earth on fire climate change from a philosophical ethical perspective

8/3/2019 Earth on Fire Climate Change From a Philosophical Ethical Perspective

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Earthonfre

Clim

atechangeromaphilosophicaland

ethicalpersp

ective

Mickey Gjerris,Christian Gamborg,

Jrgen E. Olesen

Jakob Wolf (Eds.)


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Earth on fire

Climate change from a philosophical and ethical perspective


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Earth on Fire climate change from a philosophical and ethical perspective is an electronic open

access version of the bookJorden brnder klimaforandringerne i videnskabsteoretisk og

etisk perspektiv published by ALFA 2009. ALFA has kindly given their permission to this

translation under the conditions that the English text is in no way used for commercial

purposes. The printed Danish version of the book can be bought in book stores or

at the publishers web-site: http://www.forlagetalfa.dk/alfa_detail.asp?ID=2859

The English translation has been published with economic support from

Theme Cluster 1 and The Institute of Food and Resource Economics, both

from the University of Copenhagen and from the University of Aarhus.
http://www.forlagetalfa.dk/alfa_detail.asp?ID=2859http://www.forlagetalfa.dk/alfa_detail.asp?ID=2859


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Earth on fire

Climate change

from a philosophical andethical perspective

Edited byMickey Gjerris,

Christian Gamborg,Jrgen E. Olesen &

Jakob Wolf

2009


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Earth on fire

Climate change from a philosophical and ethical perspective

Edited by Mickey Gjerris, Christian Gamborg, Jrgen E. Olesen, Jakob Wolf

The authors and The Institute of Food and Resource Economics,

The Faculty of Life Sciences, University of Copenhagen

Cover: @ Arne Naevra (Norway); Polar meltdown

Translation: Overstterhuset A/S

Layout and typesetting: Narayana Press

Cover: Religionspdagogisk Center, Bjarne Jensen

Printed by: Narayana Press

ISBN: 978-87-993282-0-8

The publishers have been unable to contact the legal copyright holders

of some of the pictures in this book. Any violation of their copyrights

etc. has been unintentional. Legal obligations arising will, of course,

be honoured as if permission had been granted in advance.

The Danish edition was published with funding from Torben & Alice Frimodts Fond,

Direktr Einar Hansen og hustru fru Vera Hansens Fond, the Institute of Food and

Resource Economics at the University of Copenhagen, the Faculty of Life Sciences at the

University of Copenhagen and the Faculty of Agricultural Sciences at Aarhus University.


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7Content

Content

Foreword to the English edition

Mickey Gjerris 9

Introduction

Mickey Gjerris 11

The climate is changing but why?

Jrgen E Olesen 17

What will happen?Scenarios of the future

Jrgen E Olesen 37

Climate science how did it come about?

Matthias Heymann 55

What is climate science all about?Philosophical perspectives

Matthias Heymann, Peter Sande & Hanne Andersen 69

The price of responsibility ethical perspectives

Christian Gamborg & Mickey Gjerris 89

A religious perspective on climate change

Jakob Wolf 115

The climate debates debating climatePolarisation of the public debate on climate change

Gitte Meyer and Anker Brink Lund 135

Case 1 Biofuels

Biofuels Crops for food and energy

Claus Felby 163


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8 Content

Biofuels: Hunger, subsidies and lack of effect on CO2 emissions

Christian Friis Bach 169

Study questions 173

Case 2 Genetically modified organismsGMOs: A solution to changed climate conditions

Preben Bach Holm 175

GMOs: The right way of taking responsibility?

Rikke Bagger Jrgensen 182

Study questions 189

Case 3 Trading in CO2 quotasCO2 trading. A cost-efficient tool to achieve political goals?

Alex Dubgaard 191

CO2 trading. Should you be able to buy your way outof the problems?

Peder Agger 200

Study questions 207

Further reading 209

About the authors 215

Index 2 1 9


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9Foreword to the english edition

Foreword to the English editionMiCkey gjerris

This book is about climate change and what it does to us and our planet.

But even more it is about the philosophical and ethical challenges that arise

from the changing weathers. The book was originally written for Danish

students by Danish researchers, but just as global warming is a global phe-

nomenon so is the questions that are put forth here. The book has therefore

been translated into English so as to make it available for a wider audience

The English online version is free for all to use. All we ask you is that youshare the existence of the book with your colleagues and fellow students so

that as many as possible might benefit from it.

Should you have any comments or ideas for improvements to the next

edition, please mail Mickey Gjerris [email protected].

The editors would like to thank Forlaget ALFA and our editor Jeanne Dal-

gaard for their generous permission to translate the original text and their

good cooperation throughout the process. Furthermore we would like to

thank Overstterhuset A/S for their efficient work with the translation and

Annette Larsen for her help. Finally we would like to thank Theme Cluster

1 and The Institute of Food and Resource Economics from the University

of Copenhagen and the University of Aarhus for their economic support to

this translation.
mailto:[email protected]:[email protected]


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11introduCtion

IntroductionMiCkey gjerris

The Earth is on fire. Our world is getting warmer, and the climate is chang-

ing. There is a lot to suggest that this is due to how we are using the Earths

resources. Also, it is a matter of urgency if we want to be able to exercise

just a modicum of control over what the future will bring. So, in a manner

of speaking, the Earth is getting too hot under our feet. We need to find out

what is behind the climate change, but we also need to find a solution fast.

At least that is how things stand at the moment. Just a few years ago,however, many scientists, politicians and laymen still questioned whether

the climate was in fact changing, let alone whether human activities had

any role to play. How could it be that all this doubt evaporated, and that

everyone suddenly started talking about the climate and marketing them-

selves on low CO2 emissions? A significant shift has occurred. Today, very

few people question that climate change is happening and that it is largely

due to human activity. Have we arrived at a new scientific certainty, or is it

the result of a less transparent process where ethical values and political

considerations have come to influence the scientific agenda? How definite

actually are the climate models on which we are basing our actions, and

how much of the discussion about them is science and how much relates

to the ethical and philosophical considerations which have shaped them?

It is not absolutely clear what will happen with the climate in the coming

years, but there is general agreement that the world will change. And man

has started to prepare for these changes. This gives rise to important ethi-

cal questions. What must we do, who must we consider, and what does the

natural world mean in an ethical sense? Should we save endangered speciesfor their own sakes or for ours? Should we help the people who will benefit

most from our help or those that most need the help and do we in fact

have a duty to help anybody apart from ourselves? Major changes threaten

and the solutions risk being rushed through without careful consideration.

Thats what happens when the Earth suddenly gets too hot under ones feet.

This book is about climate change, one which will contribute to our

understanding of what is happening and why it is happening. The objective

is to show how climate change raises not only a number of questions to do

with natural science, but also many questions of a more universal nature


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12 MiCkey gjerris

that are based on philosophical, political, ethical and religious assumptions

about how the world is and how itshould be. We hope that this book willencourage critical reflection and ethical consideration of what is happen-

ing, why it is happening and what we ought to do. Because something is

happening:James A. Hansen, as head of NASAs Goddard Institute for Space Stud-

ies and one of the worlds leading climate researchers, is one of those who

repeatedly points out that the situation is far more serious than we are

willing to acknowledge. According to him, the targets for CO2 reductions

which have been set in the international agreements which applied for 2008

already exceed what is necessary to stabilise the situation. According to

Hansen we must act far more effectively and radically and we must take

action now. In a speech given to The National Press Club in Washington DC

on 23 June 2008, he said:

Changes needed to preserve creation, the planet on which civilisation de-

veloped, are clear. But the changes have been blocked by special interests,

focused on short-term profits, who hold sway in Washington and other

capitals. I argue that a path yielding energy independence and a healthier

environment is, barely, still possible. It requires a transformative change of

direction in Washington in the next year.

