader could wish for.

© ® . µ§® , ¦ is a former Chairman of the
Scienti¬c Assessment Working Group of the Intergovernmental Panel
on Climate Change, Chairman of the UK™s Royal Commission on
Environmental Pollution, Vice President of the World Meteorological
Organization, President of the Royal Meteorological Society, and
Professor of Atmospheric Physics at Oxford University. He was Chief
Executive of the UK Meteorological Of¬ce from 1983 to his retirement
in 1991. As well as the previous editions of this book, he is author of The
Physics of Atmospheres (Cambridge University Press, in three editions),
and has published numerous research papers and contributed to many
in¬‚uential research documents. Sir John and his wife Sheila live in
Wales.


From reviews of previous editions
˜It is dif¬cult to imagine how Houghton™s exposition of this complex body of
information might be substantially improved upon . . . Seldom has such a
complex topic been presented with such remarkable simplicity, directness and
crystalline clarity . . . Houghton™s complete brie¬ng is without doubt the best
brie¬ng the concerned citizen could hope to ¬nd within the pages of a
pocketable book.™
John Perry, Bulletin of the American Meteorological Society

˜I can recommend (this book) to anyone who wants to get a better perspective
on the topic of global warming . . . a very readable and comprehensive guide to
the changes that are occurring now, and could occur in the future, as a result of
human action . . . brings the global warming debate right up to date . . . Read
Houghton™s book if you really want to understand both the scienti¬c and
political issues involved.™
William Harston, The Independent

˜. . . precise account of the science, accompanied by ¬gures, graphs, boxes on
speci¬c points, and summaries at the end of each chapter, with questions for
students . . . ranges beyond the science into the diplomacy, politics, economics
and ethics of the problem, which together present a formidable challenge to
human understanding and capacity for action.™
Sir Crispin Tickell, The Times Higher Education Supplement

˜. . . a widely praised book on global warming and its consequences.™
The Economist
˜. . . an interesting account of the topic for the general reader.™
Environmental Assessment

˜. . . very thorough and presents a balanced, impartial picture.™
Jonathan Shanklin, Journal of the British Astronomical Association

˜I would thoroughly recommend this book to anyone concerned about global
warming. It provides an excellent essentially non-technical guide on scienti¬c
and political aspects of the subject. It is an essential brie¬ng for students and
science teachers.™
Tony Waters, The Observatory

˜For the non-technical reader, the best program guide to the political and
scienti¬c debate is John Houghton™s book Global Warming: The Complete
Brie¬ng. With this book in hand you are ready to make sense of the debate and
reach your own conclusions.™
Alan Hecht, Climate Change

˜This is a remarkable book . . . It is a model of clear exposition and
comprehensible writing . . . Quite apart from its value as a background reader
for science teachers and students, it would make a splendid basis for a college
general course.™
Andrew Bishop, Association for Science Education

˜Global Warming remains the best single-volume guide to the science of
climate change.™
Greg Terrill, Times Literary Supplement

˜This very readable and informative book is valuable for anyone wanting a
broad overview of what we know about climate change, its potential impacts on
society and the natural world, and what could be done to mitigate or adapt to
global warming. To this end, discussion questions are included at the end of
each chapter. The paperback edition is especially good value . . . Houghton™s
compact book is an accessible, well-researched, and broadly based introduction
to the immensely complicated global warming problem.™
Dennis L. Hartmann, Department of Atmospheric Sciences, University of Washington,
Seattle, USA

˜I have no hesitation in endorsing this important book.™
Wilfrid Bach, International Journal of Climatology

˜. . . a useful book for students and laymen to understand some of the
complexities of the global warming issue. Questions and essay topics at the end
of each chapter provide useful follow-up work and the range of material
provided under one cover is impressive. At a student-friendly price, this is a
book to buy for yourself and not rely on the library copy.™
Allen Perry, Holocene

˜In summary I would thoroughly recommend this book to anyone concerned
about global warming. It provides an excellent non-technical guide on
scienti¬c and political aspects of the subject. It is an essential brie¬ng for
students and science teachers.™
Tony Waters, Weather

˜This book is one of the best I have encountered, that deal with climate change
and some of its anthropogenic causes. Well written, well organised, richly
illustrated and referenced, it should be required reading for anybody concerned
with the fate of our planet.™
Elmar R. Reiter, Meteorology and Atmospheric Physics

˜Sir John Houghton is one of the few people who can legitimately use the
phrase “the complete brie¬ng” as a subtitle for a book on global warming . . . Sir
John has done us all a great favour in presenting such a wealth of material so
clearly and accessibly and in drawing attention to the ethical underpinnings of
our interpretation of this area of environmental science.™
Progress in Physical Geography

˜. . . this complete brie¬ng on global warming is remarkably factual and
inclusive. Houghton™s concern about planet Earth and its people blends well
with this his hopes for global cooperation in concert with the spirit of the
Intergovernmental Panel on Climate Change.™
Choice

˜Throughout the book this argument is well developed and explained in a way
that the average reader could understand especially because there are many
diagrams, tables, graphs and maps which are easy to interpret.™
SATYA

˜. . . this book is the most comprehensive guide available. Ignore it at your peril.™
The Canadian Field-Naturalist
Global Warming
The Complete Brie¬ng
T H I R D E D I T IO N




Sir John Houghton
cambridge university press
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo

Cambridge University Press
The Edinburgh Building, Cambridge cb2 2ru, UK
Published in the United States of America by Cambridge University Press, New York
www.cambridge.org
Information on this title: www.cambridge.org/9780521528740

© C J. T. Houghton 1994, 1997, 2004


This publication is in copyright. Subject to statutory exception and to the provision of
relevant collective licensing agreements, no reproduction of any part may take place
without the written permission of Cambridge University Press.

First published in print format 2004

978-0-511-21276-5 eBook (EBL)
isbn-13
isbn-10 0-511-21276-3 eBook (EBL)

978-0-521-52874-0 paperback
isbn-13
0-521-52874-7 paperback
isbn-10




Cambridge University Press has no responsibility for the persistence or accuracy of urls
for external or third-party internet websites referred to in this publication, and does not
guarantee that any content on such websites is, or will remain, accurate or appropriate.
To my grandchildren,
Daniel, Hannah, Esther, Max, Jonathan, Jemima and Sam and
their generation
Contents




List of ¬gures page xiv
List of SI unit pre¬xes xxi
List of chemical symbols xxii
Preface to the First Edition xxiii
Preface to the Second Edition xxvii
Preface to the Third Edition xxix

1
1 Global warming and climate change
Is the climate changing? 1
The remarkable last decades of the twentieth century 2
El Ni±o events 5
The effect of volcanic eruptions on temperature
extremes 7
Vulnerable to change 8
The problem of global warming 9
Adaptation and mitigation 10
Uncertainty and response 12
Questions 12
Notes 13

14
2 The greenhouse effect
How the Earth keeps warm 14
The greenhouse effect 16
Mars and Venus 21
The ˜runaway™ greenhouse effect 22
The enhanced greenhouse effect 23
Questions 25
Notes 26

28
3 The greenhouse gases
Which are the most important greenhouse gases? 28
Radiative forcing 29


ix
x Contents



Carbon dioxide and the carbon cycle 29
Future emissions of carbon dioxide 39
Other greenhouse gases 42
Gases with an indirect greenhouse effect 47
Particles in the atmosphere 48
Estimates of radiative forcing 51
Questions 53
Notes 54

