Select Committee on Economic Affairs Second Report

Chapter 7: the IPCC Process

106.  In the previous chapters we have several times referred to some limitations in the IPCC process. This process is an international one involving all governments and hundreds if not thousands of experts. Inevitably, in such a large-scale venture there will be weaknesses and errors. But the stakes are high and it is imperative that the process is an open one, capable of receiving criticism, and insistent on the highest standards of scientific and economic procedures. While HM Government and the many UK experts comprise just one collective player in the IPCC process, it is important that they are vigilant in ensuring that any errors and defects are brought to the attention of the IPCC and the scientific community in general. In this chapter we elaborate on our previous concerns and introduce some others.

The Special Report on Emissions Scenarios

107.  In Chapter 4 we listed a number of criticisms of the IPCC Special Report on Emissions Scenarios (SRES). We noted that the original criticisms advanced by Professor David Henderson and Mr Ian Castles on the use of market exchange rates in aggregating world income has generated a much broader literature that questions (a) the credibility of the IPCC high emissions scenarios, and (b) the relevance of purchasing power parity exchange rate conversions. Whatever the resulting outcomes of making the scenario exercise more robust, it is clear to us that IPCC does need to reconsider its SRES exercise. This requires more than making allowance for new data, which Dr Nakicenovic told us would figure in the 2007 exercise[88]. We urge the IPCC to go beyond making adjustments for improved data. There is a need to reconsider the economic basis on which the scenarios are constructed.

108.  In terms of process, we heard from several witnesses that the IPCC SRES exercise does not reflect the most appropriate expertise. While there are some national accounts statisticians involved in the exercise, it seems to us that a broader representation from the economics and statistics community is called for, along with a perspective from economic historians. The failure to take adequate account of the consistency between projections and past experience is a case in point, and an issue that was raised early on by Professor Henderson and Mr Castles, and again by Professor Tol and by Professor Ross McKitrick in their evidence to us[89].

The policy-makers' summaries

109.  The IPCC main reports of Working Groups I to III consist of detailed technical chapters. Each chapter then has a "policy-makers summary" designed for those who need a fairly rapid guide to what the technical chapter has said. But there is a stark contrast in the way the technical chapter and the summary are written. The former is written by lead authors who in turn have a team of experts who make inputs to that chapter. The latter may be written by the same authors but is scrutinised in detail by government representatives to the IPCC meetings. As Dr Barker put it to us:

"governments…do have a say in the Summary for Policy Makers [which is] taken extremely seriously by governments, and it is a line-by-line acceptance, and each word can count, and the process can actually collapse if governments will not accept a particular phrasing, a particular word".

110.  Dr Barker went on to say that government representatives can be very sensitive to some issues. For example, wording that suggests costs of control are large might upset governments whose policy stance is based on the view that costs are small and easily bearable. Dr Barker concluded that:

"…what happens is that there is a political process which uses words which can have different meanings for different people and the outcome is a Summary for Policy Makers that everybody will sign up to"[90].

111.  We can see no justification for this procedure. Indeed, it strikes us as opening the way for climate science and economics to be determined, at least in part, by political requirements rather than by the evidence. Sound science cannot emerge from an unsound process.

112.  We sought examples of the kind of problem that has arisen because of such interference in what should be a scientific process. Examples were not hard to find. In the 1995 Second Assessment Report, the Summary of Chapter 6 on The Social Costs of Climate Change bears little resemblance to the technical chapter it is supposed to summarise. Indeed, the lead authors of that chapter disowned the Summary. In the 2001 Working Group II Report our attention was drawn to the following statement in the Summary for Policymakers (p.8):

"Benefits and costs of climate change effects have been estimated in monetary terms and aggregated to national, regional and global scales. These estimates generally exclude the effects of changes in climate variability and extremes, do not account for the effects of different rates of change, and only partially account for impacts on goods and services that are not traded in markets. These omissions are likely to result in underestimates of economic losses and overestimates of economic gains [from climate change]"(our emphasis).

113.  Chapter 19 (p.942), on which the Summary quotation above is supposedly based, actually says:

"Overall, the current generation of aggregate estimates may understate the true cost of climate change because they tend to ignore extreme weather events, underestimate the compounding effect of multiple stresses, and ignore the costs of transition and learning. However, studies also may have overlooked positive impacts of climate change. Our current understanding of (future) adaptive capacity, particularly in developing countries, is too limited, and the treatment of adaptation in current studies is too varied, to allow a firm conclusion about the direction of the estimation bias" (our emphasis).

