Weaning humanity from its fossil fuel habit will take decades, and it will take decades more for global warming to stop. But one simple measure could slow warming in some of Earth's most sensitive regions, effective immediately — and it would cost just $15 billion.

That's a rough price tag for providing clean stoves to the 500 million households that use open fires, fed by wood and animal dung and coal, to heat their homes and cook. Those fires produce one-quarter of all so-called "black carbon," a sooty pollutant that's adding to the planetary heat burden.

"We know how to cook without smoke," said Veerabhadran Ramanathan, a University of California, San Diego climatographer. "A clean stove costs $30. Multiply that by 500 million households, and it's only $15 billion. This is a solvable problem."

After floating to the atmosphere, black carbon mixes with dust to form a solar heat-absorbing particulate layer. Raindrops form around the particles, trapping even more heat. Soot deposited by the rain heats up, too.

The climate dynamics of the black carbon process have been fully described only in the last decade, but scientists now say their short-term impact sometimes rivals that of carbon dioxide. As much as one-half of the 3.4 degree Fahrenheit rise in Arctic temperatures since 1890 is attributed to black carbon. By disrupting weather patterns, it may be responsible for weakening seasonal rains in South Asia and West Africa. And black carbon is also a major reason why Himalayan glaciers, which provide water to hundreds of millions of people, are vanishing.

Unlike carbon dioxide, however, which can hang in the atmosphere for centuries, black carbon returns to Earth in less than a month. And that makes it a ripe target for immediate action. Though Ramanathan is quick to warn that eliminating black carbon is no substitute for controlling carbon dioxide emissions, which in coming centuries could have a far greater effect, he estimates that a 50% reduction in black carbon could delay the onset of severe global warming by one to two decades.

In addition to being emitted by unclean stoves, black carbon also comes from coal-fired power plants, and burning diesel fuel and forests. Halting deforestation and installing filters on power plants and cars will cost more than clean stoves, though the price would likely be small compared to the environmental, agricultural and health benefits.

In the meantime, clean stoves remain a very practical target. Black carbon emissions are not being considered as part of whatever agreement comes from the ongoing United Nations climate conference in Copenhagen, but Ramanathan hopes that regional agreements will address the problem. Many non-governmental organizations are already working to distribute clean stoves.

"We're not talking about a trillion dollar problem. We're talking about a few billion dollars. There's no downside here," said Ramanathan.

Image: Atmospheric black carbon intensity/Nature Geoscience.

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Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecosystem and planetary tipping points.