Select Committee on Science and Technology Minutes of Evidence

Annex I

  A description of the formation and the work of the IPCC based on a draft prepared for an Environmental Encyclopaedia to be published by Wiley.

  The Intergovernmental Panel on Climate Change: Working Group I.

  John Houghton, Co-chairman, Working Group I (Scientific Assessment), Intergovernmental Panel on Climate Change (IPCC).


  It has been known for well over 100 years that the presence in the atmosphere of gases such as carbon dioxide leads to a warming of the Earth's surface. In 1896, Sverre Arrhenius, a Swedish chemist, first computed the amount of warming that would occur should the amount of carbon dioxide in the atmosphere double. In the 1960s, observations made by Charles Keeling from the Manna Loa Observatory on Hawaii showed that atmospheric carbon dioxide concentrations were increasing significantly. However, it was not until the 1980s that it began to be generally recognised that increased human activities involving the burning of fossil fuels (coal, oil and gas) was resulting in a large increase in atmospheric carbon dioxide and a probable doubling of its pre-industrial concentration before the end of the 21st century. The possibility of serious consequences to the world's climate was increasingly raised by scientists and those with environmental concern.[2] This is an example of global pollution—pollution by one person locally that has global effects.

  In 1988 an international conference was held in Toronto which for the first time pressed for specific international action to mitigate climate change. It was in that year too that world leaders began to speak out about it; for instance, Mrs Thatcher expressed her concern in a speech to the Royal Society of London that was widely publicised. It was therefore timely that in 1988 a new scientific body to address the issue, the Intergovernmental Panel on Climate Change (IPCC) was set up jointly by the World Meteorological Organisation (WMO) and the United Nations Environment Programme (UNEP). Bert Bolin from Sweden, a scientist with a distinguished record of contributions to the science of climate, agreed to chair the IPCC. Three Working Groups were established, WGI to address the science of anthropogenic climate change, WGII to address the impacts of climate change, and WGIII to address the policy options. IPCC WGI has prepared comprehensive assessments of the science of anthropogenic Climate Change in 1990 and 1995 together with a number of other more limited assessments and technical reports. A further comprehensive report is being prepared for publication in 2001.

  In its structure the IPCC followed closely the structure of the Assessment Panels of the Montreal Protocol which had been set up in 1987 by UNEP and WMO to address the problems of the depletion of stratospheric ozone by CFCs and related chlorine containing chemicals—another example of global pollution. Through the negotiation of the Protocol, with its arrangements for inputs from scientists and other experts, methods had begun to be developed in the international community through which global pollution problems could be addressed. Although this problem addressed by the Montreal Protocol was a more limited one than that of global climate change, especially in the range and size of the human activities that contribute to it, it was appropriate that the IPCC should build on this experience in addressing climate change issues. The development within the IPCC of ways to involve large numbers of scientists and of formal procedures for peer review in turn influenced the ongoing work of the Assessment Panels of the Montreal Protocol.


  It was agreed at the first meeting of the IPCC that a new assessment of the whole issue of anthropogenic climate change should be prepared. There had, of course, been assessments before of the climate change issue, notably one published in 1986[4] organised under the auspices of the Scientific Committee on Problems of the Environment (SCOPE) of the International Council for Science (ICSU) again under the chairmanship of Bert Bolin. The IPCC saw its task as updating previous assessments but with a difference. Previous assessments had involved relatively few of the world's leading climate scientists. Because of the global nature of the issue that brought with it a large measure of international concern, the IPCC's ambition from the start was to involve as many representatives as possible from the world scientific community in the new assessment.

  To assist in the preparation of the WGI report, a small Technical Support Unit was set up within the part of the UK Meteorological Office at Bracknell which was concerned with Climate Research. The report comprised 11 chapters totalling over 300 pages dealing with different components of the scientific issue together with a Policymakers' Summary and an Executive Summary. Twelve international workshops were held to address these different components. One hundred and seventy scientists from 25 countries contributed to the report either through participation in the workshops or through written contributions. A further 200 scientists were involved in the peer review of the draft report. The thorough peer review played an important part in ensuring the achievement of a high degree of consensus amongst the authors and reviewers regarding the report's conclusions.

