Tag Archives: Micahel Mann

The Wegman report sees red (noise)

By Deep Climate

The recent focus on George Mason University’s investigation into plagiarism allegations concerning the Wegman “hockey stick” report and related scholarship has led to some interesting reactions in the blogosphere. Apparently, this involves trifling attribution problems for one or two paragraphs, even though the allegations now touch on no less than 35 pages of the Wegman report, as well as the federally funded Said et al 2008. Not to mention that subsequent editing has also led to numerous errors and even distortions.

But we are also told that none of this “matters”, because the allegations and incompetence do not directly touch on the analysis nor the findings of the Wegman report. So, given David Ritson’s timely intervention and his renewed complaints about Edward Wegman’s lack of transparency, perhaps it is time to re-examine  Wegman report section 4, entitled “Reconstructions and  Exploration Principal Component Methodologies”. For Ritson’s critique of the central Wegman analysis itself remains as pertinent today as four years ago, when he expressed his concerns directly to the authors less than three weeks after the release of the Wegman report.

Ritson pointed out a major error in Wegman et al’s exposition of the supposed tendency of “short-centred” principal component analysis to exclusively “pick out” hockey sticks from random pseudo-proxies.  Wegman et al claimed that Steve McIntyre and Ross McKitrick had used  a simple auto-regressive model to generate the random pseudo-proxies, which is the same procedure used by paleoclimatologists to benchmark reconstructions. But, in fact, McIntyre and McKitrick clearly used a very different – and highly questionable – noise model, based on a “persistent” auto-correlation function derived from the original set of proxies. As a result of this gross misunderstanding, to put it charitably, the Wegman report failed utterly to analyze the actual scientific and statistical issues. And to this day, no one – not Wegman, nor any of his defenders – has addressed or even mentioned this obvious and fatal flaw at the heart of the Wegman report.

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