Henderson: Received Opinion Published Article

12 March 2008


Climate Change Issues: The Case Against Received Opinion

David Henderson1

The text that follows formed the basis for a presentation at the International Conference on Global Warming held in New York on 2-4 March 2008.


I am an economist, not a climate scientist. At the time when I became involved with climate change issues, by accident rather than design, towards the end of 2002, my involvement was limited to some economic aspects of the debate. Since then my interests and concerns have broadened, in ways that were neither planned nor expected by me. They now extend to the whole spectrum of climate change issues, and in particular to the treatment of those issues by governments and international agencies.

I have come to believe that governments are mishandling the issues. This mishandling has two related aspects. First, actual official policies to curb (so-called) ‘greenhouse-gas’ emissions too often take the form of costly specific schemes and regulations, rather than a general price-based incentive such as a carbon tax. There is also, however, a more fundamental aspect. In my view, there is good reason to question the basis and rationale of current policies – the arguments, beliefs and presumptions which have led so many governments, with considerable public support, to take decisive action and to agree that further action is required. It is this latter aspect that I shall focus on today.

The official policy consensus

In relation to climate change issues, there exists what I call an official policy consensus. With few exceptions, governments across the world are firmly committed to the view that anthropogenic global warming constitutes a serious problem which requires official action at both national and international level. A recent high-level restatement to that effect was contained in the Declaration issued at the close of the G8 Summit meeting in Heiligendamm last June. In paragraph 49 of the Declaration the G8 leaders said that ‘global greenhouse emissions must stop rising, followed by substantial global emission reductions.’ In pretty well every democratic country, this official consensus is not at all a matter of political controversy: to the contrary, it enjoys general cross-party support.

The consensus is not new. Climate change issues, and in particular the extent and possible consequences of anthropogenic global warming, have been on the international agenda for 20 years or more; and it is now over 15 years since governments decided, collectively and almost unanimously, that determined steps should be taken to deal with what they agreed was a major problem. The decisive collective commitment was made in 1992, through the Framework Convention which almost all countries have ratified. The Convention specifies that its ‘ultimate objective’ is

‘to achieve … stabilization of greenhouse gas emissions in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system’.

Precisely this form of words is repeated in the G8 Summit Declaration.

Since 1992, many governments have acted, at state and provincial as well as national level, and collectively within the European Union, through what is now a wide range of measures and programmes, to curb emissions, of CO2 in particular. They have entered into commitments accordingly. Despite the limitations of what has so far been achieved, the accepted direction of policy remains clear and virtually unquestioned. Both nationally and internationally, new and far-reaching measures to curb emissions are under consideration or in prospect.

Received opinion and ‘the science’

In taking this course, governments have met with widespread and arguably increasing public approval. Prominent among the unofficial sources of support are media commentators on environmental and scientific issues, scientific bodies including the Royal Society, environmental NGOs, and, increasingly, large business enterprises. Further, there is strong public support for the consensus position among economists, as evidenced for example in the Stern Review of the economics of climate change and the list of those (including four Nobel prizewinners) endorsing it; in a public statement of December 2005 by 25 leading American academics; and in a similar recent statement signed by 271 university economists in Australia.

In relation to climate change issues, one may speak of a widely shared diagnosis and prescription, a body of received opinion shared by most governments, generally with support from opposition parties, and by many of their citizens.

What was it that first persuaded governments across the world, more than 15 years ago, to take the possible dangers of anthropogenic global warming so seriously, and what is it that has caused them to maintain and even intensify their concerns, with substantial and arguably increasing public support? I think the answer is straightforward. From the start the main influence was, as it still is, the scientific advice provided to them.