  The Policymaker's Summary (20 pages) together with its Executive Summary (two pages) were based on the conclusions presented in the chapters and were prepared particularly to present to those without a strong background in science a clear statement of the status of scientific knowledge at the time and the associated uncertainties. In preparing the first draft of the Policymakers' Summary, the Lead Authors of the chapters were first involved; it was then sent out for the same wide peer review as the main report. A revised draft of the Summary was then discussed line by line at a Plenary Meeting of the Working Group attended by government delegates from 35 countries together with lead authors from the chapters. The final wording was agreed at that meeting. A flavour of the style and content of the report is given by the first few paragraphs of the Executive Summary that read as follows:

We are certain of the following:

    —  there is a natural greenhouse effect which already keeps the Earth warmer than it would otherwise be;

    —  emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases: carbon dioxide, methane, chlorofluorocarbons (CFCs) and nitrous oxide. These increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth's surface. The main greenhouse gas, water vapour, will increase in response to global warming and further enhance it.

We calculate with confidence that:

    —  some gases are potentially more effective than others at changing climate, and their relative effectiveness can be estimated. Carbon dioxide has been responsible for over half the enhanced greenhouse effect in the past, and is likely to remain so in the future;

    —  atmospheric concentrations of the long-lived gases (carbon dioxide, nitrous oxide and the CFCs) adjust only slowly to changes in emissions. Continued emissions of these gases at present rates would commit us to increased concentrations for centuries ahead. The longer emissions continue to increase at present day rates, the greater reductions would have to be for concentrations to stabilise at a given level;

    —  the long-lived gases would require immediate reductions in emissions from human activities of over 60 per cent to stabilise their concentrations at today's levels; methane would require a 15 to 20 per cent reduction.

Based on current model results, we predict:

    —  under the IPCC Business-as-Usual (Scenario A) emissions of greenhouse gases, a rate of increase of global mean temperature during the next century of about 0.3oC per decade (with an uncertainty range of 0.2oC to 0.5oC per decade); this is greater than that seen over the past 10,000 years. This will result in a likely increase in global mean temperature of about 1oC above the present value by 2025 and 3oC before the end of the next century. The rise will not be steady because of the influence of other factors.

  Later sections of the summary addressed the scientific uncertainties and the question of the degree to which anthropogenic climate change had been observed in the climate record.

  Over the period of the preparation of the IPCC report, a significant change occurred in the attitudes of the scientists involved. To begin with, many scientists felt that the scientific uncertainty was too large for any useful statement to be made regarding future climate change. However, increasingly the scientists realised their responsibility to articulate carefully and honestly the available knowledge. This responsibility seemed all the more important because many individuals not possessing much expert scientific knowledge were making forecasts of future climate change—often of an extreme kind. Also, it was increasingly recognised that there was enough certainty in the science to provide meaningful information regarding the likely future provided that the uncertainty was also fully explained.


  Many of the world's leading scientists in the field of climate and climate change contributed to the report. Inevitably they came mostly from developed countries. However, a significant number of contributors from developing countries were also involved. That so many of the world's scientists contributed or were involved in the review process meant that there was a genuine feeling of ownership of the report by the world scientific community.

  The IPCC process led to a significant degree of consensus. It is sometimes pointed out that "consensus" amongst scientists is not necessarily a sign of scientific health; argument and disagreement are seen to be more usual building blocks of scientific advance. But the "consensus" achieved by the IPCC is not complete agreement about everything. It is agreement particularly about what we know and what we do not know—distinguishing clearly those matters about which there is reasonable certainty from those where there remains much uncertainty and where there continues to be lively debate and disagreement. It is this limited "consensus" which is reflected in the Executive Summary of the 1990 IPCC Report which has been widely acclaimed for the clarity and crispness of its presentation.

