Marketing global warming

The papers published by McIntyre and McKitrick in 2003 and 2005 show that the hockey stick studies - among the most influential in history - were sloppy and plain wrong. Dr Mann was obliged to issue a corrigendum (PDF 44KB) in July 2004 acknowledging at least that his key IPCC study was documented in a careless way and was effectively unverifiable. Dr Mann was able to maintain a defence only because he refused to disclose all his data and code and argue that his critics were not correctly replicating his method.

Eventually the US House of Representatives became involved and two separate, independent expert groups were commissioned to provide peer reviewed reports on the matter. These reported (PDF 151MB) - under oath - to the House of Representatives six months before the IPCC began the release of AR4. They separately confirmed the work of McIntyre and McKitrick, which had shown that the “hockey stick” study contained three fatal flaws:

• it used inappropriate “strip bark” proxies that were responsible for the “hockey stick” shape;
• it used an incorrect statistical process that could find hockey stick shapes where none really existed; and
• it failed rigorous statistical validation.

The Wegman Report (PDF 1.41MB) demonstrated that the various historic reconstructions alleged to corroborate the “hockey stick” were not as independent as claimed, sharing both authors and data.

The second report was from the National Research Council (PDF 3.27MB) few of whom who could be described as climate sceptics. The views of its panel chairman Gerald North have already been mentioned, but he told the House of Representatives that he did not disagree with the methods or conclusions of Wegman and added, “In fact, pretty much the same thing is said in our report.” The NRC Report concluded, “Largescale temperature reconstructions should always be viewed as having a “murky” early period and a later period of relative clarity. The boundary between murkiness and clarity is not precise but is nominally around A.D. 1600.” Because of this they said it was only “plausible” that late 20th century warming is exceptional.

Wegman also said:

Based on the literature we have reviewed, there is no overarching consensus on MBH98/99. As analyzed in our social network, there is a tightly knit group of individuals who passionately believe in their thesis. However, our perception is that this group has a self-reinforcing feedback mechanism and, moreover, the work has been sufficiently politicized that they can hardly reassess their public positions without losing credibility.

But in the AR4 process under way it was close associates of Dr Mann and others equally committed to the “consensus” view that were charged with updating the assessment of historic global temperatures. The AR4 WGI Chapter 6 authors ignored the unequivocal invalidation of Dr Mann’s studies. Instead they extended and reinforced the earlier views based on other studies many of which were shown by Wegman not to be independent.

The IPCC tried to prevent the AR4 drafts and reviewers' comments from seeing the light of day but gave in to Freedom of Information Requests.

From them we can see that the review process was a sham and that the 16 lead authors of Chapter 6 were not willing to be deflected from their purpose. Two papers co-authored by a student of Dr Mann had been specifically commissioned - at the US tax payers’ expense - in an effort to undermine the work of McIntyre and McKitrick. One was rejected by the journal GRL but the other, which still referenced the first, was “provisionally accepted” by another journal but has never appeared in print.

Nevertheless it is relied upon in AR4 to suggest wrongly that the McIntyre and McKitrick papers do not invalidate the hockey stick. In my Energy and Environment paper (PDF 855KB), I review some of the AR4 drafting and review comments in detail but here I will conclude with the comment from the reviewer for the Government of the United States of America and the chapter authors’ reply:

Reviewers Comment 6-750: The use of Wahl and Ammann (accepted) does not comply with WG1’s deadlines and all text based on this reference should be deleted. WG1’s rules require that all references be “published or in print” by December 16, 2005. Wahl and Ammann was “provisionally accepted” on that date, and not fully accepted until February 28, 2006, at which time no final preprint was available. Substantial changes were made in the paper between December 16, 2005 and February 28, 2006, including insertion of tables showing that the MBH98 [“hockey stick”] reconstruction failed verification with r-squared statistics, as had been reported by McIntyre and McKitrick in 2003. These tables were not available in the draft considered by WG1 when developing the second-order draft.
[Govt. of United States of America (Reviewer’s comment ID #: 2023-415)]

Response: Rejected - the citation is allowed under current rules.