Tag Archives: Michael Mann

Replication and due diligence, Wegman style

By Deep Climate

Today I continue my examination of the key analysis section of the Wegman report on the Mann et al “hockey stick” temperature reconstruction, which uncritically rehashed Steve McIntyre and Ross McKitrick’s purported demonstration of the extreme biasing effect of Mann et al’s “short-centered” principal component analysis.

First, I’ll fill in some much needed context as an antidote to McIntyre and McKitrick’s misleading focus on Mann et al’s use of principal components analysis (PCA) in data preprocessing of tree-ring proxy networks. Their problematic analysis was compounded by Wegman et al’s refusal to even consider all subsequent peer reviewed commentary – commentary that clearly demonstrated that correction of Mann et al’s “short-centered” PCA had minimal impact on the overall reconstruction.

Next, I’ll look at Wegman et al’s “reproduction” of McIntyre and McKitrick’s  simulation of Mann et al’s PCA methodology, published in the pair’s 2005 Geophysical Research Letters article, Hockey sticks, principal components, and spurious significance).  It turns out that the sample leading principal components (PC1s) shown in two key Wegman et al figures were in fact rendered directly from McIntyre and McKitrick’s original archive of simulated “hockey stick” PC1s. Even worse, though, is the astonishing fact that this special collection of “hockey sticks”  is not even  a random sample of the 10,000 pseudo-proxy PC1s originally produced in the GRL study. Rather it expressly contains the very  top 100 – one percent – having the most pronounced upward blade. Thus, McIntyre and McKitrick’s original Fig 1-1, mechanically reproduced by Wegman et al, shows a carefully selected “sample” from the top 1% of simulated  “hockey sticks”. And Wegman’s Fig 4-4, which falsely claimed to show “hockey sticks” mined from low-order, low-autocorrelation “red noise”, contains another 12 from that same 1%!

Finally, I’ll return to the central claim of Wegman et al – that McIntyre and McKitrick had shown that Michael Mann’s “short-centred” principal component analysis would mine “hockey sticks”, even from low-order, low-correlation “red noise” proxies . But both the source code and the hard-wired “hockey stick” figures clearly confirm what physicist David Ritson pointed out more than four years ago, namely that McIntyre and McKitrick’s “compelling” result was in fact based on a highly questionable procedure that generated null proxies with very high auto-correlation and persistence. All these facts are clear from even a cursory examination of McIntyre’s source code, demonstrating once and for all the incompetence and lack of due diligence exhibited by the Wegman report authors.

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Wegman Report update, part 1: More dubious scholarship in full colour

This is the final instalment in a series of posts documenting dubious scholarship and unattributed sources in the background chapter of the touchstone of climate contrarians known as the Wegman Report. That report has been touted as Exhibit A proving the “destruction” of Michael Mann’s “hockey stick” graph by self-styled climate auditor Steve McIntyre.

Previously, I found extensive passages bearing “striking similarity” to a classic text by the distinguished paleoclimatologist (and “hockey stick” co-author) Raymond Bradley in the background sections on tree rings and on ice cores. Subsequently, the background section on social networks was found to contain material apparently drawn without attribution from a variety of sources, including Wikipedia and several text books.

This time, I’m looking at section 2.2 (see Wegman Report PDF at p. 15), which gives the background of key statistical concepts, including Principal Component Analysis. Astonishingly, even this section appears to contain a significant amount of unattributed material from other sources, although quite a bit less than the other sections. Again, Wikipedia appears to be a key source, along with a couple of text books.

I’ll also introduce some refinements to the text analysis, based largely on John Mashey’s recent innovations. Those refinements allow a better characterization of the relationship between various passages in Wegman et al and their apparent antecedents, as well as permitting a quantitative analysis based on word counts.

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Terence Corcoran whopper: Mann’s hockey stick “eliminated some of the data from 1960 forward … and then spliced on actual temperature data”

Terence Corcoran may well have just unleashed the National Post’s biggest whopper yet about climate science – and that’s saying something.

Corcoran’s commentary on the recent Russell “climategate” email review lays one error-laden defamation on top of another, as he attempts to demonstrate that the report “provides plenty of evidence that climate science has been and remains an uncertain shambles”. Oh, and apparently the review “portrays climate science as a field filled with uncertainty, debate, lack of openness, data hoarding and ill-will.”

Along the way, Corcoran even manages to confuse a little known Phil Jones graphic with Michael Mann’s “hockey stick” millenial temperature reconstruction. This leads to the astonishing (and entirely wrong) accusation that the hockey stick creators “eliminated some of the data from 1960 forward … and then spliced on actual temperature data”. Yet neither the “hockey stick” graph (the real one) nor the associated Mann et al study are mentioned in the report at all!

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How to be a climate science auditor, part 2: The forgotten climategate emails

In this installment, I’ll look at another technique in the climate auditor’s toolbox, namely selective quotation. Once again, our example case study will involve accusations by Steve McIntyre concerning the use of paleoclimatologist Keith Briffa’s tree-ring based reconstruction in a key figure from the IPCC Third Assessment Report.

