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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Were skeptic scientists kept out of the IPCC

What the science says...

The Independent Climate Change Email Review investigated the CRU scientists' actions as IPCC authors. Official records, Review Editors, and even the emails themselves suggest the CRU scientists acted in the spirit if not the letter of the IPCC rules. Anyway, the relevant texts were team responsibilities.

Climate Myth...

Skeptics were kept out of the IPCC?

"The Team had tampered with the complex, bureaucratic processes of the UN’s climate panel, the IPCC, so as to exclude inconvenient scientific results from its four Assessment Reports, and to influence the panel’s conclusions for political rather than scientific reasons. The Team had conspired in an attempt to redefine what is and is not peer-reviewed science for the sake of excluding results that did not fit what they and the politicians with whom they were closely linked wanted the UN’s climate panel to report." (Christopher Monckton)

Exhibit No. 1 of the climate conspiracy theory is a collection of emails stolen from the Climatic Research Unit (CRU) of the University of East Anglia (UEA), which appeared on the internet in November 2009. Though some of these "Climategate" emails can sound damning when quoted out of context, several inquiries have cleared the scientists. The most comprehensive inquiry, the Independent Climate Change Email Review, did something the media completely failed to do: it put the emails into context by investigating the main allegations. Its general findings (summarised here) were that the scientists' rigour and honesty are not in doubt, and their behaviour did not prejudice the advice given to policymakers, though they did fail to display the proper degree of openness.

One set of allegations is that CRU scientists abused their positions on Intergovernmental Panel on Climate Change (IPCC) writing groups to impede the consideration of papers challenging CRU’s work. Two papers in particular: the first about the instrumental record, and the second about tree-ring-based temperature reconstructions. The Review goes into each of these allegations in meticulous detail.

The first paper, McKitrick and Michaels (2004), or “MM2004”, argued that most of the observed late 20th century warming was due to the urban heat island effect. Jones’ reaction to the paper, according to an email dated 8/7/2004, was:

The other paper by MM is just garbage. […] I can’t see either of these papers being in the next IPCC report. Kevin and I will keep them out somehow — even if we have to redefine what the peer-review literature is!

The MM2004 paper was indeed omitted from the first and second drafts of AR4 WG1 Chapter 3, but mentioned and refuted in the final text. McKitrick claims that Jones wrote that paragraph and that it gave contrived reasons for rejecting the paper’s conclusions.

The second paper, McIntyre and McKitrick (2003), or “M&M2003”, criticized the famous “hockey stick” proxy temperature reconstruction by Mann, Bradley, and Hughes (1998), or “MBH98”. It argued that the “hockey stick” shape was primarily an artifact of statistical errors and the selection of specific tree ring series. The allegation is that Briffa, as lead author of AR4 WG1 Chapter 6, broke IPCC rules to include a paper by Wahl and Ammann then in press, or “WA2007”; which refuted M&M2003 but was clearly published after the deadline for inclusion in the AR4. Contrarians cite an email dated 18/7/2006, in which Briffa wrote to Wahl:

Gene I am taking the liberty (confidentially) to send you a copy of the reviewers comments (please keep these to yourself) of the last IPCC draft chapter. I am concerned that I am not as objective as perhaps I should be and would appreciate your take on the comments from number 6-737 onwards, that relate to your reassessment of the Mann et al work. I have to consider whether the current text is fair or whether I should change things in the light of the sceptic comments. In practice this brief version has evolved and there is little scope for additional text, but I must put on record responses to these comments — any confidential help, opinions are appreciated.

Contrarians argue the above email is evidence of Briffa breaking rules of confidentiality to ask for help in rebutting criticism of WA2007. Chapter 6 contained a paragraph referencing WA2007 as a rebuttal of M&M2003, which contrarians assumed to have been written by Briffa.

The Review asked Jones about the MM2004 allegations. He stated that the “keep them out” email was “sent on the spur of the moment and quickly forgotten”, but there were good scientific reasons for his intention to exclude MM2004. (Namely, it did not account for signals like El Niño; and in any case its conclusions about the land temperature record are at odds with the independent lines of evidence provided by the ocean and satellite records.) Jones also denied having written the paragraph in question, saying the inclusion of MM2004 was a collective decision by the Chapter 3 writing team. IPCC records confirm that MM2004 was discussed by the group.

The inquiry also took evidence from one of the three Review Editors for Chapter 3, Professor Sir Brian Hoskins. He “was very impressed by Jones’ attention to detail, and the rigour of the Chapter 3 process.” He pointed out the writing group had joint responsibility for the text and it was unlikely for one voice to have dominated.

