Letter from The Royal Society
We are pleased to respond to the Committee's
call for evidence for the inquiry into the "Aspects of the
economics of climate change."
Our comments are based primarily on the enclosed
Royal Society report Economic instruments for the reduction
of carbon dioxide emissions (Royal Society 2002) (not
printed). In this report we recommend the introduction of well-designed
economic instruments, such as a carbon tax or auctioned permits,
as the most cost-efficient way to reduce carbon dioxide (CO2)
emissions. By associating a cost with emissions of CO2, a tax
corrects a failure in the market that allows emissions to be largely
We consider the scientific understanding of
climate change is now sufficiently certain to justify taking steps,
without delay, to reduce global greenhouse gas emissions. However,
uncertainty in the economics of climate change has been used as
an argument for not taking action now on mitigating carbon dioxide
Our report concludes that although the impact
of a tax or auctioned permits may be large on some sectors within
the economy, substantial long-term reduction in global emissions
is, even in its narrowest sense, affordable (Royal Society 2002).
In chapter 4 of our report we present the result of studies assessing
the impact of mitigation using worldwide carbon taxes over the
next 100 years to achieve stabilisation of CO2 concentrations.
The average reduction in GDP below base across all models, baseline
scenarios and stabilisation levels is 1.3 per cent by 2100. This
implies a negligible fall in the average growth rate of GDP from
2.3 per cent a year to 2.299 per cent a year. The report highlights
that extending the introduction of economic instruments to Europe
and beyond greatly improves their success and benefits.
Additional environmental benefits of carbon
taxes are not included in these studies, but are potentially so
important that they may more than offset any estimated economic
costs (OECD 2000). These
benefits, which are associated with the burning of fossil fuels,
include reduction SO2, NOx, small particles and noise.
In our report (Royal Society 2002) we describe
two options for setting a price for a carbon tax. The mitigation
target approach bases targets on past levels of emissions. The
targets are then achieved through policies that should be effective,
efficient and equitable. This practical approach is used by the
United Nations Framework Convention on Climate Change and the
The other approach is the use of cost benefit
analysis. This method assesses the costs and benefits of climate
change, adaptation and mitigation, and calculates the carbon tax
required to minimise net present costs. This logical approach
requires considerable effort to estimate damage costs. We consider
the results controversial because:
Many effects of climate change are
unknown and have an impact far into the future, and involve the
Uncertainty is high and there is
a possibility of large-scale changes to the climate.
Understanding and tackling the effects of climate
change will require collaboration between natural scientists,
social scientists and economists. In our report Guide to facts
and fictions about climate change (Royal Society 2005) (Printed
we highlight the work of Bjorn Lomborg who organised an event
called the Copenhagen Consensus, which attempted to assess the
need to tackle various global problems on the basis of an economic
analysis of costs and benefits. Lomborg and colleagues controversially
re-interpreted the detailed analysis in a paper they had commissioned
to reach the conclusion that "costs [of the Kyoto Protocol]
were likely to exceed benefits." The paper, authored by William
Cline, had concluded the opposite.
In response to the Copenhagen Consensus, the
distinguished economist Jeffrey Sachs pointed out (2004)
that the Copenhagen Consensus suffered from "severe shortcomings"
because it did not include input from scientists and the "scientific
information is presented through the over-simplified lens of rudimentary
cost-benefit analysis." He described the DICE99 model used
in the analysis as "a plausible strategy for an economist,
but it doesn't come close to engaging the best natural-science
models." Sachs concluded: "While simple economic models
can be illuminating, and I applaud DICE99 for what it can do,
having climate scientists at the table to highlight the shortcomings
of grossly simplified economic models is invaluable for arriving
at proper policy conclusions."
13 April 2005
A GUIDE TO
It has become fashionable in some parts of the
UK media to portray the scientific evidence that has been collected
about climate change and the impact of greenhouse gas emissions
from human activities as an exaggeration. Some articles have claimed
that scientists are ignoring uncertainties in our understanding
of the climate and the factors that affect it. Some have questioned
the motives of the scientists who have presented the most authoritative
assessments of the science of climate change, claiming that they
have a vested interest in "playing up" the potential
effects that climate change is likely to have.
This document examines 12 misleading arguments
(presented in bold typeface) put forward by the opponents of urgent
action on climate change and highlights the scientific evidence
that exposes their flaws. It has been prepared by a group led
by Sir David Wallace FRS, Treasurer of the Royal Society, and
Sir John Houghton FRS, former chair of Working Group I of the
Intergovernmental Panel on Climate Change (IPCC). This document
has been endorsed by the Council of the Royal Society, and draws
primarily on scientific papers published in leading peer-reviewed
journals and the work of authoritative scientific organisations,
such as the IPCC and the United States National Academy of Sciences.
The IPCC is the world's leading authority on
climate change and its impacts. It was set up in 1988 under the
auspices of the United Nations Environment Programme and the World
Meteorological Organisation. Membership of the IPCC is open to
all members of the United Nations and World Meteorological Organisation.
It has the following remit:
"The role of the IPCC is to assess on a
comprehensive, objective, open and transparent basis the scientific,
technical and socio-economic information relevant to understanding
the scientific basis of risk of human-induced climate change,
its potential impacts and options for adaptation and mitigation.
The IPCC does not carry out research nor does it monitor climate
related data or other relevant parameters. It bases its assessment
mainly on peer reviewed and published scientific/technical literature."
The IPCC has a task force on national greenhouse
gas inventories and three working groups:
Working Group I assesses the scientific
aspects of the climate system and climate change;
Working Group II assesses the vulnerability
of socio-economic and natural systems to climate change, negative
and positive consequences of climate change, and options for adapting
to it; and
Working Group III assesses options
for limiting greenhouse gas emissions and otherwise mitigating
The IPCC produces periodic assessment reports
providing an overview of current knowledge about climate change
and its impacts, as well as identifying uncertainties and gaps
in knowledge. The preparation of these reports involves many hundreds
of scientists across the world. The contributors, lead authors
and reviewers of these reports include those nominated by the
governments of the countries that are members of the IPCC, and
some who do not hold mainstream views on climate change. These
reports are reviewed by both members of the scientific community
and by governments.
The IPCC Third Assessment Report was published
in 2001, and involved more than 2,000 experts in its preparation.
It is the most authoritative source of information on climate
change due to human activities, including the emission of greenhouse
gases such as carbon dioxide, and can be accessed at http://www.ipcc.ch.