The core element of received opinion comprises what is often referred to as ‘the science’. The generally accepted view is that scientific research has provided increasingly firm and now incontestable evidence of the reality and the potential threat of anthropogenic global warming, and that in consequence policy should be directed in particular towards curbing and reducing CO2 emissions. Hence (it is believed) the official policy consensus is well grounded on expert findings that can no longer be seriously doubted. Here are three high-level recent instances of this way of thinking:

  • The OECD, in a policy brief of November last year: ‘Climate change is already with us. Scientific evidence shows that past emissions of greenhouse gases are already affecting the Earth’s climate. If current trends and policies continue, the result will be a rapidly warming world. Action is needed now to significantly reduce global greenhouse emissions in the coming decades’.

  • The Stern Review, in the opening sentence of its ‘summary and conclusions’ (p. xv): ‘The scientific evidence is now overwhelming: climate change is a serious global threat, and it demands an urgent global response’.

  • Last year’s G8 Summit Declaration, as already quoted: ‘Taking into account the scientific knowledge as represented in the recent IPCC reports, global greenhouse emissions must stop rising…’ (Note the place accorded by the G8 leaders to the IPCC – the Intergovernmental Panel on Climate Change)

Received opinion thus holds that ‘the science’ is ‘settled’, and that for all practical purposes ‘the scientific debate is over’. This conviction itself rests on twin beliefs: first, that such a conclusion emerges from the elaborate and now well-established advisory process that governments have built up in this area, and second, that this process is objective, reliable and authoritative. I would question both these presumptions. Before reaching that stage of the argument, some background on the advisory process is relevant.

The advisory process and the IPCC

In relation to climate change issues, the advice that governments receive can and does come from many sources; but the main single channel for it, indeed the only channel of advice for governments collectively, has been the series of massive and wide-ranging Assessment Reports produced by the IPCC. The first of these, which appeared in 1990, formed the basis for the negotiations that led up to the drafting of the Framework Convention; and the three successor reports that have been prepared since 1992 have served to lend further support to the consensus then established. The last in the series, referred to for short as AR4, was completed and published in the course of last year. As with earlier reports, it chiefly comprises the massive separate volumes issued by each of the Panel’s three Working Groups. Between them these three volumes, each with its own Summary for Policymakers, come to around 3,000 pages, and some 2,500 experts – authors, contributors and reviewers – were directly involved in preparing them: I refer to this small army of participants as the IPCC expert network

The IPCC does not itself undertake or commission research: the Assessment Reports review and draw on the already published work of others. Most of this work is financed by governments, and the governments concerned thus have their own sources of information and advice: their thinking and actions do not necessarily depend on what the Assessment Reports have said. In the British case, for example, the Stern Review drew directly on already published scientific work, rather than on the draft texts of AR4 which were then becoming available. It may well be that if governments had never created the Panel official policies in most countries would have evolved in much the same way, in response to much the same advice. The IPCC forms one element in the advisory process, but not by any means the whole of it.

All the same, the Panel is influential and important in its own right. Its reports carry substantial weight, with public opinion as well as its member governments, because of their wide-ranging coverage of the issues, their extensive and ordered scientific participation, the extended review process that they go through, and the fact that the Panel alone is authorised to serve and inform the world as a whole. Its special place in the scheme of things has been widely acknowledged, as in the G8 Summit Declaration quoted above. More recently, the work of the Panel has received further and conspicuous international recognition through the award of the 2007 Nobel Peace Prize, which it shared with Al Gore.

The IPCC reports cover the whole range of topics that are raised by the subject of climate change, including ecconomic aspects. However, the central element in the body of advice which it provides, and which so many governments have relied on, relates to the scientific aspects which are reviewed in the reports from its Working Group I. Commenting on the latest of these reports, at the time of its release just over a year ago, a leading British climate scientist, Professor Mike Hulme, said that it ‘presents an authoritative assessment of the scientific understanding of climate change as a physical phenomenon’. This in particular is what the 20-year process of inquiry by the Panel, and the large and growing body of work that it draws on, is seen as having chiefly contributed. The WGI scientific assessment, and the published work that entered into it, are taken by governments as their agreed point of departure.

Against this background, I will present a critique of received opinion. In doing so, I shall not pass judgment on scientific issues as such. Instead, I focus on what I view as a triad of unwarranted though widely held presumptions.