Arguing from a cherrypicked selection of quotes from the “Climategate” emails, McIntyre has claimed that IPCC authors Chris Folland and Michael Mann pressured Briffa to submit a reconstruction that would not “dilute the message” by showing “inconsistency” with multi-proxy reconstructions from Mann and Briffa’s CRU colleague Phil Jones. Briffa “hastily re-calculated his reconstruction”, sending one with a supposedly larger post-1960 decline before. According to McIntyre, Mann resolved this new “conundrum” and simply “chopped off the inconvenient portion of the Briffa tree-ring data”.

But a review of the emails – including some that have never been quoted before – clearly contradicts McIntyre’s version of events:

  • Jones and Briffa were concerned that Mann had an outdated version of the Briffa reconstruction, and both urged the adoption of the newer “low frequency” one, more appropriate for comparison with other multi-century reconstructions.
  • Far from pressuring Briffa to change his reconstruction right away, Mann questioned whether an immediate change was required, or even possible, and counselled waiting for the next revision.
  • CRU colleague Tim Osborn advised Mann that he and Briffa “usually stopped” the “low frequency” reconstruction in 1960, and went one better in his later “resend” to Mann, by explicitly removing the post-1960 data.

I’ll also show how McIntyre has changed his narrative along the way , in an effort to prove that the true “context” of the famous “trick” to “hide the decline” is somehow an indictment of the IPCC. (Speaking of which, be sure to take the poll at the end about McIntyre’s next move). But first, once again, here is the cause of all the fuss, namely Figure 2-21 from Chapter 2 of the IPCC Third Assessment Report – Working Group I: The Scientific Basis (2001).

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How to be a climate auditor, part 1: Pretty pictures

Do you have what it takes to be a climate auditor? Try the following fun test and find out. And at the same time, you can’t help but learn something about the fine art of argumentation from charts as practiced by the master himself, Steve McIntyre, and refined in his most devoted media outlet, the U.K. based Mail on Sunday.

Here is the chart that is held to epitomize the “trick” to “hide the decline”: figure 2-21 from the IPCC ‘s Third Assessment Report, showing key temperature reconstructions.

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Wegman and Said on social networks: More dubious scholarship

Today I continue my exploration of the dubious scholarship in the contrarian touchstone known as the Wegman report, this time focusing on the report’s background section on social network analysis. As many readers may recall, Wegman et al used a simplistic analysis of co-author relationships to speculate about supposed lack of independence between researchers in paleoclimatology, accompanied by lapses of rigour in the peer review process. This, of course, echoed similar accusations by self-styled climate auditor Steve McIntyre.

In both the original Wegman report and a subsequent follow-up paper by Yasmin Said, Wegman and two others, the background sections on social network research show clear and compelling instances of apparent plagiarism. The three main sources, used almost verbatim and without attribution, have now been identified. These include a Wikipedia article and a classic sociology text book by Wasserman and Faust. But the papers rely even more on the third source, a hands-on text book that explores social network concepts via the Pajek analysis software package – the same tool used by the Wegman team to analyze “hockey stick” author Michael Mann’s co-author network.

Not only that, but the later Said et al paper acknowledges support from the National Institutes on Alcohol Abuse and Alcoholism, as well as the Army Research Laboratory, raising a host of new issues and questions. And chief among those questions is this: Will George Mason University now finally do the right thing and launch a complete investigation of the actions and scholarship of Wegman and Said?

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Steve McIntyre and Ross McKitrick, part 2: The story behind the Barton-Whitfield investigation and the Wegman Panel

[Updated Feb. 8: (editing and extension of summary and document list update)]

Perhaps the most disturbing episode in the “hockey stick” controversy was the investigation of climate scientists by the U.S. House Energy and Commerce Committee under Republican representatives Joe Barton and Ed Whitfield, and a subsequent report for that same committee  by an “independent” panel led by George Mason University statistics professor Edward Wegman. In light of various renewed “skeptic” allegations of scientific misconduct against Michael Mann and Phil Jones, and my recent revelation of possible plagiarism and other questionable scholarship in the Wegman report, a complete review of the events of 2005-2006 would seem to be in order.

In short, the Energy and Commerce Committee refused the offer of a proper scientific review from the National Academy of Sciences in favour of an investigative process that was ad hoc, biased and unscientific. And the report resulting from that process  is tainted with highly questionable scholarship.

I can now fill in important gaps in the timelines of the initial investigation and the Wegman panel. But more importantly my review has led to some startling conclusions:

  • Not only was the original Barton-Whitfield investigation (in the form of intimidating letters) inspired by the allegations of “climate science auditor”  Steve McIntyre, but the defining impetus seems to have been a little known Cooler Heads Coalition-Marshall Institute sponsored presentation by McIntyre and sidekick economist Ross McKitrick in Washington barely a month beforehand.
  • Energy and Commerce Committee Republican staffer Peter Spencer played a key but hitherto undisclosed role in the investigation and the subsequent Wegman panel report, and  apparently acted as the main source and gatekeeper of climate science information for the panel.
  • Steve McIntyre was in communication with the Wegman panel, at least concerning technical questions around replication of his work. The full extent of McIntyre’s communications or meetings with Spencer or other staffers, as well as Wegman panelists, is still unknown. However, the record shows there were at least two intriguing opportunities for face-to-face meetings in Washington during the Wegman panel’s mandate.

All this, along with new information about the circumstances of the Wegman panel’s formation and mandate, raises serious doubts about the supposed independence of the Wegman panel.

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