Asia smog affecting local climates
Pollution is tied to early deaths
The Boston Globe,Aug. 12, 2002
LONDON - The ''Asian Brown Cloud,'' a 2-mile-thick blanket of pollution over South Asia, may be causing the premature deaths of a half-million people in India each year, deadly flooding in some areas, and drought in others, according to one of the biggest scientific studies ever of the phenomenon.
The grimy cocktail of ash, soot, acids, and other damaging airborne particles is as much the result of low-tech polluters such as wood- and dung-burning stoves, cooking fires, and forest clearing as it is of industry, the UN-sponsored study found.
''When you think about air pollution, many people think of industry and fossil fuels as the only causes,'' said Paul Crutzen, a coauthor of the report, at a news conference in London. Crutzen is a scientist at the Max-Planck Institute for Chemistry in Mainz, Germany.
Often ignored, he said, was ''biomass burning,'' including forest fires and the burning of vegetation to clear land or to warm the homes of poor people.
More than 200 scientists contributed to the study, overseen by the UN Environment Program in preparation for the World Summit on sustainable Development opening Aug. 26 in Johannesburg. They used data from ships, planes, and satellites to study Asia's haze from 1995 to 2000.
The scientists say more research is needed but some trends are clear. Respiratory illness appears to be increasing along with the pollution in densely populated South Asia, researchers said, suggesting that the pollution plays a role in the 500,000 premature deaths annually in India.
The dense cloud of pollution - also caused by auto emissions, factories, and waste incineration - cuts the amount of sunlight reaching the ground and the oceans by 10 percent to 15 percent, cooling the land and water while heating the atmosphere, the study found.
That phenomenon appears to have altered the region's monsoon rains - increasing rainfall and flooding in Bangladesh, Nepal, and northeastern India, while reducing the needed seasonal precipitation in Pakistan and India.
Floods, drought, sunlight reduction, and acid rain all can hurt agricultural yields, and the report indicated that the pollution may be cutting India's winter rice harvest by as much as 10 percent.
Veerabhadran Ramanathan of the Scripps Institution of Oceanography in La Jolla, Calif., and one of the report's authors, said the extent of the sunlight loss was ''a major surprise.''
Scientists say it's too early to draw definite conclusions about the impact of the cloud and of similar hazes over East Asia, South America, and Africa.
''We need much more basic scientific data to be able to establish what are the consequences for human health and the environment,'' said Crutzen, corecipient of the 1995 Nobel chemistry prize for his work on the ozone layer.
But scientists warn that the impact could be global because prevailing winds push pollution clouds halfway round the world in just a week's time.
For many years, scientists believed only lighter greenhouse gases - the carbon dioxide that is produced from burning fossil fuels such as gasoline and oil, for example - were global in reach and effect.
They now say microscopic, suspended particles of pollutants - called aerosols by atmospheric scientists - also travel the globe.
It's unclear what the haze's relationship is to global warming, which most scientists contend is caused by the emission of greenhouse gases that trap the earth's heat. The pollution cloud appears to cool the area below by blocking sunlight.
Klaus Toepfer, executive director of the UN Environment Program, said scientists and policy-makers ''should avoid making premature final assessments,'' but should try to cut pollution by introducing more efficient stoves in developing countries and turning to solar power and other clean sources of energy.
Kate Hampton, climate coordinator for the environmental group Friends of the Earth International, said ''Actions must include phasing out fossil fuels and replacing them with clean, green, renewable energy, and tough laws to protect the world's forests.''
This story ran on page A6 of the Boston Globe on 8/12/2002.