Select Committee on Science and Technology Minutes of Evidence

Memorandum submitted by Sir John Houghton CBE, Co-Chairman of Working Group I of the Intergovernmental Panel on Climate Change (IPCC)

  1.  The IPCC was set up in 1988 jointly by two United Nations bodies, the World Meteorological Organisation and the United Nations Environment Programme, its purpose being to provide authoritative assessments of anthropogenic climate change. Three Working Groups (WGs) were formed, WGI to assess the Science of Climate Change and WGs II and III to assess the impacts, adaptation, mitigation and policy options associated with Climate Change. I have served as WGI Chairman or Co-chairman (each WG now has two co-chairs one from a developed country and the other from a developing country) since 1988.

  2.  Annex I describes the IPCC and its workings in some detail. I am also sending for members of the Committee copies of the Summary for Policy Makers and the Technical Summary of the IPCC 1995 Report.[1] The essential points to note are that (1) through the involvement of a high proportion of the world's climate scientists (including many of the world's leading scientists in the area) ownership of IPCC reports by the world scientific community has been achieved, and (2) through the involvement of governments in the review process and in the approval of the Summary for Policymakers, ownership of the reports by the world's governments has also been achieved. The IPCC has therefore played a key role in advising governments on the science, the impacts and the policy options regarding climate change.

  3.  The UK Meteorological Office has been involved in research into Climate Change since the 1960s when there was concern that human alteration of the climate might be used as a military weapon. Because of its strong capability in atmospheric and ocean modelling it became one of the world's leading centres in climate modelling, a position which was further strengthened by the establishment of the Hadley Centre in 1990 with joint funding from the Department of the Environment and the Ministry of Defence. The Hadley Centre also houses the Technical Support Unit (TSU) for WGI of the IPCC, a small group that organises the international process for the preparation and review of the IPCC reports. The availability of the best scientific and technical advice especially from the Hadley Centre and the IPCC has enabled the UK government to play a crucial role in the international negotiations concerning climate change in the context of the Framework Convention on Climate Change (FCCC).

  4.  I now address the particular questions raised in your letter to me requesting evidence.

  5.  Question 1. What other reasonable potential alternative explanations for climate change, other than increasing levels of CO2 exist? How does the IPCC assess these? How are its funds disseminated?

  First it is important to recognise the substantial natural variability of climate that arises especially because of interactions between the various components of the climate system (the atmosphere, the oceans, the land, the ice and the biosphere). Superposed on these variations are climate changes due to changes in factors that influence the climate. These factors may be due to natural causes (eg changes in solar radiation or volcanic eruptions emitting large quantities of dust into the atmosphere) or to human activities (eg emissions of "greenhouse" gases such as CO2, methane etc or of gases such as SO2 that lead to the production of particles in the atmosphere). In any assessment of past or future climate change all of these need to be considered. A large proportion of the IPCC reports is concerned with careful assessment of the available evidence from observations and from appropriate analysis (including modelling) regarding these factors, both natural and anthropogenic. The IPCC's clear conclusion stated in all its reports is that the influence of the anthropogenic factors, especially emissions of CO2 is likely to be by far the dominant factor determining climate change during this century.

  Regarding the dissemination of IPCC funds, these are used for the support of a small international secretariat in Geneva, for the cost of IPCC meetings and for the cost of the participation of scientists from developing and EIT countries in IPCC meetings including those of the Working Groups. This latter is essential if the IPCC is to involve scientists from a wide range of countries in its work. In addition, the UK government provides funds to support the WGI TSU to which I referred above. The IPCC is a cost effective organisation and considering its work load it employs comparatively few staff.

  6.  Question 2. Do you think the Government sufficiently scrutinises alternative explanations for climate change, other than increasing concentrations of CO2 before developing policy? By what means is this achieved? What part does the IPCC play in this?

  As I explained in (5) above the variety of factors influencing climate change is well understood by government, the main source of comprehensive information available being the IPCC assessments. These assessments distinguish clearly between what is known with reasonable certainty and the areas where there is a lot of uncertainty and debate amongst scientists. Since the hundreds of scientists involved with the IPCC come from a wide range of countries, backgrounds and scientific disciplines, a wide range of genuine scientific opinion is represented. One of the leading "sceptics", Professor Richard Lindzen, is a lead author for one of the chapters of the IPCC report currently in preparation. However, there are a few scientists, many of whom are supported by fossil fuel companies, who tend to employ the media rather than the scientific literature to express their view that the IPCC is overstating the role of greenhouse gases in climate change. There are a few others, many of whom are involved with "green" groups, who equally vocally complain that the IPCC fails to recognise adequately the more damaging anthropogenic effects on climate that might possibly be realised. Inevitably too there are others with very limited or no real scientific knowledge who use the media or who are used by the media to put forward contrary views. The government is therefore made aware of and exposed to (and sometimes replies to) the wide range of views that exist both scientific and political.

  7.  Question 3. Do you agree that climate change models provide the most robust means of gaining information on which to base policy decisions? What other means could or should be used?

  The available scientific evidence comes from observations, analysis of observations and models. It is sometimes thought that these are alternative sources of evidence. That is not the case. Observations on their own are of limited use; they need to be interpreted. Models provide the main means for the interpretation of the wide range of observations that are relevant to climate change. Observations are therefore input to models; models are of limited value without observations.

  Climate models are generated from the equations that express the physical and dynamical laws that determine the response of the atmosphere, the oceans and other parts of the climate system to the natural or anthropogenic factors controlling the climate that I mentioned in para (5) above. The simplest possible climate model is just one of these equations. Models as used in climate science, therefore, possess a sound scientific basis. Their importance arises from the fact that they are an essential tool for gaining understanding. Because all the influences on the climate lead to non-linear responses (ie there is no simple proportionality between forcing and response), without the use of models it is impossible to sum the responses of the climate to the various influencing factors. There are those who speak loudly about the inadequacies of models and try to use hand-waving arguments instead. It is true that, because of the complexities of the climate system, models are inadequate in various respects and have to be carefully appraised. However, hand-waving arguments can in no way replace even the simplest of models because they are completely unable to allow for the non-linear character of the factors involved.

  8.  Question 4. What actual appraisal of climate change models has been performed by Working Group I of the IPCC and with what conclusions?

  The IPCC reports contain results from and assessments of a wide variety of models covering different aspects of the problem of climate change—for instance models of the carbon cycle, of aerosol production, of atmospheric processes an circulation, of ocean circulation etc. The most sophisticated models are those that couple together the atmospheric and oceanic circulations together with descriptions of the hydrological cycle and the behaviour of sea ice. The large number of studies comparing results from different models have provided an important input to the IPCC assessment process; a substantial proportion of IPCC reports has been taken up with the comparative appraisal of model results. The IPCC's conclusion regarding the use of models expressed in the Summary for Policymakers of the 1995 Report is as follows: "The increasing realism of simulations of current and past climate by coupled atmosphere-ocean climate models has increased our confidence in their use for projection for future climate change. Important uncertainties remain, but these have been taken into account in the full range of projections of global mean temperature and sea level change". Confidence in models has increased further since 1995 as model development has continued and as models have been tested more thoroughly and over a greater range of conditions.

1 March 2000

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