Tag Archives: wahl

The Gift That Keeps on Giving Continued

Here is a little present for Jean S and UC. Something new from the gift that keeps on giving. Something that even I never noticed before. What we’re going to see is that in Mann-world, U.S. tree ring series are capable not merely of reconstructing world temperature, but 9 different “climate fields”. In effect, using […]

Where's Caspar?

As you know, we are eagerly awaiting the publication of the following article by Wahl and Ammann reported here: Wahl, E and C Ammann (In press). “Robustness of the Mann, Bradley, Hughes reconstruction of northern hemisphere surface temperatures: Examination of criticisms based on the nature and processing of proxy climate evidence.” Climatic Change (accepted). May […]

Overfitting by Inverse Regression

Wahl and Ammann 2006 reported that they could “get” something that was sort of HS-ish without principal component analysis. It wasn’t through a simple mean or CVM; it was through Mannian inverse regression. Juckes et al shows many reconstructions using “inverse regression”, mentioning in his conclusions that inverse regression caused over-concentration on a few proxies. […]


One point that Wahl and Ammann and ourselves agree on, but which Juckes appears to contest, is that principal components methodologies applied to AD1400 MBH98 networks result in upweighting or downweighting of bristlecones. Their Scenario 6 shows reconstruction results without bristlecones for covariance, correlation and Mannian PCs. I have no dispute with these calculations although […]

Juckes cites Wahl and Ammann

One of the really annoying things about Wahl and Ammann was their failure to cite our prior analysis of various MBH permutations and, then, having failed to cite these prior analyses, reproaching us for supposedly “omitting” these analyses. For example, in MM05 (EE) we discussed the relative impact of using 2 or 5 covariance PC2 […]

Wahl and Ammann Again #2

Here’s a pretty little graph that I think that you’re going to see more of. One is using the Wahl-Ammann variation of MBH methodology applied to MBH data; the others are from low-order red noise. Pink – no PC reconstruction from WA without strip-bark and Gaspé; black – from low-order red noise. I worked this […]

Wahl and Ammann Again #1

I asked KNMI what were the studies that had "refuted" our work. It seems to be Wahl and Ammann. I’ve never understood the traction of Wahl and Ammann with climate scientists. I doubt that any of them have worked through the details, but Wahl and Ammann issued a press release that all our claims were […]

Supplementary Comments to NAS Panel

We sent in the following two supplementary comments to the NAS Panel, one commenting on answers provided by Mann subsequent to our presentation and noting up points related to the revisions of Wahl and Ammann [2006] and rejection of the Ammann and Wahl submission to GRL here and the other responding to a question from […]

Letter to Climatic Change

I was asked to review the Wahl and Amman submission in May 2005 and recently posted up my review here. The first recommendation in my review was that all Wahl and Ammann remove all arguments that depended on their rejected GRL article. They didn’t and now it’s come back and should haunt them. Despite providing […]

The RE Benchmark in A&W

There’s an interesting irony in the GRL rejection of the Ammann & Wahl Comment and it will be interesting to see how this gets handled. It turns out that the A&W Climatic Change depends on their GRL submission for their test of statistical significance for the RE statistic. So even though the GRL referee thought […]