(Hansen, 2008)

Research published in winter 2008 by the Canadian geophysicist David

Barber suggests that, by 2015, the Arctic will be ice-free during the sum-

mer. Whether this happens in 2015, 2025 or 2035 is, in this context, fairly

irrelevant. What is important is that the temperature increases on the planet

seem to be having quite an impact and that things are developing at a pace

which, time and again, takes the scientists by surprise. The climate and the

factors which have a bearing on it are complex. Often, individual scientists

only see part of the picture, but when the various factors start reinforcingeach other, the whole picture suddenly changes. In the past eight to ten

years, the possible climate changes have led to worried minds and interna-

tional agreements which have not really put the big players under any sort

of obligation and to the setting of national targets which have basically been

ignored in practical politics. The general consensus is that we can no longer

afford such procrastination. Things are hotting up now really hotting up.

So we need to both act fast and think carefully about what we are doing.

This book is primarily intended as a textbook in ethics and science theory

at university level, where it can be used on all study programmes to provide


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13introduCtion

recurrent case material. The more technical chapters can be used depending

on the field of study. The book can also be used as a source of background

information for upper-secondary school teachers and other teachers in the

educational system and as a study book by reading groups, or simply by

readers who want to understand what the climate debate is all about. Thebook is the result of scientists from many different fields and institutions

collaborating together, which is evident from the author presentations at

the back of the book. The breadth of expertise clearly reflects the radical

significance of climate change for the future. Climate change literally cuts

across all boundaries. It is the hope of the editors that this broad approach

will contribute to understanding the complexity of the problems and a

healthy level of scepticism towards any over-simplified messages in the

climate debate.

The book consists of seven chapters which show how the climate changesare rooted in our scientific, philosophical, political, ethical and religious

understanding of the world. Chapters 1 and 2 are written by the climate

scientist and member of the UN climate panel Professor Jrgen E. Olesen

from Aarhus University. The first chapter describes the changes which the

climate is undergoing, which physical, chemical and biological mechanisms

are interacting to cause climate change, and what is driving the changes.

The second chapter looks at the consequences of climate change for life on

Earth both generally and specifically for a number of areas such as agricul-

ture, infrastructure and urban planning. The books third chapter is written

by the science historian Matthias Heymann from Aarhus University. This

chapter puts the present discussion about climate research into a historical

perspective and shows how climate research has always been embedded in

philosophical and political discussions.

Matthias Heymann has also been involved in Chapter 4, this time with

the philosopher Peter Sande from the University of Copenhagen and the

science theorist Hanne Andersen from Aarhus University. Together they

describe the science-theoretical challenges raised by the use of computermodels in climate research, and seek to show how scientific uncertainty also

becomes a political issue. Chapter 5 is written by the ethicist Mickey Gjerris

and the natural resource ethics researcher Christian Gamborg, both from

the University of Copenhagen. The chapter focuses on the ethical dilemmas

presented by climate change as far as mankind is concerned as well as in

relation to the natural world in general. In Chapter 6, the theologian Jakob

Wolf, also from the University of Copenhagen, looks at climate change from

a religious perspective, and offers his views on how religion, broadly speak-

ing, can help to fight climate change. Finally, in Chapter 7, senior lecturer


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14 MiCkey gjerris

and journalist Gitte Meyer from the University of Copenhagen and professor

in media management Anker Brink Lund from Copenhagen Business School

write about the political discussion about the climate which has dominated

the media over the past twenty years, and put this discussion into a broader

context concerning the role of science in the current debate.The seven chapters can be read independently of each other, but as they

each have something to offer, reading them all will provide a solid founda-

tion from which to relate to climate change. The chapters are written as

textbook chapters, and thus provide a general introduction to the issues

from what is hopefully a neutral perspective. Nonetheless, it is important

to note that the chapters are written by different researchers, each of whom

possesses expertise within their particular field. The various chapters are

therefore, unavoidably, coloured by their respective views. This basic condi-

tion for all communication should make the reader take a critical approachto the chapters and not be seduced by what is presented as obvious conclu-

sions. These chapters are not the final answer to anything, but invite the

reader to participate in a broader discussion about climate change.

At the end of the book, three actual cases from the climate debate are

discussed: CO2 trading, GM crops and biofuels. These cases are addressed

by experts who have played a prominent role in the public debate of these

topics. What all three cases have in common is that they describe contro-

versial solutions to problems resulting from climate change. The purpose

of these cases is partly to present some of the more controversial strategies

for countering climate change to the reader, and partly to show how the

ethical and philosophical issues on which the seven main chapters centre

can be used as keys to understanding the disagreements that arise when

discussing some of the most important issues currently faced by mankind.

Each case is preceded by various working questions which can be used as a

starting point for a discussion of the case and as a way of focusing on the

ordinary problems that lie behind the specific differences of opinion.

Each chapter is followed by a list of the references which have been usedas background material. These can be used as inspiration for further read-

ing. There is also a list at the back of the book of commented suggestions

for further reading, organised by chapter. The intention is that students and

others will easily be able to find further literature for project work, studies

etc.

The editors would like to thank all the contributors for their time, Jeanne

Dalgaard from the publishers Alfa for her good and thorough editing, and

a number of Danish financial contributors who have made the publication

of this book possible: 1: Torben & Alice Frimodts Fond 2: Direktr Einar


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15introduCtion

Hansen og hustru fru Vera Hansens Fond 3: Institute of Food and Resource

Economics, University of Copenhagen 4: Faculty of Life Sciences, University

of Copenhagen 5: Faculty of Agricultural Sciences, Aarhus University.

The changes we face are both alarming and far-reaching. They will have

a major impact on our lives. In order to meet this challenge, it is necessarythat we understand both the scientific details and the broader contexts of

the different problems. Technical solutions detached from the social reality

into which they must be incorporated cannot solve these problems, just as

theoretical musings on background, causes and values are of no use in the

present situation. However, if we gather the threads and endeavour to tackle

the task based on a high level of expertise and sound knowledge about the

context of the problems, we believe there is every possibility that the huge

challenges we face can be resolved. We hope that this book will make a

small contribution to this task.

ReferencesHansen JA: Global Warming Twenty Years Later: Tipping Points Near (2008).http://www.

columbia.edu/~jeh1/2008/TwentyYearsLater_20080623.pdf


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17the CliMate is Changing but why?

The climate is changing but why? jrgen e. olesen

1. Introduction

The mean temperature at the Earths surface is increasing, and at the same

time the patterns of precipitation are changing towards more intense rainfall

and longer periods of drought. These changes are controlled by physical

as well as biological processes. Even though there are natural processes

which can lead to global temperature increases, research shows that human(anthropogenic) activities especially CO2 emissions are most likely to

be the main reason for the increasing temperatures on Earth over the past

30 years. Model calculations show that global temperatures will probably

increase by 1.8-4.0 C during the twenty-first century depending on emis-

sions of greenhouse gases.

Following the Fourth Assessment Report (AR4) of the UNs Intergov-

ernmental Panel on Climate Change (IPCC) and Al Gores documentary An

Inconvenient Truth as well as the Nobel Peace Prize which was awarded to

the IPCC and Al Gore in 2007, there has been an unparalleled level of atten-

tion on man-made climate change. This is largely due to the fact that the

IPCC now concludes that: Most of the observed increase in global average

temperatures since the mid-20th century is very likely due to the observed

increase in anthropogenic GHG concentrations. However, in the media this

is still being debated although most researchers support this conclusion.


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18 jrgen e. olesen

IPCC the UNs climate panel Box 1

The UNs climate panel is called the IPCC, which stands for Intergovernmental

Panel on Climate Change. It was set up in 1988 as a follow-up to the Brundtland

Report Our Common Future. Based on its reviews of scientific literature,about every five years the panel publishes a summary and an assessment of

research and knowledge on climate change and the effects of these changes.

The scientific reviews are conducted by recognised scientists within the various

fields. The scientists are appointed by the UNs member countries. The assess-

ment consists of a report from each of the three main working groups:

Working group I: Describes the scientific aspects of the climate system and

climate changes.

