Attenuation in Mann et al 2005

Mann, Wahl, Ammann, Ritson, Ramsdorff are all dining out on the fact that von Storch et al 2004 did not implement a detrending step in their implementation of MBH98. (Although given that Mann would not be "intimidated" into releasing his algorithm and cited Zorita et al 2003 to us as evidence that people could implement his algorithm, they should be embarrassed that people still could misinterpret their methodology. )

They also criticize the Echo-G model as though that had anything to do with the price of eggs. For the purposes of VZ04, the Echo-G model simply gave a set of gridcell results with a covariance structure.

Anyway, the pseudoproxies for Mann et al 2005 were archived. It was very easy to do the same calculations on them that I did last week on the VZ pseudoproxies. Guess what I found. Here’s a graph comparing detrended and non-detrended calibration for the 104 pseudoproxy network; the results for a 22-gridcell sample are very similar. So far I am unable to see that detrending makes a tinker’s damn in the results. (I’m not 100% sure of these calculations, but I’m pretty sure.)


NH Temperature – Black – NH average; blue – MBH; cyan – MBH detrended.

You’ll notice that Wahl et al. did not actually produce their own calculations. They merely hyper-ventilated in their article in Popular Science. In the Burger and Cubasch discussion, Mann using the sock-puppet Anonymous Referee #2 says that VZ should “come clean” about detrending. Even if true, what does that have anything to do with the review of Bürger and Cubasch? Is this what the Team has descended to? Again, I don’t see that the detrending/detrending matters a damn for the point being made, and, in no way, justifies the bullying.

8 Comments

  1. TCO
    Posted Jul 9, 2006 at 9:55 PM | Permalink

    Were you able to duplicate the RE calcs? Any ideas on when detrending would/would not make a significant difference? IOW, for what types of data sets it would drive a difference and for what not?

  2. Steve McIntyre
    Posted Jul 9, 2006 at 10:32 PM | Permalink

    Any multivariate method just gives weighting factors for the proxies. For tame networks with equal amounts of white noise (which is what is done here), trending/detrending doesn’t make much difference.

    It does make a difference in what weight is assigned to bristlecones, but the tame networks don’t have proxies like that. The whole fuss seems like a total crock to me.

  3. Steve McIntyre
    Posted Jul 9, 2006 at 10:39 PM | Permalink

    The RE values are lower with these very tame proxies than with actual MBH proxies. It’s not because they can actually out-perform this type of system, but because the actual proxies are not signal plus white noise and there’ enough play in the method to enable amplitude tuning.

  4. TCO
    Posted Jul 9, 2006 at 10:46 PM | Permalink

    Are these the proxies that were used in MBH98 calculation of RE and can you duplicate that calculation of Mann’s.

  5. TCO
    Posted Jul 9, 2006 at 10:49 PM | Permalink

    Thanks for the info on when it makes a difference. I’m interested in method choices and the bases for them and the plusses/minuses. Sorta like covariance/correlation…

  6. Steve B
    Posted Jul 10, 2006 at 8:22 PM | Permalink

    Your rules say that “Refrain from personal abuse and swearing” and “Never attribute ulterior motives to another participant”, then I see you use words in this comment like “hyper-ventilated” and “come clean” and “descended to” and “bullying”. It seems that you are violating your own rules.

    I have not made up my mind yet on the NAS report, plan to read it, and am seeking other comments. Your web site has not yet helped. I would appreciate a not-too-technical summary in one place of what you think is wrong with that NAS report.

  7. TCO
    Posted Jul 10, 2006 at 8:35 PM | Permalink

    Steve B. those are the rules. And if you bug Steve enough he can generally be shamed into removing some teases. However, it is an accepted practice on this blog that these rules apply to all except for me. And I think you’re a wimp for spending all your time on how things are said and how much snark there is versus argying the science.

  8. Steve McIntyre
    Posted Jul 10, 2006 at 8:59 PM | Permalink

    The words “come clean” were not used by me, but were used by Mann.

    I am making comments here about published articles, not about participants in the debate here. Steve B, your views are nearly always diametrically opposed to mine, but surely you can vouch that I have been punctiliously polite to you here.

    I’ll continue to post up notes from time to time on the NAS Panel.

    TCO, the rules apply to you.

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