56
4 Climates of the past
The last hundred years 56
The last thousand years 64
The past million years 66
How stable has past climate been? 71
Questions 75
Notes 75

77
5 Modelling the climate
Modelling the weather 77
Seasonal forecasting 85
The climate system 88
Feedbacks in the climate system 90
Models for climate prediction 95
Validation of the model 100
Comparison with observations 102
Is the climate chaotic? 106
Regional climate modelling 107
The future of climate modelling 109
Questions 110
Notes 111

6 Climate change in the twenty-¬rst century
115
and beyond
Emission scenarios 115
Model projections 118
Projections of global average temperature 120
Regional patterns of climate change 124
Changes in climate extremes 128
Regional climate models 133
Longer-term climate change 135
Contents xi



Changes in the ocean thermohaline circulation 136
Other factors that might in¬‚uence climate change 137
Questions 140
Notes 140

143
7 The impacts of climate change
A complex network of changes 143
How much will sea level rise? 145
The impacts of sea level rise 150
Increasing human use of fresh water resources 155
The impact of climate change on fresh water resources 157
Impact on agriculture and food supply 164
The impact on ecosystems 167
The impact on human health 176
Adaptation to climate change 178
Costing the impacts: extreme events 179
Costing the total impacts 184
The overall impact of global warming 188
Questions 190
Notes 191

197
8 Why should we be concerned?
Earth in the balance 197
Exploitation 198
˜Back to nature™ 199
The technical ¬x 200
Future generations 200
The unity of the Earth 201
Environmental values 205
Stewards of the Earth 208
The will to act 209
Questions 211
Notes 212

216
9 Weighing the uncertainty
The scienti¬c uncertainty 216
The IPCC assessments 218
Narrowing the uncertainty 222
Sustainable development 225
Why not wait and see? 227
xii Contents



The Precautionary Principle 228
Principles for international action 230
Some global economics 230
Questions 239
Notes 239

10 A strategy for action to slow and stabilise
242
climate change
The climate convention 242
Stabilisation of emissions 244
The Montreal Protocol 245
The Kyoto Protocol 246
Forests 249
Reduction in the sources of methane 253
Stabilisation of carbon dioxide concentrations 254
The choice of stabilisation level 257
Realising the Climate Convention Objective 261
Summary of the action required 263
Questions 264
Notes 265

268
11 Energy and transport for the future
World energy demand and supply 268
Future energy projections 271
Energy conservation and ef¬ciency in buildings 278
Energy savings in transport 283
Energy savings in industry 284
Capture and storage of carbon dioxide 289
Renewable energy 289
Hydro-power 291
Biomass as fuel 293
Wind energy 297
Energy from the Sun 299
Other renewable energies 305
The support and ¬nancing of renewable
energy 306
Nuclear energy 308
Technology for the longer term 310
Summary 314
Questions 315
Notes 317
Contents xiii



322
12 The global village
The challenges of global warming 322
Not the only global problem 326
The conception and conduct of environmental research 327
The goal of environmental stewardship 328
Questions 330
Notes 331

Glossary 333
Index 340
Figures




1.1 From World Climate News, number 16, July 1999. Geneva: World Meteorological
Organisation. A similar map is prepared and published each year. Data from Climate
Prediction Center, NOAA, USA. page 3
1.2 Figure 2.7 from Watson, R. et al. (eds.) 2001. Climate Change 2001: Synthesis Report.
Contribution of Working Groups I, II and III to the Third Assessment Report of the
Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press. 5
1.3 From The role of the World Meteorological Organization in the International Decade
for Natural Disaster Reduction. World Meteorological Organization 1990; 745.
Geneva: World Meteorological Organization. 6
1.4 Adapted from: Canby, T. Y. 1984. El Ni±o™s ill wind. National Geographic Magazine,
pp. 144“83. 7
1.5 Figure SPM-1 from The summary for policymakers in Watson, Climate Change 2001:
Synthesis Report. 11
2.1 The radiation balance of planet Earth. 15
2.2 A greenhouse has a similar effect to the atmosphere on the incoming solar radiation and
the emitted thermal radiation. 18
2.3 The distribution of temperature in a convective atmosphere (full line). 19
2.4 Spectrum taken with the infrared interferometer spectrometer ¬‚own on the satellite
Nimbus 4 in 1971 and described by Hanel, R. A. et al. 1971. Applied Optics, 10:
1376“82. 19
2.5 The blanketing effect of greenhouse gases. 20
2.6 The radiation budget for the atmosphere. 21
2.7 From Houghton, J. T. 2002. The Physics of Atmospheres, third edition. Cambridge:
Cambridge University Press. 22
2.8 Illustrating the enhanced greenhouse gas effect. 24
3.1 Figure 1.1 from Bolin, B. and Sukumar, R. 2000. Global perspective. In Watson, R. T.,
Noble, I. R., Bolin, B., Ravindranath, N. H., Verardo, D. J., Dokken, D. J. (eds.) Land
use, Land-use Change, and Forestry, IPCC Special Report. Chapter 1. Cambridge:
Cambridge University Press. 30
3.2 Figure 10 from Technical summary. In Houghton, J. T., Ding, Y., Griggs, D. J., Noguer,
M., van der Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate Change
2001: The Scienti¬c Basis. Contribution of Working Group I to the Third Assessment
Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge
University Press. 32

xiv
List of ¬gures xv



3.3 Both (a) and (b) are from Schimel, D. et al. 1994. CO2 and the carbon cycle. In Climate
Change 1994. Cambridge: Cambridge University Press. For more recent data see also
House, J. I. et al. 2003. Reconciling apparent inconsistencies in estimates of terrestrial
CO2 sources and sinks. Tellus, 55B, pp. 345“63. 33
3.4 Figure 3.4 from Prentice, I. C. et al. 2001. The carbon cycle and atmospheric carbon
dioxide. Chapter 3 in Houghton, J. T., Ding, Y., Griggs, D. J., Noguer, M., van der
Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate Change 2001: The
Scienti¬c Basis. Contribution of Working Group I to the Third Assessment Report of the
Intergovernmental Panel on Climate Change. Cambridge: Cambridge University
Press. 34
3.5 From the UK Hadley Centre. See Cox, P. M. et al. 2000. Acceleration of global
warming due to carbon-cycle feedbacks in a coupled climate model. Nature, 408,
pp. 184“7. 41
3.6 Figure 4.1 from Prather, M., Ehhalt, D. et al. 2001. Atmospheric chemistry and
greenhouse gases. Chapter 4 in Houghton, J. T., Ding, Y., Griggs, D. J., Noguer, M., van
der Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate Change 2001: The
Scienti¬c Basis. Contribution of Working Group I to the Third Assessment Report of the
Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press. 42
3.7 After Kiehl, J. T., Briegleb, B. P. 1995. Summary for policymakers. In Climate Change
1994. Cambridge: Cambridge University Press. 49
3.8 Figure 6.6 from Ramaswamy, V et al. Chapter 6 in Houghton, J. T., Ding, Y., Griggs, D.
.
J., Noguer, M., van der Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate
Change 2001: The Scienti¬c Basis. Contribution of Working Group I to the Third
Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge:
Cambridge University Press. This source also gives details of regional variations of
forcings. 50
4.1 Figure 1(a) from Summary for policymakers. In Houghton, J. T., Ding, Y., Griggs, D. J.,
Noguer, M., van der Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate
Change 2001: The Scienti¬c Basis. Contribution of Working Group I to the Third
Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge:
Cambridge University Press. Improved analysis and updated to 2003 by the Hadley
Centre, UK Meteorological Of¬ce. 57
4.2 Figure 4 from Technical summary. In Houghton, J. T., Ding, Y., Griggs, D. J., Noguer,
M., van der Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate Change
2001: The Scienti¬c Basis. Contribution of Working Group I to the Third Assessment
Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge
University Press. 60
4.3 Figure 5 from Technical summary. In Houghton, J. T., Ding, Y., Griggs, D. J., Noguer,
M., van der Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate Change
2001: The Scienti¬c Basis. Contribution of Working Group I to the Third Assessment
Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge
University Press. This ¬gure is based on data from Mann, M. E. 1999. Geophysics
Research letters, 26, 759“62. 65
xvi List of ¬gures



