More shonky science
Over at Crooked Timber, Daniel Davies demolishes the latest effort by junk science writer Steve Milloy (on diet and diabetes), and admonishes Todd Zywicki of the Volokh Conspiracy for giving uncritical credence to Milloy, who has a track record of bogus work going back at least a decade, to his work for the tobacco companies, trying to cast doubt on the link between smoking and lung cancer. Of course, this track record doesn’t eliminate the need to demolish Milloy afresh each time he pops up. Still if the name didn’t ring alarm bells for Zywicki as soon as he saw it, it’s clear he hasn’t been paying attention.
Devaluation of scientific work in favor of partisan hacks like Milloy has become standard practice on the political right and is a significant subtext in the current campaign against the Greens. Many of those making these attacks are drawing their talking points from the Institute of Public Affairs, a body which has supported global warming contrarianism, denied the link between passive smoking and cancer, and attacked scientists working on the Murray-Darling basin as “environmental activists masquerading as scientists”. It’s pretty clear who the wackos are in this debate.
Meanwhile, in email Tim Lambert advises me that Ross McKitrick has conceded that he erroneously used latitude in degrees when it should have been radians in his work on causes of global warming.
In his defence, McKitrick makes the point that the detection of this error
supports our contention that empirical researchers ought to publish both their data and code in easily accessible format, even if the example in this case comes at my expense. Empirical work on large data bases is easily prone to glitches in programming or data handling. This is inevitable. So where novel and possibly controversial results are obtained it is important to ensure complete transparency in the supporting materials.
McKitrick is right on this point, and has succeeded in demonstrating that the documentation provided by Mann et al for their ‘hockey stick’ paper was inadequate, though not in showing that this made any material difference to results.
On the other hand, a trawl back through the files makes it pretty clear that this error was not exactly an innocent mistake. It seems pretty clear that McKitrick tried some regressions with (absolute) latitude as the explanatory variable, didn’t like the results he got and switched to the cosine (note that, if you were starting here, you wouldn’t need to take the absolute value, since cosine is a symmetric function). Because of the degrees-radians mistake, this variable came out insignificant, as desired, and McKitrick didn’t do the checks that would have revealed the error. Asymmetric error-checking is a standard problem with cherry picking, as illustrated by the work of John Lock Lott.
fn1. In climatesceptics, a members-only Yahoo group, so I can’t give a link.