Working group II: Describes vulnerabilities in the socio-economic and

natural systems in the face of climate change, impacts as well as the

possibilities for adaptation. Working group III: Describes how to reduce emissions ofgreenhouse gases

and other ways of preventing climate change.

In addition to these assessment reports, the IPCC also publishes a number of

special reports on specific subjects, for example emission scenarios, technolo-

gies for reducing emissions or methods for calculating greenhouse gas emis-

sions. The latest assessment report (the fourth) was published in 2007. The

IPCC does not conduct independent research itself on climate changes or their

impacts, but is charged with drawing conclusions from the available scientific

literature on the subject.

2. Climate changes whats happening?

Worldwide, the temperature has increased by 0.7-0.8 C since the end of the

nineteenth century. By far the largest share of this increase (0.55 C) has oc-

curred within the past 30 years. However, it is not just the temperature which

has increased. Other aspects of the climate systems have also changed: Sea levels worldwide have risen, and the rate of increase is growing,

such that sea levels are now rising by 3-4 mm per year.

In many places, ice caps and glaciers are melting, contributing to rising

sea levels.

Snow cover in the northern hemisphere has decreased by about 5 per

cent since 1966.

The area covered by permafrost has decreased by 10 per cent in the

northern hemisphere.

The extent of Arctic sea ice has decreased by 20 per cent since 1978.
http://en.wikipedia.org/wiki/Greenhouse_gashttp://en.wikipedia.org/wiki/Greenhouse_gas


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Precipitation has increased at high latitudes in both the northern and

southern hemispheres.

There are more periods of drought. This increase in droughts has mostly

been observed in the already dry areas of the world, i.e. the dry tropics

and subtropics. The frequency of heavy precipitation has increased, even in areas with

reductions in total rainfall.

There is no change in the number of tropical hurricanes, but they tend

to be stronger and to last longer.

Over a longer time-scale, climate on Earth has varied considerably more

than what we have seen in recent decades. However, we only have reliable

measurements of temperature and precipitation for the past 150 years or so.

To look at the climate over longer periods of time, we must resort to indirectmeasurements. Here, measurements of e.g. oxygen isotopes in ice cores and

sediment layers play an important role in describing the climate (Box 2).

However, there are considerable uncertainties associated with translating

these observations into a global average temperature. Using such measure-

ments, the IPCC assesses that the global average temperature during the

past 50 years has not been as high for the past 1,300 years.

3. The Earths radiation balance

As mentioned above, in the course of the Earths long history the climate

has varied considerably more than what has been observed within the past

100 years. Basically, the climate is determined by the balance between the

energy which is supplied by sunlight, and the energy which is lost through

longwave heat radiation from Earth (Figure 1). Two factors in particular af-

fect the radiation balance: 1) The amount of sunlight intercepted by Earth,

and 2) the strength of the greenhouse effect.

Incoming solar radiation corresponds to an average of about 342 W/m2on the entire Earths surface, day and night, 365 days a year. However, 31

per cent of this radiation is reflected by clouds, atmospheric particles and

the Earths surface. This is called the planetary albedo. It is the remaining

69 per cent (or 236 W/m2) which heats the Earth and the atmosphere.

Earth loses heat by emitting longwave infrared radiation. The amount

of longwave radiation is proportional to the absolute temperature to the

fourth power (Stefan-Boltzmans law). Over a long period of time, the

outgoing radiation will be the same as the incoming radiation (236 W/m2).

Using Stefan-Boltzmans law, this gives a mean temperature for the globe


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Measuring temperature Box 2

Traditionally, air temperature is measured by placing a thermometer in what

is termed a Stevenson screen, which provides shade and ventilation, ensuring

that it is the air temperature that is measured and not the effect of solar radi-ation on the thermometer. Such measurements have been conducted worldwide

since the mid-nineteenth century. Temperature measurements are affected lo-

cally by urban development (the urbanisation effect), and it is being discussed

whether such effects have affected the global temperature series so they show

excessive temperature increases. It is well known that the climate in large cities

is significantly warmer than beyond the city limits, but by far the most weather

stations are situated in the countryside, far away from urbanised areas. More-

over, temperature measurements from towns and cities are corrected to take

account of the urbanisation effect. A number of recent studies show that, at

most, urbanisation produces a small uncertainty (0.06 C over 100 years), whichis far less than the observed increases in temperature.

In recent decades, measurements using satellites have provided new ways of

measuring the Earths temperature. However, such measurements provide in-

formation in particular about changes in temperature distribution at various

heights in the atmosphere. Here, observations show that the temperature in

the uppermost part of the atmosphere has been falling, which ties in with the

greater greenhouse effect leading to reduced outgoing radiation from the lowest

part of the atmosphere. Reconstructing the temperature over longer time-scales

calls for other indirect methods. Geological deposits provide information

about the fauna and flora in the past, and the composition of these organismsprovides information about climatic and temperature conditions at the time

when these organisms were living. Similar information can be obtained by

studying the thickness of tree rings.

Studies of longer time-scales are concentrated on ice cores in Greenland and

on the Antarctic as it is possible to indirectly read the variations in temperature

several hundred thousand years ago. One of the most important methods of re-

constructing the temperature back in time is to measure the amount of different

forms of oxygen (oxygen isotopes), both the ordinary oxygen isotope 16O and the

heavier and rarer18O. Oxygen is the heaviest constituent of a water molecule

(H2O), and as it is easier for the lighter16O to evaporate than the heavier18O, in

colder periods there will be less 18O present in the atmosphere than in warmer

periods. The relative content of the two isotopes in the ice caps can therefore

tell us about the temperature of the atmosphere at the time when the snow fell.

In cold periods there will be less 18O present in the atmosphere than in warmer

periods. The relative content of the two isotopes in the ice caps therefore tell us

about the atmospheres temperature at the time when the snow fell.


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of 254 Kelvin (approx. -19 C). This is about 34 C lower than the mean

temperature of 15 C which has been measured. Another mechanism (the

greenhouse effect) must therefore be influencing climate on Earth.

A number of gases in the atmosphere (for example water vapour, car-

bon dioxide and methane) are, like the clouds, able to absorb some of the

outgoing longwave infrared radiation. The absorbed radiation warms theair and is emitted again as longwave radiation, just at a lower temperature

than at the Earths surface as the atmospheric temperature declines with

height. Seen from space, the heat is not emitted from the Earths surface

but from greenhouse gases and clouds some way up in the atmosphere. On

average, it is at the level where the effective outgoing radiation temperature

is 254 Kelvin (at a height of just over 5 km).

With a greater concentration of greenhouse gases in the atmosphere, the

radiation effectively takes place higher up in the atmosphere and for a period

at a lower temperature, so that heat builds up in the climatic system until

Figure 1: The Earths radiation balance consists of the balance between incoming solar radiation(shortwave radiation) and solar radiation reflected by clouds and the surface of the sea and theEarth as well as longwave heat radiation from the surface, sea, clouds and atmosphere (Taken

with permission from H Meltofte (ed.) (2008): Klimandringerne: Menneskehedens hidtil strsteudfordring. The Environmetal Library. Hovedland Publishers)


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22 jrgen e. olesen

Box 3: Feedback mechanisms

The Earths climate system consists of a

closely interconnected system involving the

atmosphere, land, ice, soil and vegetation.If the temperature changes, it will lead to

changes in the other components, which in

turn may affect the temperature. These feed-

back mechanisms can both enhance and

weaken temperature changes. Here are a few

examples of feedback mechanisms:

Water vapour

Water vapour is a greenhouse gas, but the

maximum amount of water vapour that the

atmosphere can contain greatly dependson temperature (almost 7 per cent increase

for every 1 C increase in temperature). The

warmer it is, the more water vapour the

atmosphere can hold, and the greater the

warming effect from the water vapour (posi-

tive feedback).

