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Global Warming
The Complete Brie¬ng • Fourth Edition




John Houghton™s market-leading textbook is now in full colour and includes the latest
IPCC ¬ndings and future energy scenarios from the International Energy Agency,
making it the de¬nitive guide to climate change. Written for students across a wide
range of disciplines, its simple, logical ¬‚ow of ideas gives an invaluable grounding
in the science and impacts of climate change and highlights the need for action on
global warming.

˜The addition of colour serves the diagrams so they deliver the necessary message
and information they intend . . . to instructors and students in interdisciplinary
programmes who need an accessible, broad-view text on the subject of climate
change.™
YO C H A N A N K U S H N I R , Lamont-Doherty Earth Observatory of Columbia University

˜The new edition provides the most up-to-date and comprehensive coverage of cli-
mate change for teaching in an undergraduate class. It covers the latest on climate
science, climate change impacts and adaptation, and approaches to slowing climate
change through reducing emissions from energy use, transport, and deforesta-
tion. These complex issues are presented clearly and throughly, based on the recent
Fourth Assessment Report of the Intergovernmental Panel on Climate Change and
many other sources. The new edition has signi¬cantly expanded and updated sec-
tions on slowing and stabilising climate change and on energy and transport for the
future, which complement the sections on climate science. The addition of colour
adds clarity and emphasis to the many valuable ¬gures. I will de¬nitely be using
this book in all my courses on climate change.™
P R O F DAV I D K A R O L Y , University of Melbourne (formerly of the University of Oklahoma)

˜It is dif¬cult to imagine how Houghton™s exposition of this complex body of infor-
mation 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 citi-
zen could hope to ¬nd within the pages of a pocketable book.™
JOH N P E R R Y , 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 . . . .™
WI L L I A M H A R S T O N , The Independent

˜¦ a widely praised book on global warming and its consequences.™
The Economist

˜I would thoroughly recommend this book to anyone concerned about global warm-
ing. 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.™
TON Y WAT E R S , The Observatory

˜For the non-technical reader, the best program guide to the political and scien-
ti¬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.™
A L A N H E C H T , 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.™
A N D R E W B I S H O P, Association for Science Education

˜ ¦ 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.™
A L L E N P E R R Y , Holocene

˜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.™
E L M A R R . R E I T E R , 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

˜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
GLOBAL
WAR MING



The Complete Brie¬ng Fourth Edition


Sir John Houghton
CAMBRIDGE UNIVERSITY PRESS
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo

Cambridge University Press
The Edinburgh Building, Cambridge CB2 8RU, UK
Published in the United States of America by Cambridge University Press, New York

www.cambridge.org
Information on this title: www.cambridge.org/9780521882569
© J. T. Houghton 1994, 1997, 2004, 2009


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 2009


ISBN-13 978-0-511-53365-5 eBook (EBL)

ISBN-13 978-0-521-88256-9 hardback

ISBN-13 978-0-521-70916-3 paperback



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


Preface page xvii


1 Global warming and climate change 1
Is the climate changing? 2
The last 30 years 2
El Ni±o events 7
The effect of volcanic eruptions on temperature extremes 10
Vulnerability to change 10
What is global warming? 13
Adaptation and mitigation 14
Uncertainty and response 15
16
Questions
17
Further reading and reference


2 The greenhouse effect 18
How the Earth keeps warm 19
The greenhouse effect 20
Pioneers of the science of the greenhouse effect 23
Mars and Venus 27
The ˜runaway™ greenhouse effect 28
The enhanced greenhouse effect 29
31
Summary
32
Questions
32
Further reading and reference


3 The greenhouse gases 34
Which are the most important greenhouse gases? 35
Radiative forcing 35
Carbon dioxide and the carbon cycle 35
43
The biological pump in the oceans
What we can learn from carbon isotopes 44
Future emissions of carbon dioxide 46
Feedbacks in the biosphere 48
x CO N T E N T S




Other greenhouse gases 50
Gases with an indirect greenhouse effect 57
Particles in the atmosphere 57
Global warming potentials 63
Estimates of radiative forcing 63
64
Summary
65
Questions
67
Further reading and reference


4 Climates of the past 69
The last hundred years 70
Atmospheric temperature observed by satellites 72
The last thousand years 79
The past million years 82
Palaeoclimate reconstruction from isotope data 84
How stable has past climate been? 87
90
Summary
91
Questions
92
Further reading and reference


5 Modelling the climate 93
Modelling the weather 94
Setting up a numerical atmospheric model 97
Data to initialise the model 98
Seasonal forecasting 101
Weather forecasting and chaos 102
A simple model of the El Ni±o 105
The climate system 106
Forecasting for the African Sahel region 107
108
Feedbacks in the climate system
Cloud radiative forcing 112
Climate feedback comparisons 115
Models for climate prediction 116
Validation of the model 119
The ocean™s deep circulation 120
Modelling of tracers in the ocean 124
Comparison with observations 124
Is the climate chaotic? 128
Regional climate modelling 130
xi
CO N T E N T S




The future of climate modelling 131
132
Summary
133
Questions
134
Further reading and reference


