In the August 19 Boston Globe, conservative op-ed contributor Jeff Jacoby wrote his fifth column in eight months denying climate change. His disdain for warming theorists goes back much longer; he pontificated on the subject as far back as 2002. And yet, after all this time and effort, he’s still relying on thin gruel for source material.

Jacoby’s most recent evidence against the global-warming consensus consists of:

• The Fred Singer petition — signed mostly by retired or non-practicing scientists, and some non-scientists — which merely questions whether the reality of climate change will be as horrific as the models currently predict.

• NASA administrator (since 2005) — and non-climatologist — Michael Griffin’s one-time comment that we shouldn’t worry about global warming, for which Griffin was denounced by NASA’s top climate official.

• One survey, conducted in 2003, purporting to show skepticism among environmental scientists, which was rejected for publication and generally discredited because its Web-based survey mechanism did not verify that the participants were actual scientists. (Interestingly, Jacoby cites the survey’s finding that 34 percent responded global warming might prove beneficial for some societies. This is actually a surprisingly low number, taken by some as evidence that non-experts took the survey: most serious climatologists agree, for example, that large sections of Russia are likely to benefit significantly from global warming, at least in the near-term.)

If Jacoby is going to keep at this topic, he needs to do so in a serious manner, not by citing the rare outlier. He needs to change course and stop citing evidence based on conflicting opinions. He needs to start presenting an argument for why we should listen to dissenters, rather than the overwhelming majority of people who have studied the issue.

Surely, if nine oncologists tell Jacoby that he needs a growth removed, and one tells him that the evidence of malignancy was not as strong as the others suggest, he would demand a strong argument for listening to the one over the nine. And he would demand better than what he is offering for why we should ignore calls for action on climate change.