Are we cooking the planet? Millions of stoves in developing nations in Africa and Asia are a surprising--and growing--cause of global warming.

• Author: Rosenthal, Elisabeth
• Position: ENVIRONMENT

It's hard to believe that this is what's melting the glaciers," says Veerabhadran Ramanathan, a leading climate scientist, as he walks among Kohlua's mudbrick huts, each with a small cookstove that pours soot into the atmosphere.

Women in ragged saris bake bread and stew lentils in the early evening over fires fueled by twigs and dung, while children cough from the dense smoke that fills their homes. Black grime coats the undersides of thatched roofs. At dawn, a brown cloud stretches over the central Indian village of Kohlua like a dirty blanket.

In India's booming cities, a growing middle class is using more electricity and driving more cars. Emissions of carbon dioxide--the main heat-trapping gas associated with global warming--are on the rise. But in Kohlua, with no cars and little electricity, carbon-dioxide emissions are near zero. Here, as in tens of thousands of rural villages in developing countries, it is soot--or black carbon--that is emerging as a major cause of global climate change.

While carbon dioxide may be the biggest contributor to rising global temperatures, black carbon has emerged as the next-biggest culprit. Recent studies estimate that black carbon is responsible for 18 percent of the planet's warming, compared with 40 percent for carbon dioxide.

Reducing black carbon is one of a number of relatively quick climate fixes--often called "low-hanging fruit"--that scientists say should be plucked immediately to head off the worst projected consequences of global warming.

"In terms of climate change, we're driving fast toward a cliff, and this could buy us time," says Ramanathan, a climate scientist at the Scripps Institute of Oceanography in San Diego. Ramanathan is working in India on a project to help poor families acquire new stoves.

A QUICK FIX?

Converting to low-soot stoves would remove the warming effects of black carbon quickly, while shutting a coal plant takes years before it substantially reduces global carbon-dioxide concentrations.

In Asia and Africa, cookstoves produce the bulk of black carbon, although it also comes from diesel engines and coal plants. In the United States and Europe, black-carbon emissions have been reduced significantly by filters and scrubbers.

Like tiny heat-absorbing black sweaters, soot particles warm the air and melt ice by absorbing the sun's heat when they settle on glaciers. A recent study estimated that black carbon might account for up to half of Arctic warming. While the...