2 The global objective
Limiting the rise in average global
temperature
6. Average mean global temperature has already gone
up by 0.8°C above pre-industrial levels and even if concentrations
of greenhouse gases could be fixed at 2005 levels, the world could
be committed to an eventual warming of between 1.4 to 4.3°C.[7]
In order to say what limit should be placed on emissions we must
first decide what constitutes dangerous climate change. Establishing
where the boundary between acceptable and dangerous climate change
lies is a political question but one that must be informed by
science. Defining 'dangerous climate change' is ultimately a value
judgement.[8] Lord Turner
of Ecchinswell, Chairman of the Committee on Climate Change, explained
that this was because of uncertainties in climate science and
in our understanding of how human welfare is affected by climate
change.[9] Science can
tell us what the likely response of the climate will be to a particular
concentration of greenhouse gases and what the impacts of climate
change will be. But it cannot do this with absolute certainty
and what we know is described in terms of probabilities and likelihoods.
Political judgement must be exercised to determine where boundaries
lie. A report written following a scientific congress in Copenhagen
in March 2009 said:
While there is not yet a global consensus on
what levels of climate change might be defined to be 'dangerous',
considerable support has developed for containing the rise in
global temperature to a maximum of 2°C above pre-industrial
levels.[10]
7. Recent observations have shown that societies
and ecosystems are vulnerable to even modest levels of climate
change, with poorer nations and communities, ecosystem services
and biodiversity particularly at risk. A rise in temperature of
more than 2°C is likely to cause major societal and environmental
impacts through the next century and beyond.[11]
In 2001 the consensus was that a rise of 2°C would avoid
the most serious impacts. Professor Brian Hoskins, a member of
the Committee on Climate Change, said it was quite possible that
the world would become a more dangerous place even if the rise
in temperature could be kept to 2°C.[12]
The synthesis report produced following a recent scientific congress
in Copenhagen acknowledged that adaptation strategies would help
societies cope with rises of less than 2°C but argued that
beyond 2°C the scope for adaptation of society and ecosystems
was thought to decline rapidly.[13]
We should not be complacent about the kinds of impacts that might
occur. It is likely that as temperature rises the cost of adaptation
will rise rapidly and those countries that cannot afford to adapt
will be most disadvantaged. A key point in the Copenhagen Accord
was a commitment to "reduce global emissions so as to hold
the increase in global temperature below 2°C".[14]
8. If greenhouse gas emissions continue to rise unchecked,
it is likely that global warming will exceed 4°C by the end
of the century.[15] The
Intergovernmental Panel on Climate Change (IPCC) has said that
most developed countries need to reduce their emissions (relative
to 1990 levels) by between 25% and 40% by 2020, and by between
80% and 95% by 2050, to have a 50:50 chance of stabilising temperature
increases below 2°C. The Government said its targets for
reducing emissions and carbon budgets were consistent with the
conclusions of the IPCC and its objective was to limit global
warming to 2°C.[16]
The Secretary of State for Energy and Climate Change, the Rt Hon
Edward Miliband MP, told us remaining below 2°C would prove
to be very challenging.[17]
9. The Committee on Climate Change decided the UK's
objective should be to keep the increase in average mean global
temperature by 2100 as close to 2°C as possible and the probability
of the increase in global mean temperature exceeding 2-4°C
as low as possible.[18]
The Committee believed it was no longer possible with certainty,
or even with high probability, to avoid the danger zone entirely.[19]
There is little chance of keeping temperature increases below
2°C; to do so would require action far in excess of what
the Committee on Climate Change had proposed.[20]
The goal must be to reduce the risk of exceeding 4°C to the
lowest achievable levels. According to the Committee on Climate
Change, to meet this objective global emissions must peak soon
and then fall at 3-4% per annum thereafter.
10. In setting targets for reducing emissions and
carbon budgets the Committee on Climate Change has had to make
judgements and compromises.[21]
Limiting the rise in temperature to less than 2°C could possibly
be justified scientifically[22]
(although we are already destined to experience over 1°C
of warming based on the current atmospheric concentration of greenhouse
gases) and reducing the probability of exceeding 2°C (currently
50%) can be justified against the political and social costs of
achieving that goal. However, neither is currently politically
feasible, as the outcome of the Copenhagen Summit demonstrated
only too depressingly.
