The Frontal Cortex

Is the Hockey Stick Real?

Posted by Jonah Lehrer on July 14, 2006
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The WSJ editorial page – a very suspect source – opines on a new statistical study which seems to cast doubt on the hockey stick model of global warming. This model began with Michael Mann’s 1999 paper, and is the star of Gore’s An Inconvenient Truth.

The three researchers — Edward J. Wegman of George Mason University, David W. Scott of Rice University and Yasmin H. Said of Johns Hopkins University — are not climatologists; they’re statisticians. Their task was to look at Mr. Mann’s methods from a statistical perspective and assess their validity. Their conclusion is that Mr. Mann’s papers are plagued by basic statistical errors that call his conclusions into doubt. Further, Professor Wegman’s report upholds the finding of Messrs. McIntyre and McKitrick that Mr. Mann’s methodology is biased toward producing “hockey stick” shaped graphs.

I don’t know enough to have an opinion on this study – although I have a natural bias towards disagreeing with the WSJ editorial page – but I’m curious if anyone else can comment.

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  2. #2 Hank Roberts
    July 15, 2006

    and
    http://www.realclimate.org/index.php?p=121
    Dummies guide to the latest “Hockey Stick” controversy

    My short answer as a reader, not a climate scientist — minor flaws that did not affect the conclusion of this early piece of work were found, as is typical in science.

    The many subsequent studies of the issue support the conclusion. Fundies attack early work thinking that science is somehow built on it — look up “Darwinist” to see silly examples. Science doesn’t work that way; early work calls attention to an area but later work is based on new study of the world, not on the first studies.

    Early studies are always seen as flawed in the light provided by later work.

    There’s no ‘original science’ on which all subsequent science relies for its validity.

  4. #4 Bruce
    July 16, 2006

    Errr, readers should be aware that there is another site http://www.climateaudit.org where contributors seem to reach a somewhat different conclusion. And, http://www.realclimate.org seems to be the site of the cluster of scientists responsible for the Hockey Stick, and may not be independent.

  5. #5 Dano
    July 18, 2006

    And, http://www.realclimate.org seems to be the site of the cluster of scientists responsible for the Hockey Stick, and may not be independent.

    Errrr…no.

    Not even a nice try.

    Best,

    D

  6. #6 Barry
    July 19, 2006

    Climateaudit.org is a denialist site.

    Jonah, go to http://www.scienceblogs.com, and look on the front page. The hockey stick is the subject of the day.

  7. #7 softwareNerd
    February 5, 2007

    The “Dummies Guide” pointed to above says: “Basically then the MM05 criticism is simply about whether selected N. American tree rings should have been included, not that there was a mathematical flaw”.

    Of course this is right in the sense that if one uses the wrong data and does the right calculations, it is not a “mathematical flaw”.

    So, the real issue is whether one should use the “N. American tree ring” data. The guide claims to be in language that my parents can understand, but it’s still a bit technical. Let me explain the issue with an example from a different domain.

    Suppose we are testing the proposition that eating a good breakfast keeps kids more alert during the school day. Say we have good tests to measure the breakfast and the alertness. Also suppose the test is done across 10 schools and we find a correlation.

    Now, a statistician comes along and points out that if we throw out the data from Warner Elementary, the correlation almost disappears. this is a highly significant finding, and the logical retort is not: “don’t throw out Warner data”! The correct response is to find out what’s so different about Warner.

    It’s not a question of Math but basic epistemology and logical deduction.