The report included a synthesis presenting the information in
the form of answers to a broad range of key policy-relevant, but
not policy-prescriptive, questions. The IPCC Fourth Assessment
Report is due to be published in 2007.
The following abbreviations are used in this
|GDP:||gross domestic product
|IPCC:||Intergovernmental Panel on Climate Change
|OISM:||Oregon Institute of Science and Medicine
||United Nations Framework Convention on Climate Change
||United States National Academy of Sciences
Misleading arguments: The IPCC has become too politicised and
does not accurately reflect the wide range of views within the
scientific community. The IPCC summary for policy-makers does
not adequately represent the scientific uncertainty.
The work of the IPCC is backed by the worldwide scientific
community. A joint statement of support was issued in May 2001
by the science academies of Australia, Belgium, Brazil, Canada,
the Caribbean, China, France, Germany, India, Indonesia, Ireland,
Italy, Malaysia, New Zealand, Sweden and the UK. It stated: "We
recognise the IPCC as the world's most reliable source of information
on climate change and its causes, and we endorse its method of
In 2001, the United States National Academy of Sciences was
commissioned by the Bush administration to assess the current
understanding of global climate change. Its report, published
in June 2001, stated: "The IPCC's conclusion that most of
the observed warming of the last 50 years is likely to have been
due to the increase in greenhouse gas concentrations accurately
reflects the current thinking of the scientific community on this
Each part of the IPCC 2001 report included a summary for
policymakers, each of which was agreed sentence by sentence at
meetings of the governments from member countries of the IPCC.
The purpose of the summaries was to provide an accurate and balanced
assessment of the scientific information contained in the technical
sections of the report in a manner that is clear, understandable
and relevant to the policy process.
Some have claimed that the summary for policy-makers did
not accurately reflect the technical parts of the report. The
US NAS 2001 report concluded that the summary for policymakers
from Working Group I "reflects less emphasis on communicating
the basis for uncertainty and a stronger emphasis on areas of
major concern associated with human-induced climate change."
The NAS concluded that the full report of IPCC Working Group I
in the Third Assessment is "an admirable summary of research
activities in climate science, and the full report is adequately
summarised in the Technical Summary", but pointed
out that these are "not specifically directed at policy."
The IPCC 2001 report carefully distinguishes between what
is known with reasonable certainty, and the areas in which large
uncertainties remain. The report includes quantitative estimates
of uncertainty throughout.
Misleading arguments: Many scientists do not think that climate
change is a problem. Some scientists have signed petitions stating
that climate change is not a problem.
There are some differences of opinion among scientists about
some of the details of climate change and the contribution of
human activities, such as the burning of fossil fuels. Researchers
continue to collect more data about climate change and to investigate
different explanations for the evidence. However, the overwhelming
majority of scientists who work on climate change agree on the
main points, even if there is still some uncertainty about particular
aspects, such as how the concentration of greenhouse gases in
the atmosphere will change in the future.
In the journal Science in 2004, Oreskes published
the results of a survey of 928 papers on climate change published
in peer-reviewed journals between 1993 and 2003. She found that
three-quarters of the papers either explicitly or implicitly accepted
the view expressed in the IPCC 2001 report that human activities
have had a major impact on climate change in the last 50 years,
and none rejected it.
There are some individuals and organisations, some of which
are funded by the US oil industry, that seek to undermine the
science of climate change and the work of the IPCC. They appear
motivated in their arguments by opposition to the United Nations
Framework Convention on Climate Change and the Kyoto Protocol,
which seek urgent action to tackle climate change through a reduction
in greenhouse gas emissions.
Often all these individuals and organisations have in common
is their opposition to the growing consensus of the scientific
community that urgent action is required through a reduction in
greenhouse gas emissions. But the opponents are well-organised
and well-funded. For instance, a petition was circulated between
1999 and 2001 by a campaigning organisation called the Oregon
Institute of Science and Medicine (OISM), which called on the
US Government to reject the Kyoto Protocol. The petition claimed
that "proposed limits on greenhouse gases would harm the
environment, hinder the advance of science and technology, and
damage the health and welfare of mankind."
These extreme claims directly contradict the conclusions
of the IPCC 2001 report, which states that "reducing emissions
of greenhouse gases to stabilise their atmospheric concentrations
would delay and reduce damages caused by climate change."
The petition was circulated together with a document written
by individuals affiliated to OISM and to the George C Marshall
Institute, another campaigning organisation. On 20 April 1998,
the US National Academy of Sciences (NAS) issued a warning about
the document circulated with the petition because it had been
presented "in a format that is nearly identical to that of
scientific articles published in the Proceedings of the National
Academy of Sciences." The statement pointed out: "The
NAS Council would like to make it clear that this petition has
nothing to do with the National Academy of Sciences and that the
manuscript was not published in the Proceedings of the National
Academy of Sciences or in any other peer-reviewed journal."
Misleading arguments: There is little evidence that global
warming is happening or, if it is happening, it is not very much.
Some parts of the world are actually becoming cooler. Increased
urbanisation could be responsible for much of the increase in
observed temperatures. Satellite temperature records do not show
any global warming. If there has been global warming recently,
it would not even be a unique occurrence within the past 1,000
years. Europe has been much warmer in the past.
Few scientists dispute that the global average temperature
has been rising for at least a century. The IPCC 2001 report concluded,
based on worldwide measurements, that the average surface temperature
of the Earth had risen by 0.6 centigrade degrees (+/-0.2ºC)
during the 20th century. The IPCC found that, in terms of the
global average temperature, the 1990s were very likely (a 90-99
per cent chance) to have been the warmest decade since records
began in 1861, and that 1998 was the warmest year. Furthermore,
the increase in surface temperature during the 20th century in
the Northern Hemisphere was likely (a chance of 66 to 90 per cent)
to have been greater than for any other century for the last 1,000
The IPCC report recognised that "temperature changes
have not been uniform globally but have varied over regions and
different parts of the lower atmosphere." For instance, some
parts of the Southern Hemisphere oceans and parts of Antarctica
have not warmed in recent decades.
The report also noted that there have been two major periods
of warming globally: 1910 to 1945 and since 1976. It concluded
that "it is virtually certain that there has been a generally
increasing trend in global surface temperature over the 20th century,
although short-term and regional deviations from this trend occur."