11. Professor Paul Ekins, Professor of Energy and
Environment Policy at King's College London, accepted that it
could be argued that the carbon budgets recommended by the Committee
on Climate Change were the maximum consistent with policy possibility
and credibility.[23]
Lord Turner told us that the Committee had sought to describe
a path that was technically feasible, affordable and consistent
with limiting the rise in global temperatures to a level that
was not catastrophic and that was manageable in terms of the adaptation
cost.[24] Professor Hoskins
said the Committee had been unable to identify a realistic scenario
or credible emissions reduction pathway that went beyond what
it had proposed, characterising its recommendations as a compromise
between "what is possible, just possible if we really work
at it, and what we would like in a perfect world".[25]
12. We accept that the Government is broadly right
to use the objective of limiting the rise in average global temperature
to no more that 2°C as the backbone for its targets and budgets.
But it also needs to be thinking about and planning the options
available for reducing emissions further and faster if the scale
of the crisis demands bigger sacrifices now to redeem the future.
This planning should include strategies for securing political
acceptance as well as researching and developing new technical
solutions. The Government must be ready, if needed, to establish
credible emissions reduction pathways that go well beyond what
is currently regarded as politically possible. At
the very least this will be needed as an insurance option if doing
everything that is currently planned turns out not to be enough.
Some policy options, like personal carbon trading, are currently
discounted because they are politically unachievable or too costly.
The Government must shape and inform public opinion so that the
UK will be able, if needed, to reduce its emissions at rates in
excess of what is possible currently. A
failure to make this investment now could lead to an outcome that
is more economically, socially and/or politically challenging
than the options that are currently discounted.
PEAKS AND TIPPING POINTS
13. The rate at which we emit greenhouse gases must
fall, and fall soon. The Copenhagen Accord recognised the need
to achieve "the peaking of global and national emissions
as soon as possible".[26]
The Committee on Climate Change based its analysis on an assumption
that global emissions of greenhouse gases will peak before 2020.
While it focused on 2016, David Kennedy, Chief Executive of the
Committee on Climate Change, told us that its conclusions do not
change much if the global peak in emissions occurs in 2015, 2016
or 2020.[27] But he said
the goal of limiting the rise in temperature to 2°C could
not be met if global emissions peaked later than 2020.[28]
14. But at present, global emissions continue to
rise;[29] a recent report
suggested that emissions rose 29% between 2000 and 2008 with all
of the growth in emissions in developing countries (although at
least a quarter of the growth in these countries was due to the
production of goods for consumption in developed countries).[30]
The Tyndall Centre has argued that, whilst theoretically a peak
in 2016 does permit much lower and more politically acceptable
annual emission reduction rates, it is "at best highly optimistic
and at worst dangerously misleading".[31]
The difficulty and inertia associated with decarbonising energy
supply and the growth of emissions from countries like India and
China make it unlikely that global emissions will peak in 2015
or 2016.[32]
15. Not all of the carbon dioxide released into the
atmosphere remains there. Over half of it is removed by land and
ocean carbon dioxide 'sinks'. The fraction of carbon dioxide removed
by these sinks has decreased over the last 50 years and there
is some evidence that the fraction will decrease further over
coming decades under high-emissions scenarios. As this weakening
of natural sinks progresses it will become harder and harder to
keep the concentration of greenhouse gases in the atmosphere at
a level likely to avoid dangerous climate change.[33]
16. Carbon-cycle feedbacks, where a climate induced
change accelerates climate change, are not fully understood. The
loss of sea ice due to warming seas is an example of such a feedback.
It could result in more of the Sun's energy being absorbed by
the sea rather than reflected by white ice sheets accelerating
the loss of ice sheets.[34]
Another feedback mechanism is linked to the melting tundra. Due
to global warming permafrost is melting releasing methane that
could lead to further warming.[35]
The models used in the IPCC process only include fast feedback
processes such as changes in sea ice, water vapour and aerosols.