Snow and ice

Warming leads to a melting of snow and

ice on the Earths surface and consequentlya reduction in snow cover and sea ice. This

minimises the amount of reflected sunlight

to space and leads to additional warming

(positive feedback). This is the main reason

why global warming leads to the greatest

temperature increases at high latitudes.

Clouds

Clouds affect the climate system in vary-

ing ways depending on how high they are

in the atmosphere. This is because cloudshave an insulating effect while also reflect-

ing sunlight. High clouds generally have a

warming effect while low clouds are cooling.

The overall effect of clouds is thought to be

cooling, corresponding to about 20 W/m2.

This should be seen in relation to the fact

that man-made changes in the radiation

balance so far are only approximately 1.6

W/m2 (Table 2).

CO2Man-made climate changes are particularly

due to emissions of CO2 from using fossilenergy and from deforestation. Over longer

periods of time, however, CO2 also plays a

role in feedback systems. For example, the

solubility of CO2 in sea water falls with in-

creasing temperature, which reinforces the

role of CO2 as a greenhouse gas. Warming

also increases the temperature in areas with

permafrost where very large quantities of

carbon are fixed in the soil, which is released

at higher temperatures. This too amounts toa positive feedback.

Temperature profile in the atmosphere

The temperature change will be greater

at the effective level of outgoing radiation

higher up the atmosphere than at the

Earths surface. On the surface there will

therefore be smaller temperature changes

(negative feedback).

Heat transportLarge volumes of energy are transported

in the atmosphere and in the oceans. In a

changed climate, these flow patterns can

become altered, which can lead to both posi-

tive and negative feedback.

Vegetation

The Earths vegetation influences how much

sunlight is reflected and how much water

evaporates. As vegetation is also influenced

by changes in temperature and precipita-tion, there is the possibility of many dif-

ferent feedbacks which can be very hard to

predict.


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the Earths temperature again corresponds to the loss through outgoing

heat radiation. This leads to warming in the lowest part of the atmosphere.

4. Greenhouse gases

The most important greenhouse gases are water vapour (H2O), carbon

dioxide (CO2), methane (CH4), nitrous oxide (N2O), CFC (chlorofluoro-

carbons) and tropospheric ozone (O3) (Table 1). It is not possible to rank

with any certainty the effect of the individual gases with respect to the total

greenhouse effect. This is, among other things, due to a number of feedback

mechanisms between the greenhouse gases (Box 3). Basically, the ratio

between the most important greenhouse gases water vapour, clouds and

carbon dioxide is estimated at 2-1-1.

Table 1. Estimates of the radiation contributed by a number of factors which influence the overallradiation effect of the greenhouse gases (W/m2) for 2005 compared with pre-industrial levels(Solomon et al. 2007).

Cause Type Factor Radiation effect (W/m2)

Man-made Long-lived greenhouse gases Carbon dioxide (CO2) 166 (149-183)

Methane (CH4) 048 (043-053)

Nitrous oxide (N2O) 016 (014-018)

CFC 034 (031-037)

Ozone Stratospheric -005 (-015-005)

Tropospheric 035 (025-065)

Stratospheric water from CH4 007 (002-012)

Surface albedo Land use -020 (-04-00)

Black dust on snow 010 (00-02)

Aerosols (particles) Direct effect -050 (-09- -01)

Cloud albedo -070 (-18- -03)

Contrails (vapour trails from aircraft) 001 (0003-003)

Natural Solar radiation Direct 012 (006-030)

Total man-made 160 (06-24)

The man-made sources of CO2 are the burning of fossil fuels (coal, oil

and natural gas) as well as changes in land use, particularly deforestation.

Emissions of CO2 have increased greatly since 1960 (see Figure 2), and the

atmospheric content of CO2 now exceeds by far the natural level seen over

the past 650,000 years (140 to 300 ppm). The concentration of methane and


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24 jrgen e. olesen

nitrous oxide has also increased sharply during the past 50 years. Methane

is produced anaerobically, i.e. through the transformation of organic mat-

ter under oxygen-free conditions, for example in the rumens of ruminant

animals, from livestock waste, landfills and in paddy rice fields. Methane

has a global warming potential which is 23 times greater than for CO2. Themethane content of the atmosphere has, compared to pre-industrial levels,

risen by 160 per cent, which is largely due to rapidly increasing numbers of

livestock and growing volumes of waste.

Nitrous oxide is an even more potent greenhouse gas than methane with

a global warming potential which is 298 times greater than for CO2. The

concentration in the atmosphere has increased by 17 per cent compared

to pre-industrial levels; it is also a very long-lasting greenhouse gas with a

lifetime in the atmosphere of 120 years. Nitrous oxide stems in particular

from the microbial transformation of nitrogen in the soil, and the rap-idly growing volumes of nitrogen which are added through agricultural

activities are the main cause of increased emissions of nitrous oxide to

the atmosphere. Emissions of CFC gases from refrigerators, freezers, air-

conditioning systems, fire-extinguishing agents etc. also contribute to the

greenhouse effect, which is being further intensified by ozone in the lower

part of the atmosphere the troposphere. Ozone is formed when sunlight

decomposes mono-nitrogen oxides (NOx) and carbon monoxide (CO), for

example from car and truck exhaust gases. Thus, a large number of differ-

ent sources of pollution contribute to boosting the atmospheric content of

greenhouse gases.

The combustion of coal and oil in particular also results in the emission

of many small particles to the atmosphere, which generally have a cooling

effect, because they increase the amount of sunlight which is reflected (the

albedo). Changes in land use have also increased the albedo, but there

is considerable uncertainty regarding both these effects (See Table 1). In

addition to man-made factors influencing radiation, there have been very

large but relatively brief cooling contributions in connection with volcaniceruptions when many small particles are emitted, increasing the albedo.

Finally, variations in solar radiation have also resulted in a slight increase in

radiation effects in the first half of the twentieth century (Table 1). A hand-

ful of scientists claim that these factors together with other natural causes

can be the main reasons for the observed climate changes rather than the

emission of greenhouse gases (see subsequent chapter on the suns indirect

influence on the climate).


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5. Climate sensitivity

Warming as a result of an increase in the atmospheric content of greenhouse

gases (or of the other parameters in Table 1) is described using the concept

of climate sensitivity. Climate sensitivity states how much the global tem-

perature will rise through a change in additional energy of 1 W/m2. Such a

change in added energy can be due to an increase in the atmospheric contentof greenhouse gases or a change in solar radiation.

The climate sensitivity makes it possible to calculate the temperature

increase from different forcings of the climate system which, directly or

indirectly, influence the energy addition. If we know the change in energy

addition, it is then possible, using climate sensitivity, to immediately esti-

mate the temperature change. Unfortunately, we do not know a lot about

climate sensitivity. If, for example, we only look at what a change in energy

addition should result in based on how dependent the longwave outgoing

radiation is on temperature, we arrive at a sensitivity of 0.269 K/(W/m2).

Figure 2. Development in the atmospheric concentration of carbon dioxide (CO2) following theend of the last ice age measured in air bubbles trapped in ice cores taken from Antarctic ice. Theenlarged section shows the concentration for the period 1750-2005. The full-draw line showsdirect measurements in the atmosphere (Solomon et al. 2007).

Content of CO2

(ppm)

Years before present day

CO2-concentration (PPM)

Years before now


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26 jrgen e. olesen

This produces far too small a climate sensitivity. In reality, a number of

feedback mechanisms reinforce the temperature change (Box 3). One of

the most important feedback mechanisms is the effect of temperature on

the atmospheric content of water vapour. Water vapour is a greenhouse

gas, and as a warm atmosphere can contain more water vapour than a coldatmosphere, warming will lead to an enhanced greenhouse effect due to

the presence of more water vapour in the atmosphere.

