It has been a bad—make that dreadful—few weeks for what used to be called the "settled science" of global warming, and especially for the U.N. Intergovernmental Panel on Climate Change that is supposed to be its gold standard.

First it turns out that the Himalayan glaciers are not going to melt anytime soon, notwithstanding dire U.N. predictions. Next came news that an IPCC claim that global warming could destroy 40% of the Amazon was based on a report by an environmental pressure group. Other IPCC sources of scholarly note have included a mountaineering magazine and a student paper.

Since the climategate email story broke in November, the standard defense is that while the scandal may have revealed some all-too-human behavior by a handful of leading climatologists, it made no difference to the underlying science. We think the science is still disputable. But there's no doubt that climategate has spurred at least some reporters to scrutinize the IPCC's headline-grabbing claims in a way they had rarely done previously.

Take the rain forest claim. In its 2007 report, the IPCC wrote that "up to 40% of the Amazonian forests could react drastically to even a slight reduction in precipitation; this means that the tropical vegetation, hydrology and climate system in South America could change very rapidly to another steady state."

But as Jonathan Leake of London's Sunday Times reported last month, those claims were based on a report from the World Wildlife Fund, which in turn had fundamentally misrepresented a study in the journal Nature. The Nature study, Mr. Leake writes, "did not assess rainfall but in fact looked at the impact on the forest of human activity such as logging and burning."

The IPCC has relied on World Wildlife Fund studies regarding the "transformation of natural coastal areas," the "destruction of more mangroves," "glacial lake outbursts causing mudflows and avalanches," changes in the ecosystem of the "Mesoamerican reef," and so on. The Wildlife Fund is a green lobby that believes in global warming, and its "research" reflects its advocacy, not the scientific method.
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All of this matters because the IPCC has been advertised as the last and definitive word on climate science. Its reports are the basis on which Al Gore, President Obama and others have claimed that climate ruin is inevitable unless the world reorganizes its economies with huge new taxes on carbon. Now we are discovering the U.N. reports are sloppy political documents intended to drive the climate lobbys regulatory agenda.

The lesson of climategate and now the IPCC's shoddy sourcing is that the claims of the global warming lobby need far more rigorous scrutiny.