Unwarranted presumptions

Within the generally received opinion of today, three interrelated leading elements are:

(1) That the official policy consensus, as widely interpreted today by governments and international agencies, mirrors prevailing scientific opinion and goes no further than it would warrant.

(2) That prevailing scientific opinion must now be viewed as no longer open to serious question.

(3) That the process of review and inquiry from which prevailing scientific opinion has emerged, and in particular the IPCC process as its leading element, are professionally above reproach.

All these beliefs are unfounded. They betray respectively a lack of awareness of the present extent of overstatement, over-confidence, and ingrained bias.

Forms of over-presumption: (1) going too far

Within what may be termed the environmental policy milieu, as also in many unofficial circles, it is common to find highly-coloured and presumptive assertions which go well beyond prevailing scientific opinion as reported in the text of AR4. Here are a few high-level instances:

  • Tony Blair, as British Prime Minister, together with his Dutch counterpart, in a joint letter of October 2006 to other EU leaders: ‘We have a window of only 10–15 years to take the steps we need to avoid crossing a catastrophic tipping point’.

  • President Sarkozy of France, in some remarks last year shortly before his election to office: ‘what is at stake is the fate of humanity as a whole’.

  • The Secretary-General of the UN, Ban Ki-moon, writing in the latest Human Development Report (p. 23): ‘Climate change threatens the whole human family’.

  • Sir Nicholas Stern, writing in The Guardian (30 November 2007): ‘We risk damage on a scale larger than the two world wars of the past century’.

  • Just before the Bali meeting opened, 150 business leaders placed a double full-page advertisement in the Financial Times with what they termed a ‘Bali communique’. In this document they asserted that : ‘There is no doubt that the fate of our civilisation hangs in the balance’.

Such assertions are specimens of what I have termed the heightened milieu consensus. All of them, and countless others of their kind, purport to be statements of fact; but in reality they are no more than conjecture. They represent extrapolations, not direct well-founded inferences, from AR4 and the array of studies that it draws on. Although they do not accurately mirror prevailing scientific opinion, they have now become widely accepted presuppositions of policy. One illustration of this kind of official thinking is that some governments, including my own, have seen fit to distribute to schools, as an officially recommended source, Al Gore’s film, An Inconvenient Truth.

Interestingly, assertions such as those I just quoted have been criticised by Professor Hulme, speaking in 2006, as forms of what he called ‘a discourse of catastrophe [which] is a political and rhetorical device’. Referring to the above quotation from Tony Blair, he described the then Prime Minister as among ‘recent examples of the catastrophists’, and said: ‘The language of catastrophe is not the language of science. It will not be visible in next year’s global assessment [AR4] from the world authority of [the IPCC]’.2 He went on to contrast the respective positions of the ‘catastrophists’ and the climate scientists.

However, while Hulme was right about the more guarded language of AR4, the unqualified contrast that he went on to draw does not hold good. While Blair may have deserved to have the label of ‘catastrophist’ attached to him for the remarks just quoted (and others like them), it was not with him that they originated. He and his Dutch co-signatory, as also Sarkozy and Ban in the above quotations, almost certainly did not write their own speeches. What they said was presumably sanctioned, and probably drafted, by their scientific and environmental advisers and by the departments those people work in; and had it not been so sanctioned, those advisers and departments could have ensured – they could ensure now, if they saw fit – that future public statements would take a more measured and qualified tone.

The fact is that there is no clear dividing line between ‘catastrophists’ and climate scientists. It is influential climate scientists, taking a darker view than Hulme, who write or approve the ‘catastrophist’ scripts of leading lay figures, and who in some prominent cases have made similar pronouncements of their own. Their views, though widely and perhaps increasingly held, are not fully representative.

This is not to say that the scientists in question are wrong, or that the strong above assertions by leading figures are provably mistaken. The moral to be drawn is twofold.

