Monthly Archives: August 2010

McShane and Wyner 2010

Over at ClimateAudit and WUWT they’ve broken out the champagne and are celebrating (once again) the demise, nay, the shattering into 1209 tiny splinters, of the Mann et al “hockey stick” graph, both the 1998 and 2008 editions. The occasion of all the rejoicing is a new paper by statisticians Blakely McShane and Abraham Wyner, entitled A Statistical Analysis of Multiple Temperature Proxies: Are Reconstructions of Surface Temperatures Over the Last 1000 Years Reliable? [PDF]. The paper, in press at the Annals of Applied Statistics, purports to demonstrate that randomly generated  proxies of various kinds can produce temperature “reconstructions” that perform on validation tests as well as, or even better than,  the actual proxies.

My discussion of McShane and Wyner is divided into two parts. First, I’ll look at the opening background sections. Here we’ll see that the authors have framed the issue in surprisingly political terms, citing a number of popular references not normally found in serious peer-reviewed literature. Similarly, the review of the “scientific literature” relies inordinately on grey literature such as Steve McIntyre and Ross McKitrick’s two Environment and Energy articles and the (non peer-reviewed) Wegman report. Even worse, that review contains numerous substantive errors, some of which appear to have been introduced by a failure to consult cited sources directly, notably in a discussion of a key quote from Edward Wegman himself.

With regard to the technical analysis, I have assumed that McShane and Wyner’s applications of statistical tests and calculations are sound. However, here too, there are numerous problems. The authors’ analysis of the performance of various randomly generated “pseudo proxies” is based on several questionable methodological choices. Not only that, but a close examination of the results shows clear contradictions with the findings in the key reconstruction studies cited. Yet the authors have not even mentioned these contradictions, let alone explained them.

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Open Thread # 5

Seems like a good time to start a new Open Thread and close the old one (a.k.a. the “TCO on Tiljander/MMH/CA/life in general” thread). Honours this time go to Gavin’s Pussycat, whose comment will start things off.

What have Wegman and Said done … lately?

While we’re waiting for John Mashey’s magnum opus on the Wegman report (and believe me, it is well worth the wait), let’s take a look at what Edward Wegman and his protege and report co-author Yasmin Said have been up to recently (again, a big hat tip to John).

The Interface Symposium (an annual statistical computing conference dating back to 1967) held its 2010 edition in Seattle June 16-19, with Wegman and Said as program chairs. And what a program it was!

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