Smoke rises from a clay stove and blackens the walls of a poorly ventilated kitchen hut somewhere in south Asia. The smoke eventually escapes and adds to a perpetual haze that darkens the horizons over large swaths of poverty-filled regions.
The smoke continues to rise. Its floating soot particles heat the atmosphere as they absorb sunlight and at the same time, they may also cool things at ground level with the dimness they provide. The soot and other forms of black carbon eventually fall back to the ground, having traveled as far as the Himalayas. Onto this bright snow and ice they add a veneer of blackness that hastens melt rates and diminishes glacial stores of drinking water.
The practice of biomass burning – using sticks, grass, or cow dung as free cooking fuel – combines with the production of diesel exhaust from vehicles everywhere to create a large contributor to global warming, possibly second only to carbon dioxide emissions. By accelerating snowmelt, it makes the planet more heat-absorbent as sunlight falls less on the bright ice and snow and more on dark land and water.
[See related coverage: Is global warming making us sicker?]
This smog, of course, has other unpleasant side effects carbon dioxide doesn’t have. The women using crude cookstoves and the children at their feet are first in line to suffer from respiratory problems every time they prepare a meal. Household black carbon emissions have been estimated to cause 2 million or more premature deaths throughout the developing world every year. Even with the smog control efforts in urban areas of the developed world, pollution continues to affect health even in relatively affluent countries.
Veerabhadran Ramanathan, a professor of climate and atmospheric sciences at Scripps Institution of Oceanography at UC San Diego, was one of those children. Spending summers with his grandmother in the village of Eraharam in southern India, he would watch her wheeze through the cooking hour, preparing dishes with a delicious smoky flavor infused at great cost.
Ramanathan grew up to be a scientist who was among the first to understand on a regional and global scale how particulate pollution can simultaneously attenuate and accelerate global warming. His career tracks neatly with the growth of public awareness of climate change and the dangers it poses to the planet. Now his newest project is informed as much by memory as by data.
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