In any case, publication totals may not be a good indicator of credibility or expertise, since not all publications are equally important. Researchers who want to evaluate the quality of scientists' work tend, instead, to look at how often a scientist's work gets cited by others. The PNAS study used this approach next. Looking at the number of citations received by each climate expert's top four papers, the authors find that members of the "convinced" group rack up an average of 172 citations on each one, while the "unconvinced" get 105. Since, all else being equal, more citations implies better work, they conclude that believers are more expert and prominent than skeptics.
Yet all else is not equal. As the authors note, citation counts are often used by university departments to make decisions about hiring and tenure. But those situations involve comparing people who publish in the same fields. The PNAS study included scholars whose primary research is not in climate science. (A disproportionate number of those were in the climate skeptic camp.) To be fair, the authors also included papers and citations outside climate science so that accomplished scholars in all fields would be properly recognized for their talents.
The analysis of papers from diverse fields seems to have distorted the results. Take the case of Freeman Dyson, who ranks high on the list of climate skeptics. Dyson is one of the greats of Quantum Field Theory, a central branch of particle physics; he has, in recent years, become an outspoken skeptic on climate change. His top paper, on particle physics, had 749 citations when the authors checked. That's quite a few, but not as many as were received by several dozen climate scientists for their top papers. Dyson is by all indications badly wrong when it comes to climate change. But few scientists in any field would agree that his top work is less impressive than that of 40 climate researchers, most of whom are far more obscure. So what might account for the discrepancy in citations? Perhaps climate scientists tend to include a lot more citations in their papers than particle physicists do; perhaps they publish a lot more papers. A proper analysis would make sure that these sorts of things hadn't skewed the data.
All of this would be academic quibbling if it wasn't so consequential. The authors of the paper are right that the world is running dangerous risks with the climate system. They are right to be angry at those who claim that climate change is a hoax, and at those in the media who give them a platform to confuse the public. But the way to confront those skeptics is to show that they're wrong—as many dedicated climate scientists have done, again and again. Hyping this paper, instead, simply reinforces the dangerous perception that climate activists will credulously push any news that might further their case. For those who care about this issue, that's tragic.
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