It has been argued that recent warming trends are due to
the effect of increasing urbanisation and the creation of `urban
heat islands'. However, Parker recently reported in the journal
Nature that analyses of temperature trends show that globally
"temperatures over land have risen as much on windy nights
as on calm nights, indicating that the observed overall warming
is not a consequence of urban development." The IPCC 2001
report noted that the analysis of temperature changes from across
the world took into account increases due to urbanisation, and
average temperature trends recorded over land were found to be
similar to those observed over the oceans.
The IPCC report also noted that, since 1979, both satellites
and weather balloons have recorded a lower rate of warming in
the lower atmosphere than has been measured at the surface. The
report acknowledged that the reasons for this gap are not yet
fully understood, but it is likely to be due to the fact that
temperatures in the lower atmosphere and at the surface are influenced
differently by factors such as stratospheric ozone depletion,
aerosols in the atmosphere and the El Niño phenomenon.
Satellites and weather balloons have recorded a substantial cooling
in the upper parts of the atmosphere, which is consistent with
models of climate change.
Grody and others recently indicated in the Journal of
Geophysical Research that much of the earlier inconsistency
between the satellite and surface measurements arises from errors
in analysing the data from the satellites which can "artificially
suppress the temperature trend." Fu and others pointed out
in the journal "Nature" that the same warming trends
are present in the lower atmosphere as occur at the surface, if
the effect of the cooling of the upper atmosphere is taken into
account, although this has been disputed.
Some have questioned whether natural temperature variations
in the past 1,000 years have been greater than those reported
in the IPCC 2001 report. For instance, von Storch and others argued
in the journal Science that the natural variations in average
global temperature over the last 1,000 years may have reached
one centigrade degree, instead of the 0.5 centigrade degree implied
by previous analyses. This conclusion was supported by Moberg
and others in a paper in the journal Nature, in which they
reported that natural variations in temperature may have reached
up to one centigrade degree over periods of centuries during the
last 2,000 years. But they also pointed out: "We find no
evidence for any earlier periods in the last two millennia with
warmer conditions then the post-1990 periodin agreement
with previous similar studies." They drew attention to the
fact that models show natural factors alone could not be responsible
for the recent warming trend.
According to the IPCC report, "regional temperature
trends over a few decades can be strongly influenced by regional
variability in the climate system and can depart appreciably from
a global average". For instance, there was significant cooling
in the North Atlantic between 1946 and 1975, as well as much of
the Northern Hemisphere, and warming in much of the Southern Hemisphere.
Although some regions of the world experienced significantly warmer
or colder periods during the last 1,000 years, such as the "Medieval
Warm Period" and the "Little Ice Age", these were
not worldwide changes like the increase in global average temperature
recorded during the 20th century.
Misleading arguments: The Earth is getting hotter, but not
because of emissions of greenhouse gases from human activities.
Carbon dioxide makes up such a tiny fraction of the atmosphere
that even if it doubled it would make little difference to the
climate. Variations in the sun are more likely to be the cause
of climate changing than increases in greenhouse gases.
About half of the solar energy entering the top of the Earth's
atmosphere eventually reaches the surface where it is absorbed.
Much of the solar energy is absorbed by the Earth's surface and
then released as infra-red radiation, some of which is absorbed
by greenhouse gases such as water vapour, carbon dioxide and methane.
The greenhouse gases act like a blanket over the surface of the
Earth, keeping it around 20 centigrade degrees warmer than it
otherwise would be, which is a phenomenon known as "the greenhouse
Increases in the concentrations of greenhouse gases in the
atmosphere enhance the greenhouse effect and, on average, lead
to further warming. It has been long established that carbon dioxide
strongly absorbs infra-red radiation. The IPCC 2001 report pointed
out that carbon dioxide is "the dominant human-influenced
greenhouse gas," and is responsible for more than half the
warming due to changes in atmospheric concentrations.
Based on direct analysis of gases found trapped in cores
of polar ice, it is known that the atmospheric concentration of
carbon dioxide for several thousands of years before 1750 was
about 280 parts per million. Between 1750 and 2000, during which
industrialisation has occurred, the concentration rose by about
31 per cent to 368 parts per million. The IPCC report noted that
the current concentration of carbon dioxide in the atmosphere
has not been exceeded during the past 420,000 years and that "the
rate of increase over the past century is unprecedented, at least
during the past 20,000 years".
It has been claimed that the rise in atmospheric concentrations
of carbon dioxide is actually a consequence of climate change,
rather than a cause. The IPCC report pointed out that chemical
analyses of the carbon dioxide show that the increase in the atmosphere,
and an accompanying decrease in oxygen concentrations, are primarily
due to the burning of fossil fuels and deforestation. Although
some carbon dioxide taken up and released by oceans or land, it
stressed that the average rate of increase in concentrations in
the atmosphere since 1980 has been about 0.4 per cent per year
and that this is due to emissions. It stated "Most of the
emissions during the past 20 years are due to fossil fuel burning,
the rest (10 to 30 per cent) is predominantly due to land-use
change, especially deforestation".
A number of other factors are known to influence climate
and cause change, particularly volcanic eruptions, variations
in the energy from the sun and particles released into the atmosphere
from both natural sources and human activities. Particles in the
atmosphere reduce the amount of energy from the sun that reaches
the Earth's surface, and therefore cause a cooling effect. The
IPCC has studied evidence of changes in these various factors
and their likely influence on the global average temperature.
It found that the variations over the 20th century can only be
understood by taking all factors, both natural and human, into
Land use changes such as the spread or shrinkage of forest
areas can also contribute to changes in temperature. The loss
of forests can exert a cooling effect by increasing the reflectivity
of the land surface, which means lower amounts of solar radiation
are absorbed. The IPCC 2001 report noted that the overall effect
of land use changes since pre-industrial times has been to produce
cause cooling, and that this has mainly been due to the replacement
at high latitudes of snow-covered forests by open, snow-covered
areas. The report noted that the level of understanding of the
overall effect of land use changes was lower than for other factors
affecting global temperatures.
The IPCC found that the dominant influences on climate change
in the early part of the 20th century were likely to be a small
increase in solar output and a decrease in average volcanic activity.
However, such natural factors cannot explain the warming in the
latter half of the 20th century, and the IPCC concluded that there
is "new and stronger evidence that most of the warming observed
over the last 50 years is attributable to human activities".
The report pointed out that natural factors on their own would
have produced an overall drop in global average temperatures.