6 Climate change in the twenty-¬rst century and beyond 137
Emission scenarios 138
The emission scenarios of the Special Report on Emission
Scenarios (SRES) 140
Model projections 141
Projections of global average temperature 143
Simple climate models 144
Equivalent carbon dioxide (CO2e) 147
Regional patterns of climate change 149
Changes in climate extremes 154
Regional climate models 161
Longer-term climate change 163
Changes in the ocean thermohaline circulation 164
Other factors that might in¬‚uence climate change 165
Does the Sun™s output change? 166
167
Summary
168
Questions
169
Further reading and reference


7 The impacts of climate change 172
A complex network of changes 173
Sensitivity, adaptive capacity and vulnerability:
some de¬nitions 173
How much will sea level rise? 176
Thermal expansion of the oceans 177
Impacts in coastal areas 181
Increasing human use of fresh water resources 187
The impact of climate change on fresh water resources 190
Impact on agriculture and food supply 196
Deserti¬cation 197
The carbon dioxide ˜fertilisation™ effect 199
Modelling the impact of climate change on world food supply 200
The impact on ecosystems 203
Forest“climate interactions and feedbacks 208
xii CO N T E N T S




The impact on human health 213
Heatwaves in Europe and India, 2003 215
Impacts on Africa 216
Adaptation to climate change 217
Costing the impacts: extreme events 219
The insurance industry and climate change 222
Costing the total impacts 223
Estimates of impacts costs under business-as-usual (BAU)
from the Stern Review 227
232
Summary
233
Questions
234
Further reading and reference


8 Why should we be concerned? 239
Earth in the balance 240
Exploitation 240
˜Back to nature™ 241
The technical ¬ x 242
The unity of the Earth 243
Daisyworld and life on the early Earth 246
Environmental values 247
Stewards of the Earth 250
Equity “ intergenerational and international 252
The will to act 253
254
Summary
255
Questions
257
Further reading and reference


9 Weighing the uncertainty 260
The scienti¬c uncertainty 261
The reasons for scienti¬c uncertainty 262
The IPCC Assessments 263
Narrowing the uncertainty 267
Space observations of the climate system 268
Sustainable development 270
Sustainable development: how is it de¬ned? 272
Why not wait and see? 273
The Precautionary Principle 274
Principles for international action 276
xiii
CO N T E N T S




Some global economics 276
The Rio Declaration 1992 278
Integrated Assessment and Evaluation 280
285
Summary
286
Questions
287
Further reading and reference


10 A strategy for action to slow and stabilise
climate change 290
The Climate Convention 291
Extracts from the UN Framework Convention on
Climate Change 291
Stabilisation of emissions 293
The Montreal Protocol 294
The Kyoto Protocol 294
The Kyoto mechanisms 298
Carbon trading 299
Forests 300
The world™s forests and deforestation 301
Reduction in sources of greenhouse gases other
than carbon dioxide 305
Stabilisation of carbon dioxide concentrations 307
The choice of stabilisation level 311
Realising the Climate Convention Objective 315
319
Summary
320
Questions
322
Further reading and reference


11 Energy and transport for the future 325
World energy demand and supply 326
Future energy projections 330
Energy intensity and carbon intensity 331
Socolow and Pascala™s Wedges 335
A long-term energy strategy 336
Buildings: energy conservation and ef¬ciency 336
Where are we heading? Components of energy strategy 338
Thermodynamic ef¬ciencies 339
Ef¬ciency of appliances 340
Insulation of buildings 341
xiv CO N T E N T S




Example of a ZED (Zero Emission Development) 343
Energy and carbon dioxide savings in transport 343
Technologies for reducing carbon dioxide emissions
from motor vehicles 346
Energy and carbon dioxide savings in industry 346
Carbon-free electricity supply 347
Hydropower 351
Biomass energy 353
Biomass projects in rural areas in the developing world 354
Biofuels 357
Wind energy 358
Wind power on Fair Isle 360
Energy from the Sun: Solar Heating 360
Solar water heating 361
Solar energy in building design 362
The photovoltaic solar cell 364
Local energy provision in Bangladesh 366
Other renewable energies 367
The support and ¬nancing of carbon-free energy 369
Policy instruments 370
Mitigation technologies and potential in 2030 375
Technology for the longer term 375
Fuel cell technology 376
Power from nuclear fusion 377
A Zero carbon future 378
IEA World Energy Outlook 2008 381
Energy policy in the UK 382
383
Summary
385
Questions
387
Further reading and reference


12 The global village 391
Global warming “ global pollution 392
Sustainability “ also a global challenge 393
Not the only global problem 394
Poverty and population growth 396
The challenge to all sections of community 397
The conception and conduct of environmental research 400
What the individual can do 401
xv
CO N T E N T S




The goal of environmental stewardship 402
404
Questions
406
Further reading and reference


Appendix 1 408
Sl unit pre¬ xes 408
Chemical symbols 408

Appendix 2: Acknowledgements for ¬gures, photos and tables 409
Figures 409
Photos 415
Tables 417


