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'Asian Brown Cloud' poses global threat

August 2002 -- A blanket of pollution, dubbed the "Asian Brown Cloud," is hovering over South Asia, with scientists warning it could kill millions of people in the region, and pose a global threat.

In a recent U.N.-sponsored study of the phenomenon, 200 scientists warned that the cloud, estimated to be two miles (three kilometers) thick, is responsible for hundreds of thousands of deaths a year from respiratory disease.

By slashing the sunlight that reaches the ground by 10 to 15 percent, the choking smog has also altered the region's climate, cooling the ground while heating the atmosphere, scientists said.

The scientists warned that the thick cloud puts the lives of millions of people at risk from drought and flooding, partly because rainfall patterns have been radically altered with dire implications for economic growth and health

“We have an early warning. We have clear information, and we already have some impact. But we need much, much more information,” U.N. Environment Program Chief Klaus Toepfer said at a recent news conference in London.

Global Threat

“There are also global implications, not least because a pollution parcel like this, which stretches about two miles high, can travel halfway round the globe in a week,” Toepfer said.

While haze hovers over other parts of the world, including America and Europe, what surprised scientists was how far the cloud extended and how much black carbon was in it, according to the study.

While many scientists once thought that only lighter greenhouse gases, such as carbon dioxide, could travel across the Earth, they now say that aerosol clouds can, too.

A mix of aerosols, ash, soot and other particles, the haze extends far beyond the study zone of the Indian subcontinent and toward East and Southeast Asia.

Varied Sources

"Biomass burning" from forest fires, vegetation clearing and fossil fuel was just as much to blame for the shrouding haze as dirty industries from Asian cities, the study found. A large part of the aerosol cloud comes from inefficient cookers, where fuels such as cow dung and kerosene are used to cook food in many parts of Asia, according to the preliminary report.

Toepfer said the U.N.’s preliminary report on what it dubbed the “Asian Brown Cloud” was a timely reminder to the coming Earth Summit in Johannesburg, South Africa, that action, not words, was vital to the future of the planet.     

“The huge pollution problem emerging in Asia encapsulates the threats and challenges that the summit needs to urgently address,” he said. “We have the initial findings and the technological and financial resources available. Let’s now develop the science and find the political and moral will to achieve this for the sake of Asia, for the sake of the world,” he added.

Acid rain

Using data from ships, planes and satellites to study Asia's haze during the northern winter months of 1995 to 2000, scientists were able to track its journey to pristine parts of the world to see how it affected climate.

They discovered not only that the smog cut sunlight, heating the atmosphere, but also that it created acid rain, a serious threat to crops and trees, as well as contaminating oceans and hurting agriculture.

The report calculated that the cloud -- 80 percent of which was made by people -- could cut rainfall over northwest Pakistan, Afghanistan, western China and western central Asia by up to 40 percent.

While scientists say they still need more scientific data, they suggest the regional and global impact of the haze will intensify over the next 30 years.

Scientists said In the next phase of the project, they will collect data from the entire Asian region, over more seasons with more observation sites and refine their techniques.

But because the lifetime of pollutants is short and they can be rained out, scientists are hopeful that if Asians use more efficient ways of burning fuel, such as better stoves, and cleaner sources of energy, time has not run out.

Source: U.N.-sponsored study, various U.S. news agencies

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