Honey, I shrunk the consensus!

2007: And it's all peer-reviewed	Once upon a time, there was an Intergovernmental Panel on Climate Change (IPCC). They put their heads together with those of a number of climate scientists and decided in their wisdom (for they were very wise, or so they told us) that what the world really needs is a consensus. Not just any old consensus, of course – this one would be a “scientific consensus”. It was introduced with much fanfare. And lots of scarey stories – one of the scientists called it a “barrage of intergalactic ballistic missiles“. How scarey is that, eh?
The climate scientists had written and read lots of papers produced by themselves, or their friends who had also written and read lots of papers. If special readings of a paper had resulted in the paper being published in a Journal, this meant it had been “peer-reviewed” – and therefore was the right kind of paper. But if a paper was peer-reviewed and they didn’t like what it said (or the person who wrote it) then, they declared, it was the wrong kind of Journal. And they had meetings and sent out press releases and travelled to nice places making presentations to each other about the cherries they’d picked and the data they’d smoothed and/or fudged – and the tricks of their noble trade. They weren’t very happy when some people bothered them by asking questions about the computer programs, methodology and data they were using for their papers. They were even less happy when anyone found a mistake in their work. The mistake doesn’t change anything, they invariably declared; the science is sound and the consensus is scientific. The seas will rise, and the ice will melt and the glaciers will disappear and our carbon dioxide will be the primary cause: this was the scientific consensus, they assured their journalist friends, who dutifully – and unquestioningly – passed on the word to their readership, echoing the call that we must act now! Until one day …
2010: Well, maybe not all peer-reviewed	While the Chairman of the IPCC was busy back-peddaling from his views on those who disagree with the “scientific consensus on man-made climate change”, Mike Hulme, one of the climate scientists (whose work was cited no less than 59 times in the IPCC’s 4th Assessment Report) – and who certainly knows how to manufacture a consensus when he wants to – had recently written: “Claims such as ‘2,500 of the world’s leading scientists have reached a consensus that human activities are having a significant influence on the climate’ are disingenuous.

“That particular consensus judgement, as are many others in the IPCC reports, is reached by only a few dozen experts in the specific field of detection and attribution studies; other IPCC authors are experts in other fields.”

Clearly, those who’ve been peddling the “overwhelming scientific consensus” myth (including IPCC Chair, Rajendra Pachauri) have been misleading the public. Their “consensus” has suddenly shrunk, to underwhelming (and less than lilly white) proportions.

I, for one, was not in the least surprised to learn this. Nor, I suspect, were many others who’ve often expressed doubts regarding the veracity of the all too frequent appeal to the authority of “thousands of scientists”. When I read this emanation from Hulme’s keyboard, I did think that he would have done the world a great service had he mentioned this some years ago. But better late than never. I even began to develop some respect for him.

As great as my discomfort is with Hulme’s depiction of climate change as being “so plastic”, I was even prepared to chalk this expression up to some esoteric turn of phrase that is unique to practitioners of post-normal science (of which Hulme is indisputably one) – and probably has a meaning to them that bears no relation the common understanding of this word. Not unlike … oh, I dunno …. “trick”, perhaps.

Until I read that apparently Hulme neither said what he meant – nor meant what he said, as he subsequently wrote in a further “clarification“:

The ambiguity in the original Hulme & Mahony article emerges from the caricatured example I offer of a ‘claim’ which I suggest is disingenuous [OED: ‘not straightforward or candid’], namely when I wrote ‘2,500 of the world’s leading scientists have reached a consensus that human activities are having a significant influence on the climate’. This is far too general a claim for the very specific point I was seeking to make about expert judgement and consensus-making.

I should therefore instead have written in the original PiPG article, “Claims [made by commentators, not the IPCC] such as ‘2,500 of the world’s leading scientists agree that most of the observed increase in global average temperatures since the mid 20th century is very likely [greater than 90% likelihood based on expert judgement] due to the observed increase in anthropogenic greenhouse gas concentrations’ are disingenuous”. This much more specific example would have served my point much better.

Hulme concludes this “clarification” by writing:

Some commentators have called my point pedantic, but I think it is important to explain how knowledge is assessed by experts and how headline statements come into being. By the way, I think this is an entirely credible process of knowledge assessment, but people should not claim that it is more than it is.

And for the record … I believe that the warming of the climate system is unequivocal and that 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.

Ah, he “believes”. How very, well, evangelical. Now, if he could only point to some non-computer-generated evidence that human-generated carbon dioxide is the primary cause of this “observed” increase, perhaps we could make some progress. But I won’t hold my breath.