A recent study by Solanki and others, published in the journal
Nature, found that the level of solar activity during the
past 70 years has been "exceptional" when considered
over the period of the last 11,400 years. However, they concluded
that "although the rarity of the current episode of high
average sunspot numbers may indicate that the Sun has contributed
to the unusual climate change during the twentieth century, we
point out that solar variability is unlikely to have been the
dominant cause of the strong warming during the past three decades".
Misleading arguments: There is no reliable way of predicting
how temperatures will change in the future. The climate is so
complex that it is hard to predict what might happen. The IPCC's
climate scenarios are developed by economists not scientists and
are often misleadingly presented as predictions or forecasts,
when they are actually just scenariosthe most extreme of
which are totally unrealistic The IPCC's findings are dependent
on models that are badly flawed. No climate model has been scientifically
validated. The IPCC 2001 predictions showed a wider uncertainty
range than that in earlier reports.
Climate change is complex and not easy to predict. In order
to make projections about climate change in the future, the IPCC
developed a set of scenarios that describe possible global emissions
of greenhouse gases. These scenarios produced estimates of various
concentrations of global greenhouse gas emissions in the atmosphere
up to 2100, taking into account different projected trends in
demographic, economic and technological developments, as well
as changes in the political environment. Economists and sociologists
helped to develop these scenarios. These scenarios include the
whole range of likely changes in emissions of greenhouse gases.
In the studies cited in the IPCC 2001 report, the main tools
used to describe the detailed response of the climate to any given
future scenario of greenhouse gas emissions are numerical models
that include mathematical descriptions of physical processes and
the interactions between different components of the climate system.
Because the models are based on scenarios of future human activities,
their results should be considered to be projections rather then
predictions. There has been, and continues to be, a major effort
to compare the details of climate model results with actual observations.
This leads to improvements in the representation of climate processes
in the models.
The IPCC 2001 report included results from these models showing
that carbon dioxide concentrations in the atmosphere would increase
to between 540 and 970 parts per million by 2100, compared to
280 parts per million in pre-industrial times, for the whole range
of emissions scenarios and allowing for uncertainties in the models.
According to the models, changes in carbon dioxide concentrations
in the atmosphere would affect global average temperatures during
the 21st century. They suggested global average temperatures would
rise by 0.4 to 1.1 centigrade degrees by 2025 compared to 1990,
and by 1.4 to 5.8 centigrade degrees by 2100. The report pointed
out that this rate of warming would be "much larger than
the observed changes during the 20th century and is very likely
without precedent during at least the last 10,000 years"
based on measurements from ice cores and other sources of information
about past temperatures.
The increase in temperatures would be above the global average
on nearly all land areas, particularly in the high northern latitudes
The range of changes in global average temperatures was higher
in the IPCC 2001 report than in previous assessments mainly because
the models included a better representation of interactions within
climate systems, and because a greater range of emissions of greenhouse
gases were incorporated into the scenarios. The models cited in
the IPCC 2001 report also included assumptions about a lower concentration
of particles of sulphate in the atmosphere, which reflect back
some of the incoming radiation from the sun, due to larger controls
on air pollution.
The IPCC 2001 report openly acknowledged uncertainties in
modelling climate change in the future. It stated that "because
of uncertainty in climate sensitivity, and uncertainty about the
geographic and seasonal patterns of projected changes in temperatures,
precipitation, and other climate variables and phenomena, the
impacts of climate change cannot be uniquely determined for individual
Critics of the IPCC have not offered alternative numerical
models that give different results for how climate will be affected
by the range of possible future concentrations of greenhouse gases
in the atmosphere.
Misleading arguments: Scientists have been exaggerating the
evidence by claiming that individual extreme weather events have
been caused by climate change. The recent flooding in the UK in
places like Boscastle and Carlisle would have happened anyway,
and the frequency of hurricanes hitting the Caribbean and Atlantic
coast of the United States is no different than in the past. Even
if they appear to be more severe, this is only because more people
are living in places that are affected by natural extreme weather
In general, it is not possible to state categorically that
individual weather events are due to changes in climate, and reputable
scientists are extremely cautious about such claims. However,
there is a link, albeit complex, between changes in climate and
regional and local weather events, including extreme ones. Changes
in the global climate can be expected to lead to patterns of local
and regional weather events, particularly extreme ones. While
scientists may be able to estimate the change in the likelihood
of such events because of climate change, they cannot predict
The IPCC 2001 report concluded it was very likely (with a
90 to 99 per cent chance) that there was a 5 to 10 per cent increase
in total rainfall on land areas of the Northern Hemisphere during
the 20th century, although some parts of the Mediterranean and
north and west Africa had seen falls. It was likely (with a 66
to 90 per cent chance) that the number of heavy rainfall events
had increased at middle to high latitudes in the Northern Hemisphere.
During recent decades human populations have been affected
more by extreme weather events in some areas. The IPCC 2001 report
recognised that "there is emerging evidence that some social
and economic systems have been affected by the recent increasing
frequency of floods and droughts". However, the report acknowledged
that "such systems are also affected by changes in socioeconomic
factors such as demographic shifts and land-use changes".
The report stated that, for the future, "models project that
increasing atmospheric concentrations of greenhouse gases result
in changes in frequency, intensity, and duration of extreme events,
such as more hot days, heat waves, heavy precipitation events,
and fewer cold days". It further drew attention to a projected
increase in the frequency and severity of extreme events due to
climate change in the 21st century. For instance, there are likely
to be, with a certainty of 66 to 90 per cent, intensified droughts
and floods associated with El Niño events in many different
regions (El Niño is a naturally-occurring disruption of
the ocean-atmosphere system in the tropical Pacific), and an increase
in tropical cyclone peak wind intensities and peak rainfall over
Some peer-reviewed papers have appeared in leading scientific
journals since the publication of the IPCC 2001 report, shedding
more light on the link between climate change and the occurrence
of extreme events. For instance in 2002, Palmer and Räisänen
reported in the journal Nature the results of analyses
of 19 global climate model simulations that indicate "the
probability of occurrence of a very wet winter over the UK is
estimated to increase by a factor of 5 over the next 50-100 years,
due to man's effect on climate". In this case, very wet winters
are characterised by significantly above average seasonal rainfall.
These models also imply "an increased risk of flooding in
Bangladesh" over the same period.
