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Climate Uncertainty

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SCIENCE www.sciencemag.org

VOL 314 13 OCTOBER 2006




Trying to Lasso Climate Uncertainty


An expert on climate and population looks for a way to help society avoid a

"Wile E. Coyote" catastrophe


LAXENBURG, AUSTRIA - A few weeks ago, Brian O'Neill hunkered down

around a table with a dozen other climate scientists in Cape Town,

South Africa, to talk about the future of the planet. It was no idle

speculation: Whatever they agreed upon - they knew in advance - would

have clout. They were hammering out the final draft of a chapter on

research methods for the massive "Fourth Assessment" of the

Intergovernmental Panel on Climate Change (IPCC). The product of 3

years of consensus-building among several hundred researchers from

around the world, the IPCC report is the scientific bedrock on which

policymakers will negotiate everything from carbon taxes to long-term

greenhouse gas targets.


But for all its authority, the IPCC exercise left O'Neill with a

nagging concern: What were they leaving out? "It's important that we

climate scientists speak with a single voice," he said in an

interview back in his office, high up in the attic of a former

Habsburg palace outside Vienna. But "the extreme scenarios that tend

to fall out of the IPCC process may be exactly the ones we should

most worry about," he says.


O'Neill, a climate scientist at the InternationalInstitute for

Applied Systems Analysis (IIASA) here, is frustrated to see

uncertainties in research used as a reason to delay action. At age

41, he is one of the youngest scientists in the IPCC network trying

to reformulate climate-change projections that can cope better with

uncertainty by accounting for "future learning." O'Neill hopes the

strategy will make it clear that, even with gaps in understanding, it

pays to act now.


His work is gaining notice. Although an American, O'Neill has scooped

up one of the coveted European Young Investigator Awards (EURYI), a

$1.5 million grant meant in part to keep Europe's most promising

scientists at home. "He is one of the brightest young scientists out

there, and we're all watching to see what he does," says Simon Levin,

an ecologist at Princeton University.


A winding path


O'Neill's job is to predict the future, but his own career path has

been unpredictable. With 3 years' training in engineering and a

degree in journalism, he became passionately involved in the 1980s in

efforts to prevent ozone depletion, working for Greenpeace in

California. After collecting a Ph.D. in earth-system sciences from

New York University, he did research stints at Brown University and

the Environmental Defense Fund in New York City. In 2002, he moved to

IIASA, a center for multidisciplinary research founded in 1972. Here,

O'Neill has built up a new program focusing on population and climate

change. The treatment of demographics in most climate-change

analyses, he says, is "simplistic at best." With the EURYI money,

he's assembled a team of a half- dozen demographers, economists,

statisticians, and physical scientists to sharpen the models.


A long-limbed basketball player who looks like he could be fresh out

of graduate school, O'Neill seems to peel away layers of uncertainty

as he speaks. His slow-paced answers to questions often begin with a

detailed preamble of assumptions, conditions, and footnotes. But as

the father of two daughters, he says, "thinking about how the world

will be in 50 years is not so abstract for me anymore."


At IIASA, his work focuses on building realistic demographic

projections, and China has become his main beat. Different

predictions of how the country's population will age and urbanize --

and how carbon-emission policies will shape Chinese consumption --

have an enormous effect on global climate change scenarios. But

obtaining accurate demographic data has been difficult. With the help

of a Chinese member of his new team, O'Neill has done an analysis

revealing that the IPCC assumptions about China's rate of

urbanization and energy consumption could be off by a factor of 2.


Learning about learning


Earlier this year, O'Neill organized a unique meeting at IIASA,

bringing together experts from different areas of climate science,

economics, and demography to think about how they generate knowledge.

One of the most important questions that emerged, says Klaus Keller,

a climate scientist at Pennsylvania State University in State

College, is how do you avoid "the Wile E. Coyote effect?" The cartoon

coyote often doesn't realize he's falling off a cliff until he looks

down, too late to turn back. One of the potential cliffs in climate

change involves the ocean's conveyer-belt system -- known as the

meridional overturning circulation (MOC) -- which prevents a Siberian

chill from spreading across western Europe by carrying warm water

north from the equator. Scientists worry that global warming could

abruptly change or even shut down the MOC. "These are the kind of

climate thresholds that we need to identify," says Keller.


Scientists need to know more about the natural variability in MOC

behavior, says O'Neill. But they don't even know "how precise your

measurements have to be" or how large an area must be studied before

uncertainty could be sufficiently reduced to spot "the edge of the

cliff." He argues that the only way to attack such complex

uncertainties with limited time and resources is to have scientists

from different fields work together, assessing observations over many

years to learn which approaches pay off the most. O'Neill and others

did exactly this with 2 decades of research on the carbon cycle,

finding that some kinds of observations narrowed uncertainty in model

parameters far better than others. Such big-picture,

multidisciplinary studies are low on the priority scaleof funding

agencies, but this is exactly what's needed if you want "to learn

about the potential of an MOC shutdown," he says.


The second big question to emerge from the IIASA sessions is how can

we tell if mainstream research is headed in the wrong direction?

O'Neill, Michael Oppenheimer, and Mort Webster, climate scientists at

Princeton and the Massachusetts Institute of Technology in Cambridge,

respectively, use the term "negative learning" to describe cases in

which scientific consensus builds around the wrong model. "This is

what happened with ozone," says Oppenheimer. People believed that

ozone's key interactions are with other gases, until scientists

realized that the critical reactions driving ozone depletion occur on

the surfaces of airborne particles. With revised reaction rates, it

was suddenly clear that the planet's protective ozonelayer was in

much bigger trouble than had been thought. Oppenheimer proposes that

scientists team up with philosophers and historians to find common

signs of negative scientific learning. A search for such red flags

could be built into climate science's regular review



And O'Neill says more funds should be set aside to explore hypotheses

outside the mainstream. Researchers desperately need a strategy for

tackling climate uncertainties, O'Neill says. Michael Schlesinger, a

climate scientist at the University of Illinois, Urbana-Champaign,

points to another example. Polar ice sheets are melting more rapidly

than anticipated, and some observers fear that this could lead to a

catastrophic sea-level increase ( Science , 24 March, p. 1698).

"Things are happening right now with the ice sheets that were not

predicted to happen until 2100," Schlesinger says. "My worry is that

we may have passed the window of opportunity where learning is still



Whether a catastrophe can be averted using some form of scientific

introspection -- or learning about learning, as O'Neill calls it --

remains unclear. The concept, like O'Neill's career, is still at an

early stage of development.







Cold Mountain, Cold Rivers

Working at the Crossroads of Environmental and Human Rights since 1990

PO Box 7941

Missoula Montana 59807




posted to ClimateConcern

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