An IPCC reviewer in Newsweek

Ross McKitrick, one of the 2500 "expert reviewers" who helped vet the science for the IPCC, has a piece in Newsweek: "What the U.N. Won't Tell You".

The IPCC Web site claims an impressive number of participants: 450 lead authors, 800 contributors and 2,500 expert reviewers (of which I was one). But it would be a mistake to assume all these experts endorse everything in summary, including its bottom-line assessment: "Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations." Many disagree with the conclusion itself or the claimed level of certainty, but the fact is, we were never asked. Most participants worked only on small portions of the report, handed in final materials last summer and never ventured an opinion on claims made in the summary.

Nor can readers check how well the summary reflects the underlying science. The report itself will not be distributed until May. Although it was officially "released" on Feb. 2, the IPCC is going over the wording to make sure it is consistent with the summary. This is a curious and disconcerting aspect of IPCC procedures: it needs a couple of months to revise a detailed report prepared by hundreds of scientists, to ensure it agrees with a brief summary drafted by a few dozen scientists and edited by hundreds of bureaucrats and politicians.

To be sure, the IPCC does an impressive job of mobilizing experts to produce a report it hopes will be of service to the world. No one should trivialize this achievement. But let's not make the error of allowing a glossy summary to trivialize the complexities and uncertainties in climate change. After all, if the issues were so simple, you wouldn't need 3,700 experts to write the report. It is a paradox that some of the strongest claims of unanimity in science are made on a subject involving some of the deepest intellectual disagreements and uncertainties.