In a paper published in Nature in 2004, Stott and
others noted that the summer of 2003 was probably the hottest
in Europe since at least 1500. It has been estimated that the
heatwave caused 22,000-35,000 additional deaths. Stott and others
acknowledged that it was not possible to meaningfully determine
whether the heatwave was due to increased atmospheric concentrations
of greenhouse gases "because almost any such weather event
might have occurred by chance in an unmodified climate".
However, they concluded from an analysis of instrument records
since 1851 that "it seems likely that past human influence
has more than doubled the risk of European mean summer temperatures
as hot as 2003, and with the likelihood of such events projected
to increase 100-fold over the next four decades". A further
paper in Nature in 2004 by Schar and others reported the
results of an analysis that found that "the European summer
climate might experience a pronounced increase in year-to year
variability" in response to rising greenhouse gas concentrations
in the atmosphere. It concluded: "Such an increase in variability
might be able to explain the unusual European summer 2003, and
would strongly affect the incidence of heatwaves and droughts
in the future".
The IPCC 2001 report acknowledged that it was not possible
to tell what impact climate change would have on some individual
local weather events. It concluded: "There is insufficient
information on how very small-scale extreme weather phenomena
(eg thunderstorms, tornadoes, hailstorms, and lightning) may change".
Misleading arguments: There is conflicting evidence about whether
the ice at the poles is melting and, in fact, it is actually becoming
thicker in Antarctica.
The IPCC 2001 report indicated that in 2000 Arctic ice had
thinned overall by 40 per cent in the late summer and early autumn
(with 66 to 90 per cent certainty) in the past few decades, and
decreased in extent by 10 to 15 per cent since the 1950s in the
spring and summer. There has also been a widespread retreat of
non-polar glaciers. However, there was no demonstrated change
in the overall extent of Antarctic sea ice between 1978 and 2000.
The models reported by the IPCC showed that glaciers would
continue to retreat with rises in global average temperatures.
The report recognised the complexity of projections, noting that
"the Antarctic ice sheet is likely to gain mass because of
greater precipitation, while the Greenland ice sheet is likely
to lose mass because the increase in runoff will exceed the precipitation
Looking further into the future, larger changes in the ice
sheets may begin to occur. The IPCC 2001 report also warned that
a local average warming by 3 centigrade degrees would lead, over
a thousand years, to "virtually a complete melting of the
Greenland ice sheet with a resulting sea level rise of about 7
m [metres]". The report also warned that the West Antarctic
Ice Sheet may start to break up if temperatures continue to climb.
A recent paper by Shepherd and others published in the journal
Science in 2003, suggested that the Larsen Ice Shelf in
Antarctica has begun to break-up over a very short period due
to a sustained period of thinning of the ice. They concluded that
"enhanced ocean-driven melting may provide a simple link
between regional climate warming and the successive disintegration
of sections of the Larsen Ice Shelf".
Misleading arguments: There is little evidence of a rise in
sea level due to global warming. There is no correlation between
rises in climate temperature and sea levels. There has been no
consistent trend this century, with sea level rising in some places
but not in others. Even if sea level is rising it has nothing
to do with global warming and is actually due to the fact that
southern England is sinking due to the bending of the Earth's
The IPCC 2001 report found that average sea level around
the world increased at a rate of 0.1 to 0.2 centimetres per year
during the 20th century. This had been caused by a combination
of the thermal expansion of seawater (ie the volume of a fixed
mass of water increases as it is heated) and the melting of land
ice. The report acknowledged that there had not been a significant
acceleration in the rate of sea level rise during the 20th century,
and that this was "not inconsistent with model results."
According to the IPCC models, global average sea levels would
rise by 3 to 14 centimetres by 2025 compared to 1990, and by 9
to 88 centimetres by 2100, although the amount of sea level rise
would vary very significantly between regions. The rise would
be due to thermal expansion and the melting of glaciers and ice
The IPCC 2001 report also noted that "compensating factors"
have also affected sea levels during the 20th century, which would
have reduced the rates of change. As Shennan and Horton reported
in the Journal of Quaternary Research in 2002, sea levels
around Great Britain have been influenced for instance by a phenomenon
known as isostatic rebound. During the last Ice Age, Britain was
covered by ice sheets as far south as the Thames Estuary. The
ice sheet caused the land beneath it to sink, while the land in
front of it, in southern England bulged up. When the ice sheet
retreated after the end of the Ice Age, the land that had been
beneath it started and continues to rise slowly, while the land
in the bulge is sinking slowly. Other factors, such as the compaction
of sediments, also cause changes in land movements. Shennan and
Horton found that, overall, central and western Scotland are rising
at about 1.6 millimetres per year while the south-west England
is sinking by about 1.2 millimetres per year.
Misleading arguments: Even if climate change is occurring,
it won't be that dangerous. Abrupt climate change is just another
scare story. While an atmospheric concentration for carbon dioxide
of 550 parts per million has been proposed as a political target,
there has been no scientific determination of "dangerous"
levels of greenhouse gas concentrations.
The United Nations Framework Convention on Climate Change
(UNFCCC) was adopted in 1992 by nations to set an overall framework
for intergovernmental efforts to tackle the challenges posed by
climate change. There are currently 191 parties to the UNFCCC.
It seeks to stabilise concentrations of greenhouse gas emissions
in the atmosphere, and states:
"The ultimate objective of this Convention and any related
legal instruments that the Conference of Parties may adopt is
to achieve, in accordance with the relevant provisions of the
Convention, stabilisation of greenhouse gas concentrations in
the atmosphere at such a level that would prevent dangerous interference
with the climate system. Such a level should be achieved within
a timeframe sufficient to allow ecosystems to adapt naturally
to climate change, to ensure that food production is not threatened,
and to enable economic development to proceed in a sustainable
The IPCC report considered what is meant by "dangerous
climate change". This involves taking into account not just
the scientific evidence, but issues such as risk, social and political
factors and economics. The impacts of climate change will differ
around the world, and so what is considered dangerous will also
vary. It will also depend on how well humans can adapt to climate
change or take action to prevent its worst effects. The decision
about what is "dangerous" needs to be taken by policy-makers
rather than scientists, who should present their best analysis
of all the risks as a basis for that decision.
The report also warned that rising greenhouse gas concentrations
in the atmosphere could "set in motion large-scale, high-impact,
non-linear, and potentially abrupt changes in physical and biological
systems over the coming decades to millennia, with a wide range
of associated likelihoods". It further stated: "Some
of the projected abrupt/non-linear changes in physical systems
and in the natural sources and sinks of greenhouse gases could
be irreversible, but there is an incomplete understanding of some
of the underlying processes."
