What It Would Take to Put the Brakes on Global Warming

By Steven Mufson
Washington Post Staff Writer
Sunday, July 15, 2007

If the majority of climate scientists are right, the sheer immensity of the global warming problem can make mortal measures look hopelessly tiny.

That's what one Bush administration official seemed to be saying in a speech to a 2004 conference. Energy Secretary Spencer Abraham said it would take a technological breakthrough on par with the discovery of electricity to slow climate change.

That galled a member of the audience, Princeton University professor Robert Socolow, who thought there were things people were capable of doing -- and must be doing -- now.

So Socolow and fellow Princeton professor Stephen Pacala came up with a game, with multicolor wedges, to make the global warming problem look solvable, albeit still difficult. (See http://www.princeton.edu/~cmi/resources/stabwedge.htm.)

First, they set a goal of keeping global greenhouse gas emissions constant. That would hold atmospheric concentrations of carbon dioxide to about 550 parts per million, roughly twice the level in the preindustrial era. That would not stop global warming, but it would probably limit temperature change to 3 degrees or so. Hitting Socolow and Pacala's target would still be no small feat, given that greenhouse gas emissions have been rising steadily with economic growth.

After setting their goal, Socolow and Pacala divided up the amount of savings needed into seven wedges, like pie pieces. Each wedge represented a billion tons of reductions in annual carbon emissions by 2050. (Socolow uses carbon to measure greenhouse gases and gets nice round numbers; when measured in carbon dioxide, the figures are 3.67 times greater.)

In a class exercise, the professors give students 15 wedges with different colors, each representing a way to achieve a billion tons of carbon savings, and had the students mix and match them to come up with a plausible strategy for keeping the 2050 emissions level equal to today's. Coming up with seven politically feasible wedges is no simple matter. Here are some of the choices:

Triple nuclear electricity production by building 700 new, 1,000-megawatt nuclear plants. Boost wind production 30-fold by building nearly 2 million 1-megawatt wind turbines. Halt deforestation and plant 300 million hectares of unforested land. Cover an area the size of New Jersey with photovoltaic cells. Double the fuel efficiency of cars and light trucks. Replace every incandescent light bulb in the world with a compact fluorescent bulb and change building codes, including in the developing world, where the most commercial building is occurring.

The impact of the wedges has been huge. Since the Princeton pair wrote their article in late 2004, each has given about 100 talks, prodding scientists, policymakers and companies to attack global warming in concrete ways.

There are endless scenarios because every country is different. Fast-developing countries like China and India, where greenhouse gas emissions per person are a tiny fraction of those of the average American, currently account for about half of the world's greenhouse gas emissions. Socolow and Pacala assumed that these countries, even if they restricted emissions, would generate 60 percent more greenhouse gases by 2050 than they do now. So they assumed that industrialized nations like the United States would have to cut emissions by 60 percent.

Looking at Socolow and Pacala's options can be daunting. But Socolow says, "We've gone from a problem people scarcely recognized, to one that seemed impossible to address, to a serious determination to address it."

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