  It was clear from an early stage that not only was the scientific content of the assessment important but also the way in which it was presented. Scientists left to themselves do not always recognise what is relevant to policymakers or present their material with the maximum clarity. Further, the presentation of a scientific document can appear to a policymaker to convey a political message even though none was intended.

  It has therefore been helpful in the presentation of the science of climate change to involve policymakers themselves or their representatives in the formulation of the summary of the reports. For instance they were full participants in the government review process and in the Working Group Plenary Meeting which agreed the wording of the report. The report was greatly improved in its relevance and clarity through their participation. In addition because governments participated in the process, they felt to own the report.

  The IPCC was therefore able to provide to the Earth Summit at Rio in 1992 a clear assessment of the science of climate change that was owned both by the world scientific community and by governments. These characteristics were essential to providing governments with the confidence to formulate and sign the Framework Convention on Climate Change at that 1992 Conference and to take appropriate action. They have continued to be essential in the generation of subsequent reports which have provided input to the on-going work of the FCC, for instance to the Kyoto Protocol of 1997.

THE 1992, 1994 AND 1995 IPCC REPORTS

  As soon as the 1990 report was complete, the IPCC began work on further reports. In 1992, in time for the Earth Summit, WGI produced a report updating what was known about greenhouse gases[5], their sources and sinks, and about observations and modelling of climate change. In addition the 1992 report developed various emission scenarios for the emissions of greenhouse gases over the 21st Century based on a variety of assumptions regarding factors such as world population, economic growth, availability of fossil fuels etc.

  The 1994 report updated the information and analysis regarding the radiative forcing of the various greenhouse gases[6]. Of particular importance was the new work carried out on the profiles of emissions of carbon dioxide and other greenhouse gases which would lead to the stabilisation of these gases in the atmosphere at different levels of concentration.

By 1995, when the IPCC produced its second comprehensive assessment[7], five years after the first assessment in 1990, the community of scientists involved with the IPCC had become substantially greater. More scientists from more countries were involved both in the report's preparation (about 480 scientists from more than 25 countries) and in its review (over 500 from 40 countries). The participants at the Plenary Meeting of Working Group I that approved the Summary for Policymakers included 177 delegates from 96 countries, representatives from 14 non-governmental organisations and 28 Lead Authors. Regarding climate change over the next century and its likely impacts the messages of the 1995 report were essentially the same as those of the 1990 report. Some further detail had emerged during the five years in between, especially regarding the likely contribution to climate change from atmospheric aerosols—the fine particles that are present in the atmosphere as a result of industrial activity. Also, there was more confidence amongst scientists that the historical increase in global average temperatures that has occurred since wide-scale industrialization might be the result of anthropogenic change. The WGI Plenary Meeting debated for a considerable time how to express this somewhat greater scientific confidence in the interpretation of the recent climate record—although still surrounded by much uncertainty. A sentence carefully crafted by the meeting was unanimously agreed by the delegates: "the balance of evidence suggests a discernible human influence on global climate."


  The United Nations Framework Convention on Climate Change (FCCC) signed by close to 160 countries at the Earth Summit in Rio de Janeiro in June 1992 sets the context in which international discussion regarding appropriate action can be pursued. The development of the Convention's agenda clearly requires continuous scientific and technical input. The Conference of the Parties (COP) to the FCCC has set up a Subsidiary Body for Science and Technological Advice (SUBSTA) to organise this input. The IPCC is working closely with SUBSTA through a Joint Working Group (JWG) to ensure that IPCC assessments are geared to provide the detailed scientific and technical input required.

  The objective of the FCCC is contained in Article 2. It recognises the need to prevent continued change of the climate. It reads as follows:

    "The ultimate objective of this Convention and any related legal instruments that the Conference of the Parties may adopt is to achieve, in accordance with the relevant provisions of the Convention, stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time frame 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 manner."

