Intergovernmental Panel on Climate Change Fifth Assessment Report: Review of Working Group I contribution - Energy and Climate Change Contents

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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Prepared 29 July 2014