Examples of these possible abrupt changes highlighted by
the IPCC included a weakening during the 21st century, and even
a complete shutdown thereafter, of the large-scale circulation
in the oceans associated with differences in temperature and salinity
(called the thermohaline circulation), reducing the amount of
heat reaching the high latitudes of Europe, including the UK.
The report warned: "some impacts of anthropogenic climate
change may be slow to become apparent and some could be irreversible
if climate change is not limited in both rate and magnitude before
associated thresholds, whose positions may be poorly known, are
The IPCC recognised that while human ingenuity may allow
humans to cope with some of the worst effects of climate change,
we will not be able to prevent all damage. It noted that adaptation
and mitigation are both required. Adaptation will be needed to
cope with the impacts of climate change that is already happening
and which will occur in the years before it is stabilised. Mitigation
will be needed to slow climate change and eventually stabilise
it, as set by the objective of the UNFCCC. The IPCC 2001 report
stressed that actions to cope with or avoid climate change would
take time to take effect and that "well-founded actions to
adapt to or mitigate climate change are more effective, and in
some circumstances may be cheaper, if taken earlier rather than
This is important because the report pointed out that carbon
dioxide can remain in the atmosphere for up to 200 years, and
as a result "stabilisation of CO2 emissions at near-current
levels will not lead to stabilisation of CO2 atmospheric concentration,
whereas stabilisation of emissions of shorter lived greenhouse
gases such as CH4 [methane] leads, within decades, to stabilisation
of their atmospheric concentrations." The report also noted
that the relatively long life of carbon dioxide in the atmosphere
means its effects on climate would continue for an extended period:
"After stabilization of the atmospheric concentration of
CO2 and other greenhouse gases, surface air temperature is projected
to continue to rise by a few tenths of a degree per century for
a century or more, while sea level is projected to continue to
rise for many centuries".
The UK Government stated in the February 2003 Energy White
Paper that "the UK should put itself on a path towards a
reduction in carbon dioxide emissions of some 60 per cent from
current levels by 2050". Such a strategy is consistent with
stabilisation of atmospheric concentrations of carbon dioxide
at about 550 parts per million, and was based on a recommendation
contained in a report by the Royal Commission on Environmental
Pollution in 2000.
According to the IPCC 2001 report, to stabilise concentrations
of carbon dioxide in the atmosphere at 550 parts per million (which
would be 96 per cent higher than pre-industrial levels and 49
per cent higher than in 2000), emissions from human activities
would need to fall below 1990 levels within much less than a century
and continue to decrease steadily afterwards to a very small fraction
of today's levels.
The IPCC report also considered what measures would be needed
to tackle the predicted effects of climate change. The most important
was that "the projected rate and magnitude of warming and
sea-level rise can be lessened by reducing greenhouse gas emissions".
It also pointed out that "the greater the reductions in emissions
and the earlier they are introduced, the smaller and slower the
projected warming and the rise in sea levels".
Misleading arguments: There is no evidence that climate change
will be bad for people. In fact, warmer weather will actually
be good for those people who live in cold countries. Climate change
may make some places like Russia warmer and more productive places
to live. A warmer climate will be good for the UK's economy, with
more tourists and better wine-producing conditions. Increasing
levels of carbon dioxide would produce a rise in plant productivity
and crop yields. Surely we should let the benefits and costs of
climate change even themselves out.
The IPCC models acknowledge that some parts of the globe
would benefit, at least in the short-term, from climate change.
Some high northern latitudes could experience less extreme cold
and a longer growing season for crops. In addition, the higher
concentrations of carbon dioxide in the atmosphere will boost
growth of some important crops, and given adequate water and nutrients,
will bring higher yields.
However, the IPCC models indicate that "the larger the
changes and rate of change in climate, the more the adverse effects
predominate". These adverse effects would be most severe
in the tropics and subtropics. The IPCC pointed out that "reducing
the projected increase in climate extremes is expected to benefit
all countries, particularly developing countries, which are considered
to be more vulnerable to climate change than developed countries".
While some commentators in the media have imagined that climate
change will bring benefits to the UK, such as "better wine-producing
conditions", they do not appear to take into account the
significant problems that we will face through an increase in
the likelihood of flooding in some areas, a reduction in the availability
of fresh water in others, and more threats to sea defences due
to sea level rise in many low-lying areas, as acknowledged in
the UK Government's Energy White Paper in 2003.
The focus on the UK also ignores the misery and suffering
that will increase for the world's poorest and most vulnerable
people. The IPCC concluded that "the impacts of climate change
will fall disproportionately upon developing countries and the
poor persons within all countries, and thereby exacerbate inequities
in health status and access to adequate food, clean water, and
The IPCC models indicate that the threats to human health
will increase with climate change, "particularly in lower
income populations, predominantly within tropical/subtropical
countries". They showed, with a high level of confidence,
that climate change would lead to an increase in heat-related
death and illness, a drop in cold-related death in temperate countries,
a higher frequency of epidemics of infectious diseases after storms
and floods, and significant impacts from the displacement of populations
in response to rises in sea level and greater storm activity.
In most of the IPCC models, overall crop yields would decrease
as temperatures rise. The report warned that "warming of
a few ºC or more is projected to increase food prices globally,
and may increase the risk of hunger in vulnerable populations".
Those parts of the world already experiencing water shortages
would find their problems worsen with climate change, although
some places may see an overall increase in rainfall.
Humans would not be the only life that would be affected
by climate change. The IPCC acknowledged that the average overall
growth of plants would increase with the rise in atmospheric carbon
dioxide concentrations, but this may not have an overall positive
knock-on effect on animals and micro-organisms. Increased growth
would mean a rise in the amount of carbon dioxide absorbed by
plants. However, Knorr and others recently pointed out in the
journal Nature that rising temperatures would mean higher
rates of decomposition of dead material, thus releasing more carbon
dioxide into the atmosphere.
The IPCC 2001 report also warned that natural systems are
"vulnerable to climate change, and some will be irreversibly
damaged". It stressed that "while some species may increase
in abundance or range, climate change will increase existing risks
of extinction of some more vulnerable species and loss of biodiversity".
For instance, the report projected with "high confidence"
that "future sea surface warming would increase stress on
coral reefs and result in increased frequency of marine diseases".
