The conversation around climate largely focuses on carbon dioxide, the invisible greenhouse gas building in the atmosphere mainly from the burning of fuels and forests. But there’s another emission from human activities that would be easier to curb in the short run – and that also contributes to enormous conventional pollution problems as well as the warming of the climate.
From the New York Times
It’s good old fashioned black carbon soot – a visible pollutant with measurable effects on human health both in poor places, where it comes from cooking or heating using coal, firewood or dung, and rich countries, where it is produced mainly through the combustion of diesel and similar fuels and from some industries.
James E. Hansen of NASA first drew attention to soot as a climate influence in 2000. He and others have also proposed that soot, by darkening Arctic ice and snow, could be accelerating the boreal melt well beyond what would happen only under natural climate variability or the growing warming influence from greenhouse gases.
Now a new study by V. Ramanathan of the University of California, San Diego, published online this week in Nature Geoscience, finds that soot may be more than twice as potent a warming influence as the Intergovernmental Panel on Climate Change estimated last year. The study, co-authored by Greg Carmichael of the University of Iowa, also proposes that regional emissions of dark carbon particulates in south Asia could be contributing to the melting of the ice locked in the Himalayas.
One reason for black carbon’s potent warming effect, according to the paper, is that most of it is forming vast “brown clouds” around the tropics where the sun is also at its strongest.
Dr. Ramanathan, like Dr. Hansen, has said that carbon dioxide remains the dominant concern because it can persist in the atmosphere for centuries once emitted. But cutting sooty pollution can have an immediate payoff, both in limiting climate risks and improving public health, the new study said.
One way or the other, it’s pretty clear that cooking on dried dung and firewood, the norm for about 2 billion people, will be hard to sustain as populations in south Asia and Africa climb.
The climate impact of these energy sources pales beside the direct impact on the lives of the people — mainly women and their children — who spend a significant portion of the day gathering the fuels or breathing the smoke. International development agencies estimate that more than 1.5 million people die young each year from avoidable respiratory ailments associated with cooking.
Still, the climate benefits from shifting away from such energy options count, too, Dr. Hansen said in an email. “And we need every bit of help we can get,” he said.
There’s more here on black carbon and climate, and how the issue roiled politics and environmental campaigns and science in 2000.