4.4 Adapted from Raynaud, D. et al. 1993. The ice core record of greenhouse gases.
Science, 259, 926“34. 69
4.5 Adapted from Broecker, W. S. and Denton, G. H. 1990. What drives glacial cycles.
Scienti¬c American, 262, 43“50. 71
4.6 Adapted from Professor Dansgaard and colleagues, Greenland ice core (GRIP)
members. 1990. Climate instability during the last interglacial period in the GRIP ice
core. Nature, 364, 203“7. 72
4.7 Adapted from Dansgaard, W., White, J. W. C., Johnsen, S. J. 1989. The abrupt
termination of the Younger Dryas climate event. Nature, 339, 532“3. 74
5.1 Illustrating the growth of computer power available at major forecasting centres. 78
5.2 Schematic illustrating the parameters and physical processes involved in atmosphere
models. 79
5.3 Illustration of a model grid. 81
5.4 Illustrating some of the sources of data for input into the UK Meteorological Of¬ce
global weather forecasting model on a typical day. 82
5.5 From UK Meteorological Of¬ce. 83
5.6 After Milton, S. Meteorological Of¬ce, quoted in Houghton, J. T. 1991. The Bakerian
Lecture, 1991: the predictability of weather and climate. Philosophical Transactions
of the Royal Society, London, A, 337, pp. 521“71. 83
5.7 After Lighthill, J. 1986. The recently recognized failure in Newtonian dynamics.
Proceedings of the Royal Society, London, A, 407, pp. 35“50. 84
5.8 From The Storm 15/16 October 1987. Exeter, Devon, UK Meteorological Of¬ce Report. 85
5.9 From the Hadley Centre, UK. 86
5.10 Series updated from Nicholson, S. E. 1985. Sub-Saharan rainfall 1981“84. Journal of
Climate and Applied Meteorology, 24, pp. 1388“91. 87
5.11 Updated from Folland, C. K., Parker, D. E., Palmer, T. N. 1986. Sahel rainfall and
worldwide sea temperatures 1901“85. Nature, 320, pp. 602“7. 87
5.12 From Houghton, J. T. 1991. The Bakerian Lecture, 1991: the predictability of weather
and climate. Philosophical Transactions of the Royal Society, London, A, 337, pp. 521“71. 89
5.13 Schematic of the climate system. 90
5.14 Schematic of the physical processes associated with clouds. 90
5.15 Diagram from Catherine Senior, UK Meteorological Of¬ce. 92
5.16 See Siedler, G., Church, J., Gould, J. (eds.). 2001. Ocean Circulation and Climate.
London: Academic Press. Original diagram from Woods, J. D. 1984. The upper ocean
and air sea interaction in global climate. In Houghton, J. T. The Global Climate.
Cambridge: Cambridge University Press, pp. 141“87. 94
5.17 Component elements and parameters of a coupled atmosphere“ocean model including
the exchanges at the atmosphere“ocean interface. 97
5.18 After Broecker, W. S., Denton, G. H. 1990. What drives glacial cycles? Scienti¬c
American, 262, pp. 43“50. 99
5.19 This diagram and information about modelling past climates is from Kutzbach, J. E.
1992. In Trenberth, K. E. Climate System Modelling. Cambridge: Cambridge
University Press. 101
List of ¬gures xvii



5.20 From Sarmiento, J. L. 1983. Journal of Physics and Oceanography, 13, pp. 1924“39. 102
5.21 From Hansen, J. et al. 1992. Potential impact of Mt. Pinatubo eruption. Geophysics
Research Letters, 19,
pp. 215“18. Also quoted in Technical summary of Houghton, J. T., Meira Filho,
L. G., Callander, B. A., Harris, N., Kattenberg, A., Maskell, K. (eds.) 1996. Climate
Change 1995: the Science of Climate Change. Cambridge: Cambridge University
Press. 103
5.22 From Policymakers summary. In Houghton, J. T., Ding, Y., Griggs, D. J., Noguer, M.,
van der Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate Change
2001: The Scienti¬c Basis. Contribution of Working Group I to the Third Assessment
Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge
University Press. Simulations from model at Hadley Centre, UK. 104
5.23 Figure 12.8 from Mitchell, J. F. B., Karoly, D. J. 2001. Detection of climate change
and attribution of causes. Chapter 12 in Houghton, Climate Change 2001,
Chapter 12. 105
5.24 From the Report on Hadley Centre Regional Modelling System, 2002. 108
6.1 Figure 17 from Technical summary. In Houghton, J. T., Ding, Y., Griggs, D. J.,
Noguer, M., van der Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate
Change 2001: The Scienti¬c Basis. Contribution of Working Group I to the Third
Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge:
Cambridge University Press. 116
6.2 Figure 18 from Technical summary. In Houghton, Climate Change 2001. 119
6.3 The components of a simple ˜upwelling-diffusion™ climate model. 121
6.4 Figures 9.13 and 9.14 from Cubasch, U., Meehl, G. A. 2001. Projections of future
climate change. Chapter 9 in Houghton, Climate Change 2001. 122
6.5 From Figures 3.2 and 3.3 in Watson, R. et al. (eds.) 2001. Climate Change 2001:
Synthesis Report. Contribution of Working Groups I, II and III to the Third
Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge:
Cambridge University Press. 126
6.6 From Folland C.K., Karl T. R. et al. 2001. Observed climate variability and change,
Figure 2.32. Chapter 2 in Houghton, Climate Change 2001, p. 155. 129
6.7 From Pittock, A. B. et al. 1991. Quoted in Houghton, J. T., Callander, B. A., Varney, S.
K. (eds.) Climate Change 1992: the Supplementary Report to the IPCC Assessments.
Cambridge: Cambridge University Press, p. 120. 130
6.8 From Palmer, T. N., Raisanen, J. 2002. Nature, 415, pp. 512“14. The extreme
precipitation events at the base of the study are those with winter precipitation greater
than the mean plus two standard deviations that have probability in the control runs of
2.5% or a return period of about forty years. 131
6.9 From Wilson, C. A., Mitchell, J. F. B. 1993. Simulation of climate and CO2 -indiced
climate changes over Western Europe. Climatic Change, 10, pp. 11“42. 132
6.10 From Report on Hadley Centre Regional Modeling System 2002. 135
6.11 From Hadley Centre Report 2001. The Hadley Centre climate model is from Vellinga,
M., Wood, R. A. 2002. Climatic Change, 54, pp. 251“67. 137
xviii List of ¬gures



