Asia's brown clouds 'warm planet

BBC News Wednesday, 1 August 2007, 18:34 GMT 19:34 UK
Clouds of pollution over the Indian Ocean appear to cause as much warming as greenhouse gases released by human activity, a study has suggested.
US researchers used unmanned aircraft to measure the effects of the "brown clouds" on the surrounding area.
Writing in Nature, they said the tiny particles increased the solar heating of the lower atmosphere by about 50%.
The warming could be enough to explain the retreat of glaciers in the Himalayas, the scientists proposed.
The clouds contain a mixture of light absorbing aerosols and light scattering aerosols, which cause the atmosphere to warm and the surface of the Earth to cool.
The main sources of the pollutants came from wood burning and fossil fuels, the team added.
Aerosols, also known as particulates, cool the land or sea below because they filter out light from the Sun.
While this process, known as "global dimming", is fairly well understood, the effect aerosols have on the surrounding atmosphere is still unclear.
The scientists, from the University of California San Diego and the Nasa Langley Research Center, said there remained a degree of uncertainty because, until now, estimates had largely been derived from computer models. The rest of the story.