Glossary 418
Index 426
Preface


Global Warming is a topic that increasingly occupies the attention of the world.
Is it really happening? If so, how much of it is due to human activities? How far
will it be possible to adapt to changes of climate? What action to combat it can
or should we take? How much will it cost? Or is it already too late for useful
action? This book sets out to provide answers to all these questions by providing
the best and latest information available.
I was privileged to chair or co-chair the Scienti¬c Assessments for the
Intergovernmental Panel on Climate Change (IPCC) from its inception in 1988
until 2002. During this period the IPCC published three major comprehensive
reports “ in 1990, 1995 and 2001 “ that have in¬‚uenced and informed those
involved in climate change research and those concerned with the impacts of
climate change. In 2007, a fourth assessment report was published. It is the
extensive new material in this latest report that has provided the basis for the
substantial revision necessary to update this fourth edition.
The IPCC reports have been widely recognised as the most authoritative and
comprehensive assessments on a complex scienti¬c subject ever produced by the
world™s scienti¬c community. On the completion of the ¬rst assessment in 1990,
I was asked to present it to Prime Minister Margaret Thatcher™s cabinet “ the
¬rst time an overhead projector had been used in the Cabinet Room in Number
10 Downing Street. In 2005, the work of the IPCC was cited in a joint statement
urging action on climate change presented to the G8 meeting in that year by
the Academies of Science of all G8 countries plus China, India and Brazil. The
world™s top scientists could not have provided stronger approval of the IPCC™s
work. An even wider endorsement came in 2007 when the IPCC was awarded a
Nobel Peace Prize.
Many books have been published on global warming. My choice of material
has been much in¬‚uenced by the many lectures I have given in recent years to
professional, student and general audiences.
The strengths of this book are that it is:

• up-to-date with the latest reliable, accurate and understandable
information about all aspects of the global warming problem for students,
professionals and interested or concerned citizens.
• accessible to both scientists and non-scientists. Although there are many
numbers in the book “ I believe quanti¬cation to be essential “ there are no
xviii P R E FAC E




mathematical equations. Some important technical material is included in
boxes.
• comprehensive, as it moves through the basic science of global warming,
impacts on human communities and ecosystems, economic, technological
and ethical considerations and policy options for action both national and
international.
• appropriate as a general text for students, from high-school level up to uni-
versity graduate. Questions and problems for students to consider and to test
their understanding of the material are included in each chapter.
• Its simple and effective visual presentation of the vast quantities of
data available on climate change ensures that readers can see how conclusions
are made, without being overwhelmed. Illustrations are available online.

Over the 20 years since the inception of the IPCC, our understanding of climate
change has much increased and signi¬cant changes in climate due to human
activities have been experienced. Further, studies of the feedbacks that deter-
mine the climate response have shown an increasing likelihood of enhanced
response, so leading over these years to greater concern about the future impact
of climate change on both human populations and ecosystems. Can much be
done to alleviate the impact or mitigate future climate change? Later chapters
of the book address this question and demonstrate that the technology is largely
available to support urgent and affordable action. They also point to the many
other bene¬ts that will accrue to all sectors of society as the necessary action is
taken. However, what seems lacking as yet is the will to take that action.
As I complete this revised edition I want to express my gratitude, ¬rst to those
who inspired me and helped with the preparation of the earlier editions, with
many of whom I was also involved in the work of the IPCC or of the Hadley
Centre. I also acknowledge those who have assisted with the material for this
edition or who have read and helpfully commented on my drafts, in particular,
Fiona Carroll, Jim Coakley, Peter Cox, Simon Desjardin, Michael Hambery, Marc
Humphreys, Chris Jones, Linda Livingstone, Jason Lowe, Tim Palmer, Martin
Parry, Ralph Sims, Susan Solomon, Peter Smith, Chris West, Sue Whitehouse
and Richard Wood. My thanks are also due to Catherine Flack, Matt Lloyd,
Anna-Marie Lovett and Jo Endell-Cooper of Cambridge University Press for their
competence and courtesy as they steered the book through its gestation and
production.
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 encour-
agement and support through the long hours of its production.
Global warming and climate
1
change




Hurricane Wilma hit Florida™s southern west coast on 24 October 2005.




T HE PHRASE ˜global warming™ has become familiar to many people as one of the most
important issues of our day. Many opinions have been expressed concerning it, from the
doom-laden to the dismissive. This book aims to state the current scienti¬c position on global
warming clearly, so that we can make informed decisions on the facts.
2 G LO BA L WA R M I N G A N D C L I M AT E C H A N G E




Is the climate changing?
In the year 2060 my grandchildren will be approaching 70 years old; what will
their world be like? Indeed, what will it be like during the 70 years or so of their
normal lifespan? Many new things have happened in the last 70 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 70. It seems 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 addressing future climate changes, what can be said about climate
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?
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 situ-
ations and the climate disasters (for instance, Figure 1.1 shows the signi¬cant
climate events and disasters during the year 1998 “ one of the warmest years on
record). 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), windstorms, ¬‚oods and tornadoes, also droughts whose effects occur
more slowly, but which are probably the most damaging disasters of all.