Slow feedbacks, such as ice sheet shrinkage, changes in vegetation
or changes in emissions from land and sea in response to global
warming, could mean that climate change could happen much faster
than models predict.[36]
The IPCC has acknowledged that its targets for reducing emissions
may be underestimated due to missing carbon-cycle feedbacks.[37]
They may be missing because they are insufficiently understood
for the risks to be effectively quantified.
17. Tipping points occur when a particular parameter
in a system changes, causing the system to 'flip' into alternative
stable state, for instance, from sea ice to open ocean. Dr James
Hansen has argued that they arise where, without any additional
change in climate, rapid changes in environmental or ecosystems
proceed practically out of control.[38]
A study by the Goddard Institute for Space Studies found that
global warming of 0.6°C in the past 30 years means only moderate
climate change could result in the disintegration of the West
Antarctic ice sheet and Arctic sea ice. Dr Hansen has argued that
the loss of Artic Sea Ice or the West Antarctic Ice Sheet are
potential tipping points.[39]
A recent study has reported that the East Antarctic ice sheet,
which was thought to be stable, has been losing mass for the last
three years.[40] Tim
Lenton et al have argued that society may be lulled into a false
sense of security by smooth projections of global change as variety
of elements within the Earth system could reach tipping points
within this century due to man-made climate change.[41]
It is difficult to predict when and how a system will flip. It
can be a linear response to increasing pressure or occur in a
single catastrophic event or a series of catastrophes or as an
accelerating and self-feeding disaster. Debate about the resilience
of natural systems to such changes is ongoing.
18. Aubrey Meyer, co-founder of the Global Commons
Institute, expressed concern about how carbon-cycle feedbacks
in climate models and failure of carbon sinks were treated by
the Committee on Climate Change in the work that underpinned its
recommendations.[42]
19. Irrespective of how quickly the Copenhagen Accord
can be translated into a legally binding treaty (if this can happen
at all), it is vital that global emissions peak as soon as possible
if domestic action on emissions is to be meaningful. Taking action
later will cost much more than action taken now.[43]
Delay could mean that the rate of emissions reductions needed
in the post-peak period would be much more challenging, going
beyond what the Committee on Climate Change believes is feasible.
It also increases the chance that we will pass some tipping point
in the climate system. The Government's position in international
climate change negotiations must be predicated on getting emissions
to peak as soon as possible. This will be very challenging but
a failure to reverse the rise in global emissions before 2020
could render much of the UK's domestic action meaningless. But
we have to prepare for the worst, and in doing so drive home the
message that a stitch in time is worth nine. The Committee on
Climate Change should be charged with and resourced to advise
on the changes to the UK's targets for reducing emissions and
carbon budgets which may be required if global emissions do not
peak by 2020. The impact of global emissions failing to peak before
2020 should be also considered in Defra's Climate Change Risk
Assessment so that the implications of failing to set and achieve
the necessary budgets can be fully understood. The Committee on
Climate Change's Sub-Committee on Adaptation should be asked to
consider the implications for adaptive action of global emissions
peaking after 2020.
