Indian Ocean haze helps melt Himalayan glaciers, study says

BANGKOK, Thailand — Huge haze clouds over the Indian Ocean contribute as much to atmospheric warming in Asia as greenhouse gases and play a significant role in the melting of the Himalayan glaciers, according to a study published Thursday.

Unmanned measuring devices were sent into the haze pollution, known as Atmospheric Brown Clouds, over the Indian Ocean in March 2006 near the island of Hanimadhoo to measure aerosol concentrations, soot levels and solar radiation.

Researchers concluded that the pollution — mostly caused by the burning of wood and plant matter for cooking in India and other South Asian countries — enhanced heating of the atmosphere by around 50 percent and contributed to about half of the temperature increases blamed in recent decades for the glacial retreat.

Veerabhadran Ramanathan said his team's research shows the brown clouds are an additional factor in the melting of glaciers, along with overall global warming caused by greenhouse gas emissions.

Until this study, published in the journal Nature, scientists believed the brown clouds mostly deflected sunlight, cooled the atmosphere and did not contribute much to the effects of global warming. But Ramanathan said their observations show particles also absorbed sunlight and warmed the atmosphere much more than previously believed.

"All we are saying is that there is one other thing contributing to atmospheric warming and that is the brown cloud," said Ramanathan, a chief scientist at the University of California San Diego's Scripps Institution of Oceanography in La Jolla, Calif.

Syed Iqbal Hasnain, a senior fellow at the Center For Policy Research in New Delhi and a glacial expert, agreed brown clouds could be a factor in the melting of the glaciers that supply water to most Asian rivers. But he said more research was needed to understand why the Himalayan glaciers in China are also melting at a dramatic rate.

"Glaciers across Himalaya are receding, but their response is dependent on many factors like size, orientation and intensity of monsoonal moisture," Hasnain, who was not connected with the study, said in an e-mail message from New York. "There is a great urgency on the part of the international scientific community to establish high altitude research stations across Himalaya and monitor climate accurately to develop scientifically correct models."

Scientist have expressed concerns the Himalayan glaciers will melt entirely and the rivers will run dry for months at a time, fed only by annual rains like the monsoon that sweeps across the subcontinent every summer.