Now several leading climate scientists, led by James Hansen, are calling attention to a bigger problem. They argue that the IPCC's conclusions are scientifically "too reticent" (a great frame device).
According to these scientists, it's more than just a communication problem, but rather flows from the assumptions the IPCC adopts in arriving at its predictions. They've set about to challenge these assumptions through new studies published at major journals such as Science and in taking their case to the media and the public.
Last week, Richard Kerr at Science magazine wrote a terrific feature on these emerging concerns of climate scientists. Kerr's feature is also a great example of the ability of Hansen to set the agenda and the frame on global warming. The Science feature in fact follows closely the interpretation and frame offered by Hansen in a commentary published recently at Environmental Research Letters (full text), titled "Scientific reticence and sea level rise."
Here are some key excerpts from the Science feature:
...No longer reticent, other scientists are going public about how bad things might get by the end of the century. "The IPCC has been overly cautious in not wanting to give any large number to [future] sea-level rise," says climate researcher Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany.
Scientists are still trying to strike a balance between their habitual caution and growing concern over uncertain but disastrous greenhouse outcomes. "Most scientists don't want to, but I think we need a way to explore" the extreme end of the range of possibilities, says glaciologist Robert Thomas of NASA contractor EG&G at Wallops Flight Facility in Virginia. Thomas says scientists need "a better way" than IPCC's consensus approach, "so we can communicate with the public without becoming scaremongers."
Seldom have mainstream climate scientists spoken out about the scary possibilities of global warming. "Most people [in the field] realize this really is an extremely serious problem we're facing" in sea-level rise, says Thomas. But no one understands just why the great ice sheets of Greenland and West Antarctica have accelerated their slide to the sea in recent years (Science, 24 March 2006, p. 1698). Will the acceleration continue? Speed up? Slow down? Stop? In the face of such uncertainty, most climate scientists have traditionally let IPCC speak for them. When they've gone public, it was usually to counter greenhouse contrarians arguing for an inconsequential warming with trivial impacts....
....A bolder assessment
Scientists are well aware of the hazards of straying far from the hard science of climate change, but some are eager to change the IPCC process and even move beyond it. They would begin with wording. "IPCC gets an A+ for scientific assessment," says climate modeler Richard Somerville of the Scripps Institution of Oceanography in San Diego, California, "but a gentleman's C for communication." The communication problem is largely a matter of structure, says geoscientist Michael Oppenheimer of Princeton University. "All the facts are there in the [main-report] chapter," he says, "but the SPM didn't tie those facts together in a coherent statement of risk that would allow a policymaker to make an informed decision."
Beyond the IPCC's language, a number of climate scientists think the report missed an opportunity to broaden public appreciation of the risk of the most dangerous climate change. "If you don't understand the physics, your uncertainty is larger," says Thomas. That greater uncertainty extends the range of possible ice losses to higher, more dangerous levels. But IPCC didn't capture that increased risk, says climate modeler Michael MacCracken of the Climate Institute in Washington, D.C....
...A big part of IPCC's problem, say MacCracken and others, was its strict adherence to the use of models. By IPCC standards, "if it's not in a model, it's speculation," says Rahmstorf. By ignoring factors that can't yet be modeled, he says, IPCC came up with deceptively reassuring numbers.
Although forewarned, some researchers are generating numbers for public consumption by going beyond physics-based models. In a paper published in Science in January, too late for the IPCC to consider it, Rahmstorf took "a semiempirical approach to projecting future sea-level rise." He determined how much sea level rose in the 20th century per year per degree and projected that rate through the 21st century, with its expected warming. That projection produced a sea-level rise in 2100 of 0.5 to 1.4 meters above the 1990 level, well above the IPCC's projection of 0.18 to 0.59 meter.
Then, Rahmstorf and six co-authors, including Hansen, published a paper in Science on the day the IPCC report was released. They pointed out that warming had been running toward the high side of IPCC projections during the past few decades, while sea levels rose at the upper limit of projections. "These observational data underscore the concerns about global climate change," the authors wrote. IPCC had clearly not exaggerated sea-level rise, they said, and may even have underestimated it. Reinforcing their message, news stories published a few days before the IPCC report's release quoted Rahmstorf and other scientists lamenting the expected shortcomings on sea-level projections....
....As in 1988, Hansen's pursuit of such insights has put him at odds with many in the climate community. "Maybe he's still within the error bars," says glaciologist Robert Bindschadler of GSFC, but "I'm not prepared to put centuries on [the timing] rather than millennia." No matter. Hansen has again taken to the bully pulpit as NASA's top climate scientist, publishing in peer-reviewed journals, testifying to Congress, writing op-ed articles, and appearing in documentaries. Only last week in a GISS press release announcing a new publication, Hansen warned of disastrous effects--including increasingly rapid sea-level rise--if greenhouse gas emissions continue apace for even a couple more decades. And a few days later, he took his boss, NASA Administrator Michael Griffin, to task for publicly questioning the need to tackle global warming. Hansen's take: "remarkably uninformed."