EQUITY AND BURDEN SHARING
20. Rich countries were responsible for emitting
around 70% of the current stock of greenhouse gases which dwell
in the world's atmosphere. The Kyoto Protocol recognised that
there were 'common but differentiated' responsibilities for addressing
climate change because of the historic contribution made by developed
countries. G8 nations signed up to a global target of 50% reductions
by 2050 but recognised that they would need to make much deeper
cuts in their own emissions because of the greater responsibility
borne by developed countries for the damage already done. Many
developing countries argue, with some justification, that their
energy consumption must grow and their emissions may have to rise
as they grow their economies and lift more of their citizens out
of poverty; in India some 450 million people are not connected
to the electricity grid.[44]
21. The issues of equity and burden sharing mean
different countries face different ethical choices in setting
their own targets.[45]
Lord Stern, IG Patel Professor of Economics and Government and
Chair of the Grantham Institute for Climate Change and the Environment
at the London School of Economics, believed that climate stabilisation
would need all countries to achieve broadly the same per capita
emissionspointing out the obvious truth that if any large
group of people was significantly above average a correspondingly
large group would have to be well below average. But the average
was sufficiently demanding for it to be unlikely that the latter
group could emerge and still retain a feasible lifestyle.[46]
The Committee on Climate Change found it difficult to imagine
a global deal that allowed developed countries to have emissions
per capita in 2050 that were significantly above a sustainable
global average.[47]
22. Given a world population predicted to be 9 billion
by 2050, per capita emissions will have to be running at about
2 tonnes CO2e[48]
per annum if the concentration of greenhouse gases is not to exceed
levels likely to induce dangerous climate change.[49]
Each year the United States, Canada, and Australia emit around
20 tonnes CO2e per capita, Europe and Japan around
10 tonnes, China around 5 tonnes, and India around 2 tonnes, while
most of sub-Saharan Africa emits much less than 1 tonne.[50]
An 80% reduction would therefore bring Europe down to about 2
tonnes per capita. USA, Australia and Canada need cuts nearer
90%. But even if OECD emissions can be reduced to almost zero,
non-OECD countries will have to emit no more than 2-2.5 tonnes
per capita as 8 billion people will live there.[51]
23. The Global Commons Institute said that the origins
of the advice from the Committee on Climate Change could be traced
back to the Royal Commission on Environmental Pollution's advocacy
of contraction and convergence in their report 'Energythe
Changing Climate' published in 2000.[52]
The Global Commons Institute promotes contraction and convergence
as a means of resolving the impasse in international negotiations.
Contraction and convergence is a framework for reducing global
emissions of greenhouse gases that envisages global emissions
peaking and then gradually falling (contraction). It achieves
the reduction in emissions by limiting per capita emissions in
such a way that they converge (convergence). It entails large
cuts in per capita emissions for developed countries while allowing
developing countries to continue growing their economies before
they have to make cuts to reach equal per capita emissions. Lord
Turner said that the advice of the Committee on Climate Change
was "reasonably pragmatically close to Contraction and Convergence".[53]
24. The Secretary of State for Energy and Climate
Change said it seemed unlikely that contraction and convergence
would be the basis of a deal in climate negotiations.[54]
He believed it would be opposed in international negotiations;
there was no opposition to the basic idea that per capita emissions
must converge but probably some disagreement with what that implied
about the development paths of particular countries. But he thought
it was a useful idea to have in the background of the negotiations.[55]
The long-term future must bear some relation to the contraction
and convergence modelthe only equitable solution in the
long-term is equal per capita emissions although the path to such
a future will have to take account of the greater burden rich
countries must bear.
25. An approach to setting emission reduction
targets based on equalising per capita emissions globally is sensible
and equitable.
The scientific basis for setting
budgets
26. The IPCC's assessment reports represent the best
consensus on the science of climate change. But new knowledge
is emerging all the time that furthers our understanding of the
influence human activity has on climate and the options we have
to address it.[56] Lord
Turner told us some scientists argued that since the IPCC 4th
Assessment Report new information had emerged that made them more
concerned.[57] Lord Stern
has given four reasons why the position today is more risky than
in 2006 when he published his review of the economics of climate
change:
· emissions
are growing faster than the IPCC trajectory used in the Stern
Review;
· the
absorptive capacity of the planet, including of the oceans, appears
to be lower than many earlier models had assumed;
· new evidence
suggests there might be a greater effect on eventual temperature
for a given increase in the stocks of greenhouse gases; and
· the physical
effects of climate change appear to be happening faster than had
been anticipated.[58]
We recognise that it is impractical to re-consider
policy each time there is a scientific development. Any policy
framework needs some stability if it is to bring about change.
Thus questions arise about how often new scientific developments
should be reviewed and how they should influence established policy.
The challenge is to distil what is robust from what is not.