There are many of these feedback mechanisms, and the climate sensitivity

is influenced by the combined effect of these. To calculate the overall effect,

comprehensive climate models are used which represent all the physical

processes in the atmosphere, the oceans and on land. At the same time, ob-

servations over the past 150 years have been used, as well as reconstructions

of climate changes over the past 500,000 years, to determine the climate

sensitivity. Using these methods, a value of approx. 0.75 K/(W/m2) has beenarrived at. Feedback mechanisms therefore result in almost a tripling of the

sensitivity compared to the effect without feedbacks. This means that the

warming effect of CO2 will be tripled due to feedback mechanisms in the

climate system. However, there is still considerable uncertainty associated

with establishing the climate sensitivity, and the estimates range from ap-

prox. 0.5K/(Wm2) to more than 2K/(Wm2).

Table 1 shows an overall estimated radiative forcing of man-made cli-

mate changes of approx. 1.6 W/m2. A climate sensitivity of 0.75 K/(W/m2)

leads to a temperature increase of 1.2 C. This is considerably more than the

stated temperature increase of approx. 0.75 C, which is due to inertia in

the climate system and which leads to the climate changes continuing for

a period after the radiative forcing has increased. This inertia is particularly

related to the slow warming of the oceans.

6. The suns indirect impact on the climate

In addition to the direct effect of solar radiation on the Earths climate(solar forcing), two specific indirect effects of the suns influence on the

climate have attracted attention in the climate debate. The first effect is due

to the absorption (warming) from ultraviolet radiation in the stratospheres

ozone layer, which is in the uppermost part of the atmosphere (at a height

of 15-30 km). The amount of UV radiation depends on sunspots, producing

greater warming in periods of maximum sunspots. The number of sunspots

varies over an eleven-year cycle. Some studies indicate that the warming can

be transmitted to the lower part of the atmosphere and lead to changes in

the climate systems circulation patterns.


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The second effect has been suggested by Henrik Svensmark, where the

variation in solar activity through changes in the amount of cosmic radiation

can affect the formation of ions in the atmosphere and thereby affect the

formation of the small particles which function as cloud condensation

nuclei for ice and water, and thereby affect cloud formation. Because low-lying clouds in particular have a cooling effect, a change in solar activity

can thereby perhaps indirectly affect the climate. Laboratory experiments

have shown that this type of radiation can promote the formation of cloud

condensation nuclei, but it is unknown whether this mechanism will also

work in the atmosphere.

However, there is nothing to suggest that either of these two indirect solar

effects have been significant for the global warming of the atmosphere over

the past 50 years when there has been no change in the volume of cosmic

radiation hitting Earth. On the other hand, it is possible that changes inthe cosmic radiation and in UV radiation may have been significant for the

warming which occurred in the 1910-1940 period.

7. Ice ages

There has for some time been general consensus among scientists that the

basic cause of the coming and going of the ice ages is due to changes in

the Earths orbit around the sun (see Box 4). This is called the Milankovitch

theory, and states that the ice ages are caused by small, cyclical variations

in the Earths orbit (eccentricity) and axial tilt (obliquity) around the sun.

These variations lead to a complex pattern of changes in the amount and

distribution of solar radiation reaching the Earth, influencing global energy

balances and heat transport and thereby climate.

During the ice ages, large volumes of water are accumulated in glaciers,

causing the sea level to fall. The temperature at the Earths surface is also

lower, resulting in less evaporation of water from the oceans, which in turn

leads to less precipitation. Moreover, as much of the precipitation falls assnow, the ice ages are often accompanied by marked periods of drought in

ice-free areas. This leads to a global climate which is far less favourable for

life on Earth than the present climate. During the ice ages, the climate is

not constantly cold, but there are often considerable global and regional

variations in the temperature which result in the ice sheets advancing and

retreating. The cause of these variations is still poorly understood.

Even though there is general agreement that the Milankovitch theory is

the predominant cause for initiating ice ages, it appears that more is required

to trigger a new ice age. Here, the amounts of dust and greenhouse gases


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28 jrgen e. olesen

in the atmosphere are likely to play a significant role. The geography of theEarth is another factor. Only when the position of the continents hinders an

efficient exchange between cold water at the poles and warm water at the

equator will new ice ages occur. This is actually the case with the Earths

present geography, where there is relatively little exchange between water

in the Arctic ocean and the other oceans. At the same time, the continents

are currently placed so close to the poles that long-lasting ice caps can be

formed.

An ice age typically lasts about 100,000 years, while an interglacial period

lasts 10,000-15,000 years. We are now in an interglacial period which has

Milankovitch and the ice ages Box 4

The shape of the Earths orbit around the sun is not constant but varies accord-

ing to the attractive force of the other planets. Moreover, the Earths axial tilt

(obliquity) and its precession (axial rotation) in space also vary. These variationsaffect the amount of total solar radiation reaching Earth and its distribution,

otherwise known as solar forcing. The Serbian geophysicist Milutin Milankovitch

(1879-1958) was the first person to calculate (by hand) these effects over the past

one million years and thereby demonstrate that these variations are the primary

cause of the switch between ice age and interglacial periods.

Eccentricity

The Earths orbit around the sun changes from being almost circular to slightly

elliptical and back again over a period of approx. 100,000 years. This change in

eccentricity means that the distance between the Earth and the sun changes,

resulting in minor changes in the overall solar radiation reaching the Earth.

Axial tilt

The angle of axis of the Earths rotation in relation to an axis perpendicular to

the Earths orbit around the sun varies between 21 and 24 over a period of ap-

prox. 41,000 years. Changes in the Earths axial tilt affect the distribution of solar

radiation, but not total solar radiation. When the axial tilt is large, the difference

between summer and winter at high latitudes will be greater. Cooler summers

with a low axial tilt are suspected of encouraging the start of a new ice age.

Precession

The direction of the Earths axis of rotation in space changes over a period ofabout 21,000 years. At the moment it is summer in the northern hemisphere

when the Earth is closest to the sun. In about 10,500 years, summer will be in

the southern hemisphere when the Earth is closest to the sun. This does not af-

fect the total amount of solar radiation reaching Earth but rather the seasonal

variation in temperature.


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lasted 11,700 years. However, this does not mean we are on the threshold

of a new ice age. Thus, the IPCC states that it is very unlikely that the Earth

will enter a new ice age within the next 30,000 years as a result of natural

causes. This is because the next major fall in summer radiation to the north-

ern hemisphere will not happen for 30,000 years (see Box 4).

Climate models Box 5

Climate models describe the atmosphere as a physical system based on physi-

cal laws which can be expressed mathematically. As the oceans are also an

important factor for the climate, climate models often include models of the

heat transport and heat exchange taking place within the oceans. In the global

climate models (GCM), the atmosphere is described using a number of boxes

distributed in a spatial network across the entire globe. There are about 200 km

between the grid points, with 30-40 vertical layers in the atmospheric models

and 20-30 layers in the ocean models.

The most important physical laws used in the climate models are:

Equations of motion based on Newtons laws

Mass and energy conservation

Equation of state for ideal gases

Radiation equations, which describe how solar and thermal radiation are

transmitted and deposited in the atmosphere.

Moreover, the models include a number of empirical relations based on obser-

vations. These empirical relations do not necessarily have a reliable theoretical

basis but are necessary to describe processes which occur at temporal and spatial

scales which are not sufficiently resolved in the models. Such empirical relations

often contain a number of parameters which have to be tuned by comparing

model simulations with observations. One example of this is cloud formation,

which often takes place on a much smaller scale than what is represented in

the models.

The empirical relations are necessary, but they also reduce the degree of preci-

sion in the model calculations. This can to some extent be remedied by increas-

ing the models spatial and temporal resolution, but this leads to vastly greater

requirements for computer processing power when running the models. Often

calculations are therefore performed with an increased resolution for a smaller

geographical area with the help of regional climate models (RCM), where a GCM

supplies the boundary conditions for the regional model, i.e. temperature, air

pressure, water vapour at the edge of the geographical extent of the regional

model.