Misleading arguments: There are too many uncertainties about
climate change and its impacts to justify taking action. It would
be better to wait until we are more certain about climate change
The UNFCCC has been signed by 191 parties which recognise
the need to tackle climate change, even if there are some uncertainties
in our understanding. The parties to the UNFCCC are committed
to stabilising concentrations of greenhouse gases in the atmosphere.
The UNFCCC commits signatories to adopt policies and measures
that are cost-effective. It states:
"The Parties should take precautionary measures to anticipate,
prevent, or minimise the causes of climate change and mitigate
its adverse effects. Where there are threats of serious irreversible
damage, lack of full scientific certainty should not be used as
a reason for postponing such measures, taking into account that
policies and measures to deal with climate change should be cost-effective
so as to ensure global benefits at the lowest possible costs.
To achieve this, such policies and measures should take into account
different socio-economic contexts, be comprehensive, cover all
relevant sources, sinks and reservoirs of greenhouse gases and
adaptation, and comprise all economic sectors. Efforts to address
climate change may be carried out collectively by interested Parties."
In 1997 parties to the UNFCCC agreed to an addition to the
treaty, called the Kyoto Protocol, which has more powerful and
legally binding measures for industrialised countries that are
party to both the Convention and the Protocol, to limit or reduce
their greenhouse gas emissions. The Protocol became international
law in February 2005.
The IPCC report notes that the UNFCCC aims to identify short-term
"hedging strategies" in light of long-term uncertainties.
It suggests that "the relevant question is not `what is the
best course of action for the next hundred years' but rather `what
is the best course of action for the near-term given the long-term
uncertainties'". The report states:
"Several studies have attempted to identify the optimal
near-term hedging strategy based on the uncertainty regarding
the long-term objective. These studies find that the desirable
amount of hedging depends upon one's assessment of the stakes,
the odds, and the cost of mitigation. The risk premiumthe
amount that society is willing to pay to avoid riskultimately
is a political decision that differs among countries."
The UK Government carried out an analysis of the cost of
stabilising atmospheric concentrations of carbon dioxide at 550
parts per million, assuming that the world's leading industrial
nations acted together. It reported in the 2003 Energy White Paper
that "the cost impact of effectively tackling climate change
would be very smallequivalent in 2050 to just a small fraction
(0.5-2.0 per cent) of the nation's wealth, as measured by GDP,
which by then will have tripled as compared to now". The
2000 report by the Royal Commission on Environmental Pollution
outlined four scenarios in which the UK could use current technologies
to reduce its carbon dioxide emissions by 60 per cent by the year
Misleading arguments: The Kyoto Protocol is a waste of time
because the United States will not ratify it. The emission reduction
targets required under the Kyoto Protocol are "trivial"
and would do no more than postpone global warming by six years.
Implementing the Kyoto Protocol would be too costly. The trillions
of dollars that would be wasted on the Kyoto Protocol should be
spent on helping developing countries tackle poverty.
The 38 parties listed in Annex B of the Kyoto Protocol each
agreed to individual targets for their total annual greenhouse
gas emissions, relative to levels in 1990, over the period 2008
to 2012. These targets if achieved would result in an overall
reduction of emissions by 5.2 per cent in 2008-12 compared to
The IPCC report summarised the results of studies into the
potential cost to the 23 developed countries listed in Annex II
of the UNFCCC of implementing the cuts in greenhouse gas emissions
set out for the 38 industrialised countries listed in Annex B
of the Kyoto Protocol. Without emissions trading between the Annex
B countries, the majority of global studies show reductions in
projected GDP of about 0.2 per cent to 2 per cent below the baseline
by 2010 for different Annex II regions. With full emissions trading
between Annex B countries, the estimated reductions by 2010 are
between 0.1 per cent and 1.1 per cent of projected GDP. The report
notes that there are many ways of presenting the potential costs:
"For example, if the annual costs to developed countries
associated with meeting Kyoto targets with full Annex B trading
are in the order of 0.5 per cent of GDP, this represents US$125
billion (1,000 million) per year, or US$125 per person per year
by 2010". The report points out that "this corresponds
to an impact on economic growth rates over ten years of less than
0.1 percentage point".
One vociferous critic of the UNFCCC and Kyoto Protocol is
Bjorn Lomborg, author of the book The Skeptical Environmentalist
and organiser of the Copenhagen Consensus, an event organised
in 2004 during which a group of economists attempted to assess
the need to tackle various global problems on the basis of an
economic analysis of costs and benefits alone.
Lomborg had previously labelled the benefits of the Kyoto
Protocol as "marginal" and claimed that "global
warming is not expected to have a severe impact on human welfare
as a whole" in an article in The Lancet in December
2002, but did not offer any evidence to counter the findings of
the IPCC 2001 report.
In a paper commissioned by the Copenhagen Consensus, William
Cline used an analysis of the DICE99 economic model to show that
the overall benefits of the Kyoto Protocol would be higher than
the costs, with the advantage accruing to developing countries
rather than the industrialised countries that agreed to targets
under the Kyoto Protocol. Lomborg and colleagues controversially
re-interpreted the detailed analysis by Cline to reach the conclusion
that "costs were likely to exceed benefits" for the
Kyoto Protocol. Furthermore, the distinguished economist Jeffrey
Sachs pointed out in The Lancet that the Copenhagen Consensus
suffered from "severe shortcomings" because it did not
include input from scientists and "scientific information
is presented through the over-simplified lens of rudimentary cost-benefit
analysis". He described the DICE99 model as "a plausible
strategy for an economist, but it doesn't come close to engaging
`the best natural-science models'". Sachs concluded: "While
simple economic models can be illuminating, and I applaud DICE99
for what it can do, having climate scientists at the table to
highlight the shortcomings of grossly simplified economic models
is invaluable for arriving at proper policy conclusions".
Although opponents of the Kyoto Protocol, such as Lomborg,
have made many criticisms, they have not put forward any robust
viable alternative mechanisms that are consistent with the principles
set out by the UNFCCC.
In a paper published in The Energy Journal in 2004,
Barker and Ekins examined the costs that the United States government
has estimated of meeting its agreed target under the terms of
the Kyoto Protocol of reducing annual emissions of greenhouse
gases by 7 per cent in 2008-12 compared to 1990. They concluded
that as long as the target was achieved through policies that
are gradual and well designed that "the net costs for the
US of mitigation are likely to be insignificant", amounting
to no more than 1 per cent of GDP.
