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 dioxidethe main heat-trapping gas associated with global warmingare 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 sootor black carbonthat 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 fixesoften 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 particles don't have the global reach of greenhouse gases, they do travel, according to scientists. Soot from India has been found in the Maldives, south of India, and on the Tibetan Plateau.
The environmental and geopolitical implications of soot emissions are enormous. Himalayan glaciers are expected to lose 75 percent of their ice by 2020, according to Syed Iqbal Hasnain, a glacier specialist. These glaciers are the source of most of the major rivers in Asia. The number of floods from glacial lakes is already rising sharply, Hasnain says. Once the glaciers shrink, Asia's rivers will run low or dry for part of the year, which could lead to battles over water in a region already rife with conflict.
In March, a bill was introduced in Congress that would require the U.S. Environmental Protection Agency to specifically regulate black carbon and fund related projects abroad, including introducing new cookstoves in 20 million homes. The new stoves either use solar power, or are more fuel-efficient, and would reduce soot by more than 90 percent.
That remote villages like Kohlua could play a role in tackling the warming crisis is hard to imagine. Like the majority of India's 1.1 billion people, the 1,500 residents here are farmers and laborers. Many work in nearby Agra, home to the Taj Mahal. Unlike the university-educated Indians who work in high-tech jobs, the villagers earn about $2 a day; most haven't heard of climate change. But they have noticed frequent droughts that may be linked to global warming. And they know that soot corrodes: Cookstoves are forbidden near the Taj Mahal because black carbon damages the marble faŤade of the domed structure, which was built by the Emperor Shah Jahan in 1648 as a monument to his wife.
Still, replacing millions of stovesthe source of heat, food, and sterile waterwon't be easy. "I'd have to see them, to try them," says Chetram Jatrav, as she squats by her stove making tea. Her children are coughing. She'd like a stove that "made less smoke and used less fuel" but can't afford one.
The cookstove project, called Surya after the Hindu sun god, recently began testing in rural India. Researchers are concerned that the new stoves look like lab instruments and are fragile; one broke when a villager pushed twigs in. Equally important, the open fires of the old stoves give some of the traditional foods their taste.
But if black carbon is ever to be addressed on a large scale, acceptance of the new stoves is crucial.
"I'm not going to go to the villagers and say carbon dioxide is rising, and in 50 years you might have floods," says Ibrahim Rehman, who is working with Ramanathan. "I'll tell her about the lungs and her kids, and I know it will help with climate change as well."