The latest false scandal in climate science hit the blogosphere over the weekend. National Post columnist Lawrence Solomon [not to be confused with atmospheric chemist and IPCC WG1 chair Susan Solomon] wrote a column with the outlandish claim:

The UN’s IPCC misled the press and public into believing that thousands of scientists backed its claims on manmade global warming, according to Mike Hulme, a prominent climate scientist and IPCC insider.

Charges of a “phony UN IPCC consensus” are already reverberating on contrarian blogs around the world, thanks to the quick efforts of climate science disinformation specialist Marc Morano.

But now Mike Hulme, a professor of climate change at the University of East Anglia, has set the record straight. His “correcting and clarifying” statement is unambiguous in its disavowal of Solomon’s and Morano’s misinterpretation:

I did not say the ‘IPCC misleads’ anyone – it is claims that are made by other commentators, such as the caricatured claim I offer in the paper, that have the potential to mislead.

Solomon, who is also Executive Director of of the right-wing, anti-science group Energy Probe, posted the following piece on the National Post website early last Sunday.

The IPCC consensus on climate change was phoney, says IPCC insider Lawrence Solomon – June 13, 2010 – 8:50 am The UN’s Intergovernmental Panel on Climate Change misled the press and public into believing that thousands of scientists backed its claims on manmade global warming, according to Mike Hulme, a prominent climate scientist and IPCC insider. The actual number of scientists who backed that claim was “only a few dozen experts,” he states in a paper for Progress in Physical Geography, co-authored with student Martin Mahony. “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,” the paper states unambiguously, adding that they rendered “the IPCC vulnerable to outside criticism.” … Hulme’s depiction of IPCC’s exaggeration of the number of scientists who backed its claim about man-made climate change can be found on pages 10 and 11 of his paper, found here.

Never mind waiting until the ink dries. Marc Morano swung into action within hours, while readers of the National Post print edition have yet to benefit from Solomon’s latest wisdom. Climate Depot breathlessly announced:

Will Media Now Apologize for being complicit in the ‘Consensus Con’? UN IPCC ‘consensus’ on climate was phony, says IPCC Lead Author Mike Hulme!

The results were depressingly predictable. The piece has already been reproduced or excerpted hundreds of times, including at Nigel Lawson’s Global Warming Policy Foundation website and PrisonPlanet.

Now it turns out that Solomon’s post was based on selective quotation and gross misinterpretation of an article by Hulme and his student, Martin Mahony, in press at Progress in Physical Geography. But don’t just take my word for it.

This morning, Mike Hulme prominently posted a statement “correcting misleading newspaper and internet blog reports of the Hulme and Mahony paper on the IPCC”. Here is the key passage (see below for the entire text):

First, I did not say the ‘IPCC misleads’ anyone – it is claims that are made by other commentators, such as the caricatured claim I offer in the paper, that have the potential to mislead. Second, they have a potential to mislead if they give the impression that every statement in IPCC reports is ‘signed off’ by every IPCC author and reviewer. Patently they are not, and cannot. Third, it is the chapter lead authors – say 10 to 20 experts – on detection and attribution who craft the sentence about detection and attribution, which is then scrutinised and vetted by reviewers and government officials. Similarly, statements about what may happen to the meridional overturning circulation (MOC) of the ocean are crafted by those expert in ocean science, statements about future sea-level rise by sea-level experts, and so on.

The piece concludes thus:

Giving the impression that the IPCC consensus means everyone agrees with everyone else – as I think some well-meaning but uninformed commentaries do (or have a tendency to do) – is unhelpful; it doesn’t reflect the uncertain, exploratory and sometimes contested nature of scientific knowledge.

So clearly, Hulme is not criticizing the IPCC itself or touting “IPCC exaggeration”, but rather “well-meaning but uninformed commentaries” from groups such as Greenpeace that do refer to a “consensus” of 2500 scientists in support of specific IPCC statements, for example on attribution of climate change.

Even more important, though, is Hulme’s recognition that the IPCC’s “consensus” approach can lead to findings that are perceived as overly conservative by many experts in a given field. As the Progress in Physical Geography paper states:

But consensus-making can also lead to criticism for being too conservative, as Hansen (2007) has most visibly argued. Was the IPCC AR4 too conservative in reaching its consensus about future sea-level rise? Many glaciologists and oceanographers think they were (Kerr, 2007; Rahmstorf, 2010), leading to what Hansen attacks as ‘scientific reticence’. Solomon et al. (2008) offer a robust defence, stating that far from reaching a premature consensus, the AR4 report stated that in fact no consensus could be reached on the magnitude of the possible fast ice-sheet melt processes that some fear could lead to 1 or 2 metres of sea-level rise this century. Hence these processes were not included in the quantitative estimates.

That tendency to conservative caution is an inconvenient aspect of IPCC “consensus-making” that Solomon somehow forgot to mention.

Now that it is clear the only thing phony about the whole affair is Solomon’s story itself, the most important remaining question is whether the National Post and Energy Probe will issue much-needed corrections. Based on past form, I wouldn’t hold my breath.

[Hat tip for alerting me to Solomon’s post: MapleLeaf]

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The full text of Mike Hulme’s statement follows. The original may be viewed at Hulme’s website.

Correcting and Clarifying Hulme and Mahony on the IPCC Consensus



Various newspaper and internet blogs are reporting me as saying that the IPCC has ‘misled the press and public into believing that thousands of scientists backed its claims on manmade global warming’ whereas in fact only ‘a few dozen experts’ did so. This story emanates from an article, in press with Progress in Physical Geography and posted on my website http://mikehulme.org/wp-content/uploads/2010/01/Hulme-Mahony-PiPG.pdf, which reviews 20 years of published literature on the nature of the IPCC and its functions and governance. The relevant section from this paper is the following, which is part of a longer discussion about the nature of uncertainty and consensus in the IPCC assessments …

“Without a careful explanation about what [consensus] means, this drive for consensus can leave the IPCC vulnerable to outside criticism. 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. But consensus-making can also lead to criticism for being too conservative, as Hansen (2007) has most visibly argued.”



Three things should be clear from this. First, I did not say the ‘IPCC misleads’ anyone – it is claims that are made by other commentators, such as the caricatured claim I offer in the paper, that have the potential to mislead. Second, they have a potential to mislead if they give the impression that every statement in IPCC reports is ‘signed off’ by every IPCC author and reviewer. Patently they are not, and cannot. Third, it is the chapter lead authors – say 10 to 20 experts – on detection and attribution who craft the sentence about detection and attribution, which is then scrutinised and vetted by reviewers and government officials. Similarly, statements about what may happen to the meridional overturning circulation (MOC) of the ocean are crafted by those expert in ocean science, statements about future sea-level rise by sea-level experts, and so on.



The point of this bit of our article was to draw attention to the need for a more nuanced understanding of what an IPCC ‘consensus’ is – as I say: “Without a careful explanation about what it means, this drive for consensus can leave the IPCC vulnerable to outside criticism.” The IPCC consensus does not mean – clearly cannot possibly mean – that every scientist involved in the IPCC process agrees with every single statement in the IPCC! Some scientists involved in the IPCC did not agree with the IPCC’s projections of future sea-level. Giving the impression that the IPCC consensus means everyone agrees with everyone else – as I think some well-meaning but uninformed commentaries do (or have a tendency to do) – is unhelpful; it doesn’t reflect the uncertain, exploratory and sometimes contested nature of scientific knowledge.



Mike Hulme, Norwich

15 June 2010



