Klimaat: Het sprookje van de 97% consensus

Ziekelijke tendenties in het klimaatdebat.

Enige tijdje geleden veroorzaakte de publicatie van een artikel van Cook et al opschudding in het klimaatdebat. Op basis van een literatuurstudie waren zij tot de conclusie gekomen gekomen dat in 97% van de door hen onderzochte studies steun tot uitdrukking werd gebracht voor de menselijke broeikashypothese (AGW = Anthropogenic Global Warming). Door sommige politici werd deze studie aangegrepen om te verkondigen dat de consensus onder klimatologen sterker was dan ooit. Dat gold bijvoorbeeld voor de Amerikaanse president Obama en de Britse minister voor energie en klimaat, Ed Davey.

Verschillende prominente klimaatonderzoekers, zoals Joanne Nova, Marcel Crok en Richard Tol, hebben de resultaten van dit onderzoek geanalyseerd en kwamen tot de conclusie dat deze niet deugden.

Jo Nova:

Thousands of papers support man-made climate change, but not one found the evidence that matters. Cook may have found 3,896 papers endorsing the theory that man-made emissions control the climate, but he cannot name one paper with observations that shows that the assumptions of the IPCC climate models about water vapor and cloud feedbacks are correct. These assumptions produce half to two-thirds of the future projected warming in models. If the assumptions are wrong (and dozens of papers suggest they are) then the predicted warming is greatly exaggerated. Many of the papers in his list are from these flawed models. In other words, he’s found 3,896 inconclusive, subsequently-overturned, or correct but irrelevant papers. What is most important about his study is that after thousands of scientists have pored over the best data they could find for twenty years, they still haven’t got any conclusive support.

Lees verder hier.

Marcel Crok concludeerde: 'Cook’s survey not only meaningless but also misleading.'

Marcel Crok:

So what’s all the fuzz about? Cook et al. selected around 12,000 scientific abstracts that contained the words “global warming” or “global climate change” published in the period 1991-2011. With a large group of volunteers they then rated the papers using 7 categories. Around 8000 of the abstracts (2/3) take no clear position on Anthropogenic Global Warming (AGW). Of the remaining ~4000 abstracts more than 97% “endorse AGW” according to the paper. Only a tiny amount (78 papers) “reject AGW”. Hence they claim again that there is a consensus, that the debate is over and also that there is a gap between scientists and the public (….). A much larger percentage of the scientists “endorses AGW” than the public at large.

Lees verder hier.

Richard Tol schreef naar de Universiteit waaraan Cook was verbonden om opheldering te krijgen over de methode die was toegepast bij het onderzoek.

Richard Tol:

Open letter on access to data for replication

Dear Professor Høj,

I was struck by a recent paper published in Environmental Research Letters with John Cook, a University of Queensland employee, as the lead author. The paper purports to estimate the degree of agreement in the literature on climate change. Consensus is not an argument, of course, but my attention was drawn to the fact that the headline conclusion had no confidence interval, that the main validity test was informal, and that the sample contained a very large number of irrelevant papers while simultaneously omitting many relevant papers. My interest piqued, I wrote to Mr Cook asking for the underlying data and received 13% of the data by return email. I immediately requested the remainder, but to no avail.

I found that the consensus rate in the data differs from that reported in the paper. Further research showed that, contrary to what is said in the paper, the main validity test in fact invalidates the data. And the sample of papers does not represent the literature. That is, the main finding of the paper is incorrect, invalid and unrepresentative. ….

Lees verder hier.

Onder de titel. 'Consensus? What Consensus?', heeft ook Andrew Montford (misschien beter bekend als de klimaatsceptische blogger Bishop Hill) een brochure geschreven over de studie van Cook et al. Hij kwam tot overeenkomstige conclusies.

Andrew Montford:

Recent reports that 97% of published scientific papers support the so-called consensus on man-made global warming are based on a paper by John Cook et al. Precisely what consensus is allegedly being supported in these papers cannot be discerned from the text of the paper. An analysis of the methodology used by Cook et al. shows that the consensus referred to is trivial:

• that carbon dioxide (CO2) is a greenhouse gas

• that human activities have warmed the planet to some unspecified extent.

Almost everybody involved in the climate debate, including the majority of sceptics, accepts these propositions, so little can be learned from the Cook et al. Paper. The extent to which the warming in the last two decades of the twentieth century was man-made and the likely extent of any future warming remain highly contentious scientific issues. ….

In recent months it has been repeatedly stated that 97% of scientists agree that global warming is real and man-made. These claims are based on a paper published by John Cook et al. in the journal Environmental Research Letters. The authors are all associated with the controversial global warming activist website Skeptical Science. Their conclusions were as follows: Among abstracts expressing a position on AGW [Anthropogenic Global Warming], 97.1% endorsed the consensus position that humans are causing global warming. The paper received an extraordinary reception, being downloaded more than 20,000 times in the first few days after it was published, and receiving hundreds of citations from around the internet. It was even referred to on President Obama’s Twitter feed:

@BarackObama: Ninety-seven percent of scientists agree: #climate change is real, man-made and dangerous.

It should be noted that the Obama statement misrepresented the Cook et al. paper, which said nothing about global warming being dangerous and was based on analysis of published abstracts rather than the opinions of scientists. This confusion over exactly what the paper was about also seemed to affect Ed Davey, the Secretary of State for Energy and Climate Change, who cited it in an interview with the BBC’s Andrew Neil:

We’ve had a complete unchallenged view of the climate change deniers. I think e need to have rather more balance in the debate, particularly when we saw a recent analysis of 12,000 scientific papers… and of the scientists who expressed a view – these were climate change papers – of the scientists who expressed a view 97% said that climate change was happening and that it was human-made activity.

Lees verder hier.

Intussen is het kwaad al weer geschied. De media en de politiek pikken wèl de loze beweringen van Cook et al op, maar niet de weerlegging ervan. De sabotage van een serieus klimaatdebat van de kant van sommige extremistische AGWers gaat vrolijk door.

Gelukkig dat regeringen nu ook in de gaten hebben dat de AGW–hypothese tekortkomingen vertoont en het VN–klimaatpanel het vuur na aan de schenen legt om met een verklaring te komen (zoals ik hier eerder berichtte). Dit is nog nooit eerder vertoond in het klimaatdebat. Naar mijn stellige overtuiging komt er geen bevredigende verklaring van het IPCC, want die is er niet. Daarmee heeft het IPCC een groot geloofwaardigheidsprobleem.

Voor mijn eerdere DDS-bijdragen, zie hier.