  • First, and to repeat: the alarm-prone positions widely taken by political leaders, top international civil servants, eminent scientists in fields other than climate science, leading industrialists, widely read commentators and media outlets, and an array of NGOs, not to mention some eminent economists, do not mirror the more considered language of AR4: they go well beyond it.

  • Second, and not surprisingly: in relation to most if not all aspects of this whole complex of issues, there exists a range of expert views concerning the evidence and the conclusions to be drawn from it.

This brings me to my second category of over-presumption.

Forms of over-presumption: (2) overstating the bounds of what is known

The G8 Summit Declaration which I already quoted refers to ‘the scientific knowledge as represented in the recent IPCC reports…’. Had I been a pre-Summit Sherpa, I would have argued for changing ‘scientific knowledge’ to ‘the weight of scientific opinion’.

The fact is that what is in question here is a climate system of extraordinary complexity which is far from being well understood. Indeed, the IPCC itself, in its Third Assessment Report (TAR) of 2001 contained an instructive diagram showing what it described as ‘the cascade of uncertainties’. The cascade includes the future course of economic change; the resulting changes in emissions of CO2 and other anthropogenic greenhouse gases; the effects of projected emissions on atmospheric concentrations of those gases; the resulting effects on estimated radiative forcing, and the further consequences for surface temperatures; and the possible biophysical and socio-economic impacts of specified temperature increases. All of these uncertainties remain today; and I would add, as a further aspect, that since the TAR appeared new questions have been raised about evidence which the Panel has drawn on of past temperature changes: hence the actual extent and significance of recent global warming are now more in doubt than before.

The extent of continuing uncertainty about the properties of the system, and the range of views to be found among informed persons, form the subject-matter of a document recently brought out by the office of the Republican ranking member of the Environment and Public Works Committee of the US Senate. This report is a kind of nonconformist anthology: it presents, through summary direct quotation, the recently-expressed views of some 400 variously qualified persons, all of whom question one or more aspects of prevailing views on climate change issues.3

Of course, the fact that nonconformist views of various kinds are still widely held, by well qualified persons, does not in itself serve to discredit the received opinion that ‘dangerous anthropogenic interference with the climate system’ is taking place, or the official policy consensus that is linked to it. Nor does it justify inaction. But the contents of the dossier lend weight to a conclusion drawn by an instructive document, published a year or so ago, called the Independent Summary for Policymakers.4 The authors conclude that, while the hypothesis of anthropogenic global warming ‘is credible, and merits continued attention’, it ‘cannot be proven by theoretical arguments, and the available data allow [it] to be credibly disputed’.

Received opinion to the effect that ‘the science’ is ‘settled’, and that the scientific evidence is now ‘overwhelming’, are unwarranted. As I have noted, such assertions are not drawn direct from AR4. However, they could not have gained such widespread acceptance were it not for the continuing flaws that have characterised the large-scale established official process of review and inquiry which, though it extends well beyond the work of the IPCC, finds its fullest expression in the Assessment Reports.

Forms of over-presumption: (3) uncritically accepting a flawed process

Over the past 20 years governments everywhere, and many outside observers too, have placed uncritical reliance on the advisory process as a whole and the work of the IPCC in particular. I believe that this widespread trust is unwarranted, and that this fact puts in doubt the accepted basis of official climate policies. This is not, as suggested by Stern Review authors, a matter merely of ‘procedures’ as distinct from substance. If and in so far as the advisory process that the world relies on is lacking in objectivity, and is not professionally watertight, the basis and rationale of the official policy consensus are put in question.

Panel and process

Why do governments, and outsiders too, place so much trust in the IPCC? I think that the trust largely results from the wide and structured expert participation that the IPCC process ensures. People visualise an array of technically competent persons whose knowledge and wisdom are effectively brought to bear through an independent, objective and thoroughly professional scientific inquiry. Indeed, many outside observers identify the Panel with the network, as though well-qualified and disinterested experts were the only people involved. The reality is both more complex and less reassuring.

A basic distinction has to be made between the IPCC as such, that is to say the Panel, and the IPCC process. The two are not the same, and the process involves three quite distinct groups of participants.