The last 30 years
The closing decades of the twentieth century and the early years of the pre-
sent century were unusually warm. Globally speaking, the last 30 years have
been the warmest since accurate records began somewhat over 100 years ago.
Twelve of the 13 years 1995 to 2007 rank among the 13 warmest in the instru-
mental record of global surface air temperature that began around 1850, the
3
THE L AST 30 YEARS




Jul“Oct up to
May“Jun
Wetness/flooding Hot and dry
Jun“Aug 2870 mm rain;
heatwave
Sep“Nov
Wet/severe weather Jun“Aug
heat waves surpluses
temp. to 48°C May“Aug floods
Apr“Jun to 915 mm up to 2168 mm rain Warm and Dry
Wet/cool Mild Jan“Mar wildfires
surpluses to 772 mm
Jan“May and Dec
Jul“Oct
Crop losses
Frequent
warmth Cold Nov“Dec
throughout Severe Jan
year ice storm
Stormy
Periodic warmth
Jan“Jun Dry
Nov“Dec Very dry
throughout year
drought Jun“Dec Oct.“Dec. Flooding
Bonnie (Aug) up Apr“May
Dry
Very Jul“Aug Brief but severe
to 250 mm rain
Jul“Sep
Death Valley, CA. flooding Aug flooding
Severe Unseasonably wet
approaches 54 °C hot
Jun Dry
Jan“Mar 50% of
warmest in Wet Jan“Jun
July Extreme
May fires normal rain Warm and Dry Oct“Nov
North America Abundant tropical Warm Jul“Aug
Oct“Dec
fires
for 36 years (Jul) rains Jul“Nov Jan“Mar Zeb (Oct)
flooding
Georges (late Sep) much Babs (Oct)
Wetness/flooding
Charley (Aug) O3B (Jun)
Mitch (late Oct) severe damage to of the Jul“Sep
up to 450 mm wind damage up Dry Jun“Jul
northern Caribbean; year
ends drought Wet
to 685 mm rain heavy rain, Wet/numerous
Sep“Oct
and flooding central USA Gulf Coast tropical systems
Hot and dry Mar “Jul
Sep“Dec
(Up to $US 8 billion Wet
Dry Oct“Dec
drought damage Powerful El Ni±o
Jan“Apr
in southern USA) gives way to
Wet Nov“Dec
moderate La Ni±a
Sep 97“May 98 Dry Feb“May
11 to 49 times normal rainfall
Warm and dry
Very warm & wet
wildfires Wet
Severely Dry Jan“May;
Jan“May Stormy
Jan“Apr Jun“Dec
Indonesian fires
Oct“Dec
Largest Sep 97“May 98
Wetness/flooding Rainfall deficits:
Jan“May Philippines: 2472 mm
Dry Sep“Dec
Indonesia: 1613 mm
Highest global annual average surface Malaysia: 1430 mm
temperature on record


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


years 1998 and 2005 being the warmest (different analyses disagree which is the
warmer of the two). The Intergovernmental Panel on Climate Change in its 2007
Assessment1 states:

Warming of the climate system is unequivocal, as is now evident from
observations of increases in global average air and ocean temperatures,
widespread melting of snow and ice, and rising global average sea level.

The period has also been remarkable (just how remarkable will be considered
later) for the frequency and intensity of extremes of weather and climate. Let
me give a few examples. An extremely unusual heatwave in central Europe
occurred in the summer of 2003 and led to the premature deaths of over 20 000
people (see Chapter 7, page 215). Periods of unusually strong winds have been
experienced in western Europe. During the early hours of the morning of 16
October 1987, over 15 million trees were blown down in southeast 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 expe-
rienced 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.
4 G LO BA L WA R M I N G A N D C L I M AT E C H A N G E




Hurricane Mitch was one of the deadliest and most powerful hurricanes on record in the Atlantic basin,
with maximum sustained winds of 180 mph (290 km h’1). The storm was the thirteenth tropical storm,
ninth hurricane and third major hurricane of the 1998 Atlantic hurricane season.



But those storms in Europe were mild by comparison with the much more
intense and damaging storms other parts of the world have experienced dur-
ing these years. About 80 hurricanes and typhoons “ other names for tropi-
cal cyclones “ occur around the tropical oceans each year, familiar enough to
be given names: Hurricane Gilbert caused devastation on the island of Jamaica
and the coast of Mexico in 1988, Typhoon Mireille hit Japan in 1991, Hurricane
Andrew caused a great deal of damage in Florida and other regions of the
southern United States in 1992, Hurricane Mitch caused great devastation in
Honduras and other countries of central America in 1998 and Hurricane Katrina
caused record damages as it hit the Gulf Coast of the United States in 2005 are
notable recent examples. Low-lying areas such as Bangladesh are particularly
vulnerable to the storm surges associated with tropical cyclones; the combined
5
THE L AST 30 YEARS



70 000

Decade comparison (losses in US$ billion, 1999 values)
60 000
Factor Factor
1950“59 1960“69 1970“79 1980“89 1990“99 90s:50s 90s:60s

50 000 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
40 000
Insured losses 0/unknown 6.7 10.8 21.6 91.9 “ 13.6

Economic
30 000
Insured

20 000


10 000


0
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2004
Year

Figure 1.2 The total economic costs and the insured costs of catastrophic weather events for the period 1950
to 2004 as recorded by the Munich Re insurance company. For 2005, because of Hurricane Katrina in the
USA the ¬gures are off the page “ over $US200 billion for economic losses and over $US80 billion for insured
losses. Both costs show a rapid upward trend in recent decades. The number of non-weather-related disasters
is included for comparison. Tables 7.3 and 7.4 in Chapter 7 provide some regional detail and list some of the
recent disasters with the greatest economic and insured losses.




