Friday, January 21, 2005

The Dubious Hockey Stick

Thanks to Slashdot for this MIT Technology Review article about the flawed mathematics behind global warming. The conventional wisdom about global warming is that human activities creating atmospheric CO2 are rapidly ramping up average temperatures. This is based on work by University of Massachusetts geoscientist Michael Mann and colleagues. Two Canadian researchers, Stephen McIntyre and Ross McKitrick, have found what they think is a fundamental flaw in that: by applying a Monte Carlo simulation to the data, it turned out that any data fed in to the model would tend to create a hockey stick shape! McIntyre and McKitrick tried to get their research published in Nature, but it was ultimately rejected; instead, they self-published on their own website.

In some fairness to Mann, that same Slashdot article posts a link to a story rebutting McIntyre and McKitrick's work. He points out an egregious error in an earlier work in a different paper (part of the code used for the modeling incorrectly uses radians rather than degrees, which the raw data is in), but even so, I remain skeptical. As with a lot of environmentalists, there's an itch to throw ad hominems around, which John Quiggan, the author of this piece, scratches in public. Given the apparent difficulty with which McIntyre and McKitrick had in publishing their article, one wonders what the full story, as told by Nature, would be. Moreover, in a note dated January 7, 2005, they write

It is now conceded, for instance, that MBH98 used a decentering procedure that elevated the role of a small group of hockey stick-shaped proxies from the low-order PC#4, right up into the dominant PC#1. This raises a host of important questions about the robustness of the MBH98 results, and one unimportant question. Mann's posting focuses on the unimportant one and hammers at it with furious energy. Our papers will raise and address the important questions, as well as the unimportant one.