Controlling 'Black Carbon' May Be Key to Slowing Climate Change

CLIMATE CHANGE -- December 17, 2009 at 5:27 PM EDT

Black carbon is a relatively new entrant into the climate change lexicon. Professor V. Ramanathan, a leading climate scientist, ranks it behind only carbon dioxide as a cause of global warming. He says it is a major cause of the worrisome Himalayan glacier melt.

Anyone who has lived or traveled in the developing world is familiar with black carbon - known for years by its far more common name, soot. The air in India can make Los Angeles seem like paradise on its most smoggy days.

Diesel engines are the chief culprit but our story concerned an effort to contain the second most prolific soot emitters: hundreds of millions of crude stoves that cook the meals for perhaps three billion people across the developing world.

The pall of smoke spewed by the incomplete combustion of bio-mass fuels-crop residues, wood and cow dung-is a fixture in most households in rural India. As many as 1.5 million people in India alone die each year from the effects of this unhealthy indoor air. And once it becomes outdoor air, black carbon forms a blanket that traps heat that would normally escape into the atmosphere, says Ramanathan, who is with the Scripps Institution of Oceanography at the University of California, San Diego.

But Ramanathan, who grew up in India and remembers his grandmother suffering over a biomass stove, sees a huge opportunity for a double dividend. Reducing black carbon will not only clean up people's lungs, he says, but it will immediately slow global warming. Unlike carbon dioxide-the major greenhouse gas which can linger for centuries, he says black carbon dissipates in weeks. Clean it up and you've instantly slowed global warming.

Other scientists are more cautious about the climate dividend, though no one disputes the public health benefits of cleaner stoves.

How to create more efficient stoves then place them in a billion kitchens? The sociological and economic challenges are plain to see and we decided to focus our report on one pilot effort by Colorado-based Envirofit. And then there's the physics of developing cleaner burning stoves. The models being tested in our story aren't exactly clean-burning but every incremental improvement helps. And better biomass stoves will help restore the reputation of the rather crude-sounding fuels they use. In truth, Ramanathan says, biomass fuels are the most climate friendly, since they do not burn fossil fuels.

Fred de Sam Lazaro's full report on "black carbon" in India will air on Thursday's NewsHour.

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