6.12 Figure 6.8(c) from Ramaswamy, V. et al. 2001. Radiative forcing of climate change.
Chapter 6 in Houghton, Climate Change, 2001. See also Lean, J., Beer, J., Bradley, R.
S. 1995. Reconstruction of solar irradiation since 1610: implications for climate
change. Geophysics Research Letters, 22, pp. 3195“8; and Hoyt, D. V., Schatten, K. H.
1993. A discussion of plausible solar irradiance variations, 1700“1992. Journal of
Geophysics Research, 98, pp. 18895“906. 138
7.1 Figure 11.12 from Church, J. A., Gregory, J. M. et al. 2001. Changes in sea level.
Chapter 11 in Houghton, Climate Change 2001, Chapter 11. 148
7.2 From Warrick, R. A., Oerlemans, J. 1990. In Houghton, J. T., Jenkins, G. J.,
Ephraums, J. J. (eds.) 1990. Climate Change: the IPCC Scienti¬c Assessments.
Cambridge: Cambridge University Press. 148
7.3 Figure 11.16 from Church, J. A., Gregory, J. M. et al. 2001. Changes in sea level.
Chapter 11 in Houghton, Climate Change 2001, Chapter 11 (data from Huybrechts
and De Wolde). 149
7.4 From Broadus, J. M. 1993. Possible impacts of, and adjustments to, sea-level rise: the
case of Bangladesh and Egypt. In Warrick, R. A., Barrow, E. M., Wigley,
T. M. L. (eds.) 1993 Climate and Sea-level Change: Observations, Projections and
Implications. Cambridge: Cambridge University Press, pp. 263“75; adapted from
Milliman, J. D. 1989. Environmental and economic implications of rising sea level and
subsiding deltas: the Nile and Bangladeshi examples. Ambio, 18, pp. 340“5. 151
7.5 From Maurits la Riviere, J. W. 1989. Threats to the world™s water. Scienti¬c American,
261, pp. 48“55. 155
7.6 Figure 11.4(a) from Shiklomanov, I. A., Rodda, J. C. (eds.) 2003. World Water
Resources at the Beginning of the 21st Century. Cambridge: Cambridge
University Press. 156
7.7 Gleick, P. H. 1987. Regional hydrologic consequences of increases in atmospheric
CO2 and other trace gases. Climatic Change, 10, pp.137“61. 158
7.8 From Report on Hadley Centre Regional Modelling System, 2002. The RCM was
developed in collaboration with the Indian Institute of Technology. See also Lal, M.
et al. 2001. In McCarthy, J. J., Canziani, O., Leary, N. A., Dokken, D. J., White, K. S.
(eds.) 2001. Climate Change 2001: Impacts, Adaptation and Vulnerability.
Contribution of Working Group II to the Third Assessment Report of the
Intergovernmental Panel on Climate Change. Cambridge: Cambridge University
Press, Chapter 11. 162
7.9 From Tolba, M. K., El-Kholy, O. A. (eds.) 1992. The World Environment 1972“1992.
London: Chapman and Hall, p. 135. 163
7.10 Illustrating key elements of a study of crop yield and
food trade under a changed climate. From Parry, M. et al. 1999. Climate change and
world food security: a new assessment. Global Environmental Change, 9, S51“S67. 169
7.11 Adapted from Gates, D. M. 1993. Climate Change and its Biological Consequences.
Sunderland, Mass.: Sinauer Associates Inc., p. 63. The original source is Delcourt, P.
A., Delcourt, H. R. 1981. In Romans, R. C. (ed.) Geobotany II. New York: Plenum
Press, pp. 123“65. Gates™ book contains a detailed review of natural ecosystems and
climate change. 171
List of ¬gures xix



7.12 From Gates, D. M. 1993. Climate Change and its Biological Consequences.
Sunderland, Mass.: Sinauer Associates Inc., p. 63. 172
7.13 Data from Bugmann, H. quoted in Miko U. F. et al. 1996. Climate change impacts on
forests. In Watson, R. et al. (eds.) 1996. Climate Change 1995. Impacts, Adaptation
and Mitigation of Climate Change. Cambridge: Cambridge University Press, Chapter 1. 174
8.1 Daisyworld after Lovelock, J. E., 1988. The Ages of Gaia. Oxford: Oxford University
Press. 203
8.2 From Lovelock, J. E. 1988. The Ages of Gaia. Oxford: Oxford University Press, p. 82. 203
9.1 Figure 13.2 from Mearns, L. O., Hulme, M. et al. 2001. Climate scenario
development. In Houghton, J. T., Ding, Y., Griggs, D. J., Noguer, M., van der Linden,
P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.) Climate Change 2001: The Scienti¬c
Basis. Contribution of Working Group I to the Third Assessment Report of the
Intergovernmental Panel on Climate Change. Cambridge: Cambridge University
Press, Chapter 13. 219
9.2 ENVISAT showing the instruments included in its payload. From European Space
Agency. 224
9.3 From Munasinghe, M. et al. 1996. Applicability of techniques of cost-bene¬t analysis
to climate change. In Bruce, J., Hoesung Lee, Haites, E. (eds.) 1996. Climate Change
1995: Economic and Social Dimensions of Climate Change. Cambridge: Cambridge
University Press, Chapter 5. 233
9.4 Figure SPM-9 from Watson, R. T. et al. 2001. Climate Change 2001: Synthesis
Report. Contribution of Working Groups I, II and III to the Third Assessment Report of
the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University
Press. 235
10.1 Figure SPM 6 from The summary for policymakers. In Watson, R. et al. (eds.) 2001.
Climate Change 2001: Synthesis Report. Contribution of Working Groups I, II and III
to the Third Assessment Report of the Intergovernmental Panel on Climate Change.
Cambridge: Cambridge University Press. These pro¬les are known as WRE pro¬les
after Wigley, Richels and Edmonds who suggested them. Rather than immediately
reducing from ˜business-as-usual™ scenarios such as A2, they follow those pro¬les for
the ¬rst few decades of the twenty-¬rst century before the reduction starts. 256
10.2 From Grubb, M. 2003. The economics of the Kyoto Protocol. World Economics, 3,
p. 145. 258
10.3 From the Global Commons Institute, Illustrating their ˜Contraction and Convergence™
proposal for achieving stabilisation of carbon dioxide concentration. 262
11.1 Adapted and updated from Davis, G. R. 1990. Energy for planet Earth. Scienti¬c
American, 263, September, pp. 21“7. 269
11.2 Figure 7.5 from Watson, R. et al. (eds.) 2001. Climate Change 2001: Synthesis
Report. Contribution of Working Groups I, II and III to the Third Assessment Report
of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge
University Press. 271
11.3 From Goldemberg, J. (ed.) World Energy Assessment: Energy and the Challenge of
Sustainability. United Nations Development programme (UNDP), United Nations
Department of Economic and Social Affairs (UN-DESA) and World Energy Council
xx List of ¬gures



