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Jolly hockey sticks

Cross posted from The Great Beyond

The contentious ‘hockey stick’ climate change graph has again been upheld as broadly accurate, doubtless to the rage of climate denialists/sceptics/whatevers.

A team led by Michael Mann of Penn State University has looked at a whole range of proxies for surface temperatures over the last 2,000 years in an attempt to counter criticism of the graph, which showed a long ‘handle’ and a sharp upturn (the blade).

Their findings? As the Christian Science Monitor puts it: “It still looks a lot like the much-battered, but still rink-ready stick of 1998. Today the handle reaches further back and it’s a bit more gnarly. But the blade at the business end tells the same story.”

The previous hockey stick had been accused of relying too much on data from tree rings so this PNAS study may silence some of the critics when it appears later.

gretzky graph.jpg

Proxy types denoted with different symbols. Dates of proxy records represented by color scale (National Academy of Sciences, PNAS 2008) View large image

“We used two different methods that are quite complementary in the assumptions they make about data, so that provides a test of the sensitivity of data to the methods used,” Mann told BBC News. “We also made use of a far wider network of proxy data than previously available.”

Of course, some people are never convinced. Just a few days before this paper came out Christopher Booker was writing in the Telegraph of Mann’s original hockey stick graph: “it turned out he had built into his programme an algorithm which would produce a hockey stick shape whatever data were fed into it. Even numbers from the phonebook would come out looking like a hockey stick.”

Christopher Brooker normally writes jokes for satirical magazine Private Eye and I’d really like to believe that piece is a particularly brilliant joke on climate change denialists that he’s managed to sneak past the Telegraph sub-editors. For the past ten years.

Daniel Cressey


  1. Report this comment

    Bishop Hill said:


    What on earth are you talking about? Are you saying that Wegman got it wrong and that Mann’s “novel” statistical techniques were in fact wrong. Are you goint to tell him?

    From the Wegman report

    “The net effect of the

    decentering is to preferentially choose the so-called hockey stick shapes."

    Wegman reproduced the creation of hockey stick graphs from red noise too. Are you saying he faked this?


  2. Report this comment

    George said:

    The same guys who generated the hockey stick with (to put it charitably) a highly selective use/weighting of proxy data, have done it again—and you think this constitutes verification and vindication?

    What are the chances that when the dust settles, it will again be a case of elaborate methodological cherry-picking that minimizes the MWP and maximizes the current warming period?

    Proxy studies are all over the map with respect to past climate. However, most indicate that the MWP was as warm or warmer than the present as apparently do most of the studies cited by Mann et al.

    In essence, Mann et al claim to have a new and improved mathematical method for excluding/minimizing the data they don’t like and including/emphasizing the data they like, And so…. drum roll, please … Hockey Stick II!!

    Color me unimpressed.

  3. Report this comment

    sesli chat said:

    also remember the last few years for both USA and UK were aflood with housing bubble money.

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