27. The Association for the Conservation of Energy
was concerned that the carbon budgets needed to take account of
the latest science[59]
and the Met Office recognised that there might be a need to update
targets and budgets in light of new scientific evidence.[60]
Professor Kevin Anderson, Professor of Energy and Climate Change
at the University of Manchester and Director of the Tyndall Energy
Programme, saw this as a job for the Committee on Climate Change,
which he felt should be "driven by the science with some
awareness of the broader political issues".[61]
Lord Turner, however, told us that the Committee was not a scientific
commission and was not geared up to carry out its own research.[62]
While it is vital to take new science and new mitigation options
arising from technical and engineering advances into account,
none of the recent developments have warranted a change in the
Committee on Climate Change's recommendations.[63]
The Government "considers that the Committee [
] has
given full weight to the science in advising on carbon budgets
and targets".[64]
28. Lord Turner told us that the Committee on Climate
Change accepted the IPCC 4th Assessment Report as the clearest
statement of the scientific consensus.[65]
It is true that IPCC reports are developed over an extended timescale
so that they can be subject to extensive peer review and to allow
significant differences to be taken into account; the cut-off
date for submissions to the 2007 IPCC 4th Assessment Report was
December 2006[66] and
scientific papers cited in the IPCC's 4th Assessment Report had
to be published or in press by December 2005.[67]
Professor John Mitchell OBE, Director of Climate Science at the
Met Office, acknowledged that there were concerns about the length
of the IPCC process and the currency of the consensus it represented,[68]
and argued that while it could validly base its recommendations
on the IPCC assessments it should also look carefully at any new
developments that stood up to scientific scrutiny.[69]
Lord Turner said the Committee would look at the scientific evidence
every four or five years and did not see any value in reviewing
it every year.[70] The
Committee on Climate Change will review scientific developments
as part of the work that it will do to prepare its advice for
the fourth budget period (2023-2027) to be published in 2010.[71]
29. Science will always run ahead of policy and it
is a key part of the process that the scientific evidence base
will be used to inform political judgements and decisions. Uncertainties
are fundamental to all science and are not just a feature of climate
science; other policy areas, like public health, face similar
challenges. The Committee on Climate Change is right to use
the IPCC's findings as a basis for its work. But they must keep
scientific developments under review, first as part of the review
that will be undertaken in preparing its advice on the fourth
budget period, and second following the publication of the IPCC's
5th Assessment Report. The Government should provide the resources
to allow the Committee on Climate Change to strengthen its scientific
capability so that it can monitor developments in between these
formal review points.
30. The need to review budgets in the light of new
scientific developments must be weighed against the need for stability
and predictability in the policy framework. Science has several
times revised upwards the estimates of the extent of the temperature
rise for a given increase in the concentration of greenhouse gases
and the extent of the impacts of a given temperature rise. The
constant message, and one that is entirely consistent with the
Stern Review, is that the emphasis should be on reducing emissions
as much as possible and as early as possible.[72]
Notwithstanding that the IPCC reports currently represent the
best consensus in the science the Committee on Climate Change
and the Government should take into account that the growing evidence
base for climate change impacts is reducing levels of scientific
uncertainty, emissions are still growing and impacts are occurring
faster and in more damaging ways than was previously thought likely.
Both the Committee on Climate Change and the Government must be
open to the possibility that as our scientific knowledge and understanding
grows the case for taking action beyond the commitments we have
already made will grow. There is a case for taking a more precautionary
approach and adopting targets at the upper end or in excess of
what is currently recommended by the IPCC.
AN APPROPRIATE LEVEL OF RISK?
31. The targets and budgets recommended by the Committee
on Climate Change are designed to give about a 50:50 chance that
temperatures will exceed 2°C by 2100, on the basis of the
current state of scientific knowledge. The key question that needs
to be addressed is whether it is possible to increase the chance
of keeping any rise in temperature to below 2°C by cutting
emissions faster.