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 hurricanes with insured losses
exceeding $US1 billion (thousand million) 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 that make losses of $US10 billion seem common-
place. Hurricane Andrew, for instance, left in its wake insured losses estimated
at nearly $US21 billion (1999 prices) with estimated total economic losses of
nearly $US37 billion. Figure 1.2 shows the costs of weather-related disasters2
over the past 50 years as calculated 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 present day. Some of this increase can be attributed
6 G LO BA L WA R M I N G A N D C L I M AT E C H A N G E




Flooded McDonald™s, Festus, Missouri in 1993. The spot where this photo was taken
is nearly 1.5 miles (2.5 km) and 30 feet (9 m) above the river.
7
EL NI‘O EVENTS




to the growth in population in particularly vulnerable areas and to other social
or economic factors; the world community has undoubtedly become more vul-
nerable to disasters. However, a signi¬cant part of it has also arisen from the
increased storminess in the recent years 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, and 80% of the entire country was affected; China expe-
rienced 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; two widespread ¬‚oods
in Mozambique occurred within a year in 2000“1 leaving over half a million
homeless; and in the summer of 2002 Europe experienced its worst ¬‚oods for
centuries. Droughts during these years have been particularly intense and pro-
longed 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
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 (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 (˜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 twentieth cen-
tury, occurred in 1982“3; the anomalous highs in ocean surface temperature
8 G LO BA L WA R M I N G A N D C L I M AT E C H A N G E




The Great Flood of 1993 occurred in the American Midwest, along the Mississippi
and Missouri rivers from April to October 1993. The ¬‚ood was among the most costly
and devastating to ever occur in the United States, with $US15 billion in damages,
and a ¬‚ooded area of around 30 000 square miles (80 000 km2). These images from
Landsat-5 Thematic Mapper show the Mississippi near St Louis before and during the
¬‚ood.


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 climate, El Ni±os often differ very
much in their detailed character; that has been particularly the case with the El
Ni±o events of the 1990s. For instance, the El Ni±o event that began in 1990 and
reached maturity early in 1992, apart from some weakening in mid 1992, con-
tinued 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
9
EL NI‘O EVENTS




are probably linked with this unusually protracted El Ni±o. This, the longest El
Ni±o of the twentieth century, was followed in 1997“8 by the century™s most
intense El Ni±o which brought exceptional ¬‚oods to 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 which was experienced over
1000 miles away (Figure 1.1).
Studies with computer models of the kind described later (in Chapter 5) pro-
vide a scienti¬c basis for links between the El Ni±o and these extreme weather
events; they also give some con¬dence that useful forecasts of 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 climate change.
10 G LO BA L WA R M I N G A N D C L I M AT E C H A N G E




The effect of volcanic
1 000 000

Dead
eruptions on temperature
Homeless
100 000
extremes
Number of victims




Natural events such as volcanoes can also
10 000
affect the climate. Volcanoes inject enor-
mous quantities of dust and gases into the
1000
upper atmosphere. Large amounts of sulphur
dioxide are included, which through photo-
chemical reactions using the Sun™s energy are
100

transformed to sulphuric acid and sulphate
particles. Typically these particles remain in
10
es
t s ses
s
s l
u gh noe ea
uak
od a the stratosphere (the region of atmosphere
rm
pic Sto
Flo thq Volca Dis
Tro lones Dro
Ear
c
cy
above about 10 km in altitude) for several
Figure 1.3 Recorded disasters in Africa, 1980“9, years before they fall into the lower atmos-
estimated by the Organization for African Unity. Note phere and are quickly washed out by rainfall.
the logarithmic scale.
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 20 million
tonnes of sulphur dioxide into the stratosphere 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 2%. 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.


Vulnerability to change
Over the centuries, although 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 that emphasise the importance of climate to our lives and
that demonstrate to countries around the world their vulnerability to climate
change “ a vulnerability that is enhanced by rapidly increasing world popula-
tion and demands on resources.
11
V U L N E R A B I L I T Y TO C H A N G E




Drought
I nd i an
Floods
Ocean
India
Sri Sea-surface temperatures
Lanka above normal

Indonesia Asia


A ustral i a
Philippine
Islands


Paci fi c Europe
Ocean

Africa

N orth
A m eric a
Hawaiian
Islands
New Zealand
At l a n t i c
Ocean
or
at
u
Eq
Tahiti


South
Am eri c a




Figure 1.4 Regions where droughts and ¬‚oods occurred associated with the 1982“3 El Ni±o.