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8. Models of the climate system

As described above, the climate is the result of a complex interplay between

many different physical, chemical and biological processes which are si-

multaneously influenced by the geographical distribution of the oceans,land masses, ice caps, lakes and rivers. In order to better understand this

complex system, several mathematical models of the climate system have

been developed (Box 5). These are complex models which demand some of

the worlds fastest computers to simulate the Earths climate.

The most important criterion for assessing whether a climate model is

reliable consists of comparing the model simulations of the present climate

with observations. The climate models are continually being improved, and

at the moment there are about twenty models worldwide which are capable

of producing satisfactory simulations of the climate system. The deviationsbetween the calculated and the observed temperature distribution on Earth

are in most cases just a few degrees, with the biggest deviations being seen

in areas with snow and ice. Generally speaking, the climate models can be

regarded as providing a solid basis for calculating future climate change.

9. Scenario calculations of climate changes

An important question when assessing future climate changes is how society

will develop over the next century and how this will affect the emission of

greenhouse gases to the atmosphere. To assess the uncertainty in this area

and the effect of different social developments, including environmental

awareness and new environmentally friendly technologies, the IPCC has

developed a number of scenarios for the future (Box 6). These scenarios

range from sustainable societies based on the widespread use of renewable

energy and resources to an even more resource-hungry society than that we

know today.

The global increase in temperature up until 2100 is shown in Figure 3for three of these scenarios. In about 2100, the temperature globally will

have increased by 3-4 C if the world develops as shown in the A2 scenario,

but only by 1.3-2.4 C according to the B1 scenario.

Most of the other scenarios show temperature increases which fall within

this interval (see Table 2). It is worth noting that the differences between

the scenarios first become really apparent during the second half of the

twenty-first century. This is partly due to the fact that it takes a long time

to make the very resource-consuming technologies more sustainable and

partly because of inertia in the climate system.


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The IPCCs emissions scenarios Box 6

Future population developments and economic and technological developments

will cause additional anthropogenic emissions of greenhouse gases and thereby

lead to a greater atmospheric concentration and a continued forcing of thegreenhouse effect. At the moment it is difficult to predict how the factors which

determine emissions will develop because different international trends have

an important bearing, including issues such as the development of the global

economy versus a regionalisation of the markets as well as potential changes

in peoples lifestyles. These changes can either lead to less consumption and

thereby relatively small greenhouse gas emissions, or greater consumption of

energy and resources and thereby higher emissions. Another important factor

is the future of the developing countries where high rates of economic growth

and energy consumption on a par with that in the industrialised countries can

become a major source of greenhouse gas emissions. The climate issue is thusclosely integrated with general development issues.

To assess the necessity/effect of possible measures to reduce the emissions of

greenhouse gases, it is necessary to make a number of assumptions about the

future. As mentioned, such assumptions are subject to considerable uncertainty,

and therefore so-called scenarios are presented which describe possible future

global social and technological developments. In 2000, the IPCC carried out

extensive scenario work that shows a number of possible alternative develop-

ment perspectives which are gathered in four groups labelled A1, A2, B1 and B2.

A1. A future world with very fast economic growth. The world population peaksin the middle of the century, and new and more efficient technologies are quickly

introduced. The A1 family comprises three sub-families where fossil fuels are

primarily used (A1FI) or non-fossil energy sources (A1T) as well as a mix of all

energy types (A1B).

A2. A more heterogeneous world with continued population growth and a slower

pace of technological development.

B1. A world which is similar in some respects to A1, but which focuses more on a

service and information-based economy as well as sustainable technologies.

B2. A world which still sees population growth, although at slower rates than

in A2, as well as slower and more diversified technological developmentsthan in A1 and B1.

Together, the scenarios cover the many combinations of world population growth

(approx. 7-15 billion), growth in GDP (approx. 11-26 times), distribution of

energy production on fossil and non-fossil energy sources etc. Even though

some optimistic scenarios predict a reduction in CO2, most show an increase

in CO2 concentration from the present level of 370 ppm to including a level

of uncertainty from under 500 ppm to more than 1000 ppm up until 2100.


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32 jrgen e. olesen

Table 2. Model-calculated projections of global warming and rising sea levels during the twenty-first century (Solomon et al. 2007).

Temperature increase (C) Sea level rise (m)

Scenario Best estimate Likely interval Without accelerated

increase in mel-

ting rate of ice

Constant year 2000 concentration 06 03-09

B1 18 11-29 018-038

A1T 24 14-38 020-045

B2 24 14-38 020-043

A1B 28 17-44 021-048

A2 34 20-54 023-051

A1FI 40 24-64 026-059

The climate systems inertia is illustrated by the lower curve in Figure 2,

which shows the temperature development if the concentration of green-

house gases is maintained at the year 2000 level. Calculations based on the

climate models show that the temperature will increase by 0.4-0.8 C in any

case. This is because the Earths climate and especially the temperature

in the oceans is still out of balance with the present level of greenhouse

gases. The climate will therefore continue to warm, regardless of how the

world and our emissions develop.

10. Regional climate changes

However, what is crucial for the effects of climate changes is not how the

global average temperature develops but how temperature and precipitation

develop regionally. Calculations based on the climate models show large

regional changes occurring basically everywhere around the world. Warming

above land will be higher than above water, and consequently higher than

the global average. The temperature increase over land is usually 50 per centgreater than the global mean value. Moreover, the increase in temperature

is much greater during winter in the Arctic, usually twice the global mean,

which is largely due to the fact that the warming reduces the amount of ice

and snow (see Box 3).

Significant changes will also occur in the distribution of precipitation.

The general picture is that it will become drier in areas which are dry at

present and even wetter where it already rains a lot. In addition, the dry

areas will spread, with increased risk of drought in many places. This is

particularly true in the dry tropics and subtropics, while increases in rainfall


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will be seen at higher latitudes in cooler climates. Where rainfall increases,

there will be a greater risk of flooding.

The changes in the atmospheres circulation will mean that the storm

paths in the middle latitudes will move slightly further towards the poles.

At the same time, calculations suggest that the maximum wind speeds instorms above the sea will increase, leading to a greater frequency of very

intense and destructive hurricanes.

More extreme weather

An enhanced greenhouse effect will not just lead to a generally warmer

climate, it will also result in changes in the frequency, intensity and dura-

tion of extreme weather events. Model calculations show that there will be

more and longer-lasting heat waves, but also heavier precipitation. The

model calculations show increasing precipitation intensity across most ofthe Earth, but also that the number of dry days increases. This accords with

observations of climate changes over the past 50 years, and is linked to the

intensification of the hydrological cycle which stems especially from the

fact that higher temperatures enhance evaporation and the maximum water

vapour content in the atmosphere before clouds form. When evaporation is

limited (e.g. due to dry soils), this leads to less rainfall, whereas it leads to

higher rainfall where evaporation is not limited by water availability.

All in all, this increases the risk of both flooding and drought in many

places worldwide. Again, this is in line with what has been observed over

the past 50 years, where the frequency of flooding has increased throughout

almost all of Europe, while periods of drought have become more extensive,

particularly in southern Europe. Similar changes are seen across the globe.

Rising sea levels

When the temperature increases as a result of anthropogenic emissions of

greenhouse gases, two factors can contribute to rising sea levels worldwide.

On the one hand the water expands as a result of being warmed, and on theother glaciers and ice caps melt in a warmer climate.

The likely range for the increases in sea levels worldwide during the

twenty-first century is reported by IPCC as 15-59 cm depending on the

chosen emissions scenario (see Table 2). The thermal expansion of water

is responsible for 70-75 per cent of this increase. Recent studies suggest

that the ice, especially on Greenland, will melt at a faster rate. However,

these studies are still regarded as being very uncertain and are therefore

not included in the IPCCs estimates in Table 2.

