Yale Env360: UN Climate Panel


Has the U.N. Climate Panel Now Outlived Its Usefulness?

Some scientists are saying the latest report from the Intergovernmental Panel on Climate Change is overly conservative and fails to mention some of the most worrisome possible scenarios. The panel, they contend, is no longer fulfilling its mission of informing policy makers of the risks of global warming.

By Fred Pearce, September 30 2013.

After four years of work, it took the U.N. Intergovernmental Panel on Climate Change until 5 a.m. on the morning of publication last Friday to agree on the final wording of its new report. Agreement was only reached at the end of an all-night closed session at which delegates from governments cross-questioned the scientists and at times sought to put their own spin on the findings. It is not called an “intergovernmental panel” for nothing, and every last nation had to agree to the text before it was published.

So is this science or politics? 

Leaving aside the hysterical fringes, most mainstream media coverage of the IPCC report took one of two lines. Some concentrated on its “stark warning” about how scientists are “more sure than ever” about climate change and humanity’s role in it. Others more skeptically stressed that the panel had confirmed for the first time a slowdown in warming in the past 15 years, and that, partly as a result, it had slightly lowered its projections of future warming.

Both stories are true. As Thomas Stocker of the University of Bern, the co-chair of the scientists behind the report, put it at the press launch: “Human influence on the climate is clear,” and “climate change is the greatest challenge of our time.” The assessment had concluded that scientists are now 95 percent certain that the warming since 1950 is due primarily to human activity, up from 90 percent in their last report in 2007.

Yet Stocker also talked about scientific interest in what lay behind what he termed the “hiatus” in warming. Nobody, the report says, is yet sure whether it is a blip — perhaps caused by some natural redistribution of heat between the atmosphere and the oceans — or whether it means climate models have got something wrong about global warming.

But there is a third narrative about the IPCC that has received less attention. Some of those involved in the report process believe the natural caution among scientists — coupled perhaps with a wish not to repeat some exaggerations that marred some previous IPCC reports, and the effect of politicians looking over their shoulders — has created a report that is overly conservative, even biased, in its conclusions. Rather than lowering its expectations of warming, these scientists say, perhaps the panel should be raising them.

Some “scary scenarios” arising from possible positive feedbacks — in which nature amplifies man-made warming — have been left out of the model projections on which the IPCC’s headline forecasts are based. Surely, some critics say, it is the scary scenarios that politicians need to know about if they are to do their duty under the UN climate change convention and act together to prevent “dangerous climate change.” Even the U.S. signed that, under George Bush senior in 1992.

The report’s headline conclusions include:

— Global warming is “unequivocal.” The last three decades were the warmest in the atmosphere for at least 1,400 years. While atmospheric warming has slackened unexpectedly in the past 15 years, it continues, and warming is unabated in the oceans. This oceanic warming is melting ice on land and at sea, most notably with the dramatic summer declines in Arctic sea ice. The melting of land ice and thermal expansion mean that sea-level rise is now twice the average rate before 1993, at over 3 centimeters a decade. This too is unprecedented in recent times.

— The warming slowdown is one reason for a marginal reduction in expected warming over the coming century. Modelers now expect a doubling of greenhouse gas concentrations in the atmosphere to bring warming somewhere between 1.5 and 4.5 degrees Celsius, rather than the between 2 and 4.5 degrees projected last time.

— New research identifies clear evidence of an intensification of the water cycle, with wet areas and seasons becoming wetter, and dry areas and seasons drier. But the IPCC has retreated on some statements made in 2007 that this is creating more droughts, or more hurricanes.

The vast tome, which will come to over 3,000 pages, was written by more than 250 authors, reviewed by over 1,000 other experts, and cites more than 9,000 pieces of peer-reviewed science. And yet, in places, the scientists had to work hard last week to restrict political interference with the findings. 

Hence that 5 a.m. finish last Friday. Yale Environment 360 has established that the meeting of scientists and government delegates called to sign off on the report was virtually done at midnight on Thursday, when they got to a final paragraph about something the IPCC had not mentioned in previous reports, but which the scientists felt was hardly contentious.

