Has the UN climate panel now outlived its usefulness?

Such methane releases could dramatically accelerate global warming, but the threat is not included in existing climate models, notes Kevin Schaefer of the University of Colorado at Boulder. Schaefer said leaving out the permafrost feedback means that "all climate projections in the [IPCC report] are likely to be biased on the low side."

He says the omissions are not the fault of the scientists writing the report, but of the IPCC's cumbersome processes. The deadline for including new data in model runs was 2009, whereas "the first estimates of the permafrost [methane] feedback came out in 2011, way too late to include," said Schaefer. But he warned the upshot could be governments setting targets for greenhouse gas emissions that resulted in an "overshoot" of their promise, in Copenhagen in 2009, to cap warming at 2 degrees Celsius.

Nicholas Stern of the London School of Economics, author of an influential economic assessment of climate change for the British government in 2006, takes a similar view about the failings of the IPCC and its models. He complained at a meeting at the International Monetary Fund in Washington, D.C., in April that "the scientific models mostly leave out dangerous feedbacks." He called for "a new generation of models [that] focus on understanding probabilities of events with severe consequences for people [rather than] those effects that can be modeled more easily."

For more than two decades, since it was created by the UN in 1988, the IPCC has done the job politicians asked of it: to synthesise scientific thinking around climate change and deliver a series of consensus assessments to policymakers. In the process, the IPCC won the Nobel peace prize in 2007. But the question is now being asked: Is the IPCC still fit for its purpose? It may do good science, but does it deliver what policymakers need?

David Keith, a Harvard University professor who recently resigned as an author of the IPCC report, says "The IPCC is showing typical signs of middle age, including weight gain, a growing rigidity of viewpoint, and overconfidence in its methods. It did a great job in the early days, but it's become ritualized and bureaucratic, issuing big bulk reports that do little to answer the hard questions facing policymakers." It needs, he says, "a reinvention."

The irony may be that the IPCC has stood up to political pressure, and maintained its scientific purity, perhaps just a tad too well.