Category Archives: MBH98

Articles relating to the Mann, Bradley and Hughes 1998 reconstruction of past climate

When Was Wahl and Ammann 2007 "Accepted"?

Last summer, on Aug 28, 2007, I wrote a post observing that Wahl and Ammann 2007, although being cited in IPCC AR4, had still not appeared in print. I think that it was then the only article cited in IPCC AR4 chapter 6 in that situation. In that post, I observed that it seemed anomalous […]

MBH99 and Proxy Calibration

UC and Hu McCulloch have been carrying on a very illuminating discussion of statistical issues relating to calibration , with UC, in particular, drawing attention to the approach of Brown (1982) towards establishing confidence intervals in calibration problems. In order to apply statistical theory of regression , you have to regress the effect Y against […]

The RE Benchmark of 0

In MM2005a,b,c, we observed that the RE statistic had no theoretical distribution. We noted that MBH had purported to establish a benchmark by simulations using AR1 red noise series with AR1=0.2, yielding a RE benchmark of 0. We originally observed that high RE statistics could be obtained from PC operations on red noise in MM2005a […]

Supplementary Information and Flaccid Peer Reviewing

Based on my limited experience, it seems to me that journal peer reviewing faces an interesting challenge with the increased use of Supplementary Information (and I absolutely endorse detailed SI and obviously encourage even more detailed SI). In a very non-random of articles that I know inside-out (Team journal publications), my conclusion is that, in […]

The MBH AD1450 Network

Most of my previous discussion of MBH pertained to the AD1400 network. In recent discussion over at Tamino, some of the posters have stated that BCPs only matter for the AD1400 network and that everything is fine for the AD1450 and later networks, relying here on statements in Wahl and Ammann 2007. (I don’t suppose […]

More on Li, Nychka and Ammann

by Hu McCulloch A recent discussion of the 2007 Tellus paper by Bo Li, Douglas Nychka and Caspar Ammann, “The ‘hockey stick’ and the 1990s: a statistical perspective on reconstructing hemispheric temperatures,” at OSU by Emily Kang and Tao Shi has prompted me to revive the discussion of it with some new observations. A PDF […]

An Example of MBH "Robustness"

In the MBH source code, they apply steps that purport to weight the temperature PCs in their regression calculations proportional to their eigenvalues. Comments on their code say: c set specified weights on data … c weights on PCs are proportional to their singular values This is one of two weighting procedures in MBH for […]

Squared Weights in MBH98

A couple of weeks ago, I said that I would document (at least for Jean S and UC) an observation about the use of squared weights in MBH98. I realize that most readers won’t be fascinated with this particular exposition, but indulge us a little since this sort of entry is actually a very useful […]

Tamino and the Magic Flute

Tamino has recently re-iterated the climate science incantation that Mann’s results have been “verified”. He has done so in the face of the fact that one MBH98 claim after another has been shown to be false. In some cases, the claim has not only been shown to be false, but there is convincing evidence that […]

Rule N and Weighted Regression

Today’s post, which has a forbidding title, contains an interesting mathematical and statistical point which illuminates the controversy over how many PCs to retain. In my re-visiting the totally unknown corner of Mannian methodology – regression weights and their determination – I re-parsed the source code, finding something new and unexpected in Mannian methodology and […]

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