(WEC), New York. Original source, Energy Balances of OECD Countries. Paris:
International Energy Agency, 1999. 272
11.4 From Energy for Tomorrow™s World “ the Realities, the Real Options and the Agenda
for Achievement. WEC Commission Report. New York: World Energy Council, 1993. 273
11.5 From Energy for Tomorrow™s World “ the Realities, the Real Options and the Agenda
for Achievement. WEC Commission Report. New York: World Energy Council,
1993, p. 28. 274
11.6 From Energy for Tomorrow™s World “ the Realities, the Real Options and the Agenda
for Achievement. WEC Commission Report. New York: World Energy Council,
1993, p. 29. 275
11.7 From Energy Needs, Choices and Possibilities; Scenarios to 2050. 2001. London:
Shell International, p. 39. 283
11.8 From National Academy of Sciences, Policy Implications of Greenhouse Warming,
pp. 211, 212. 282
11.9 Figure 3.7 from Moomaw and Moreira, 2001. In Metz, Climate Change 2001:
Mitigation. 284
11.10 Twidell, J., Weir, T. 1986. Renewable Energy Resources. London: Spon Press. 296
11.11 Adapted from Twidell and Weir, Renewable Energy Resources, p. 100. 300
11.12 Construction of a ˜solar wall™. 301
11.13 From Shell Renewables. 302
11.14 Williams, N., Jacobson, K., Burris, H. 1993. Sunshine for light in the night. Nature,
362, pp. 691“2. For more recent information on solar home systems see Martinot, E.
et al. 2002. Renewable energy markets in developing countries. Annual Review of
Energy and the Environment, 27, pp. 309“48. 304
11.15 Adapted from Twidell and Weir, Renewable Energy Resources, p. 399. 311
11.16 From Ogden, J. M., Nitsch, J. 1993. Solar hydrogen. In Johansson, Renewable
Energy, pp. 925“1009. 312
SI unit pre¬xes




Quantity Pre¬x Symbol

1012 tera T
109 giga G
106 mega M
103 kilo k
102 hecto h
10’2 centi c
10’3 milli m
10’6 µ
micro
10’9 nano n




xxi
Chemical symbols




CFCs chloro¬‚uorocarbons
CH4 methane
CO carbon monoxide
CO2 carbon dioxide
H2 molecular hydrogen
HCFCs hydrochloro¬‚uorocarbons
H2 O water
N2 molecular nitrogen
N2 O nitrous oxide
NO nitric oxide
NO2 nitrogen dioxide
O2 molecular oxygen
O3 ozone
OH hydroxyl radical
SO2 sulphur dioxide




xxii
Preface to the First Edition




Climate change and global warming are well up on the current political
agenda. There are urgent questions everyone is asking: are human activ-
ities altering the climate? Is global warming a reality? How big are the
changes likely to be? Will there be more serious disasters; will they be
more frequent? Can we adapt to climate change or can we change the
way we do things so that we can slow down the change or even prevent
it occurring?
Because the Earth™s climate system is highly complex, and because
human behaviour and reaction to change is even more complex, provid-
ing answers to these questions is an enormous challenge to the world™s
scientists. As with many scienti¬c problems only partial answers are
available, but our knowledge is evolving rapidly, and the world™s scien-
tists have been addressing the problems with much energy and determi-
nation.
Three major pollution issues are often put together in people™s minds:
global warming, ozone depletion (the ozone hole) and acid rain. Al-
though there are links between the science of these three issues (the
chemicals which deplete ozone and the particles which are involved in
the formation of acid rain also contribute to global warming), they are
essentially three distinct problems. Their most important common fea-
ture is their large scale. In the case of acid rain the emissions of sulphur
dioxide from one nation™s territory can seriously affect the forests and
the lakes of countries which may be downwind of the pollution. Global
warming and ozone depletion are examples of global pollution “ pol-
lution in which the activities of one person or one nation can affect all
people and all nations. It is only during the last thirty years or so that
human activities have been of such a kind or on a suf¬ciently large scale
that their effects can be signi¬cant globally. And because the problems
are global, all nations have to be involved in their solution.
The key intergovernmental body which has been set up to assess the
problem of global warming is the Intergovernmental Panel on Climate
Change (IPCC), formed in 1988. At its ¬rst meeting in November of
that year in Geneva, the Panel™s ¬rst action was to ask for a scienti¬c
report so that, so far as they were known, the scienti¬c facts about global

xxiii
xxiv Preface to the First Edition



warming could be established. It was imperative that politicians were
given a solid scienti¬c base from which to develop the requirements for
action.
That ¬rst scienti¬c report was published at the end of May 1990. On
Monday 17 May I presented a preview of it to the then British Prime
Minister, Mrs Margaret Thatcher, and members of her Cabinet at 10,
Downing Street in London. I had been led to expect many interruptions
and questions during my presentation. But the thirty or so Cabinet mem-
bers and of¬cials in the historic Cabinet room heard me in silence. They
were clearly very interested in the report, and the questions and discus-
sion afterwards demonstrated a large degree of concern for the world™s
environmental problems.
Since then the interest of many political leaders has been aroused “ as
has been shown by their attendance at two important world conferences
concerned with global warming: the Second World Climate Conference
in Geneva in 1990 and the United Nations Conference on Environment
and Development (UNCED) in Rio de Janeiro in 1992. The Rio confer-
ence with over 25 000 people attending the main sessions and the many
side meetings, was the largest conference ever held. Never before had
a single conference seen so many of the world™s leaders, and for that
reason it is often referred to as the Earth Summit.
Much of the continuing assessment of climate change has been fo-
cused on the IPCC and its three working groups dealing respectively
with science, impacts and response strategies. The IPCC™s ¬rst report
published in 1990 was a key input to the international negotiations which
prepared the agenda for the UNCED Conference in Rio de Janeiro; it
was that IPCC assessment which provided much of the impetus for the
Framework Convention on climate change signed at Rio by over 160
countries. As chairman or co-chairman of the Science Working Group
I have been privileged to work closely with hundreds of scienti¬c col-
leagues in many countries who readily gave of their time and expertise
to contribute to the IPCC work.
For this book I have drawn heavily on the 1990 and 1992 reports of
all three working groups of IPCC. Further, in putting forward options
for action I have followed the logic of the Climate Convention. What I
have said I believe to be consistent with the IPCC reports and with the
implications of the Climate Convention. However, I must also empha-
sise that the choice of material and any particular views I put forward
are entirely my own and should in no way be construed as the views of
the IPCC.
During the preparation of both IPCC reports so far there has been
considerable scienti¬c debate about just how much can be said about
likely climate change next century. Some researchers initially felt that
Preface to the First Edition xxv



the uncertainties were such that scientists should refrain from making any
estimates or predictions for the future. However, it soon became clear
that scientists have a responsibility to communicate the best possible
information about the likely magnitude of climate change, along with
clear statements of the assumptions made and the level of uncertainty in
the estimates. Like weather forecasters, their results will not be entirely
accurate, but can provide useful guidance.
Many books have been published on global warming. This book
differs from the others because I have attempted to describe the science
of global warming, its impacts and what action might be taken in a way
which the intelligent non-scientist can understand. Although there are
many numbers in the book “ I believe the quanti¬cation of the problem to
be very important “ there are no mathematical equations. I have also used
the minimum of jargon in the main text. Some technical explanations
which would be of interest to the scienti¬cally trained are included in
some of the boxes. Others contain further material of speci¬c interest.
I am grateful to many who have helped me with the provision
and preparation of particular material for this book and to those who
have read and helpfully commented on my drafts. There have been
those who have been involved with the IPCC: Bert Bolin, the IPCC
Chairman, Gylvan Meira Filho, my co-chairman on the IPCC Science
Working Group, Robert Watson, co-chairman of the IPCC Working
Group on Impacts and Response Strategies, Bruce Callander, Chris Fol-
land, Neil Harris, Katherine Maskell, John Mitchell, Martin Parry, Peter
Rowntree, Catherine Senior and Tom Wigley. Others I wish to thank are
Myles Allen, David Carson, Jonathan Gregory, Donald Hay, David Fisk,
Kathryn Francis, Michael Jefferson, Geoffrey Lean and John Twidell.
The staff at Lion Publishing, Rebecca Winter, Nicholas Rous and Sarah
Hall, have been most helpful in preparing the book for publication, espe-
cially in ensuring that it is as attractive and readable as possible. Finally,
I owe an especial debt to my wife, Sheila, who gave me strong encour-
agement to write the book in the ¬rst place, and who has continued her
encouragement and support through the long hours of its production.
Preface to the Second Edition