The first of these groups comprises the Panel itself, which controls the preparation of the reports, along with its two subsidiary bodies. The Panel comprises those officials whom governments choose to send to Panel meetings. Working directly for the Panel is the IPCC Secretariat, though this is a small group whose functions are mainly of a routine administrative kind. A more influential body is the 28-strong IPCC Bureau, comprising high-level experts in various disciplines from across the world, chosen by the Panel. The Bureau acts in a managing and coordinating role under the Panel’s broad direction.

A second group is made up of the now 2,500-strong expert network, the persons who put together the draft Assessment Reports. This network is separate and distinct from the Panel itself. There is little or no overlap between the two bodies.

Last but far from least, there are the government departments and agencies which the Panel reports to: it is here, and not in the Panel itself, that the ultimate ‘policymakers’ are to be found. The relevant political leaders and senior officials within these departments and agencies form the core of the environmental policy milieu. The milieu also comprises leading non-official members of the IPCC Bureau, past as well as current; and together with the most influential members of the Panel itself, these latter persons make up what may be termed the informal directing circle of the IPCC.

Policy commitment

The IPCC as such has been formally instructed by its member governments, in the ‘principles governing IPCC work,’ that its reports ‘should be neutral with respect to policy’. However, this instruction must be interpreted as referring specifically and exclusively to the contribution made by the expert network through the reporting process. It does not, and could not, apply to the other two participating groups. The official Panel members, as also the policy milieu which they report to, are almost without exception far from neutral: they are committed, inevitably and rightly, to the objective of curbing emissions, as a means to combating climate change, which their governments agreed on when they ratified the Framework Convention; and in many cases they are likewise committed to the kinds of policies that their governments have adopted in pursuit of that objective. As officials, they are bound by what their governments have decided. That is the context within which the three successive IPCC Assessment Reports prepared since 1992 have been put together by the network and reviewed by member governments. The clients and patrons of the expert network, with few exceptions, take it as given that anthropogenic global warming is a serious problem which demands, and has rightly been accorded, both national and international action.

It is against this background, of a Panel and a controlling policy milieu that are not and could not be ‘policy-neutral’, that some basic features of the expert reporting process have to be borne in mind:

  • The choice of lead authors for the Assessment Reports largely rests with the already-committed member governments, since lists that they provide form the starting point for the selection process;

  • Complete draft texts of the Working Group reports go to those governments for comment and review; and

  • It is governments, as represented in the Panel, that sign off on the final versions of the Assessment Reports and which amend the draft Summaries for Policymakers, and the final Synthesis Report, before they approve these also for publication.

Thus departments and agencies which are not—and cannot be—uncommitted in relation to climate change issues are deeply involved, from start to finish, in the preparation of the Assessment Reports.

Does this fact in itself put in question the expert reporting process and the Assessment Reports? As a former official myself, I would say: No, not necessarily. Policy commitment on the part of member governments could in principle go together with a resolve on the part of the policy milieu, and of the Panel which they appoint and control, to ensure that the reporting process is open, thorough, objective and policy-neutral. This indeed is what governments believe, or at least maintain, is the state of affairs that they have created; and I think many outside persons believe or presume the same. In this generally accepted picture of the IPCC process, an invisible Chinese wall separates the committed patrons and clients of the reporting process from the array of disinterested scientists, policy-neutral in their expert capacity, who take part in it.

I have come to believe that this picture is not accurate, and that the expert reporting process is flawed. Despite the numbers of persons involved, and the lengthy formal review procedures, the preparation of the IPCC Assessment Reports is far from being a model of rigour, inclusiveness and impartiality.

Critics of the IPCC process have drawn attention, in my opinion with good reason, to flaws which include:

  • Weaknesses in the treatment of some economic issues

  • Over-reliance on peer review procedures which do not serve as a guarantee of quality and do not ensure due disclosure

  • Failures of disclosure in relation to studies which the IPCC has drawn on

  • Basic errors in the handling of data, allied to failure to consult or involve trained statisticians

  • Failure to ensure an adequate range of views and expertise

  • Failure to take due note of critics in the preparation of the Assessment Reports

  • Failure on the part of the Panel and the IPCC directing circle to recognise and deal with the above deficiencies.

