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Expertise, bias and argument ad hominem

September 2nd, 2002

As I’m well aware, petitions and counterpetitions are controversial. So before raising some issues with Ken Parish about the Leipzig and Oregon statements on global warming, I want to make a few things clear.
First, climate change is too important to be left to the experts. Everyone should have their say on this topic. But, if people want to call themselves “scientists” or “economists” they should be prepared to have their qualifications scrutinised.
Second, criticism of qualifications and motives is not a legitimate reason for ignoring arguments (the ad hominem fallacy). But it is a perfectly reasonable response to another ‘use with care’ rhetorical device, the argument from authority, as in “over 17,000 scientists declare that global warming is a lie with no scientific basis whatsoever.”
Third, among those who can reasonably be classed as experts, it’s a mistake to give too much weight to active researchers on a particular topic. It’s easy for a research community to develop the same kind of taboos as any other community, obvious to outsiders but unchallengeable within the group. Others in the same discipline often provide a more realistic perspective.
Finally, there’s nothing inherently wrong with partisanship and there’s nothing immoral about conflicts of interests, as long as they are openly declared. I’m obviously partisan on a number of issues, and, like most economists, I’ve done some consulting. I try to be upfront about this and to argue honestly at all times. But it’s obvious that a new study from me, finding that some particular privatisation was a bad idea, would be received differently from a similar study from an equally prominent economist who was not identified with any particular viewpoint or interest group.
With these caveats, let’s look at the Leipzig and Oregon statements. Both are typically presented as evidence that there is significant disagreement among scientists about the global warming hypothesis. For someone’s opinion to count on this score, I think they should:
(i) be an expert in the relevant field, that is, hold an academic or equivalent position in climate science or some closely related field such as meteorology or oceanography (as opposed to, say, areas of physics unrelated to climate modelling)
(ii) have no conflict of interest, such as employment by fossil fuel companies or thinktanks with a stated viewpoint on the issue
The Leipzig declaration was made in 1997, and relies in part on some outdated arguments, such as the satellite data I discussed previously. More relevantly, of the 100 or so signatories, I can’t identify more than 30 who meet criteria (i) and (ii), even applied loosely. The balance is made up of people like consultants, retired physicists and (I am not making this up!) TV weathermen.
The Oregon petition, with nearly 20000 signatures is harder to assess. Anyone who claimed to have university-level qualifications in science was invited to sign – the criteria would include me, and most members of my family, although I have only one relative who would normally be called a ‘scientist’. In fact, the list includes quite a few cases where whole families seem to have signed.
It seems reasonable to focus on the subgroup (about 2600) who claim to be “physicists, geophysicists, climatologists, meteorologists, oceanographers, and environmental scientists”. Of these, less than half the signatories claimed a PhD, which is a basic requirement for a serious scientific job in the US. I Googled a sample of about 30 PhD’s of whom none were climate scientists (only about half met the much broader stated description). They included petroleum geologists, physicists working in weapons labs and others with research fields very distant from climate science. I also emailed the petition organisers, asking for a list of climate scientists who had signed, and got no reply.
Based on this sample analysis, I doubt that there are more than 50 independent climate scientists in the world who could be regarded as overt critics of the global warming hypothesis. This is a relatively easy claim to refute, if anyone cares to go through the Oregon list and the various ‘skeptical’ sites, and produce more than 50 names fitting criteria (i) and (ii) above. Thanks to Google, all that would be required is an Internet connection and few hours of boring work.
It’s natural to ask how the Australian economists petition, which I helped to organise, stands up against the criteria I’ve set out. All of the signatories meet criterion (i), and none, so far as I am aware, has a direct financial conflict of interest. Some prominent signatories, including Clive Hamilton and myself, are well-known supporters of environmentalist and social-democratic views, and are associated with bodies like the Australia Institute. On the other hand, others like Peter Dixon and John Hewson are well-known advocates of free-market views. The total number of signatories, nearly 300 with some late entries, is also fairly impressive, given that there are only about 1000 academic economists in Australia, and the response rate to mass mailings of any kind is usually about 40 per cent.
Of course, it may well be that the counterpetition being promoted by my colleague Alex Robson will achieve a similar response. If so a majority of the profession will have displayed a view one way or the other. This would certainly speak volumes for the public-spiritedness of Australian academic economists.

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