Curbing Emissions Won't Be Enough

Like many people who are scrambling for ways to stave off climate disaster, Klaus Lackner is thinking trees. But not the kind with green leaves and roots, and certainly not the sweet little specimens that "carbon offset" purveyors hawk as a way to balance out the carbon dioxide emitted when you tool around town in a Hummer. Lackner, a professor of geophysics at Columbia University, is helping to design a synthetic tree. It would stand roughly 1,000 feet tall with a footprint a little bigger than a football field, and be crisscrossed with scaffolding holding liquid sodium hydroxide, which is best known as lye. For in addition to cleaning drains, sodium hydroxide has a chemical property that promises to be in great demand if, as seems likely, the nations of the world fall short of stabilizing the atmosphere's load of greenhouse gases: it sucks carbon dioxide out of the air.

A new phrase has emerged in the debate over climate change: managing the unavoidable. To grasp "unavoidable," consider a few simple numbers. Before the Industrial Revolution, the atmosphere held 280 parts per million of carbon dioxide (CO₂). We are now at 380 and climbing. Since the 1992 Rio Convention on Climate Change, which obligated its signatories (including the United States) to inventory their greenhouse-gas emissions and devise plans to control them, global emissions have risen from 6 billion metric tons of carbon to 7.3 billion in 2003, 7.85 billion in 2005 and an estimated 8 billion last year, says Gregg Marland of Oak Ridge National Laboratory. Combine that pathetic record with another number: molecules of carbon dioxide stay in the atmosphere as long as 200 years; yes, carbon dioxide molecules belched out by Model Ts are still up there. As a result, "incremental reductions in CO₂ emissions" as called for by the 1997 Kyoto Treaty and legislation pending in Congress "will not stabilize atmospheric CO₂ levels," argues climate researcher Wallace Broecker of Lamont-Doherty Earth Observatory, part of Columbia. "They only slow the rate of increase."

As we head toward 450, 550, even 750ppm this century—according to projections by the Intergovernmental Panel on Climate Change (IPCC)—environmental leaders are therefore getting serious about carbon capture and storage. The idea is to suck carbon out of the ambient air or—even more feasible—out of power plants where it's produced, and store it in the deep ocean or in depleted oil and natural-gas fields. The U.S. Department of Energy is spending $100 million this year for R&D on carbon storage, up from $1 million in 1997. Just before his death in 2006, Gary Comer, founder of Lands' End, funded a start-up company in Tucson, Ariz., called Global Research Technologies to develop ways to pull CO₂ out of the air. In February, Sir Richard Branson, chairman of the Virgin Group, and Al Gore announced the creation of a $25 million prize for devising a way of, as Branson put it, "removing the lethal amount of CO₂ from the Earth's atmosphere."

Gore's involvement was notable. Until recently, environmental activists viewed carbon capture and storage as an evil scheme (probably hatched by the Bush administration) to let SUVs and coal-fired power plants keep polluting. But with emissions rising and plans to cut them alarmingly slow to kick in—especially in China, which accounts for half the rise in emissions since 1992—"we are now facing a planetary emergency," Gore said in announcing the prize.

The growing interest in carbon capture also reflects the fact that the climate we have at 380ppm of CO₂ is dire enough that even the inevitable 450ppm—perhaps 40 years away—looks scarier than it once did. Hurricane Katrina happened at 380. Glaciers are melting and coral reefs are dying at 380. The 2003 heat wave in Europe, which killed an estimated 35,000 people, happened at 380. The seas are rising at 380. Arctic sea ice is vanishing at 380; according to an analysis in the journal Science last month, by 2040 the Arctic may have zero summer sea ice. However you feel about polar bears not having floating platforms from which to hunt seals, the vanishing ice will shift wind patterns in a way that intensifies midlatitude storms, increasing wintertime precipitation over Western and Southern Europe, but reduces rainfall in the American West. Since 1998 that region has been mired in a historic drought. According to a study led by Lamont-Doherty's Richard Seager to be published in Science, the Dust Bowl drought of the 1930s "will become the new climatology of the American Southwest."

Enter Lackner's synthetic, carbon-sucking tree. It is only conceptual, but he calculates that an area of sodium hydroxide the size of a television screen (not a 103-inch plasma behemoth but the 20-inch diagonal that people found just fine once upon a time) would soak up an amount of carbon equivalent to what one American is responsible for emitting. Or, to use another comparison, one tree could absorb about as much as 15,000 cars emit. Paired with a windmill, the carbon-capture tree would generate about 3 megawatts of power, Lackner calculates, making the operation self-sufficient in energy. "The carbon-capture efficiency is better than a [living] tree," he says. "We can, with such a system, collect a significant fraction of the carbon from the air." Carbon capture from the air has the advantage of removing this pollutant no matter where it came from—cars, planes, factories, power plants. No other carbon-capture technology now on the drawing boards would work on moving sources, such as cars and planes.