Wednesday, July 19, 2006

When Statistical Mistakes Don't Matter

The famous "hockey stick" reconstruction of Northern Hemisphere temperatures over the last 600 years has recently come under fire because of an error in using a statistical technique called principal components analysis. RealClimate points out that this really doesn't matter. At a Congressional hearing on the subject, "no-one (with sole and impressive exception of Hans von Storch during the Q&A) went on to mention what the effect of the PC centering changes would have had on the final reconstruction - that is, after all the N. American PCs had been put in with the other data and used to make the hemispheric mean temperature estimate. Beacuse, let's face it, it was the final reconstruction that got everyone's attention. Von Storch got it absolutely right - it would make no practical difference at all."

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