32. Several witnesses suggested that it was possible
to reduce the risk of exceeding 2°C.[73]
The Institute of Actuaries' Resource and Environment Group argued
that the level of risk associated with the Committee on Climate
Change's recommendations was at least an order of magnitude higher
than society would accept.[74]
Friends of the Earth contended that the carbon budgets embodied
too high a level of risk. They noted that the IPCC had defined
levels of risk[75] and
'unlikely' was equated to a risk of 33% or lower[76]
and a probability between 33% and 66% was regarded as 'as likely
as not' on the IPCC's scale. The German Advisory Council on Global
Change, using a global budget that had a 66% chance that warming
could be kept below 2°C, came up with a much smaller available
carbon budget.[77] The
Global Commons Institute proposed a scenario for reducing emissions
that it argued had better odds of keeping within 2°C than
that proposed by the Committee on Climate Change.[78]
33. In the modelling done for the Committee on Climate
Change, the Met Office examined several distributions of uncertainty
for climate sensitivity and selected ones that tended to give
a lower probability of staying under a 2°C global warming
target.[79] Dr Jason
Lowe, from the Met Office, argued that the choice of climate sensitivity
meant the Committee on Climate Change's recommendations were based
on an inherently precautionary approach.[80]
Lord Turner said it was possible to devise a pathway that would
limit the chances of going above 2°C to less than 20% but
this would have produced targets which were not be politically
achievable. Nor might such targets be a rational economic and
political choice (that is to say that the world might be better
off accepting a slightly greater degree of warming and then adapting
to it).[81] He pointed
out that "If you were to set the target as being [
]
a 99% certainty of not going above 2°C we would have to start
dramatically de-industrialising today."[82]
He was more concerned about keeping the risk of exceeding 3 or
4°C to very low levels than reducing the risk associated
with exceeding 2°C.[83]
34. There are currently no credible ways to reduce
emissions faster than the Committee on Climate Change has recommended.
The Government should prioritise reducing the likelihood that
temperatures will exceed 2°C down from a level that is 'as
likely as not' to at least 'unlikely'. This is more important
than aiming for a lower temperature rise target. In the meantime
the Committee on Climate Change should continue to ensure that
its advice is framed in terms of keeping the risks of exceeding
3 or 4°C to very low levels.
7 Committee on Climate Change, First Report of the
Committee, Building a low carbon economy- the UK's contribution
to tackling climate change, December 2008, p20. Back
8
University of Copenhagen, Synthesis Report from Climate Change:
Global Risks, Challenges & Decisions, held in Copenhagen
March 2009, http://climatecongress.ku.dk/pdf/synthesisreport Back
9
Q 228 Back
10
University of Copenhagen, Synthesis Report from Climate Change:
Global Risks, Challenges & Decisions, held in Copenhagen
March 2009, http://climatecongress.ku.dk/pdf/synthesisreport Back
11
University of Copenhagen, Synthesis Report from Climate Change:
Global Risks, Challenges & Decisions, held in Copenhagen
March 2009, http://climatecongress.ku.dk/pdf/synthesisreport Back
12
Q 2 [Hoskins] Back
13
University of Copenhagen, Synthesis Report from Climate Change:
Global Risks, Challenges & Decisions, held in Copenhagen
March 2009, http://climatecongress.ku.dk/pdf/synthesisreport Back
14
UNFCCC, The Copenhagen Accord, December 2009, http://unfccc.int/files/meetings/cop_15/application/pdf/cop15_cph_auv.pdf Back
15
Met Office, Four degrees and beyond, September 2009 Back
16
Ev 101 Back
17
Q 257 Back
18
Qq 228-229 Back
19
Committee on Climate Change, First Report of the Committee, Building
a low carbon economy- the UK's contribution to tackling climate
change, December 2008, p20 Back
20
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Qq 3-4 Back
21
Q 155 [Allen] Back
22
Ev 75 Back
23
Ev 75 Back
24
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Q 6 Back
25
Q 5 [Hoskins] Back
26
UNFCCC, The Copenhagen Accord, December 2009, http://unfccc.int/files/meetings/cop_15/application/pdf/cop15_cph_auv.pdf Back
27
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Q 2 [Mr Kennedy] Back
28
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Q 2 [Mr Kennedy] Back
29
Q 76 Back
30
BBC News website, Earth heading for 6°C of warming,
4 November 2009, news.bbc.co.uk/1/hi/sci/tech/8364926.stm Back
31
Tyndall Centre, Making a climate commitment: analysis of the
first report (2008) of the UK Committee on Climate Change,
March 2009 Back
32
Tyndall Centre, Making a climate commitment: analysis of the
first report (2008) of the UK Committee on Climate Change,
March 2009 Back
33
Ev 22-23 Back
34
Parliamentary Office of Science and Technology, POSTnote, Artic
changes, Number 334, June 2009 Back
35
Parliamentary Office of Science and Technology, POSTnote, Artic
changes, Number 334, June 2009 Back
36
New Scientist, 'Climate Catastrophe', 28 July 2007 Back
37
Public Interest Research Centre, Climate Safety, November
2008 Back
38
Hansen et al, Target Atmospheric CO2: where should
humanity aim?, Open Atmospheric Science Journal. (2008), vol.
