From Climate Scepticism

By John Ridgway

Oh no, wait…

It doesn’t matter how many people agree with you; it doesn’t matter if there’s some poll to back you up, it doesn’t matter how many subscribers you have on YouTube. The only thing that matters is whether you have a good argument.

Thus says the physicist Professor Sabine Hossenfelder in a recent podcast, in which she lambasts a paper written by a team of sociologists and philosophers who seem to have got it into their heads that science should be conducted as a popularity contest. Being the outspoken lady that she is, Hossenfelder wastes no time in putting them in their place. I like that. In fact, I am having a whale of a time until about halfway through the video when she says this:

That’s why the IPCC does NOT write their reports by a consensus mechanism. It’s not how science works. What they do, or at least try to do, is to go through all scientific claims and look at the evidence for them. Yes, the IPCC process has problems, but at least it’s not consensus based.

The emphasis in the above quote is actually not mine; ‘NOT’ appears in the subtitles that accompany the podcast. It’s Hossenfelder’s way of showing how confident she is in the workings of the IPCC. Which is important, because if she were to be wrong, the condemnation she directed at those sociologists and philosophers for obsessing over scientific consensus would have to be levelled equally at the IPCC. If, as Hossenfelder correctly points out, science is not supposed to work by consensus, and if the IPCC did in fact write their reports by a ‘consensus mechanism’, then Hossenfelder would have to conclude that the IPCC is not doing science. But hey, that’s no problem, because Hossenfelder is one hundred percent sure that the IPCC is NOT ‘consensus based’.

Let’s put Hossenfelder’s confidence aside for one moment and look at what the IPCC itself says on this matter. Specifically, this is what climate scientists and IPCC Lead Authors Gary Yohe and Michael Oppenheimer said in a paper written way back in 2011 when discussing the IPCC’s approach to report writing:

Achieving consensus is, to be clear, one of the major objectives of IPCC activities. Paragraph 10 of the amended Procedures Guiding IPCC Work, for example, states that “In taking decisions, and approving, adopting and accepting reports, the Panel, its Working Groups and any Task Forces shall use all best endeavors to reach consensus”.

Whichever way you read the above, the inescapable conclusion is that contrary to Professor Hossenfelder’s understanding, the IPCC is most emphatically consensus based. And just in case you needed any more persuading, there is also this from an IPCC guideline document on the consistent evaluation and communication of uncertainties:

Use the following dimensions to evaluate the validity of a finding: the type, amount, quality, and consistency of evidence (summary terms: ‘limited’, ‘medium’, or ‘robust’), and the degree of agreement (summary terms: ‘low’, ‘medium’, or ‘high’).

This time the emphasis is all mine; if it is okay for Hossenfelder to use capital letters then it must be fine for me to use bold. The only difference is that she was inadvertently emphasising her ignorance, whilst I am emphasising the facts.

But it gets worse. Not only is the IPCC very much consensus based, for years it tirelessly resisted proposed improvements that would at least have mitigated the worst impacts of its obsession with consensus. As Yohe and Oppenheimer explain:

Two proposals have been advanced repeatedly for beginning to address the problem of creating, defending and communicating consensus results as well as departures from the consensus. The degree to which IPCC, through its working group leadership structure, resisted these proposals during the AR4 process is unsettling, given that the scientific communities from which IPCC authors are drawn are supposed to think analytically about the world as a whole. Apparently, this dictum does not extend to reflexive consideration within the IPCC process as it performs its assessments.

Not only is the IPCC most definitely consensus based — in a way that Professor Hossenfelder would recognise as being unscientific — it has also failed in the past to abide by dictums of ‘reflexive consideration’ that would be considered the norm by any self-respecting scientific community. And that’s not just me saying that it’s a pair of former IPCC Lead Authors who, I might add, are far from being climate change sceptics. But let’s be honest here. The real reason the consensus approach worries the likes of Yohe and Oppenheimer is not because it is unscientific. Their concern is that it fails to give sufficient weighting to the more extreme pessimists within the climate science community (no one is concerned about ignoring extreme optimists; they were removed from the system years ago).

Honestly, I have no idea where Hossenfelder gets her ideas from regarding the workings of the IPCC. By saying “the IPCC process has problems” she would have you believe that she has some detailed knowledge. But in insisting that the IPCC is NOT consensus based, she betrays that her position hasn’t been informed by reading any of the IPCC documents that actually specify its processes! And this matters to me because Hossenfelder is one of many intelligent and influential scientists who comment approvingly on the scientific rigour of the IPCC and hence perpetuate falsehoods that have the effect of giving climate change sceptics a very hard time. Even worse, they embolden the Millibands of this world in a way that the world could really do without.

Hossenfelder’s convenient ignorance regarding the IPCC is both disappointing and perplexing. It’s an ignorance that, no doubt, plays a part in her insistence that climate science sceptics are just anti-science deniers who use ‘sceptic’ to deceive both the public and themselves. But why she can’t recognise the overtly political purpose of the IPCC is a mystery to me. Is she really that naïve, or is there more than a little of her own self-deception going on here? And if it is the latter, is there any reason to assume that she is the only expert who suffers from this expedient but damaging blind spot?