But the question must be asked: how remarkable are these extreme events
that I have been listing? Do they point to a changing climate due to human
activities? 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 some-
where would itself be something of a record!
Many of us may remember the generally cold period over large areas of
the world during the 1960s and early 1970s that caused speculation that the
world was heading for an ice age. A British television programme about climate
change called ˜The ice age cometh™ was prepared in the early 1970s and widely
screened “ but the cold trend soon came to an end. We must not be misled by
our relatively short memories.
12 G LO BA L WA R M I N G A N D C L I M AT E C H A N G E




The El Ni±o event of 1997“8 is the most intense on record. One result was the drought that led to forest
¬res in Asia, which burned thousands of square miles of rainforest, plantations, conversion forest and
scrubland in Indonesia alone. The above shows a superposition of sea surface temperature anomalies on
anomalies of the sea surface elevation, showing warm water building up eastwards across the Paci¬c
Ocean and reaching South America.



We may be sure about the warming that has occurred over the last few dec-
ades but do we have the evidence that this is linked with the development of
human industry over the last 200 years? To identify climate change related to
this development, we need to look for trends in global warming over similar
lengths of time. They are long compared with both the memories of a gener-
ation and the period for which accurate and detailed records exist. Although,
therefore, it can be ascertained that there was more storminess, for instance,
in the region of the north Atlantic during the 1980s and 1990s than in the pre-
vious three decades, it is dif¬cult to know just how exceptional those decades
were compared with other periods in previous centuries. There is even more
dif¬culty in tracking detailed climate trends in many other parts of the world,
13
W H AT I S G LO BA L WA R M I N G ?




owing to the lack of adequate records; further, trends in the frequency of rare
events are not easy to detect.
What is important is continually to make careful comparisons between prac-
tical observations of the climate and its changes and what scienti¬c knowledge
leads us to expect. During the last few years, as the occurrence of extreme
events has made the public much more aware of environmental issues,4 scien-
tists in their turn have become more sure about just what human activities are
doing to the climate. Later chapters will look in detail at the science of global
warming and at the climate changes that we can expect, as well as investigating
how these changes ¬t in with the recent climate record. First, however, I present
a brief outline of our current scienti¬c understanding.


What is global warming?
We know for sure that because of human activities, especially the burning of
fossil fuels, coal, oil and gas, together with widespread deforestation, the gas
carbon dioxide has been emitted into the atmosphere in increasing amounts
over the past 200 years and more substantially over the past 50 years. Every year
these emissions currently add to the carbon already present in the atmosphere
a further 8000 million tonnes, much of which is likely to remain there for a
period of 100 years or more. Because carbon dioxide is a good absorber of heat
radiation coming from the Earth™s surface, increased carbon dioxide acts like a
blanket over the surface, keeping it warmer than it would otherwise be. With
the increased temperature the amount of water vapour in the atmosphere also
increases, providing more blanketing and causing it to be even warmer. The gas
methane is also increasing because of different human activities, for instance
mining and agriculture, and adding to the problem.
Being kept warmer may sound appealing to those of us who live in cool cli-
mates. However, an increase in global temperature will lead to global climate
change. If the change were small and occurred slowly enough we would almost
certainly be able to adapt to it. However, with rapid expansion taking place
in the world™s industry the change is unlikely to be either small or slow. The
estimate I present in later chapters is that, in the absence of efforts to curb the
rise in the emissions of carbon dioxide, the global average temperature will rise
by about a third of a degree Celsius or more every ten years “ or three or more
degrees in a century.
This may not sound very much, especially when it is compared with normal
temperature variations from day to night or between one day and the next.
But it is not the temperature at one place but the temperature averaged over
the whole globe. The predicted rate of change of 3 °C a century is probably
faster than the global average temperature has changed at any time over the
14 G LO BA L WA R M I N G A N D C L I M AT E C H A N G E




past 10 000 years. And as there is a difference in global average temperature
of only about ¬ve or six degrees between the coldest part of an ice age and
the warm periods in between ice ages (see Figure 4.6), we can see that a few
degrees in this global average can represent a big change in climate. It is to this
change and especially to the very rapid rate of change that many ecosystems
and human communities (especially those in developing countries) will ¬nd it
dif¬cult to adapt.
Not all the climate changes will in the end be adverse. While some parts of
the world experience more frequent or more severe droughts, ¬‚oods or signi¬-
cant sea level rise, in other places crop yields may increase due to the fertilising
effect of carbon dioxide. Other places, perhaps for instance in the sub-arctic,
may become more habitable. Even there, though, the likely rate of change will
cause problems: large damage to buildings will occur in regions of melting
permafrost, and trees in sub-arctic forests like trees elsewhere will not have
time to adapt to new climatic regimes.
Scientists are con¬dent about the fact of global warming and climate change
due to human activities. However, uncertainty remains about just how large the
warming will be and what will be the patterns of change in different parts of
the world. Although useful indications can be given, scientists cannot yet say in
precise detail which regions will be most affected. Intensive research is needed
to improve the con¬dence in scienti¬c predictions.