Their draft of the summary report said that, since much of the carbon dioxide emitted into the air by human activity stays there for many centuries, the warming it produces is “irreversible on a human timescale” — at least without massive geo-engineering. Therefore, if the world is serious about restricting warming to below two degrees Celsius since pre-industrial times, it needed in effect to impose a carbon budget. It had to restrict total man-made emissions forever to below about one trillion tons of carbon — or to 800 billion tons if we assume that our emissions of other greenhouse gases are unlikely to halt anytime soon. We are already two-thirds of the way there, at around 530 billion tons.

That was the bald scientific calculation. But three governments in particular objected to this statement. According to sources who attended the meeting, they were China, Brazil and Saudi Arabia. The U.S. was not involved.

The scientists dug in. “I sat for five hours defending this paragraph,” said Reto Knutti of ETH Zurich, a Swiss science university, who was the coordinating lead author for the relevant chapter on “projections, commitments, and irreversibility.”

“There was very strong opposition from many governments. It was obviously political, though they were using strange scientific arguments,” Knutti said. The governments saw this statement as, in effect, scientists imposing emissions restrictions through the back door. “I am proud to say we didn’t lose any figures,” he added, “though some of the text was rewritten a bit.”

Drew Shindell of NASA’s Goddard Institute for Space Studies, another lead author on the report, was also in the room. “Some people were very sensitive to this cumulative carbon issue,” he said. “They had agendas beyond the science.”

Another contentious topic was how the report should deal with the recent warming hiatus. The draft acknowledged the scientists’ concerns and noted that climate models “do not generally reproduce the observed reduction in surface warming trend over the last 10-15 years.” This was reportedly met with opposition from some delegates who wanted to remove all references to a slowdown. Some argued that the hiatus had not lasted long enough to be considered a temperature trend. Perhaps they also felt it would be seized on by climate-change deniers.

“We looked at this very carefully,” said Stocker. There was, he noted, “not a lot of published literature” on the phenomenon. This was a problem, since the IPCC does not do its own research and can only review published literature. But again, the authors of that passage stuck to their guns, and retained most of the message, though the direct statement about the failings of the models does not appear in the report.

Science is not naturally a consensual process. Reaching agreement is hard for people more used to spending their time refuting each others’ hypotheses. So the question arises: Is the IPCC’s self-imposed task of producing massive consensual documents about every aspect of climate science — and then resisting politicians’ efforts to change them — worth it? 

For one thing, the consensus even among scientists is creaking. In interviews with Yale Environment 360 in recent weeks, a number of past and present IPCC authors have expressed strong dissatisfaction with what they saw as the conservatism of the emerging text for the scientific assessment. (There is, if anything, even more contention over the two companion reports that will be published next year, covering the impacts of climate change and what to do about it.)

Some researchers are angered about the marginal reduction in predicted warming. They say that may be justified by the outputs of the climate models, but that those models do not include some worrying positive feedbacks that could accelerate warming in coming decades. Other critics say that, even though the report has upped its estimates of sea level rise this century to as much as one meter, the lead authors did not accept findings from reputable researchers suggesting that a rise of as much as two meters was possible.

The problem, in essence, is that factors that climatologists cannot yet successfully model are left out of the modeling studies that deliver the headline predictions.

Michael Mann of Penn State University, a past IPCC lead author, is concerned about the sidelining of the potential for higher sea level rises due to collapsing ice sheets on land. Before the report’s publication, he said the report “should not be dismissing impacts with lower probability, but higher threat potential. Such potential outcomes are a critical part of the societal risk.” For instance, people designing flood risk defenses want to know about the worst expectations of possible sea level rise, not those scientifically most likely.

One lead author of the IPCC chapter on sea level rises, spoken to after the report’s publication, conceded the point. “I agree there can be a conflict between good science and what policymakers and engineers like flood designers want to know,” said Tony Payne of the University of Bristol, England.

Another concern is methane, a potent greenhouse gas that could escape into the atmosphere as Arctic permafrost melts and sea beds warm. The methane is the frozen product of rotting vegetation in centuries past. The IPCC estimates that up to 80 percent of the Arctic permafrost could melt this century.

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.

See Fred Pearce, Has the UN Climate Panel Outlived Its Usefulness?, Yale Environment 360, September 30 2013.

(Emphasis added)