Sea levels worldwide during the previous interglacial period (the Eemian


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34 jrgen e. olesen

Interglacial) 125,000 years ago were probably four to six metres higher than

during the twentieth century, probably due to the polar ice caps melting. It

is therefore likely that the melting of the ice caps on Greenland will con-

tribute significantly to rising sea levels in the coming centuries. However,

thousands of years may pass before the Greenland ice sheet has melted awaycompletely. Once so, sea levels would have risen by 7 metres.

Uncertainties

There is no doubt that the Earths climate is changing towards a warmer

and more extreme climate. There is also no doubt that at least the major-

ity of the observed climate change is due to anthropogenic emissions of

greenhouse gases.

However, considerable uncertainty remains on how climate will change

in future. This is not so much due to the obviously chaotic nature of theweather systems or the natural fluctuations in the climate caused by changes

in solar radiation or volcanic eruptions. Rather, the uncertainty is largely at-

tributable to our current lack of understanding of the feedback mechanisms

Figure 3. Model calculations of the global rise in temperature from 1900 to 2100 for three emis-sion scenarios (see Box 3) as well as for the hypothetical situation where the atmospheric contentof greenhouses gases remains constant at 2000 levels. All temperatures are shown relative to the

mean temperature for 1980-1999 (Solomon et al. 2007).

Global temperature increase

A2A1BB1

Year 2000 constantconcentrations20th century


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in the climate system. This can make the climate change both larger and

smaller than the present projections.

In terms of how society adapts to climate changes, reliable projections

of temperature and precipitation distribution play a key role at regional

level. In many cases, it is also important to have detailed information aboutchanges in the frequency of extreme weather events such as storms, heavy

rainfall and drought. Here, the climate models have improved markedly in

recent years, but improvements are still badly needed.

For projections towards the end of the twenty-first century, the uncer-

tainties regarding the future emissions of greenhouse gases are far more

important than the uncertainty about the climate sensitivity. This shows

that at we now have a reliable climatic basis for deciding whether we as

a society must take steps to avoid the climate changes. It also shows that

mankind will be forced to adapt to changes in climate some warming isunavoidable.

ReferencesDawson AG (1992): Ice Age Earth. Routledge.Houghton J (2004): Global warming. The complete briefing. Cambridge University Press.Marsh N & Svensmark H (2003): Solar influence on Earths climate. Space Science

Reviews. 107, pp. 317-325.Nakicenovic N, Alcamo J, Davis G, DeVries B, Fenhann J, Gaffin S, Gregory K,

Gruebler A, Jung TY, Kram T, La Rovere EL, Michaelis L, Mori S, Morita T, PepperW, Pitcher H, Price L, Riahi K, Roehrl A, Rogner HH, Sankovski A, Schlesinger M,

Shukla P, Smith S, Swart R, VanRooijen S, Victor N & Dadi Z (2000): Special Reporton Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panelon Climate Change. Cambridge University Press, Cambridge.

Philander SG (2008): Encyclopedia of global warming and climate change. SAGE.Silver J (2008): Global warming & climate change demystified. A self-teaching guide.

McGraw Hill.

Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M & Miller

HL (eds.) (2007): Climate Change 2007: The Physical Science Basis. Contribution of

Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on ClimateChange. Cambridge University Press, Cambridge, UK.Svensmark H & Friis-Christensen E (1997): Variation in cosmic ray flux and global

cloud coverage a missing link in solar-climate relationships.Journal ofAtmospheric and Solar-Terrestrial Physics. 59, pp. 1225-1232.


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37what will happen?

What will happen?

Scenarios of the future

jrgen e. olesen

1. Introduction

Climate change is nothing new. In the history of Earth there have been con-siderable climate changes from very warm periods to an almost complete

freezing of the planet (snowball Earth). Over the past half a million years,

the biggest climate changes have happened in connection with the coming

and going of the ice ages. Nevertheless, life on Earth has survived even

though many species have become extinct, especially at the onset of the ice

ages. So, history also shows that life on Earth generally speaking is

pretty robust. However, we should remember that the climate change we

currently face is expected to lead to a warmer climate than the Earth has

experienced for several million years and this will take place over just 100

years! We are therefore on the threshold of a new type of climate change

which will take place at a speed that surpasses what has previously been

seen.

Climate change is undoubtedly one of the biggest challenges faced by

mankind. This is not least because of the huge consequences that climate

change will have for the worlds ecosystems and for our living conditions.

At the same time, climate change poses a colossal political problem where

democracies around the world risk failing to make the right decisions intime.

The political and democratic problem stems from the fact that people

experience only to a very small degree any connection between lifestyle,

greenhouse gas emissions, climate change and the effect of the climate

change on the living standards of individual citizens. This is because there

is both a spatial and a temporal separation between emissions and effects.

The worlds industrial countries, which emit the largest volumes of green-

house gases, are generally less vulnerable to the effects of climate change.

This is because industrial countries have a higher adaptive capacity than


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39what will happen?

change results from greenhouse gas emissions and that these are harmful.

Likewise, the will to act assumes that future harmful effects are deemed

relevant for decisions being made now. It is therefore important to be able

to establish the effects of climate change and their economic consequences.

As climate change in one form or another must be regarded as unavoidable,it is crucial that society adapts in the most appropriate way.

2. The effects are already evident

The effects of climate change do not just belong to the future. Climate

change is already happening as are the effects. The global mean tem-

perature has increased by 0.55 C over the past 30 years. This has led to

documented changes in biological and physical systems across all conti-

nents. Examples include: Increased instability of the ground in areas with permafrost and more

rock slides in alpine areas.

Changes in some Arctic and Antarctic ecosystems, for example for the

polar bears (Box 4).

Increased run-off and earlier spring floods in many rivers which are fed

by glaciers and snow.

Warming of many rivers and lakes with consequences for the food chains

and water quality.

Earlier occurrence of springtime events such as leaf unfolding and bird

migration.

Shift towards the poles in the spread of flora and fauna.

Change in the distribution area of algae, plankton and fish in the oceans

at high latitudes.

Increased occurrence of algae and zooplankton in lakes at high latitudes

(Box 5).

Incipient bleaching of many coral reefs as a result of rising sea tem-

peratures.

A number of changes have been documented in both natural and human

systems, even though it can be difficult to distinguish climate effects from

adaptations to other non-climatic trends:

In northern areas changes are taking place in agricultural and forestry

systems involving earlier sowing and growth in the crops as well as

changes in the occurrence of windfalls, forest fires and pest infestation.


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40 jrgen e. olesen

Changes in health-related risks, for example the occurrence of heat-

related deaths in Europe (see Box 2) and a greater incidence of allergenic

pollens at the mid and high latitudes in the northern hemisphere.

Certain human activities in the Arctic (e.g. hunting and moving across

snow and ice) as well as winter sports in low-lying alpine areas.

There are also indications that climate change is affecting other natural and

human systems. Even though these changes are described in the literature,

they are still not documented trends which can be ascribed to anthropogenic

climate change.

Buildings in mountain areas are subject to an increased risk of flood-

ing from melting glaciers. Governments and other authorities have in

several places initiated the construction of dams and ducts to mitigate

the risk.

Heatwave over Europe in 2003 Box 2

From June to August 2003, many parts of Europe suffered a serious heatwave

with summer temperatures 3-5 C above normal over much of southern and

central Europe. The highest temperatures were recorded at the beginning of

August when the maximum temperature for several days running was 35-40 C.

The average summer temperature was way above normal, which shows that it

was an extremely unusual phenomenon under normal climate conditions. How-ever, the phenomenon is consistent with the combined increase in both mean

temperature and temperature variability that is expected as a result of climate

change. As such, the 2003 heatwave simply represents what can be expected to

be normal for central and southern Europe towards the end of the twenty-first

century. Consequently, the heatwave in 2003 has been taken by many as a sign

of what is to come.

