1 Introduction
1. The Intergovernmental Panel on Climate Change
(IPCC) is an international body for the assessment of climate
change. Its aim is to provide the world with a scientific view
on the current state of climate change knowledge and its potential
environmental and socio-economic impacts. The IPCC has been influential
in providing the justification for national and international
action to prevent dangerous climate change. It has, however, come
under criticism that it is unduly influenced by national political
agendas and that it has not satisfactorily addressed criticisms
which have been levelled against it.
2. Our inquiry aimed to explore the latest conclusions
of the IPCC's Working Group I (WGI) contribution to its Fifth
Assessment Report (AR5) which looked at the physical science of
climate change.[1] Specifically,
we were interested in the process the IPCC went through to produce
the report, the extent to which the conclusions were robust and
what impact, if any, these conclusions had on national and international
policy making. We launched our inquiry on 22 October 2013. The
terms of reference can be found online.[2]
We received 62 pieces of written evidence. We held three oral
evidence sessions. A full list of witnesses can be found at the
back of this report and on our website.[3]
We are very grateful to all those who took the time to contribute
to this inquiry.
3. In Chapter 1 we provide a summary of the work
of the IPCC and the WGI contribution to AR5. Chapter 2 assesses
the procedures by which the report was produced. Chapter 3 evaluates
the scientific conclusions drawn in the report. Finally, Chapter
4, explores the implications of the report for national and international
policy making.
WGI contribution to the Fifth
Assessment Report
4. The IPCC was founded in 1988 under the auspices
of the United Nations (UN) with the aim of reviewing, assessing
and reporting on the most recent scientific, technical and socio-economic
information produced worldwide and relevant to the understanding
of climate change. The IPCC consists of three Working Groups (WGI,
WGII and WGIII). Every six or seven years, each reports on a certain
aspect of climate change, together generating a comprehensive
Assessment Report. WGI exclusively reports on the physical scientific
evidence for climate change, WGII focuses on impacts, adaptation
and vulnerability and WGIII examines options for mitigating the
impacts. Over the course of its lifetime, the IPCC has overseen
the publication of five such Assessment Reports. The latest (AR5)
was published over the course of 2013 and 2014.
5. The WGI contribution to the AR5 is large and comprehensive.
In over 1,500 pages containing more than 1 million words, it details
the current thinking on the state of the climate through reference
to 9,200 published scientific papers, compiled over a five-year
period by more than 250 authors from nearly 40 countries. Across
the 14 chapters of the report, the WGI contribution to AR5 addresses
the most recent observations of changes to the land, sea and air
temperatures, atmospheric composition and dynamics, rainfall,
glaciers, ice sheets and oceans. The report also offers explanations
for the observed changes and, crucially, projects what climate
changes are likely to occur in the future. The key conclusion
from the WGI contribution to AR5 concerns the impact of greenhouse
gases emitted by humans:
Human influence has been detected in warming
of the atmosphere and the ocean, in changes in the global water
cycle, in reductions in snow and ice, in global mean sea level
rise, and in changes in some climate extremes. This evidence for
human influence has grown since AR4. It is extremely likely
that human influence has been the dominant cause of the observed
warming since the mid-20th century. […]. Continued emissions
of greenhouse gases will cause further warming and changes in
all components of the climate system. Limiting climate change
will require substantial and sustained reductions of greenhouse
gas emissions.[4]
6. The IPCC's Assessment Reports are respected by
the international scientific and policy communities alike. Some
have argued that there is no equivalent process in any other area
of science.[5] Professor
Sir David King, the Foreign Secretary's Special Representative
for Climate Change and a former Chief Scientific Adviser to the
Government, remarked that:
[The IPCC AR5] is an enormous piece of work by
the scientific community and it can only be said that there is
no better account of the current state of understanding of climate
science than represented by that report. It is a very hefty piece
of work. It has been extremely carefully constructed and the summary
is exemplary in its presentation.[6]
The conclusions of the IPCC's past Assessment Reports
(notably AR3 and AR4) have provided the justification for national
and international action to prevent dangerous climate change and
formed the scientific underpinning of UK legislation such as the
Climate Change Act 2008. This Act sets a legal obligation for
the UK to cut its greenhouse gas emissions by 80% (compared to
1990 levels) by the year 2050.[7]
The target is to be achieved through the setting of a series of
interim carbon budgets-which set an emissions reduction trajectory
across key sectors in the economy. The scientific conclusions
of the IPCC underpin the setting of these targets.[8]
With such challenging targets in place to prevent the impacts
of dangerous climate change, it is critical that the IPCC presents
the most accurate and up-to-date conclusions and projections possible.
The importance of the conclusions of the reports in terms of their
policy implications understandably places the IPCC under a lot
of scrutiny. Criticism has been levelled at both the process by
which the IPCC Assessment Review is undertaken and the conclusions
that are drawn. We explore these issues further in Chapters 2
and 3.
1 IPCC Working Group I Contribution to AR5, Climate Change 2013: The Physical Science Basis
(2013) Back
2
Energy and Climate Change Committee, Call for evidence on IPCC 5th Assessment Review,
22 October 2013 Back
3
Energy and Climate Change Committee, 'IPCC 5th Assessment Review, oral evidence'
accessed 15 July 2014 Back
4
IPCC Working Group I Contribution to AR5, Summary for Policymakers, Climate Change 2013: The Physical Science Basis
(2013) p17 and p19 Back
5
Q232 [Professor MacKay], Corinne Le Quéré and Andrew
Watkinson (IPC 050) Back
6
Oral evidence taken on 25 March 2014, HC (2013-14) 1190, Q86 [Professor
Sir David King] Back
7
Climate Change Act 2008, section 1 Back
8
Climate Change Act 2008, section 4 Back
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