South Asia — Huge haze clouds over the Indian Ocean contribute as much toatmospheric warming as greenhouse gases and play a significant role in themelting of the Himalayan glaciers, according to a study published Thursday.
Scientist Veerabhadran Ramanathan and his colleagues sent unmanned measuringdevices into the haze pollution, known as Atmospheric Brown Clouds, over theIndian Ocean in March 2006 near the island of Hanimadhoo.
Measuring aerosol concentrations, soot levels and solar radiation, the teamconcluded that the pollution mostly caused by the burning of wood and plantmatter for cooking in India and other South Asian countries enhanced heatingof the atmosphere by around 50 percent and contributed to about half of thetemperature increases blamed in recent decades for the glacial retreat.
Ramanathan said his team’s research shows that the brown clouds are thereforean additional factor in the melting of glaciers, along with overall globalwarming caused by greenhouse gas emissions.
Until this study, which is published in the journal Nature, scientistsbelieved the brown clouds mostly deflected sunlight, cooled the atmosphere anddid not contribute much to the effects of global warming. But Ramanthan saidtheir observations show that particles also absorbed sunlight and warmed theatmosphere much more than previously believed.
“All we are saying is that there is one other thing contributing toatmospheric warming and that is the brown cloud,” said Ramanathan, a chiefscientist at the University of California San Diego’s Scripps Institution ofOceanography in La Jolla, Calif.
Prof. Syed Iqbal Hasnain, a senior fellow at the Center For Policy Researchin New Delhi and a glacial expert, agreed that brown clouds could be a factor inthe melting of the glaciers that supply water to most Asian rivers. But he saidmore research was needed to understand why the Himalayan glaciers in China arealso melting at a dramatic rate.
“Glaciers across Himalaya are receding but their response is dependenton many factors like size, orientation and intensity of monsoonal moisture,”he said in an e-mail message from New York. “There is a great urgency onthe part of the international scientific community to establish high altituderesearch stations across Himalaya and monitor climate accurately to developscientifically correct models.”
Scientist have expressed concerns that the Himalayan glaciers will meltentirely and the rivers will run dry for months at a time, fed only by annualrains like the monsoon that sweeps across the subcontinent every summer.Exacerbated by India and China’s fast-growing, coal-fed economies, scientistshave predicted that the glaciers are melting at a rate up to 15 meters (49 feet)a year and could further decline with temperatures projected to rise as much as6.4 degrees Celsius by 2100.
While much of the melting has been blamed on global warming, Ramanathan saidthe new findings offer another way to tackle the problem of the melting glaciers.He said he was hopeful the findings would spur regional governments to step upefforts to replace wood-burning stoves, for example, with solar powered cookersand biogas plants that capture methane and carbon dioxide emissions and convertthem to fuel.
Achim Steiner, the executive director of the United Nations EnvironmentProgram, which helped fund the project, said the research showed that brownclouds are “complicating and in some cases aggravating” the effects ofgrowing greenhouse gases.
“It is likely that in curbing greenhouse gases we can tackle the twinchallenges of climate change and brown clouds and, in doing so, reap widerbenefits from reduced air pollution to improved agriculture yields,”Steiner said in a statement.
Ramanathan is now in India working on a pilot project with the EnergyResearch Institute in New Delhi that would provide fuel alternatives to 1,000families in Kumaon region in the foothills of the Himalayas. If the projectproves successful, he said he is hoping that it can be expanded in other partsof India.
“If the pollution increases, the glacier retreat will be much worse thanprojected,” he said. “It now depends on what energy path that Indian,China and Asia will take.”