Since the publication of the ¬rst edition nearly three years ago, interest
in the issue of Global Warming and concern about it has continued to
grow. The Framework Convention on Climate Change (FCCC) agreed
at the Earth Summit in 1992 has been rati¬ed and machinery for its
implementation is gradually being developed. At the end of 1995, the
IPCC produced a further comprehensive report updating the 1990 report.
Although the main conclusions have not changed, much has been added
to the detail of our knowledge regarding all aspects of the issue, the
science, the impacts and the possible response. This revised edition takes
into account this further information from the 1995 IPCC reports.
In the ¬rst edition I included a chapter, Chapter 8, with the heading
˜Why should we be concerned?™ which addresses the question of the
responsibility of humans for the Earth and for looking after the environ-
ment. In it I presented something of the basis for my personal motivation
as a Christian for being concerned with environmental problems. Al-
though I believe that it is important that science is presented in the broad
context of human values, I realised that the inclusion of such a chapter
was something of a departure and wondered how it would be received.
Some have expressed surprise that in the middle of a science book,
there should be, unusually, a chapter of this kind which deals with ethical
and religious issues. However, it has been pleasing that scienti¬c col-
leagues and reviewers of the book have referred favourably to the chapter
stressing the value and importance of placing environmental science in
the context of the reasons for its pursuit. For instance, John Perry, in the
Bulletin of the American Meteorological Society, writes:

Many scientists, including avowed agnostics such as myself, will ¬nd this
forth-right declaration of religious belief and divine purpose a bit startling
in an otherwise rigorously scienti¬c volume. However, in a line of
argument that I have no dif¬culty whatever in supporting, Houghton
demonstrates that the domains of science and religion are simply
complementary ways of looking at truth. The former deals with how the
world works and the latter with why. In Houghton™s framework, we and the
earth are each other™s reasons for existence in a divine plan that we must

xxvii
xxviii Preface to the Second Edition



struggle to understand but must inescapably follow. Thus, Houghton holds
that we have no choice but to care for the earth solicitously as its
˜gardeners™ in a ˜partnership with God™. His lucid precis of the complex
factual substance of global warming is an authoritative guide to the issue™s
scienti¬c dimensions; his inspiring synthesis of science, faith and
stewardship is an even more illuminating handbook to its moral and ethical
dimensions. Together, they constitute a uniquely valuable Baedeker to one
of the most important issues of our science and our time.

In revising Chapter 8 for this edition, I have been somewhat more
objective and less personal “ which I felt was more appropriate for stu-
dent readers from a wide range of disciplines, for whom the edition is
particularly suited. As a didactic aid I have also included a number of
problems and questions for discussion at the end of all the chapters.
Some of my colleagues sometimes comment on how formidable is
the task of sewardship of the Earth feeling that it is perhaps beyond the
capability of the human race to tackle it adequately. I feel optimistic
about it, however, for three main reasons. Firstly, I have seen how the
world™s scientists, coming from very different countries, cultures and
backgrounds, have worked closely and responsibly in the IPCC to provide
a consensus presentation of the science of global warming. Secondly, the
technologies required to provide for greater ef¬ciency in the use of fossil
fuels and for their replacement with renewable sources of energy are
available and, when developed on the necessary scale, also affordable.
Thirdly, my belief in God™s commitment to the material world coupled
with his offer of partnership in caring for it, makes stewardship of the
Earth an especially exciting and challenging activity.
In the preparation of this revised volume I wish to express again
my gratitute to the scienti¬c colleagues with whom I have worked
in the ongoing activity of the IPCC and from whom I have learnt
much. My thanks are also due to John Twidell and Michael Banner
who have commented on particular chapters, and to Catherine Flack,
Matt Lloyd and other staff of the Cambridge University Press for their
competence, courtesy and assistance in the preparation of the book.
John Houghton
1997
Preface to the Third Edition




Since the Second Edition seven years ago, research and debate on the is-
sue of human-induced climate change have grown at a rapidly increasing
pace. Observations of climate during this period have provided further
information about the warming Earth and there has been substantial
improvement in the models that simulate both past and future climate.
Although the main messages regarding the fact of human-induced cli-
mate change and its impact have not changed signi¬cantly (on the whole
they have been strengthened) more detailed understanding has been
achieved regarding the basic science (including the uncertainties), the
likely impacts and the imperative for action. Hence the need to update this
book.
In 2001 the Intergovernmental Panel on Climate Change (IPCC)
published its Third Assessment Report“even more thorough and com-
prehensive than the ¬rst two. As co-chair of the scienti¬c assessment
working group for all three of the IPCC reports, I have been privileged
to be a part of the IPCC process, which has been so effective in informing
the scienti¬c community. Then, through that community, information has
been spread to decision makers and others regarding what is known about
climate change with some degree of certainty and also about the areas
where there remains much uncertainty. I have leant heavily on the IPCC
2001 Report in revising this text and wish to express my deep gratitude to
those many IPCC colleagues with whom I have worked and from whom
I have learnt so much. I have also bene¬ted greatly from my association
with the UK Hadley Centre for Climate Prediction and Research, which
has become the world™s premier centre for climate modelling research.
My especial thanks are due to those who have provided me with
particular new material; Peter Cox, Chris Jones, Colin Prentice and Jo
House for Chapter 3; Chris Folland and Alan Dickinson for Chapters 4
and 5; Tim Palmer and Jonathan Gregory for Chapter 6; Martin Parry and
Rajendra Pachauri for Chapter 7; Stephen Briggs for material regarding
Envisat for Chapter 9; Aubrey Meyer for Chapter 10; Mark Akhurst,
Andre Romeyn, Robert Kleiburg, Gert Jan Kramer, Chris West, Peter
Smith and Chris Llewellyn Smith for Chapter 11; and William Clark for
Chapter 12. John Mitchell, Terry Barker and Susan Baylis kindly read

xxix
xxx Preface to the Third Edition



and commented on some of the draft chapters. I am also particularly
grateful to David Griggs, Geoffrey Jenkins, Philippe Rekacewicz and
Paul van der Linden who assisted with the sourcing and preparation of
the ¬gures. Finally, I wish to thank Matt Lloyd, Carol Miller, Sarah Price
and other staff of Cambridge University Press who have carefully steered
the book through its gestation and production.
In January of this year I attended the World Economic Forum in
Davos and engaged in discussion and debate regarding global warming
and climate change. Nearly everyone there accepted the fact of climate
change due to human activities and the need for action to reduce green-
house gas emissions in order to reduce its impact. However, many partic-
ipants knew little of the likely impacts of climate change or of the extent
of the action required to address it; they just believed that it was one of
those problems that would have to be addressed sometime. I hope that
this book will assist in making the necessary information more readily
available and so help to provide the foundation for the urgent action that
is required.
John Houghton
Chapter 1
Global warming and climate change




The phrase ˜global warming™ has become familiar to many people as
one of the important environmental issues of our day. Many opinions
have been expressed concerning it, from the doom-laden to the dis-
missive. This book aims to state the current scienti¬c position on global
warming clearly, so that we can make informed decisions on the facts.