2, pp. 217-231 Back
39
Hansen et al, Target Atmospheric CO2: where should
humanity aim?, Open Atmospheric Science Journal. (2008), vol.
2, pp. 217-231 Back
40
BBC News, East Antarctic ice sheet may be losing mass,
22 November 2009 Back
41
Lenton, T. M., H. Held, E. Kriegler, J. W. Hall, W. Lucht, S.
Rahmstorf and H. J. Schellnhuber (2008) Tipping elements in
the Earth's climate system, Proceedings of the National Academy
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42
Qq 62-63 and Ev 16-18 Back
43
HMT, The Stern Review: The Economics of Climate Change,
October 2006 Back
44
Q 264 Back
45
Ev 102 Back
46
Stern, Key elements in a global deal on climate change,
LSE, 2008 Back
47
Committee on Climate Change, First Report of the Committee, Building
a low carbon economy- the UK's contribution to tackling climate
change, December 2008 Back
48
Greenhouse gas emissions are often given in terms of an equivalent
amount of carbon dioxide-CO2e. Back
49
Stern, Key elements in a global deal on climate change,
LSE, 2008 Back
50
Hepburn and Stern, A new global deal on climate change,
Oxford Review of Economic Policy, Vol 24, Nov 2008, p266 Back
51
Hepburn and Stern, A new global deal on climate change,
Oxford Review of Economic Policy, Vol 24, Nov 2008, p266 Back
52
Ev 14 Back
53
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Q 10 Back
54
Q 261 Back
55
Q 261 Back
56
University of Copenhagen, Synthesis Report from Climate Change:
Global Risks, Challenges & Decisions, held in Copenhagen
March 2009, http://climatecongress.ku.dk/pdf/synthesisreport Back
57
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Q 13 Back
58
Stern, Key elements of a global deal on climate change,
LSE, 2008 Back
59
Ev 127 Back
60
Ev 53 Back
61
Q 91 Back
62
Q 228 Back
63
Qq 39-45 Back
64
Ev 105 Back
65
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Q 13 Back
66
Public Interest Research Centre, Climate Safety, November
2008 Back
67
IPCC Working Group I, Schedule for Fourth Assessment Report, http://ipcc-wg1.ucar.edu/wg1/docs/wg1_timetable_2006-08-14.pdf Back
68
Q 127 Back
69
Q 128 Back
70
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Q 13 Back
71
Q 45 [Kennedy] Back
72
Ev 75 Back
73
Ev 39, Ev 131 and Q 66 and Q 71 Back
74
Ev 122 Back
75
IPCC, Guidance Notes for Lead Authors of the IPCC Fourth Assessment
Report on Addressing Uncertainties, July 2005, www.ipcc.ch/pdf/supporting-material/uncertainty-guidance-note.pdf Back
76
Ev 131 Back
77
German Advisory Council on Global Change, The WBGU Budget Approach,
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78
Ev 39 ff. Back
79
Ev 54 Back
80
Q 115 [Lowe] Back
81
Oral evidence taken before the Environmental Audit Committee on
4 February 2009, HC (2008-09) 234, Q 6 Back
82
Q 228 Back
83
Q 229 Back
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