As best as I can gather in trying to follow these series of threads in which your good self, Jean S, UC, Jeff ID and others attempt to audit Mann et al 2008, despite the NAS Panel report, despite the Wegman report and despite the congressional hearing, our esteemed friend ,who struggles to get babysitters, has carried on with business as usual almost as if these events had never happened?

Correct me if I’m mistaken but to summarise what you have laid out so far, Mann et al 2008 looks like its just a re-hash of MBH 98/99 but with more proxies (particularly non-tree ring proxies) and with slightly different (but equally flawed) methods for picking the same cherries to make pretty much the same cherry pie (i.e. a hockey stick)? It would however seem that at least the handle has now changed though, but that the blade section spliced to the instrumental temperature record nonetheless stays the same?

No doubt in concocting his new statistical methodology this time round he’s done his best to make sure that the MWP and LIA aren’t completely filtered out as this is after all what caused you to start digging into MBH 98/99 in the first place? It is a matter of some speculation but may I ask you, if the original TAR poster child hockeystick had actually shown prominent MWP and LIA’s in the handle (albeit obviously with a significantly lower MWP versus modern relationship/ratio), would you have still gone to the trouble you have done to audit it?

Regards

KevinUK

I must admit I’m more than usually baffled by a methodology whose purpose uses the wrong metric to produce a “signal” that scores strongly with that wrong metric. Am I wrong to be baffled?

It’s simple. You use whatever promotes your theory. You use R2 when it is convenient, and you ignore it when it’s not, for example.

I hope you’d indulge me by answering a couple of questions that nag me.

1. As you remember, Wegman noted in the Reply to Stupak that

A cardinal rule of statistical inference is that the method of analysis must be decided before looking at the data. The rules and strategy of analysis cannot be changed in order to obtain the desired result. Such a strategy carries no statistical integrity and cannot be used as a basis for drawing sound inferential conclusions.

…which begs the question as to what Mann is doing sifting through proxies accepting or rejecting them according to how well the chosen statistical metric (RE in this case) is “enhanced” or not. Can a method like this have any statistical integrity or is it more like a self-constructed delusion?

2. As Bishop Hill noted, RE is a measure only for linear sequences yet clearly Mann 2008 isn’t linear. What is Mann enhancing? I must admit I’m more than usually baffled by a methodology whose purpose uses the wrong metric to produce a “signal” that scores strongly with that wrong metric. Am I wrong to be baffled?

The statistical “authorities” (32,42) are Mann et al 2007 and Wahl and Ammann 2008. Given the supposed “deficiencies” of the squared correlation coefficient, it is perhaps a little surprising that the unsquared correlation coefficient r is used both to screen proxies for inclusion in the Mannian network and to invert the sign of proxies, but, hey….

I was under the impression that the screening in Mann et al. was done using p (the probability that the correlation was different than zero) and not r.

There are a lot of new proxies in Mann et al 2008 and to be fair to it, one has to look at the new proxies, just in case there is more to this one than the others. So far it seems unlikely.