Adaptation and mitigation
An integrated view of anthropogenic climate change is presented in Figure 1.5
where a complete cycle of cause and effect is shown. Begin in the box at the
bottom where economic activity, both large and small scale, whether in
developed or developing countries, results in emissions of greenhouse gases
(of which carbon dioxide is the most important) and aerosols. Moving in a
clockwise direction around the diagram, these emissions lead to changes in
atmospheric concentrations of important constituents that alter the energy
input and output of the climate system and hence cause changes in the cli-
mate. These climate changes impact both humans and natural ecosystems
altering patterns of resource availability and affecting human livelihood
and health. These impacts in their turn affect human development in all its
aspects. Anticlockwise arrows illustrate possible development pathways and
global emission constraints that would reduce the risk of future impacts that
society may wish to avoid.
Figure 1.5 also shows how both causes and effects can be changed through
adaptation and mitigation. In general adaptation is aimed at reducing the effects
15
U N C E R TA I N T Y A N D R E S P O N S E




Precipitation
Temperature
change
change

Climate change

Extreme
Sea level
events
rise



EARTH SYSTEMS Ecosystems Water
Climate process drivers resources

Impacts and
Concentrations
vulnerability
Aerosols
Greenhouse
gases
Emissions
Food Human
Settlements
security health
and society



HUMAN SYSTEMS
Governance Health
Literacy
Equity
Trade
Socio-economic
development
Technology Population
Socio-cultural
Production and
preferences
consumption patterns



Mitigation Adaptation



Figure 1.5 Climate change “ an integrated framework (see text for explanation).




and mitigation is aimed at reducing the causes of climate change, in particular
the emissions of the gases that give rise to it.


Uncertainty and response
Predictions of the future climate are surrounded with considerable uncertainty
which arises from our imperfect knowledge both of the science of climate change
and of the future scale of the human activities that are its cause. Politicians
and others making decisions are therefore faced with the need to weigh all
aspects of uncertainty against the desirability and the cost of the actions that
16 G LO BA L WA R M I N G A N D C L I M AT E C H A N G E




can be taken in response to the threat of climate change. Some mitigating
action can be taken easily at relatively little cost (or even at a net saving of cost),
for instance the development of programmes to conserve and save energy, and
many schemes for reducing deforestation and encouraging the planting of trees.
Other actions such as a large shift to energy sources that are free from signi¬-
cant carbon dioxide emissions (for example, renewable sources: biomass, hydro,
wind or solar energy) both in the developed and the developing countries of the
world will take some time. Because, however, of the long timescales that are
involved in the development of new energy infrastructure and in the response
of the climate to emissions of gases like carbon dioxide, there is an urgency to
begin these actions now. As we shall argue later (Chapter 9), to ˜wait and see™ is
an irresponsible response.
In the following chapters I shall ¬rst explain the science of global warming,
the evidence for it and the current state of the art regarding climate predic-
tion. I shall then go on to say what is known about the likely impacts of climate
change “ on sea level, extreme events, water and food supplies, for instance. The
questions of why we should be concerned for the environment and what action
should be taken in the face of scienti¬c uncertainty are followed by considera-
tion of the technical possibilities for large reductions in the emissions of carbon
dioxide and how these might affect our energy sources and usage, including
means of transport.
Finally I will address the issue of the ˜global village™. So far as the environment
is concerned, national boundaries are becoming less and less important; pollu-
tion in one country can now affect the whole world. Further, it is increasingly
realised that problems of the environment are linked to other global problems
such as population growth, poverty, the overuse of resources and global secu-
rity. All these pose global challenges that must be met by global solutions.




Q U E S TI O N S
1 Look through recent copies of newspapers and magazines for articles that
mention climate change, global warming or the greenhouse effect. How
many of the statements made are accurate?
2 Make up a simple questionnaire about climate change, global warming and
the greenhouse effect to ¬nd out how much people know about these sub-
jects, their relevance and importance. Analyse results from responses to the
questionnaire in terms of the background of the respondents. Suggest ways
in which people could be better informed.
17
N OT E S F O R C H A P T E R 1




FURTHER READING AND REFERENCE
Walker, Gabrielle and King, Sir David. 2008. The Hot Topic. London: Bloomsbury. A
masterful paperback on climate change for the general reader covering the science,
impacts, technology and political solutions.




N OTE S F O R C HA P TE R 1
1 Summary for policymakers, p. 5 in Solomon, S., 3 A description of the variety of El Ni±o events
Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, and their impacts on different communities
K. B., Tignor, M., Miller, H. L. (eds.) 2007. Climate worldwide over centuries of human history
Change 2007: The Physical Science Basis. Contribution of can be found in a paperback by Ross Couiper-
Working Group 1 to the Fourth Assessment Report of the Johnston, El Ni±o: The Weather Phenomenon that
Intergovernmental Panel on Climate Change. Cambridge: Changed the World. 2000. London: Hodder and
Cambridge University Press. Stoughton.
2 Including windstorms, hurricanes or typhoons, 4 A gripping account of some of the changes over
¬‚oods, tornadoes, hailstorms and blizzards but recent decades can be found in a book by Mark
not including droughts because their impact is not Lynas, High Tides: News from a Warming World. 2004.
immediate and occurs over an extended period. London: Flamingo.
2 The greenhouse effect




This view of the rising Earth greeted the Apollo 8 astronauts as they came out from behind the Moon.