114.  In short, the Summary says that economic studies underestimate damage, whereas the chapter says the direction of the bias is not known.

IPCC and scientific expertise

115.  Given the global scale of the IPCC process, it should be expected that it will attract the best experts. In his evidence to us, Professor Paul Reiter raised doubts about the extent to which this is the case[91]. He refers to the Second Assessment Report of Working Group II in 1995, Chapter 18 of which is concerned with human health impacts of warming. A significant part of this chapter discussed malaria. Yet, according to Professor Reiter, none of the lead authors had ever written a paper on malaria, the chapter contained serious errors of fact, and at least one of the chapter's authors continues to make claims about warming and malaria that cannot be substantiated. Professor Reiter's concerns extend to the same chapter in the Third Assessment Report of 2001, where he was initially a contributory author. While he expresses far more confidence in this chapter than the equivalent one in the Second Assessment Report, Professor Reiter notes that "the dominant message was that climate change will result in a marked increase in vector-borne disease, and that this may already be happening". In Professor Reiter's view, no such conclusion is warranted by the evidence, and he speaks as a malaria specialist of more than thirty years' experience. While nominated by the US Government to serve on the comparable group for the Fourth Assessment Report, the next one that will appear from IPCC, Professor Reiter learned that his nomination had not been accepted by IPCC. Yet Professor Reiter tells us that of the two lead authors for that chapter, one had no publications at all and the other only five articles.

116.  We cannot prove that Professor Reiter's nomination was rejected because of the likelihood that he would argue warming and malaria are not correlated in the manner the IPCC Reports suggest. But the suspicion must be there, and it is a suspicion that lingers precisely because the IPCC's procedures are not as open as they should be. It seems to us that there remains a risk that IPCC has become a "knowledge monopoly" in some respects, unwilling to listen to those who do not pursue the consensus line. We think Professor Reiter's remarks on "consensus" deserve repeating:

"Consensus is the stuff of politics, not science. Science proceeds by observation, hypothesis and experiment. Professional scientists rarely draw firm conclusions from a single article, but consider its contribution in the context of other publications and their own experience, knowledge and speculations".

We are concerned that there may be political interference in the nomination of scientists whose credentials should rest solely with their scientific qualifications for the tasks involved.

IPCC and economics expertise

117.  In his evidence to us, Professor Ross McKitrick suggested that the IPCC no longer commanded the allegiance of mainstream economists[92]. In scrutinising the authorship of chapters, we believe his perception has arisen because some of the economics that was originally subsumed in Working Group III was moved in the 2001 Report to Working Group II. Working Group II is concerned with impacts, adaptation and vulnerability. Its authorship is dominated by impact specialists who tend not to be economists. The fact that the chapter that deals with monetised benefits of warming control now appears in that volume may explain its apparent downgrading, although we note that this is also consistent with IPCC's desire to avoid the politically-inspired debates over the benefit estimates. Working Group III deals with the remaining economic issues and the amount of economic expertise is more significant.


118.  Overall, we are concerned that the IPCC process could be improved by rethinking the role that government-nominated representatives play in the procedures, and by ensuring that the appointment of authors is above reproach. If scientists are charged with writing the main chapters, it seems to us they must be trusted to write the summaries of their chapters without intervention from others. Similarly, scientists should be appointed because of their scientific credentials, and not because they take one or other view in the climate debate. The IPCC publications as a whole contain some of the most valuable summary information available to the world on what we know about climate change. The standards employed are clearly very high. But this is all the more reason to ensure that procedures are unimpeachable. At the moment, it seems to us that the emissions scenarios are influenced by political considerations and, more broadly, that the economics input into the IPCC is in some danger of being sidelined. We call on the Government to make every effort to ensure that these risks are minimised.

88   Evidence from N. Nakicenovic (Vol II, pp 131-137) Back

89   See, for instance, evidence from R. Tol (Vol II, pp 69-77) Back

90   Evidence from T. Barker (Vol II, pp 78-86) Back

91   Evidence from P. Reiter (Vol II, pp 284-288) Back

92   Evidence from R. McKitrick (Vol II. Pp 262-266) Back

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