  The IPCC has been at pains to explain that what constitutes "dangerous" is a policy not a scientific decision. But the need to make such policy decisions immediately raises many scientific and technical questions. For instance, what carbon dioxide emission profiles will lead to stabilisation of atmospheric concentration and by when? What effect will current proposed emission limitations by developed countries have on atmospheric concentrations? What technologies, policies and measures might be available for mitigating climate change? How vulnerable are different regions of the world to possible climate change? To assist in answering these questions the IPCC has produced a series of Technical Papers addressing the detail of some of the issues involved.

  An issue which has been highlighted by the third session of the COP at Kyoto in 1997 is that of the contributions which are made by deforestation, aforestation, reforestation and changes in land use to the sources or sinks of greenhouse gases, especially of carbon dioxide. This is an area where what is meant by different human activities (eg de-, a-, or re-forestation) requires very careful definition, where there is much scientific uncertainty and where there are large possibilities for the propagation of perverse incentives. The IPCC is already very involved in this area through its work on the development of detailed guidelines[8] for the production of national inventories of greenhouse gases which include both sources and sinks. It is the IPCC Guidelines to which the Kyoto Protocol refers. A Special Report on Land Use and Forestry addresses these issues[9].


  Preparation is now starting for a third comprehensive assessment report to be completed in 2001 that will take into account the large growth in research in both the natural sciences and the social sciences in topics related to climate change, its impacts and its mitigation. In carrying out this assessment the IPCC will ensure that it is relevant to the policy needs of the FCCC and will also ensure that the process of assessment continues to be open, transparent and rigorous and continues to involve as many in the world scientific community as possible.

  The question is often asked as to whether the IPCC provides a pattern or a model for providing the means for scientists from all disciplines to provide input to policy determination in other areas of concern. The elements which we have mentioned which have been critical to the success of the IPCC have been those of: (1) ensuring the widest possible participation by experts from all relevant disciplines; (2) ensuring a clear separation between scientific assessment and policy determination and (3) through the close involvement of the expert community, of governments and, more recently, of relevant industry, ensuring wide ownership not only by the community of experts but also by those who have a stake in the policy process. Although anthropogenic climate change is perhaps the largest and most complex problem concerned with the global environment that we face, it is not unique. Models similar to that of the IPCC with its essential elements could be applied elsewhere. The development of the work of the IPCC has demonstrated the enormous capacity for the international community to work together towards the common aims of care for humanity and care for the environment and provides encouragement in the belief that problems as complex as that of climate change are capable of solution.

2   A comprehensive account of Global Warming and Climate Change can be found in, John Houghton, "Global Warming: the Complete Briefing" second edition, Cambridge University Press, 1997. Back

3   Climate change, the IPCC Scientific Assessment, eds JT Houghton, GJ Jenkins and JJ Ephraums, Cambridge University Press, 1990. Back

4   SCOPE 29, The Greenhouse Effect, Climatic Change and Ecosystems, eds Bert Bolin, Bo Doos, Jill Jager and Richard Warrick, John Willey 1986. Back

5   Climate Change 1992: the Supplementary Report to the IPCC Assessment, eds J T Houghton, B A Callander and S K Varney, CUP, 1992. Back

6   Climate Change 1994: Radiative Forcing of Climate Change and an Evaluation of the IPCC IS92 Scenarios, eds J T Houghton, L G Meira Filho, J Bruce, Hoesung Lee, B A Callander, E Haites, N Harris and K Maskell, CUP, 1996. Back

7   Climate Change 1995: the Science of Climate Change, eds J T Houghton, L G Meira Filho, N Harris, A Kattenberg and K Maskell, CUP, 1996; Climate Change 1995: Impacts, Adaptation and Mitigation of Climate Change, eds R T Watson, M C Zinowera and R H Moss, CUP, 1996; Climate Change 1995: Economic and Social Dimensions of Climate Change, eds J Bruce, Hoesung Lee and E Haites, CUP, 1996. Back

8   IPCC Guidelines for National Greenhouse Gas Inventories. IPCC Secretariat, World Meteorological Organisation, Geneva, 1995. Back

9   IPCC Special Report on Land Use Change and Forestry due for completion in May 2000-reference to completed in proof. Back

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