T HE BASIC principle of global warming can be understood by considering the radiation energy
from the Sun that warms the Earth™s surface and the thermal radiation from the Earth and the
atmosphere that is radiated out to space. On average these two radiation streams must balance.
If the balance is disturbed (for instance by an increase in atmospheric carbon dioxide) it can be
restored by an increase in the Earth™s surface temperature.
19
H OW T H E E A R T H K E E P S WA R M




How the Earth keeps warm Radiation
from Sun
To explain the processes that warm the Earth
and its atmosphere, I will begin with a very
simpli¬ed Earth. Suppose we could, all of a
sudden, remove from the atmosphere all the
clouds, the water vapour, the carbon dioxide
and all the other minor gases and the dust, leav-
ing an atmosphere of nitrogen and oxygen only.
Everything else remains the same. What, under Thermal radiation
emitted by Earth
these conditions, would happen to the atmos-
Figure 2.1 The radiation balance of planet Earth. The
pheric temperature?
net incoming solar radiation is balanced on average by
The calculation is an easy one, involving a rel-
outgoing thermal radiation from the Earth.
atively simple radiation balance. Radiant energy
from the Sun falls on a surface of one square metre in area outside the atmos-
phere and directly facing the Sun at a rate of about 1370 watts “ about the power
radiated by a reasonably sized domestic electric ¬re. However, few parts of the
Earth™s surface face the Sun directly and in any case for half the time they are
pointing away from the Sun at night, so that the average energy falling on one
square metre of a level surface outside the atmosphere is only one-quarter of
this1 or about 342 watts. As this radiation passes through the atmosphere a
small amount, about 6%, is scattered back to space by atmospheric molecules.
About 10% on average is re¬‚ected back to space from the land and ocean surface.
The remaining 84%, or about 288 watts per square metre on average, remains
actually to heat the surface “ the power used by three good-sized incandescent
electric light bulbs.
To balance this incoming energy, the Earth itself must radiate on average
the same amount of energy back to space (Figure 2.1) in the form of thermal
radiation. All objects emit this kind of radiation; if they are hot enough we can
see the radiation they emit. The Sun at a temperature of about 6000 °C looks
white; an electric ¬ re at 800 °C looks red. Cooler objects emit radiation that
cannot be seen by our eyes and which lies at wavelengths beyond the red end
of the spectrum “ infrared radiation (sometimes called longwave radiation to
distinguish it from the shortwave radiation from the Sun). On a clear, starry
winter™s night we are very aware of the cooling effect of this kind of radiation
being emitted by the Earth™s surface into space “ it often leads to the forma-
tion of frost.
The amount of thermal radiation emitted by the Earth™s surface depends on
its temperature “ the warmer it is, the more radiation is emitted. The amount
of radiation also depends on how absorbing the surface is; the greater the
20 THE GREENHOUSE EFFEC T




Table 2.1 The composition of the atmosphere, the main constituents
(nitrogen and oxygen) and the greenhouse gases as in 2007

Mixing ratio or mole fraction a expressed as
Gas fraction* or parts per million (ppm)

Nitrogen (N2) 0.78*
Oxygen (O2) 0.21*
Water vapour (H2O) Variable (0“0.02*)
Carbon dioxide (CO2) 380
Methane (CH4) 1.8
Nitrous oxide (N2O) 0.3
Chloro¬‚uorocarbons 0.001
Ozone (O3) Variable (0“1000)

a
For de¬nition see Glossary.



absorption, the more the radiation. Most of the surfaces on the Earth, includ-
ing ice and snow, would appear ˜black™ if we could see them at infrared wave-
lengths; that means that they absorb nearly all the thermal radiation which
falls on them instead of re¬‚ecting it. It can be calculated2 that the 288 W m-2
of incoming solar radiation received by the Earth™s surface can be balanced by
thermal radiation emitted by the surface at a temperature of “6 °C.3 This is over
20 °C colder than is actually the case. In fact, an average of temperatures meas-
ured near the surface all over the Earth “ over the oceans as well as the land
“ averaging, too, over the whole year, comes to about 15 °C. Some factor not yet
taken into account is needed to explain this difference.


The greenhouse effect
The gases nitrogen and oxygen that make up the bulk of the atmosphere
( Table 2.1 gives details of the atmosphere™s composition) neither absorb nor
emit thermal radiation. It is the water vapour, carbon dioxide and some other
minor gases present in the atmosphere in much smaller quantities (Table
2.1) that absorb some of the thermal radiation leaving the surface, acting
as a partial blanket for this radiation and causing the difference of 20 to
30 °C between the actual average surface temperature on the Earth of about

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