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Princeton professor Robert Socolow's paper suggested that actions such as installing wind farms or halving auto travel could help cap greenhouse gas emissions. But he says the theory created oversimplifications and a false sense of confidence about the prospect of mitigating global warming.

Photograph by Raphael Gaillarde, Gamma-Rapho/Getty Images

Doug Struck in Cambridge, Massachusetts

For National Geographic News

Published May 17, 2011

When the torrent of predictions about global warming got too depressing, there were Robert Socolow's "wedges."

The Princeton physics and engineering professor, along with his colleague, ecologist Stephen Pacala, countered the gloom and doom of climate change with a theory that offered hope.  If we adopted a series of environmental steps, each taking a chunk out of the anticipated growth in greenhouse gases, we could flatline our emissions, he said. That would at least limit the global temperature rise, he said in a 2004 paper in the journal Science.

(Related: What Is Global Warming?)

The Princeton colleagues even created a game out of it: choose your own strategies, saving a billion tons of emissions each, to compile at least seven "wedges," pie-shaped slices that could be stacked up in a graph to erase the predicted doubling of CO2 by 2050.

It was a mistake, he now says.

"With some help from wedges, the world decided that dealing with global warming wasn't impossible, so it must be easy," Socolow says.  "There was a whole lot of simplification, that this is no big deal."

He said his theory was intended to show the progress that could be made if people took steps such as halving our automobile travel, burying carbon emissions, or installing a million windmills. But instead of providing motivation, the wedges theory let people relax in the face of enormous challenges, he now says.

(Related: Quiz: Know Much About Global Warming?)

"The job went from impossible to easy" in part because of the wedges theory.  "I was part of that."

And from there, he says, a disturbing portion of the population moved to doubt that the problem is even real.

"I know no one who predicted that the climate change message would be rejected on a scale that it is now," Socolow said at a recent seminar at Harvard's Kennedy School of Government.  "Scientists and environmentalists interested in getting climate taken seriously have failed beyond their wildest imaginations.

"This is a time for self-assessment," he said.

Taking a Theory Too Far?

Socolow said he believes that well-intentioned groups misused the wedges theory. His theory called for efficiency, conservation, and energy alternatives that could keep greenhouse gas emissions at roughly today's levels, offsetting the growth of population and energy demands. Global temperatures would rise by 3°C.

"I said hundreds of times the world should be very pleased with itself if the amount of emissions was the same in 50 years as it is today," he said.

But those inspired by the theory took it farther.  If Socolow's wedges could stabilize emissions with a 3-degree rise, they said, even bigger wedges could actually bring greenhouse gases back down to a level resulting in only a 2-degree rise. (This is the goal that 140 nations have pledged to try to achieve in the Copenhagen Accord.)

"Our paper was outflanked by the left," Socolow said.  But he admits he did not protest enough: "I never aligned myself with the 2-degree statement, but I never said it was too much."

In holding out the prospect of success, adherents stressed the minimal goals, and overestimated what realistically could be achieved.

"The intensity of belief that renewables and conservation would do the job approached religious," Socolow said.  But the minimum goals "are not enough," he said, and "the fossil fuel industry will not be pushed over."Some experts see the wedges paper in a different light.

Professor Dan Kammen of the University of California Berkeley, currently serving as the chief technical specialist for renewable energy and energy efficiency at the World Bank, said that one should be far less surprised with the response to the paper. Of course, the paper was seen as offering a simple prescription for tackling global warming, he said; its very title was "Solving the Climate Problem for the Next 50 Years With Current Technologies." [emphasis added]

But Kammen added, "Socolow and Pacala made a vitally important contribution, connecting the energy and climate communities with the simple statement of the 'Rosetta Stone' of the climate equivalence of greenhouse gas emissions" (that 1 gigaton of emissions was equal to 2.12 parts per million of atmospheric carbon dioxide increase in 2004, when the paper came out.) Kammen said the paper then made the important contribution of highlighting the emerging wisdom that heterogeneous, technologically diverse suites of solutions were needed.

Henry Lee, who directs the environment program at the Harvard Kennedy School's Belfer Center for Science and International Affairs, said many people were optimistic that, by now, the world would be making considerable progress on climate.

"I think we were victimized more by the advocacy community than by science," Lee said.  Using Socolow's wedges theory and similar arguments, advocates suggested "you could get all of this and pay nothing. I think people feel angry now, that it's going to cost them."

Lee agreed Socolow's ideas were misused, or at least misread. "If you look at the wedges they weren't a little. There was nothing in the Socolow plan that says this is a slam-dunk and easy to do."

"The wedge theory still is valuable," Lee added. "The price tag may be higher, but I think he made an important contribution. If you're going to do something about climate change, there is not one silver bullet. That's the point he made at the time, and it's still valid."

The Hard Way Forward

Socolow's prescription for the climate problem today is to confront the problem, and take the bitter medicine.  Those seeking to curb climate change must acknowledge  "the news is unwelcome," he said, "and the job is hard."

Scientists and advocates also should admit that minimal goals for greenhouse gas reductions are not enough, and the challenge to humanity now is to reduce emissions of the rich to the level of the poor—not to simply allow the poor to catch up.

He also said the world must take a more sober and realistic look at "high-consequence outcomes," the scenarios at the extremes of probability.  Those have been largely hidden from the discussion, Socolow said, in part because they are so scary—scenarios such as an average temperate change greater than 4.5°C, which would fundamentally change the world.

"The probability of very bad outcomes is poorly known," he warned.  Neither mild nor severe climate change can be ruled out." And the climatic clock is ticking, as the world continues to pump warming emissions into the air, foreclosing options.

"We have a limited amount of time to have a serious dialogue," Socolow said, "before we probably will not have a whole lot to say."

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