The IPCC claims that it is “policy relevant, but policy neutral.” What this phrase actually means is clear as mud. According to various statements by its chairman Rajendra Pachauri over the past few years (e.g., link), one might be excused for thinking that the IPCC is really an advocacy document clothed in the language of science. Mr. Pachauri’s most recent comments about the report in a Reuters news report today do nothing to dispel that view:

The IPCC review, grouping over 2,000 scientists who advise the United Nations, is published in February and is expected to show stronger evidence for climate change and man’s part in it.

“I think the conditions are just right for this report to make a perceptible impact,” said IPCC chairman Rajendra Pachauri. “I think there’s enough observed evidence now that certainly will influence the policymakers.”

“I’ve just come back from one of the small mountain states of India, and they regard the melting of the glaciers as the most important problem they’re facing. Their entire water supply gets completely distorted.”

Talks this year on extending the U.N.’s Kyoto Protocol on curbing emissions beyond 2012 could also focus action.

“There is a bit of shadow boxing going on, each group of countries is waiting for what the others are going to do,” said Pachauri. “My feeling is that in the next year and a half things will accelerate and perhaps you will see some action.”

If the IPCC is being prepared with a goal of making a “perceptible impact” and “influencing policymakers” then no matter what the IPCC says, it is certainly not “policy neutral.” Its leadership clearly has a political agenda and it would be appropriate to include that agenda in the report, rather than hiding it behind science. Using science to advance a political agenda, but not openly acknowledging that agenda, is a form of stealth issue advocacy and a recipe for the pathological politicization of climate science. Stealth issue advocacy will severely limit the contributions of the IPCC to debate over climate policy. As an alternative approach, the IPCC should openly discuss a wide range of policy options, rather than perpetuating the continuing, fairly obvious fiction that it is “policy neutral.”