‘Consensus’ in science

One of the standard themes in the orthodoxy about ‘climate change’ is that there is ‘consensus’ within science that anthropogenic global warming is happening, that it is unprecedented and that it is dangerous. I was thinking about writing a piece on what has happened in the AGW domain since I became interested in the subject six years ago, but a long and interesting thread on ‘consensus’ in Judith Curry’s Climate etc blog got my attention first. If the subject interests you, the whole long thread is worth reading, because there are some excellent contributions on it. What follows is my own reaction to the subject.

To start, the thread began with a chapter in a book about scientific advice in the UK by Mike Hulme. Hulme is a professor of climate change in the University of East Anglia, and was the head of the Tyndall Centre for Climate Change there. So he is at the heart of the orthodoxy. But in recent years he has distanced himself from the orthodox, and written a number of papers and books that suggest that some re-thinking about ‘climate change’ needs to be done. His chapter, much of which Judith Curry reproduces, is a good indication of his shift. Judith Curry has herself written an excellent paper on consensus about climate change, which is now in print. Both she and Hulme argue that the  insistence that there is consensus about climate change is harmful to our appreciation of what is happening to climate, and harmful to the IPCC itself, since (for example) the apparent pause in global warming was not predicted, despite the claimed high degree of certainty with which the IPCC’s writers put forward their case.

I have always disliked the consensus argument, because it is used as a discussion-stopper. ‘Who are you, to go against the consensus of the world’s climate scientists?’ comes the supposedly crushing rejoinder if one dares to question any of the tenets of global warming. (If you want to see this process in action, go the The Conversation, about which I have written, and look for any contribution on ‘climate change’ — they come pretty regularly.) It puzzles me that people with a university education are prepared to use it, since everything that we learn at university comes with the warning that what we presently know could change. My current supposition is that beliefs in the reality of ‘climate change’ can be held in almost religious way, so that to question aspects of global warming is akin to challenging religious belief. Why people should embrace ‘climate change’ as a religion is a puzzle to a non-religious person like me, and I have had a go at it in an earlier post.

Surely it is plain that there are various degrees of consensus within science. That there is a solar system, and that the planets in it have orbits around the sun, is now not disputed. It was, of course, a revolutionary idea some centuries ago. But a long series of confirming measurements and successful predictions has occurred to the point where that building block of astronomy is now firmly in place. When consensus has been established the general picture of the matter is clear, even if some details have still be clarified. And sometimes the establishment of agreement can be quite speedy: Einstein’s general relativity notion seems to have been accepted by the physics community within a decade, as was, by all accounts, Newton’s theory of gravitation. Others take longer, like Wegener’s theory of continental drift and plate tectonics, which was fiercely resisted for half a century.

It is as though those working in the climate science area believed that they had solved it all, and that the truth was clear and irresistible. They were in the position of Einstein or Newton, possessors of a beautiful and important scientific reality. What happened then should have been the confirmation of their predictions through observations, experiment and measurement. And for brief moment it might have appeared that this was occurring. But after 1998, which was in any case pronounced to be an el Nino year, temperatures stopped rise coincidentally with carbon dioxide accumulations.

What to do now? There was a lot at stake, and the IPCC became more and more confident. In its first report, in 1990, the IPCC had said, about the attribution of global warming to human activity, that it was ‘broadly consistent with predictions of climate models’, while the second, in 1995, stated that ‘the balance of evidence suggests a discernible human influence on global climate’. These are balanced, temperate statements.  In the third (2001) we learn that ‘[t]here is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities’. By 2007, and the last published report, there is near-certainty: ‘Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations’.

Yet the increasing confidence went in contradiction to the evidence. Hence, at least in my view, the insistence on consensus, the refusal to accept that there could be anything to be said for natural variability, the denunciation of deniers. This isn’t science at all. We have crossed over into the much murkier worlds of politics and religion. And, as I keep on saying, in the long run this will do the whole world of science no good at all.