The Hockey Stick and Mann’s ignorance and dishonesty

 Stephen McIntyre discusses the Hockey Stick's discover's ignorance and dishonesty.

Another nail in climate alarmism.

Here is the link.

Here are some excerpts.

-------------------------------------------

In today’s post, I will report on some excellent work on MBH98 by Hampus Soderqvist, who discovered an important but previously unknown Mike’s Nature Trick: Mann’s list of proxies for AD1400 and other early steps was partly incorrect (Nature link now dead – but see NOAA or here). Mann’s AD1400 list included four series that were not actually used (two French tree ring series and two Moroccan tree ring series), while it omitted four series that were actually used. This also applied to his AD1450 and AD1500 steps. Mann also used an AD1650 step that was not reported.

Soderqvist’s discovery has an important application.

The famous MBH98 reconstruction was a splice of 11 different stepwise reconstructions with steps ranging from AD1400 to AD1820. The proxy network in the AD1400 step (after principal components) consisted 22 series, increasing to 112 series (after principal components) in the AD1820 step. Mann reported several statistics for the individual steps, but, as discussed over and over, withheld the important verification r2 statistic. By withholding the results of the individual steps, Mann made it impossible for anyone to carry out routine statistical tests on his famous reconstruction.

However, by reverse engineering of the actual content of each network, Soderqvist was also able to calculate each step of the reconstruction – exactly matching each subset in the spliced reconstruction. Soderqvist placed his results online at his github site a couple of days ago and I’ve collated the results and placed them online here as well. Thus, after almost 25 years, the results of the individual MBH98 steps are finally available.

Remarkably, Soderqvist’s discovery of the actual composition of the AD1400 (and other early networks) sheds new light on the controversy about principal components that animated Mann’s earliest realclimate articles – on December 4, 2004 as realclimate was unveiled. Both articles were attacks on us (McIntyre and McKitrick) while our GRL submission was under review and while Mann was seeking to block publication. Soderqvist’s work shows that some of Mann’s most vehement claims were untrue, but, oddly, untrue in a way that was arguably unhelpful to the argument that he was trying to make. It’s quite weird.

Soderqvist is a Swedish engineer, who, as @detgodehab, discovered a remarkable and fatal flaw in the “signal-free” tree ring methodology used in PAGES2K (see X here). Soderqvist had figured this out a couple of years ago. But I was unaware of this until a few days ago when Soderqvist mentioned it in comments on a recent blog article on MBH98 residuals.

---------------

Soderqvist’s discovery that MBH98 used six North American PCs not only refutes Mann’s claim that he used two North American PCs, but refutes his claim that he used Preisendorfer’s Rule N to select two PCs. Soderqvist’s discovery raises a new question: how did Mann decide to retain six North American PCs in the AD1400: it obviously wasn’t Preisendorfer’s Rule N. So what was the procedure? Mann has never revealed it.

Subsequent to the original controversy, I’ve written many Climate Audit posts on properties of principal components calculations, including (some of what I regard as the most interesting) Climate Audit posts on Chaldni patterns arising from principal components applied to spatially autocorrelated tree ring series. The takeaway is that, for a large-scale temperature reconstruction, one should not use any PCs below the PC1. The reason is blindingly obvious once stated: the PC2 and lower PCs contain negative signs for approximately half the locations i.e. they flip the “proxies” upside down. If the tree ring data are indeed temperature “proxies”, they should be used in the correct orientation. Thus, no need for lower order PCs. In many important cases, the PC1 is similar to a simple average of the series. Lower order PCs tend to be contrasts between regional groupings. In the North American network, southeastern US cypress form a grouping that is identifiable in the PC5 (centered) and, needless to say, the stripbark bristlecones form another distinct grouping.

He then observed that, under MM05 (correct) centering, the “hockey stick” pattern appeared in the PC4. For the subsequent inverse regression step of MBH98 methodology, it didn’t matter whether the hockey stick pattern appeared in the PC1; inclusion even as a PC4 was sufficient to impart a hockey stick shape to the resulting reconstruction:

------------

Our response has always been that the relevant question was not whether the hockey stick pattern of the stripbark bristlecones was a distinctive pattern within the North American tree ring network, but whether this pattern was local and specialized, as opposed to an overall property; and, if local to stripbark bristlecones, whether the stripbark bristlecones were magic world thermometers. The 2006 NAS panel recommended that stripbark bristlecones be avoided in temperature reconstructions, but their recommendation was totally ignored. They continued in use in Mann et al 2008, PAGES2K and many other canonical reconstructions, none of which are therefore independent of Mann et al 1998-99.