Is the climate changing?
In the year 2060 my grandchildren will be approaching seventy; what
will their world be like? Indeed, what will it be like during the seventy
years or so of their normal life span? Many new things have happened
in the last seventy years that could not have been predicted in the 1930s.
The pace of change is such that even more novelty can be expected in the
next seventy. It is fairly certain that the world will be even more crowded
and more connected. Will the increasing scale of human activities affect
the environment? In particular, will the world be warmer? How is its
climate likely to change?
Before studying future climate changes, what can be said about cli-
mate changes in the past? In the more distant past there have been very
large changes. The last million years has seen a succession of major ice
ages interspersed with warmer periods. The last of these ice ages began
to come to an end about 20 000 years ago and we are now in what is called
an interglacial period. Chapter 4 will focus on these times far back in
the past. But have there been changes in the very much shorter period of
living memory “ over the past few decades?


1
2 Global warming and climate change



Variations in day-to-day weather are occurring all the time; they
are very much part of our lives. The climate of a region is its average
weather over a period that may be a few months, a season or a few years.
Variations in climate are also very familiar to us. We describe summers
as wet or dry, winters as mild, cold or stormy. In the British Isles, as
in many parts of the world, no season is the same as the last or indeed
the same as any previous season, nor will it be repeated in detail next
time round. Most of these variations we take for granted; they add a
lot of interest to our lives. Those we particularly notice are the extreme
situations and the climate disasters (for instance, Figure 1.1 shows the
signi¬cant climate events and disasters during the year 1998). Most of
the worst disasters in the world are, in fact, weather- or climate-related.
Our news media are constantly bringing them to our notice as they occur
in different parts of the world “ tropical cyclones (called hurricanes or
typhoons), wind-storms, ¬‚oods, tornadoes and droughts whose effects
occur more slowly, but which are probably the most damaging disasters
of all.



The remarkable last decades of the
twentieth century
The 1980s and 1990s were unusually warm. Globally speaking, the
decades have been the warmest since accurate records began somewhat
over a hundred years ago and these unusually warm years are continuing
into the twenty-¬rst century. In terms of global average near-surface air
temperature, the year 1998 was the warmest in the instrumental record
and the nine warmest years in that record have occurred since 1990.
The period has also been remarkable (just how remarkable will be
considered later) for the frequency and intensity of extremes of weather
and climate. For example, periods of unusually strong winds have been
experienced in western Europe. During the early hours of the morning
of 16 October 1987, over ¬fteen million trees were blown down in south-
east England and the London area. The storm also hit Northern France,
Belgium and The Netherlands with ferocious intensity; it turned out to be
the worst storm experienced in the area since 1703. Storm-force winds
of similar or even greater intensity but covering a greater area of western
Europe have struck since “ on four occasions in 1990 and three occasions
in December 1999.1
But those storms in Europe were mild by comparison with the much
more intense and damaging storms other parts of the world have experi-
enced during these years. About eighty hurricanes and typhoons “ other
names for tropical cyclones “ occur around the tropical oceans each year,
MAJOR GLOBAL CLIMATE ANOMALIES AND EPISODIC EVENTS IN 1998
May-Aug. floods:
May-Jun.
Mild Jan.-Mar. up to 2 168mm rain
heat wave surpluses to 772mm
Wetness/flooding
temp. to 48°C Hot & dry
Frequent Jun.-Aug. Sep.-Nov. Jun.-Aug.
warmth Cold Nov.-Dec.
heat waves
Wet/severe weather throughout Warm & dry/
year Severe Jan.
Apr.-Jun. wildfires
ice storm
Stormy
Jul.-Oct.
Dry Jul.-Oct. up to
Wet/cool Nov.-Dec. Very dry
Jan.-May & Dec. 2 870mm rain;
Jun.-Dec. Oct.-Dec. Flooding Periodic warmth
Crop losses surpluses to 915mm
Bonnie (Aug.) up Apr.-May throughout year
Dry
Very Jul.-Aug.
Jan.-Jun. to 250mm rain
Jul.-Sep. Brief but severe
Severe flooding
drought hot Unseasonably wet Jan.-Mar. Aug. flooding
Jun. 50% of Dry
Death Valley, CA. Abundant tropical Extreme
normal rain Warm & dry Wet Jan.-Jun.
July May fires Oct.-Nov.
Warm
approaches 54°C rains Jul.-Nov. Jul.-Aug.
Oct.-Dec.
Jan.-Mar.
fires Zeb (Oct.)
warmest in North America flooding
Georges (late Sep.) much
for 36 years (Jul.) Babs (Oct.)
Wetness/flooding
Mitch O3B (Jun.)
severe damage to of the
Jul.-Sep.
(late Oct.) Dry Jun.-Jul.
Charley (Aug.) northern Caribbean;
wind damage, Wet
year
up to 450mm rain heavy rain, Wet/numerous
up to 685mm rain Sep.-Oct.
ends drought central USA Gulf Coast tropical systems
& flooding
Dry Sep.-Dec.
Wet
Hot & dry Mar.-Jul. Powerful El Ni±o
Oct.-Dec.
(Up to US$ 8 billion Jan.-Apr.
gives way to
drought damage moderate La Ni±a
in southern USA) Wet Nov.-Dec.
Sep. 97-May 98
11 to 49 times normal rainfall Dry Feb.-May
Wet
Very warm & wet Warm & dry/
Jun.-Dec.
Jan.-May wildfires
Stormy Severely Dry Jan.-May;
Jan.-Apr. Oct.-Dec. Indonesian fires
Wetness/flooding
Largest Sep.97-May 98
Jan.-May Dry Sep.-Dec. Rainfall deficits:
Philippines: 2 472mm
Highest global annual average surface Indonesia: 1 613mm
temperature on record Malaysia: 1 430mm




Source: Climate Prediction Center, NOAA, USA

Figure 1.1 Signi¬cant climate anomalies and events during 1998 as recorded by the Climate Prediction
Center of the National Oceanic and Atmosphere Administration (NOAA) of the United States.
4 Global warming and climate change



familiar enough to be given names. Hurricane Gilbert that caused devas-
tation on the island of Jamaica and the coast of Mexico in 1988, Typhoon
Mireille that hit Japan in 1991, Hurricane Andrew that caused a great
deal of damage in Florida and other regions of the southern United States
in 1992 and Hurricane Mitch that caused great devastation in Honduras
and other countries of central America in 1998 are notable recent ex-
amples. Low-lying areas such as Bangladesh are particularly vulnerable
to the storm surges associated with tropical cyclones; the combined effect
of intensely low atmospheric pressure, extremely strong winds and high
tides causes a surge of water which can reach far inland. In one of the
worst such disasters in the twentieth century over 250 000 people were
drowned in Bangladesh in 1970. The people of that country experienced
another storm of similar proportions in 1999 as did the neighbouring
Indian state of Orissa also in 1999, and smaller surges are a regular
occurrence in that region.
The increase in storm intensity during recent years has been tracked
by the insurance industry, which has been hit hard by recent disasters.
Until the mid 1980s, it was widely thought that windstorms or hurri-
canes with insured losses exceeding one billion (thousand million) US
dollars were only possible, if at all, in the United States. But the gales
that hit western Europe in October 1987 heralded a series of windstorm
disasters which make losses of ten billion dollars seem commonplace.
Hurricane Andrew, for instance, left in its wake insured losses estimated
at nearly twenty-one billion dollars (1999 prices) with estimated total
economic losses of nearly thirty-seven billion dollars. Figure 1.2 shows
the costs of weather-related disasters2 over the past ¬fty years as calcu-
lated by the insurance industry. It shows an increase in economic losses
in such events by a factor of over 10 in real terms between the 1950s and
the 1990s. Some of this increase can be attributed to the growth in pop-
ulation in particularly vulnerable areas and to other social or economic
factors; the world community has undoubtedly become more vulner-
able to disasters. However, a signi¬cant part of it has also arisen from
the increased storminess in the late 1980s and 1990s compared with the
1950s.
Windstorms or hurricanes are by no means the only weather and
climate extremes that cause disasters. Floods due to unusually intense
or prolonged rainfall or droughts because of long periods of reduced
rainfall (or its complete absence) can be even more devastating to human
life and property. These events occur frequently in many parts of the
world especially in the tropics and sub-tropics. There have been notable
examples during the last two decades. Let me mention a few of the ¬‚oods.
In 1988, the highest ¬‚ood levels ever recorded occurred in Bangladesh,
eighty per cent of the entire country was affected; China experienced
El Ni˜ o events
n 5