The Review found the rebuttal of MM2004 does not appear to have been “invented”. Instead there has been “a consistence of view amongst those who disagree with MM2004 that has been sustained over the last 6 years”. Overall, the Review found no more than “mere speculation” that MM2004 was unfairly excluded:

We conclude that there is evidence that the text was a team responsibility. It is clear that Jones (though not alone) had a strongly negative view of the paper but we do not find that he was biased, that there was any improper exclusion of material or that the comments on the MM2004 paper in the final draft were “invented” given the (continuing) nature of the scientific debate on the issue. [9.3.6]

What about the treatment of M&M2003? Briffa says the text was the responsibility of the entire Chapter 6 writing group, and they took M&M2003 very seriously. That paper excluded 77 of the 95 pre-1500 tree ring series used in MBH98, and WA2007 showed that the results of MBH98 could be replicated very closely using all the data. The AR4 text did not state that WA2007 had disproved the criticisms made by M&M2003, merely that their impact might be relatively small. Besides, MBH98 was only one of the 12 reconstructions shown in Figure 6.10 (M&M2003 was not shown because McKitrick commented that “we are not trying to offer ‘our’ climate history curve”).

Professor John Mitchell, one of the two Chapter 6 Review Editors, confirmed there was group responsibility, and told the Review that referencing unpublished material in the AR4 was not prohibited, but only allowed under exceptional circumstances. However, he says Briffa’s confidential email is “problematic”:

On the one hand it appears to reflect an honest request to an expert for a comment about the extent to which the author is being balanced and fair. On the other hand, it stresses the need for confidentiality in three places, implying that the author realizes that the approach may be improper. There was also a leak of an early draft of the WG1 report to the press which led to IPCC emphasizing the need to maintain confidentiality in general which may have been at the back of the author’s mind. [9.4.5]

The Review was persuaded that M&M2003 was “dealt with in a careful and reasonable fashion”. They found that the inclusion of WA2007 was “to ensure that assessments were as up to date as possible” and “appear[s] to be consistent with IPCC principles”. As for the allegation of breaking confidentiality, the IPCC rules do not prevent authors asking experts for objective advice.

But arguably the best evidence that Briffa was acting in good faith can be found in the emails themselves. Many of Briffa’s emails actually suggest a desire to ensure that uncertainty was fully explained. (Indeed, as the Review points out, “the e-mail correspondence with Wahl stresses in several places Briffa’s concern to be fair to sceptical views.”) I think they are worth quoting at some length. In an email dated 29/4/2003, Keith Briffa wrote (my emphasis):

Can I just say that I am not in the MBH camp — if that be characterized by an unshakable “belief” one way or the other, regarding the absolute magnitude of the global MWP. I certainly believe the “medieval” period was warmer than the 18th century — the equivalence of the warmth in the post 1900 period, and the post 1980s, compared to the circa Medieval times is very much still an area for better resolution. […] On present evidence, even with such uncertainties I would still come out favouring the “likely unprecedented recent warmth” opinion…

In an email dated 3/2/2006, Briffa wrote:

we are having trouble to express the real message of the reconstructions — being scientifically sound in representing uncertainty, while still getting the crux of the information across clearly. It is not right to ignore uncertainty, but expressing this merely in an arbitrary way (and a total range as before) allows the uncertainty to swamp the magnitude of the changes through time. We have settled on this version (attached) of the Figure which we hoe [sic] you will agree gets the message over but with the rigor required for such an important document.

In an email dated 15/2/2006, Briffa wrote:

We should be careful not to push the conclusions beyond what we can securely justify — and this is not much other than a confirmation of the general conclusions of the TAR. […] Let us not try to over egg the pudding. For what it worth, the above comments are my (honestly long considered) views — and I would not be happy to go any further. Of course this discussion now needs to go to the wider Chapter authorship, but do not let Susan (or Mike) push you (us) beyond where we know is right.

To the Review Team (and to me), these emails suggest “Briffa was unlikely to be an uncritical defender of the MBH view of the ‘hockey stick’, and wished to respect the view of the writing team as a whole”. Basically, it looks like Briffa adhered to the spirit if not the letter of the IPCC rules.

The Review concluded that neither allegation of misuse of the IPCC process could be upheld: “neither Jones nor Briffa behaved improperly”, and both “were part of large groups of scientists taking joint responsibility” for the relevant IPCC texts. [9.5]

Despite being heralded as “the final nail in the coffin of anthropogenic global warming”, Climategate did not even demonstrate corruption of the IPCC process, let alone corruption of the climate science community. In any case, the CRU scientists' influence extended to a couple of IPCC chapters covering only a small part of the large body of evidence for anthropogenic global warming. That mountain of evidence cannot be explained away by the behaviour of a few individuals.

Last updated on 24 December 2010 by James Wight.

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Comments 1 to 2:

  1. In fact the IPCC includes many skeptical reviewers. Here is an incomplete list
  2. You don't have a question mark on the question (first title, at the very top of the page), and you do put one on the statement (second title, in the pink box).

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