by Judith Curry
The drive for consensus within the IPCC process, and its subsequent public marketing, has becomes a source of scientific weakness rather than of scientific strength in the turbulent social discourses on climate change. – Mike Hulme
A provocative essay by Mike Hulme is included in the recent volume Future Directions for Scientific Advice in Whitehall. Some excerpts:
One of the common public expectations of science is that it speaks authoritatively about the way the physical world works and thereby what the physical consequences of different human actions and policy interventions are likely to be. Science and scientists are believed to offer something different to public life compared to that offered by politicians, journalists, lawyers, priests or celebrities. But what is meant by ‘authoritative’? And how does scientific practice best earn and maintain its authority in the face of public challenge and scepticism? The question I wish to answer can be put simply: does the pronouncement of a scientific consensus on an issue such as climate change increase or weaken the authority of science? And for whom exactly are such pronouncements effective – scientists, different publics, policymakers, politicians?
In favour of consensus
The argument in favour of consensus as authoritative is that it reflects what science supposedly is uniquely disposed to be good at: applying rules of reasoning and inference which lead unambiguously and universally from evidence to conclusion. The same evidence presented to the same disciplined mind leads to precisely the same conclusion. In this view, a lack of consensus would undermine the authority of science because it might suggest either that conflicting conclusions had been reached prematurely or that personal or cultural biases and values had protruded into the reasoning process.
This is the position that seems to be implicitly assumed by many protagonists in the climate change debate, whether they be mainstream or critical voices.
It is also the view of many critics of the scientific mainstream who assert that science properly conducted – through unbiased reasoning processes – should lead to unanimous consent. By pointing out the mere existence of minority dissenting positions outside the IPCC’s statements, ipso facto they undermine the authority of science in the eyes of the public. This of course reflects a very particular (purist) view of scientific knowledge which scholars such as Bruno Latour have described as the ‘modernist illusion of science.’ And yet it is one that offers a wide variety of protagonists a useful defence against cultural relativists.
Against consensus
But the argument against consensus as authoritative, at least in the context of wicked problems like climate change and at least in the way in which the IPCC has promoted it, seems to me to be compelling.
First is an argument by analogy. Majority rule works very effectively in maintaining authority in social institutions such as parliaments and the courts, which involve voting MPs and juries. Consensus is not required for a ruling or judgement to carry authority in wider public settings. And whatever differences we might insist on between the nature of scientific enquiry and political (or jury) debate, we must recognise that scientific assessments such as the IPCC are established explicitly as social (i.e., deliberative) institutions which scrutinise evidence.6 There are many other dimensions to the making of authoritative and trustworthy institutions than unanimity amongst members; for example, fair and agreed procedure, respect for dissent, acceptance of outcomes. Maybe the IPCC’s authority – in the eyes of critics and publics, if not also in the eyes of politicians – would therefore be enhanced if it acted on its own rules for minority reporting in the Summary for Policymakers (which it never has).
Second, the requirement of consensus is pernicious – in order to protect the authority of the group it encourages agreement in a group of experts where there is none. Maybe the IPCC should more openly embrace the idea of expert elicitation, or even expert voting as has been suggested by David Guston: “A scientific body that does not partake in … a politics of transparent social choice – one that hides both its substantive disagreements and its disciplinary and sectoral interests beneath a cloak of consensus – is not a fully democratic one.” For example, such an approach to disagreement could usefully have been applied to the case of the sea-level rise controversy in the IPCC’s 4th Assessment Report. It makes disagreements explicit and better reflects the quasi-rationality of scientific deliberation. Another example of how this might strengthen authority would be the case of the IUCN’s Polar Bear Specialist Group and the embrace of expert elicitation.
And, third, the presence of officially sanctioned – even welcomed! – credible minority views, thereby revealing the extent of dissensus, actually enhances the authority of science. It shows that it is ‘OK to disagree’ and thus indicates that the deliberative procedures of a body like the IPCC are fair and accommodating to the full range of accredited views. For science to be authoritative, it should therefore welcome – indeed seek out – its critics. In the case of large international assessments like the IPCC . . ., the process should not just allow minority reporting in its rules of procedure, but ensure that minority reporting is actively facilitated. As Dan Sarewitz has argued: “Science would provide better value to politics if it articulated the broadest set of plausible interpretations, options and perspectives, imagined by the best experts, rather than forcing convergence to an allegedly unified voice.”
Climategate, consensus and the weakening of authority
The single-minded drive for an exclusionary consensus was the true tragedy of Climategate. Not that the emails from the Climatic Research Unit (CRU) revealed any fundamental faking of substantive data or fraudulent practice, but that they showed a scientific culture which was closed to criticism and which was resistant to the open sharing of data. When these practices were publicly exposed, the tenacity of scientists’ defence of in-group/out-group boundaries paradoxically weakened the public authority of climate science rather than strengthened it. The outcome was the exact opposite of what climate scientists in CRU and elsewhere thought they were doing. As a consequence, climate scientists handed the scientifically-credentialed critics of climate science an easy target – exclusionary practices which run counter to the nature of open debate and criticism. And this in turn handed to politically-credentialed critics of mainstream climate policies a powerful diversionary strategy. It opened the way to convert the agonistic spaces of legitimate and healthy democratic argument about climate policies into distracting – yet attention-grabbing and entertaining – arguments about the authority of science.
By refusing to embrace and legitimise minority reporting, the IPCC has opened the way for powerful counter rhetoric to emerge around the idea of consensus. The relationship between scientific evidence and public policymaking is sufficiently underdetermined to warrant large-scale assessments such as the IPCC finding multiple ways of accommodating dissenting or minority positions. They would be the more authoritative for doing so.
JC comments: I find this essay to be very interesting and insightful, particularly in context of my own paper No consensus on consensus (which has now been published). My argument against an explicit consensus seeking approach for climate change science was twofold:
- it introduces bias into the scientific process
- it is unnecessary in context of decision making strategies under deep uncertainty, which arguably characterized the complex issues surrounding climate change.
Hulme argues that the emphasis on consensus can reduce the political authoritativeness of an assessment.
In this light, it will be very interesting to see what the reaction is to my forthcoming congressional testimony (scheduled for Apr 25, stay tuned).