Pollution in India may affect climate.

Computer models show that air pollution in India could be having significant effects on the climate there.

Simulations by researchers at the National Center for Atmospheric Research in Boulder, Colo., show that sulfate aerosols over India are preventing up to 15 percent of the sun's light from reaching the ground in the springtime. The aerosols, which form from industrial emissions and exhaust from high-sulfur coal fires, scatter sunlight more strongly in the winter, says William Collins, a researcher at the center.

The 15 percent reduction in sunlight is more than twice that typically caused by clouds and could cause temperature drops over the Indian subcontinent of up to 2 [degrees] C, says Collins.

Although the pollution has a cooling effect at ground level, it warms the atmosphere at heights where the aerosols absorb or scatter solar radiation. This high-altitude warming tends to reduce cloud cover, somewhat counteracting the reduction in sunlight reaching the surface. Incorporating such localized effects into global climate models could lead to improved long-range predictions, Collins notes.