The major source of potentially climate-changing soot in the air over south Asia is home cooking fires, according to a team of Indian and American researchers.
The burning of wood, agricultural waste and animal manure for cooking is the largest source of black carbon in the air in that region, according to the team led by C. Venkataraman of the Indian Institute of Technology Bombay.
"We therefore suggest that the control of these emissions through cleaner cooking technologies, in addition to reducing health risks to several hundred million users, could be of crucial importance to climate change mitigation in south Asia," the researchers wrote in a paper appearing in Friday's issue of the journal Science.
The effect of soot in the air over the Indian Ocean is some 10 times that of the so-called greenhouse gases, according to the researchers. The pollution causes the air to absorb more sunlight, warming the atmosphere and cooling the surface beneath. Such changes can affect rainfall patterns, contributing to intensity of floods and droughts, the group said in their paper.
Worldwide, most atmospheric scientists are concerned that increasing greenhouse gases, such as carbon dioxide, from industrial processes are trapping heat increasing the planet's overall temperature in ways that could lead to climate change.
The researchers conducted tests, burning various fuels used in home cooking in India to determine the type of soot produced, and measured soot in the air.
They calculated that, of the black soot in the atmosphere, 42 percent originates from cooking fires, 25 percent from burning fossil fuels and 13 percent from open burning such as forest fires.
The research also included scientists from the University of California, Los Angeles. The work was funded by the Indian Space Research Organization; Center for Clouds, Chemistry and Science, University of California, San Diego; U.S. National Institute of Environmental Health Sciences; and U.S. Environmental Protection Agency.