I believe that over time the expert network has become more numerous but less inclusive: the scope for dissenting views has narrowed.

I believe that the flaws in the reporting process can be largely accounted for by a pervasive bias on the part of the people and organisations that direct and control it. From the earliest days, members of the environmental policy milieu and the IPCC directing circle have been characterised by what Clive Crook has termed ‘pre-commitment to the urgency of the climate cause’.10 They have subscribed to, or acquiesced in, the heightened milieu consensus.

By way of illustration, here are three high-level public statements made in February last year, following the publication of the AR4 Working Group I report:

  • Dr R. K. Pachauri, the Chairman of the IPCC, and hence of the IPCC Bureau: ‘I hope this report will shock people [and] governments into taking more serious action’.

  • Achim Steiner, the Director-General of the UNEP: ‘in the light of the report’s findings, it would be “irresponsible” to resist or seek to delay actions on mandatory emissions cuts’5.

  • Yvo de Boer, Executive Secretary of the Framework Convention: ‘the findings leave no doubt as to the dangers that mankind is facing and must be acted on without delay’.

These are strong assertions. In none of them was the wording taken directly from the report in question: these eminent persons were going beyond the AR4 text, to draw their own confident and unqualified personal conclusions as to the lessons for policy. While they were fully entitled to form and air such opinions, their statements were not just summaries of ‘the science’, nor of course were they ‘policy-neutral’.

In speaking as they then did, these leading figures were conforming to an established pattern. From the earliest days, most if not all of those directing the IPCC process, within governments and outside, have shared the pre-commitment referred to by Crook; and had this not been the case, and known to be the case, they would not have attained their leading positions within the process. To take only the three current examples just quoted: Pachauri, Steiner and de Boer would not have sought their respective posts, nor would they have been seen by UN agencies and member governments as eligible to hold them, had they not been identified as fully committed to heightened milieu consensus views. The process is run today, as it has been from the start, by true believers. This accounts for the readiness of many of those concerned to make strong public pronouncements of the kind quoted above, which go beyond the more nuanced language of the Assessment Reports; to turn an unseeing eye to the disclosure failures and other professional flaws in the reporting process; and to view with equanimity or approval the lack of balance that characterises public debate. The official handling of climate change issues has been, and continues to be, suffused with bias.

Summing up

To summarise: currently received opinion on climate change issues, official and unofficial, embodies over-presumptive conclusions which are biased towards alarm. These conclusions form the basis of current government policies to curb emissions and proposals to go further. They take as their point of departure the results of a flawed process, and they represent a dubious extension of those results.

The chief moral to be drawn for policy is a simple one. In relation to climate change, there is a clear present need to build up a sounder basis for reviewing and assessing the issues. Governments should try to ensure that they and their citizens are more fully and more objectively informed and advised.

1 Formerly Head of the Economics and Statistics Department of the OECD, and currently a Visiting Professor at the Westminster Business School, London. This paper draws without specific attribution on a number of recently-published articles of mine.

2 In a piece entitled ‘Viewpoint: Chaotic world of climate truth’, BBC News World, November 2006.

3 I have to declare an interest here, since I am one of those cited – though not in relation to scientific aspects.

4 The ISPM was prepared by a group of ten scientists, in the light of comments from 43 other named reviewers, under the auspices of the Fraser Institute of Canada and with Ross McKitrick as Coordinator. It is presented as an alternative summary of the relevant science to that provided in the official draft Summary for Policymakers of the IPCC’s Working Group I which forms part of AR4.

10 Financial Times, 2 August 2006. Crook wrote there of the IPCC that ‘It is a seriously flawed enterprise and unworthy of the slavish respect accorded to it by most governments and the media’.

5 This and the following quotation are taken from a report (3 February 2007) in the Financial Times.