The heatwave was accompanied by a significant shortfall in precipitation, and

the resulting drought led to a loss of productivity of 30 per cent for agricultural

and forestry production in large parts of Europe. This obviously reduced agri-

cultural production and increased costs. It has been estimated that total losses

amounted to EUR 11 billion within agriculture and forestry. The warm and dry

conditions also resulted in many very large forest fires, especially in Portugal.

Several large rivers (e.g., the Po, Rhine, Donau and Loire) had record low stream-

flows, affecting river navigation and the use of the river water for cooling and

irrigation. The Alpine glaciers melted at extremely high rates, which helped to

prevent even lower rates of flow in the Rhine and Donau. In large towns and

cities, the heatwave from June to August led to excessive mortality of more than

35,000 people, especially among senior citizens. Many of these large towns and

cities have now introduced emergency plans to prevent a repeat of this in future.


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41what will happen?

In the Sahel in Africa, warmer and drier conditions have led to a shorter

growing season with devastating consequences for the crops. In south-

ern Africa, a longer dry season and more uncertain rainfall has led to

changes in patterns of crop cultivation.

Rising sea levels, increased settlement and urban development have ledto a loss of wetlands and mangroves as well as increased damage from

flooding along the coasts in many areas.

Effects depend on the extent of the warming

It probably does not come as any surprise to learn that the greater the extent

of the global warming, the greater the consequences. However, it is only

since the publication of the IPCCs Fourth Assessment Report that an overall

picture has been presented of the consequences across various sectors and

across the worlds continents. Examples of this are given in Figure 1 wherethe expected effects are shown for a number of areas which are deemed to

be relevant for people and the environment.

Figure 1 shows the effects in relation to a rise in the global mean tem-

perature. However, only a few of the most serious consequences of global

warming can solely and directly be ascribed to temperature changes. Most

of the effects are associated with changes in patterns of rainfall or the

increased frequency of extreme weather phenomena such as storms, heat-

waves, droughts and torrential rain. In coastal areas, the rising sea levels

also play a big role.

Figure 1 illustrates what could happen during the present century. Far

more serious effects are likely in the following centuries. These effects will,

in particular, be associated with significant rises in the sea level, leading

to the large-scale displacement of people, economic activities and infra-

structure away from the present coastlines. This will both be extremely

expensive and will pose social, cultural and political challenges of as yet

unseen dimensions. It is expected that parts at least of the Greenland ice

sheet and possibly the ice cap in West Antarctica will melt in the comingcenturies with temperature increases of 1-4 C, leading to sea level rises of

4-6 metres or more. This is on top of the sea level rises resulting from the

fact that water expands when warmed.

3. Water resources

The availability of clean and ample drinking water is regarded as a human

right. At the same time, water is fundamental to agricultural production. Of

total agricultural production, 40 per cent comes from irrigated farming, but


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worldwide agriculture accounts for 80 per cent of total freshwater consump-

tion. In addition, water plays a role in many different contexts which will

be affected by climate change, for example river navigation, hydroelectric

power, cooling of thermal power plants and private and industrial uses.

More than a sixth of the worlds population live on floodplains wheremuch of the water comes from melting glaciers and snow. Here, global

warming will initially lead to increased streamflow in rivers and thereby

greater possibilities for agricultural irrigation. In the long term, the conse-

quences will be smaller volumes of water stored in the glaciers and snow,

resulting in bigger differences between summer and winter streamflow in

the rivers with an increased risk of both flooding and drought.

By the middle of the twenty-first century, the annual run-off in the rivers

and the availability of water is expected to have increased by 10-40 per cent

in the high latitudes and in certain tropical regions. The run-off will cor-

Figure 1. Illustration of how different degrees of global warming during the twenty-first centurywill affect various resources, ecosystems and human health. The solid lines show where the ef-

fects are calculated to take place, and the dashed lines show that the effects continue and arereinforced by increasing temperatures. Adaptation to climate change is not included in theseestimates (Parry et al. 2007).


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43what will happen?

respondingly fall by 10-30 per cent in certain dry areas at medium latitudes

(e.g. southern Europe, South Africa and Australia) as well as in the dry trop-

ics, which are at present among the most water-stressed areas. Increased

drought will often be linked to greatly increased summer temperatures, and

the effect of this can be illustrated by the heatwave over Europe in 2003 (seeBox 2).

The size of the drought-struck area is also likely to grow. At the same

time, the risk of very heavy rainfall increases, increasing the risk of flooding.

The effect of more extensive flooding can be illustrated with the widespread

flooding along the River Elbe in 2002 (see Box 3).

There are a number of options available for adapting to changes to a

rivers water flow, the frequency of flooding and to more frequent drought.

As human society is so dependent on water, most of these methods are

already known by the authorities and private organisations handling water

Major flooding along the River Elbe in 2002 Box 3

On 10 August 2002, a large low-pressure system moved slowly in across central

and eastern Europe. The storm had started several days earlier above the British

Isles and then swung south where it gathered large volumes of humid air from

the warm Mediterranean. While gradually making its way over the central part

of the continent, it released its humidity in the form of sustained and heavy

rain. In some places, almost 250 millimetres of rain fell over a four-day period.

The flooding started in the Czech Republic, where the Vltava River, one of the

main tributaries of the Elbe, caused flooding in the medieval towns of Cesky

Krumlov and Ceske Budejovice. The next victim further downstream was the

low-lying districts in Prague. The flood wave continued into the Elbe and, on 15

August, caused widespread flooding in Dresden. While the flood wave moved

further down the Elbe, the river burst its banks in Wittenberg, Dessau and other

towns in Saxony. The high water levels finally reached the mouth of the Elbe on

24 August. Even though most flooding was seen along the Elbe, the streamflow

increased considerably in the Danube, which led to flooding in many towns inAustria and Slovakia.

When the Elbe and the Danube burst their banks, fertile farmland was flooded

along the rivers, destroying crops which were about to be harvested. The muddy

flood water which swept across low-lying areas forced many businesses along the

river to stop production and trade, and bridges, roads and other infrastructure

was extensively damaged or destroyed. Private homes and other property were

also to a large extent lost in the flooding waters. If the damage from all the

floods in central and eastern Europe is put together, the financial losses from

the floods in August 2002 amount to approximately EUR 15 billion.


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44 jrgen e. olesen

resources in many countries around the world. The possibilities open to us

for managing changes in water supplies basically fall under the following

points:

Political instruments such as regional strategic water plans, which con-

solidate and document the initiatives which the authorities and otherplayers can implement to adapt to climate change.

Technological and structural instruments such as new water reservoirs andimplementing programmes designed to ensure the renewal of ground-

water to safeguard water supplies in the long term as a way of countering

the increasing frequency of droughts.

Risk sharing and spreading in the form of insurance policies against ex-treme climate events and which are made available to poor and vulner-

able societies.

Changes in use, activity and place covers measures for overcoming climatechange, e.g. special zones along rivers to protect the population from

the risk of flooding. This also includes a large number of initiatives to

boost the efficient use of water (especially in farming) and water-saving

methods (in industry and in private and public housing).

Figure 2. Illustration of how the effects of climate change on freshwater resources affect the pos-sibility for sustainable development in various regions (Parry et al. 2007). The background mapshows the estimated difference in annual run-off (in per cent) between the present (1981-2000)and future (2081-2100) climate for the SRES A1B emissions scenario. The blue colours showincreasing run-off, the red declining run-off.


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45what will happen?

4. Ecosystems

Climate change will have serious consequences for the worlds ecosystems.

However, it is important to remember that, globally, ecosystems already

have to contend with considerable impacts of human activities. In the areaswhich are at the moment bearing the brunt of deforestation, agricultural

expansion and pollution, it is expected that these effects and not climate

change will be largely responsible for the loss of biodiversity over the next

50 years. However, climate cha

earth on fire climate change from a philosophical ethical perspective

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