An Overview of the Intergovernmental Panel on Climate Change (IPCC) and Its Process of Science Assessment

SIR JOHN HOUGHTON

1 Background

It has been known for about 175 years that the presence in the atmosphere of 'greenhouse gases' such as carbon dioxide that absorb in the infrared part of the spectrum leads to a warming of the Earth's surface through the 'greenhouse' effect. The first quantitative calculation of the effect on the atmosphere of increased carbon dioxide concentrations was made by the Swedish scientist Svante Arrhenius in 1896. In the 1960s, Charles Keeling and his colleagues began a regular series of accurate observations of atmospheric carbon dioxide concentration from the Mauna Loa Observatory in Hawaii. These showed increasing values as a result of human activities, mainly the burning of fossil fuels. By the 1980s, as the rate of increase of carbon dioxide concentration became larger, the possible impact on the global climate became a matter of concern to politicians as well as scientists. The report of a scientific meeting held at Villach, Austria in 1985 (SCOPE 29,1986) under the auspices of the Scientific Committee on Problems of the Environment (SCOPE) of the International Council of Scientific Unions (ICSU) began to alert governments and the public at large to the potential seriousness of the issue. Estimates were made that the carbon dioxide concentration could double before the end of the 21st century. In 1986, three international bodies, the World Meteorological Organisation (WMO), the United Nations Environment Programme (UNEP) and the International Council of Scientific Unions (ICSU), who had co-sponsored the Villach conference, formed the Advisory Group on Greenhouse Gases (AGGG), a small international committee with responsibility for assessing the available scientific information about the increase of greenhouse gases in the atmosphere and the likely impact.

2 Formation of the IPCC

What was new about the problem of global warming' (as the climate change due to the increase of gases began to be called) was that it is an example of global pollution or pollution on the global scale, i.e. pollution emitted by one person locally that has global effects. This can be compared with pollution due to human activities on a local scale, of air, water or land that has been around for a very long time. The other example of global pollution which was recognized about the same time is the damage to the ozone layer in the stratosphere that results from the release of small quantities of chemicals containing chlorine (e.g. the chloro-fiuorocarbons or CFCs).

The existence of global pollution requires global solutions, i.e. solutions that are organized on a global scale. In the late 1980s, therefore, as political concern began to be expressed about the possibility of deleterious climate change, the organization of that concern was international, as indeed had been the work of the scientists on which the political concern was based. In June of 1988 an international conference was staged 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 publicized.

It was therefore timely that in 1988 a new international scientific body to address the issue, the 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 and WGIII to address the policy options. I was appointed chairman of WGI and I will illustrate from my experience of that Working Group the work of the IPCC and how, through the IPCC, scientists have been able to assist in the determination of policy.

The establishment of the IPCC followed closely that of the Montreal Protocol which had been set up in the previous year, 1987, by UNEP and WMO to address the problem of the depletion of stratospheric ozone by CFCs and related chlorine-containing chemicals. 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. However, 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 arena through which problems of global pollution could be addressed. It was therefore appropriate that the IPCC should build on this experience. The development within the IPCC of ways to involve large numbers of scientists and of formal procedures for peer review in turn influenced the on-going work of the Assessment Panels of the Montreal Protocol.

3 The IPCC 1990 Report

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 that resulting from the Villach conference (SCOPE 29), again under the chairmanship of Bert Bolin as mentioned in the introduction. 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 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 eleven 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...