"Better for Our Purposes"

Can anyone explain to me the meaning of the following email from Hughes to Mann, dated July 29, 1997, archived at Mann’s FTP site at ftp://holocene.evsc.virginia.edu/pub/MBH98/TREE/VAGANOV/ORIG/malcolm_29-JUL-97.

As follow-up, the site arge030 was listed in the original SI as being used in MBH98, but was not actually used in MBH98 calculations evidenced at Mann’s FTP site. We complained about this and other inconsistencies to Nature in November 2003, leading to the Corrigendum by Mann et al. in July 2004. The Corrigendum listed arge030 as one of 35 series in the original SI, which was not actually used in calculations.

The Corrigendum stated that the discrepancies resulted from the application of additional quality control measures i.e. the excluded series were not "conservatively standardized" or their standardization methods were not known to the authors in 1997. I’ve checked this supposed explanation and it can be shown not to be accurate. I’ll post on this on another occasion.


  1. John A.
    Posted Feb 13, 2005 at 8:01 AM | Permalink

    I have a word for it. “Cherry-picking”

  2. Posted Feb 13, 2005 at 8:26 AM | Permalink

    Wow! That’s a tough reading. No, I don’t have any other explanation what does it mean
    that a set of data is “better for our purposes” except for the obvious one.

    As a consistency check, do you have both the replaced one and the new one to check
    whether the new one is really better for their purposes, in the sense how we seem
    to understand it?

  3. Steve McIntyre
    Posted Feb 13, 2005 at 10:06 AM | Permalink

    Lubos, It actually doesn’t make any material difference to the final answer under their method, because the final reconstruction is essentially imprinted by the bristlecone pines and hardly any other variations “matter”.

    A copper trader once told me: people who cheat on big things cheat on little things. I’m not saying that this is what happened here – I’m merely saying that that is my philosophy in approaching things and that’s one of the reasons that I pay attention to details. Whether it “matters” to the final results is a different issue. Steve

  4. Andre
    Posted Feb 13, 2005 at 11:19 AM | Permalink


    Why certainly, that can only mean one thing. His purpose was obviously to conduct objective science. That must be the purpose.

    If I was a Kyoto signee I would insist on an independent inquiry. But then again, who is independent?

  5. Ed Snack
    Posted Feb 13, 2005 at 2:16 PM | Permalink

    Any chance of posting the text ? The ftp server is either down or won’t let me connect.

    Thanks, Ed

  6. John A.
    Posted Feb 13, 2005 at 3:05 PM | Permalink


    The e-mail says:

    Mike – the only one of the new S.American chronologies I just sent
    you that already appears in the ITRDB sets you already have is
    ARGE30. You should remove this from the two ITRDB data sets, as the
    new version should be different (and better for our purposes)
    Cheers, Malcolm

  7. John S.
    Posted Feb 13, 2005 at 9:55 PM | Permalink

    I think you might be jumping at shadows here. I could well imagine myself collating data for a project and using some criteria for data selection that would be correlated with ‘quality’ and then comment that some series or another might be ‘better for our purposes’ e.g. better for getting an accurate result or whatever. Doesn’t mean data-mining isn’t occurring, just that this doesn’t shed light on it.
    The comment is ambiguous and would only be conclusive in the hands of a very skilled barrister.

  8. Steve McIntyre
    Posted Feb 13, 2005 at 10:59 PM | Permalink

    I’m making no accusations, as I agree that the probability is that the sentence has some reasonable explanation. But at a minimum it points to one of the frustrating aspects to these multiproxy studies – the procedures for selecting proxies are never stated (this isn’t just Mann, it’s the same for all the Hockey Team and Moberg as well.)

    Mann et al [2000] stated that the MBH98 proxies were selected according to "objective criteria", but then frustratingly failed to state those criteria and Mann et al. have refused to provide them upon request. It doesn’t help when an explanation easily shown not to reconcile with actual selections is provided in a Corrigendum. Also Jones and Mann [2004] set out correlation standards for inclusion, noting that some proxies used in earlier studies were excluded because they did not meet the standards of Jones and Mann [2004]. That’s well and good, but are we not then entitled to an explanation of how the proxies not meeting the standards of Jones and Mann [2004] passed the earlier tests of MBH98.

    One of the recent areas of medical controversy is bias in medical reviews (which have some analogies to multiproxy studies). A movement called "evidence-based medicine" (which you would have thought to be automatic) has a program for clearly stating criteria for inclusion of a study in a review. one of the centers of this is in Ontario (Guyatt, one of the authors, plays squash). I think that all these studies would benefit from clear statements of criteria and purposes used in proxy selection,

  9. TCO
    Posted Sep 11, 2005 at 1:51 PM | Permalink

    You would think this would be standard in meta-analysis. HAve you looked at papers from the social sciences on methods and philosophy of meta-analysis?

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