70000
Decade Comparison (losses in US$ billion, 1999 values)
60000 Factor Factor
1950“59 1960“69 1970“79 1980“89 1990“99 90s:50s 90s:60s

50000 Number
Losses (US$ million)




Weather-Related 13 16 29 44 72 5.5 4.5
Non-Weather-Related 7 11 18 19 17 2.4 1.5
Economic Losses 38.7 50.8 74.5 118.4 399.0 10.3 7.9
40000
Insured Losses 0/unknown 6.7 10.8 21.6 91.9 ” 13.6

Economic Trend
Economic
30000
Insured Trend
Insured

20000


10000


0
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
Year
Figure 1.2 The total economic costs and the insured costs of catastrophic
weather events for the second half of the twentieth century as recorded by the
Munich Re insurance company. Both costs show a rapid upward trend in recent
decades. The number of non-weather-related disasters is included for
comparison. Tables 7.2 and 7.3 in Chapter 7 provide some regional detail and
list some of the recent disasters with the greatest economic and insured losses.


devastating ¬‚oods affecting many millions of people in 1991, 1994“5
and 1998; in 1993, ¬‚ood waters rose to levels higher than ever recorded
in the region of the Mississippi and Missouri rivers in the United States,
¬‚ooding an area equivalent in size to one of the Great Lakes; major ¬‚oods
in Venezuela in 1999 led to a large landslide and left 30 000 people dead,
and two widespread ¬‚oods in Mozambique occurred within a year in
2000“1 leaving over half a million homeless. Droughts during these
years have been particularly intense and prolonged in areas of Africa,
both north and south. It is in Africa especially that they bear on the most
vulnerable in the world, who have little resilience to major disasters.
Figure 1.3 shows that in the 1980s droughts accounted for more deaths
in Africa than all other disasters added together and illustrates the scale
of the problem.


El Ni˜ o events
n
Rainfall patterns which lead to ¬‚oods and droughts especially in
tropical and semi-tropical areas are strongly in¬‚uenced by the surface
temperature of the oceans around the world, particularly the pattern of
ocean surface temperature in the Paci¬c off the coast of South America
6 Global warming and climate change



Figure 1.3 Recorded
disasters in Africa, 1980“9,
estimated by the Organization
for African Unity.




(see Chapter 5 and Figure 5.9). About every three to ¬ve years a large
area of warmer water appears and persists for a year or more. Because
they usually occur around Christmas these are known as El Ni˜ o n
(˜the boy child™) events.3 They have been well known for centuries
to the countries along the coast of South America because of their
devastating effect on the ¬shing industry; the warm top waters of the
ocean prevent the nutrients from lower, colder levels required by the
¬sh from reaching the surface.
A particularly intense El Ni˜ o, the second most intense in the twen-
n
tieth century, occurred in 1982“3; the anomalous highs in ocean surface
temperature compared to the average reached 7 —¦ C. Droughts and ¬‚oods
somewhere in almost all the continents were associated with that El
Ni˜ o (Figure 1.4). Like many events associated with weather and cli-
n
mate, El Ni˜ os often differ very much in their detailed character; that
n
has been particularly the case with the El Ni˜ o events of the 1990s. For
n
instance, the El Ni˜ o event that began in 1990 and reached maturity
n
early in 1992, apart from some weakening in mid 1992, continued to be
dominated by the warm phase until 1995. The exceptional ¬‚oods in the
central United States and in the Andes, and droughts in Australia and
Africa are probably linked with this unusually protracted El Ni˜ o. This,
n
the longest El Ni˜ o of the twentieth century, was followed in 1997“8 by
n
the century™s most intense El Ni˜ o that brought exceptional ¬‚oods to
n
China and to the Indian sub-continent and drought to Indonesia “ that
in turn brought extensive forest ¬res creating an exceptional blanket of
thick smog that was experienced over a thousand miles away (Figure 1.1).
The effect of volcanic eruptions on temperature extremes 7




Studies with computer models of the kind described later in Chapter 5 Figure 1.4 Regions where
droughts and ¬‚oods
provide a scienti¬c basis for links between the El Ni˜ o and these extreme
n
occurred associated with
weather events; they also give some con¬dence that useful forecasts of
the 1982“3 El Ni˜ o.
n
such disasters will in due course be possible. A scienti¬c question that is
being urgently addressed is the possible link between the character and
intensity of El Ni˜ o events and global warming due to human-induced
n
climate change.


The effect of volcanic eruptions on
temperature extremes
Volcanoes inject enormous quantities of dust and gases into the upper
atmosphere. Large amounts of sulphur dioxide are included, which
through photochemical reactions using the Sun™s energy are transformed
to sulphuric acid and sulphate particles. Typically these particles remain
in the stratosphere (the region of atmosphere above about 10 km in alti-
tude) for several years before they fall into the lower atmosphere and are
8 Global warming and climate change



quickly washed out by rainfall. During this period they disperse around
the whole globe and cut out some of the radiation from the Sun, thus
tending to cool the lower atmosphere.
One of the largest volcanic eruptions in the twentieth century was
that from Mount Pinatubo in the Philippines on 12 June 1991 which
injected about twenty million tonnes of sulphur dioxide into the strato-
sphere together with enormous amounts of dust. This stratospheric dust
caused spectacular sunsets around the world for many months following
the eruption. The amount of radiation from the Sun reaching the lower
atmosphere fell by about two per cent. Global average temperatures
lower by about a quarter of a degree Celsius were experienced for the
following two years. There is also evidence that some of the unusual
weather patterns of 1991 and 1992, for instance unusually cold winters
in the Middle East and mild winters in western Europe, were linked
with effects of the volcanic dust.


Vulnerable to change
Over the centuries different human communities have adapted to their
particular climate; any large change to the average climate tends to bring
stress of one kind or another. It is particularly the extreme climate events
and climate disasters which emphasise the importance of climate to
our lives and which demonstrate to countries around the world their
vulnerability to climate change “ a vulnerability which is enhanced by
rapidly increasing demands on resources.
But the question must be asked: how remarkable are these events?
Do they point to a changing climate due to human activities? Do they
provide evidence for global warming because of the increased carbon
dioxide and other greenhouse gases being emitted into the atmosphere
by burning fossil fuels?
Here a note of caution must be sounded. The range of normal natural
climate variation is large. Climate extremes are nothing new. Climate
records are continually being broken. In fact, a month without a broken
record somewhere would itself be something of a record! Changes in
climate that indicate a genuine long-term trend can only be identi¬ed
after many years.
However, we know for sure that, because of human activities espe-
cially the burning of fossil fuels, carbon dioxide in the atmosphere has

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