De niet–bestaande en nietszeggende 97% klimaatconsensus

Op weg naar de klimaattop in Parijs draait de propagandamachine weer op volle toeren.

Reeds verschillende malen heb ik aandacht geschonken aan de niet–bestaande en nietszeggende 97% klimaatconsensus. Toch duikt die steeds maar weer op in het klimaatdebat – thans in het bijzonder in de aanloop naar de klimaattop in december in Parijs om druk uit te oefenen op de uitkomst daarvan. Zelfs president Obama heeft er over getwitterd: “97 per cent of climate scientists agree that climate change is real and man-made … Find the deniers near you — and call them out today.” Dit is bepaald niet het hoogtepunt van zijn presidentschap.

De Canadese econoom Ross McKitrick heeft dit fenomeen onlangs opnieuw gefileerd.

Onder de titel, 'The con in consensus: Climate change consensus among the misinformed is not worth much', schreef hij voor de 'Financial Post'.

Lots of people get called “climate experts” and contribute to the appearance of consensus, without necessarily being knowledgeable about core issues. A consensus among the misinformed is not worth much.

Not only is there no 97 per cent consensus among climate scientists; many misunderstand core issues

In the lead-up to the Paris climate summit, massive activist pressure is on all governments, especially Canada’s, to fall in line with the global warming agenda and accept emission targets that could seriously harm our economy. One of the most powerful rhetorical weapons being deployed is the claim that 97 per cent of the world’s scientists agree what the problem is and what we have to do about it. In the face of such near-unanimity, it would be understandable if Prime Minister Harper and the Canadian government were simply to capitulate and throw Canada’s economy under the climate change bandwagon. But it would be a tragedy because the 97 per cent claim is a fabrication.

Like so much else in the climate change debate, one needs to check the numbers. First of all, on what exactly are 97 per cent of experts supposed to agree? In 2013 President Obama sent out a tweet claiming 97 per cent of climate experts believe global warming is “real, man-made and dangerous.” As it turns out the survey he was referring to didn’t ask that question, so he was basically making it up. …

One commonly-cited survey asked if carbon dioxide is a greenhouse gas and human activities contribute to climate change. But these are trivial statements that even many IPCC skeptics agree with. And again, both statements are consistent with the view that climate change is harmless. So there are no policy implications of such surveys, regardless of the level of agreement. ...

The most highly-cited paper supposedly found 97 per cent of published scientific studies support man-made global warming. But in addition to poor survey methodology, that tabulation is often misrepresented. Most papers (66 per cent) actually took no position. Of the remaining 34 per cent, 33 per cent supported at least a weak human contribution to global warming. So divide 33 by 34 and you get 97 per cent, but this is unremarkable since the 33 per cent includes many papers that critique key elements of the IPCC position.

In 2012 the American Meteorological Society (AMS) surveyed its 7,000 members, receiving 1,862 responses. Of those, only 52 per cent said they think global warming over the 20th century has happened and is mostly manmade (the IPCC position). The remaining 48 per cent either think it happened but natural causes explain at least half of it, or it didn’t happen, or they don’t know. Furthermore, 53 per cent agree that there is conflict among AMS members on the question.

So no sign of a 97 per cent consensus. Not only do about half reject the IPCC conclusion, more than half acknowledge that their profession is split on the issue. ….

En dat schenkt Ross McKitrick aandacht aan een studie van het PBL (Planbureau voor de Leefomgeving) die onder leiding van Bart Verheggen werd uitgevoerd.

The Netherlands Environmental Agency recently published a survey of international climate experts. 6550 questionnaires were sent out, and 1868 responses were received, a similar sample and response rate to the AMS survey. In this case the questions referred only to the post-1950 period. 66 per cent agreed with the IPCC that global warming has happened and humans are mostly responsible. The rest either don’t know or think human influence was not dominant. So again, no 97 per cent consensus behind the IPCC.

But the Dutch survey is even more interesting because of the questions it raises about the level of knowledge of the respondents. Although all were described as “climate experts,” a large fraction only work in connected fields such as policy analysis, health and engineering, and may not follow the primary physical science literature. ...

Regarding the recent slowdown in warming, here is what the IPCC said: “The observed global mean surface temperature (GMST) has shown a much smaller increasing linear trend over the past 15 years than over the past 30 to 60 years.” Yet 46 per cent of the Dutch survey respondents – nearly half – believe the warming trend has stayed the same or increased. And only 25 per cent agreed that global warming has been less than projected over the past 15 to 20 years, even though the IPCC reported that 111 out of 114 model projections overestimated warming since 1998.

Three quarters of respondents disagreed or strongly disagreed with the statement “Climate is chaotic and cannot be predicted.” Here is what the IPCC said in its 2003 report: “In climate research and modelling, we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.” ...

Ross McKitrick concludeert:

What can we take away from all this? First, lots of people get called “climate experts” and contribute to the appearance of consensus, without necessarily being knowledgeable about core issues. A consensus among the misinformed is not worth much.

Second, it is obvious that the “97 per cent” mantra is untrue. The underlying issues are so complex it is ludicrous to expect unanimity. The near 50/50 split among AMS members on the role of greenhouse gases is a much more accurate picture of the situation. The phony claim of 97 per cent consensus is mere political rhetoric aimed at stifling debate and intimidating people into silence.

… What we really need to call out is the use of false propaganda and demagoguery to derail factual debate and careful consideration of all facets of the most complex scientific and policy issue of our time.

Aldus Ross McKitrick.

Lees verder hier.

Voor mijn eerdere DDS–bijdragen zie hier.