The government of the United States indicated in 2001 that
it would not ratify the Kyoto Protocol and would not be bound
by its agreed target. According to figures published by the UNFCCC
secretariat in October 2004, annual emissions of greenhouse gases
from the United States by 2002 had increased by 13.1 per cent
compared to 1990. The Royal Society has calculated that, even
if annual emissions from the United States remain at the same
level until 2012, the rise per year in greenhouse gases of 805,000
tonnes of carbon dioxide equivalents compared to 1990 levels will
still be larger than the combined cut per year of 523,000 tonnes
of carbon dioxide equivalents by all the other parties listed
in Annex B of the Kyoto Protocol.
Therefore, with the conservative estimate that emissions
by the United States will remain at the 2002 value until 2012
and all other Parties meet their targets, the Annex B countries,
including the United States, will achieve an overall 1.6 per cent
increase instead of a 5.2 per cent reduction.
Nevertheless, the Kyoto Protocol, which came into force on
16 February 2005, remains a crucial first step towards the substantial
cuts in emissions that will be required this century if atmospheric
concentrations of greenhouse gases are to be stabilised. It is
essential that the next commitment period for the Protocol, beyond
2012, includes both developing countries and industrialised countries
such as the United States.
The joint statement by 16 national academies of science in
May 2001 demonstrated support from the international scientific
community for the Kyoto Protocol. It stated:
"The ratification of this Protocol represents a small
but essential first step towards stabilising atmospheric concentrations
of greenhouse gases. It will help create a base on which to build
an equitable agreement between all countries in the developed
and developing worlds for the more substantial reductions that
will be necessary by the middle of the century."
The statement continued:
"There is much that can be done now to reduce the emissions
of greenhouse gases without excessive cost. We believe that there
is also a need for a major co-ordinated research effort focusing
on the science and technology that underpin mitigation and adaptation
strategies related to climate change. This effort should be funded
principally by the developed countries and should involve scientists
from throughout the world."
Barker T and Ekins, P. 2004. The costs of Kyoto for the US
economy. The Energy Journal, volume 25, pages 53-71.
Intergovernmental Panel on Climate Change 2001. Climate
Change 2001. Third Assessment Report. Four volumes, Cambridge
University Press, Cambridge, United Kingdom.
Fu, Q, Johanson, CM, Warren, SG and Seidel, DJ. 2004. Contribution
of stratospheric cooling to satellite-inferred tropospheric temperature
trends. Nature, volume 429, pages 55-58.
Grody, NC, Vinnikov, KY, Goldberg, MD, Sullivan, JT and Tarpley,
JD 2004. Calibration of multisatellite observations for climatic
studies: Microwave Sounding Unit (MSU). Journal of Geophysical
Research, volume 109, D24104, doi: 10.1029/2004JD005079.
Houghton, JH 2004. Global warming: the complete briefing.
Third edition. Cambridge University Press, Cambridge, United Kingdom.
Knorr, W, Prentice, IC, House, JI and Holland, EA 2005. Long-term
sensitivity of soil carbon turnover to warming. Nature,
volume 433, pages 298-301.
Lomborg, B 2002. How healthy is the world? The Lancet,
volume 325, pages 1461-1464.
Lomborg, B 2004. Global Crises, Global Solutions. Cambridge
University Press, Cambridge, United Kingdom.
National Academy of Sciences, 1998. Statement by the council
of the National Academy of Sciences regarding global change petition.
Washington, United States.
National Academy of Sciences. 2003. Climate Change Science:
An Analysis of Some Key Questions. Washington, United States.
Moberg, A, Sonechkin, DM, Holmgren, K, Datsenko, NM, and
Karlén, W 2005. Highly variable Northern Hemisphere temperatures
reconstructed from low- and high-resolution proxy data. Nature,
volume 433, pages 613-617.
Oreskes, N 2004. The scientific consensus on climate change.
Science, volume 306, page 1686.
Palmer, TN and Räisänen, J 2002. Quantifying the
risk of extreme seasonal precipitation events in a changing climate.
Nature, volume 415, pages 512-514.
Parker, DE 2004. Large-scale warming is not urban. Nature,
volume 432, page 290.
Royal Commission on Environmental Pollution 2000. Energy-The
Changing Climate. Her Majesty's Stationery Office, London,
Royal Society and 15 others. 2001. The Science of Climate
Change. London, United Kingdom.
Sachs, J 2004. Solving global crises: economists alone are
not enough. The Lancet, volume 364, pages 2087-2088.
Schär, C, Vidale, PL, Luthi, D, Frei, C, Häberli,
C, Liniger, MA, and Appenzeller, C 2004. The role of increasing
temperature variability in European summer heatwaves. Nature,
volume 427, pages 332-336.
Shennan, I and Horton, B 2002. Holocene land- and sea-level
changes in Great Britain. Journal of Quaternary Science,
volume 17, pages 511-526.
Shepherd, A Wingham, D, Payne, T and Skvarca, P 2003. Larsen
Ice Shelf has progressively thinned. Science, volume 302,
Solanki, SK, Usoskin, IG, Kromer, B, Schüssler, M and
Beer, J 2004. Unusual activity of the Sun during recent decades
compared to the previous 11,000 years. Nature, volume 431,
Stott, P, Stone, DA and Allen, MR 2004. Human contribution
to the European heatwave of 2003. Nature, volume 432, pages
United Nations Framework Convention on Climate Change secretariat.
2004. Information on national greenhouse gas inventory data
from Parties included in Annex 1 to the Convention for the period
1990-2002, including the status of reporting. Executive summary.
Von Storch, H, Zorita, E, Jones, JM, Dimitriev, Y, González-Rouco,
F and Tett, SFB 2004. Reconstructing past climate from noisy data.
Science, volume 306, pages 679-682.
Royal Society (2002). Economic instruments for the reduction
of carbon dioxide emissions. Back
OECD (Organisation for Economic Cooperation and Development)
(2000). Behavioural responses to energy and transport- related
taxes; a survey of price elasticity estimates. OECD. Paris. Back
Royal Society (2005). A guide to facts and fictions about climate
change http://www.royalsocac.uk/-page.asp?id=2986 Back
Sachs, J. 2004. Solving global crises: economists alone are not
enough. The Lancet, volume 364, pages 2087-2088. Back