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A vast blanket of pollution stretching across South Asia is damaging agriculture, modifying rainfall patterns, and putting hundreds of thousands of people at risk, a new study suggests.
The findings, by scientists working with the United Nations Environment Programme (UNEP), indicate that the spectacular economic growth seen in this part of the world in the past decade may soon falter as a result of the "Asian Brown Haze."
Vital follow-up studies are needed to unravel the precise role this three-kilometer-deep pollution blanket may be having on the region's climate and the world's.
The preliminary results indicate that the buildup of the haze, a mass of ash, acids, aerosols and other particles, is disrupting weather systems including rainfall and wind patterns and triggering droughts in western Asia.
The concern is that the regional and global impacts of the haze are set to intensify over the next 30 years as the population of the Asian region rises to an estimated five billion people.
"The haze is the result of forest fires, the burning of agricultural wastes, dramatic increases in the burning of fossil fuels in vehicles, industries, and power stations, and emissions from millions of inefficient cookers burning wood, cow dung, and other 'bio fuels,'" said Klaus Toepfer, Executive Director of UNEP.
"More research is needed, but these initial findings clearly indicate that this growing cocktail of soot, particles, aerosols, and other pollutants are becoming a major environmental hazard for Asia. There are also global implications, not least because a pollution parcel like this, which stretches three kilometers high, can travel halfway round the globe in a week," said Toepfer.
Toepfer said that the discovery of the haze highlights the need to figure out "how to achieve economic growth without sacrificing the long-term health and natural wealth of the planet. 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."
The findings on the Asian Brown Cloud have come from observations gathered by 200 scientists working on the Indian Ocean Experiment (INDOEX), supplemented by new satellite readings and computer modelling.
Changing Climate
The blanket of pollution is reducing the amount of solar energy hitting the Earth's surface by as much as 10 to 15 percent. Meanwhile, its heat-absorbing properties are estimated to be warming the lower parts of the atmosphere considerably.
This combination of surface cooling and lower atmosphere heating appears to be altering the winter monsoon, leading to a sharp fall in rainfall over northwestern parts of Asia and an increase of rainfall along the eastern coast of Asia. However, the regional details of the predicted changes need to be verified with more comprehensive regional models and regional aerosol and climate observations.
The global models used in the report suggest that the haze may reduce precipitation over northwest India, Pakistan, Afghanistan, western China, and the neighboring western Central Asian region by between 20 and 40 percent.
"There have been two consecutive droughts in 1999 and 2000 in Pakistan and the northwestern parts of India while increased flooding in the high rainfall areas of Bangladesh, Nepal and the northeastern states of India," the report said.
The aerosols and particles in the haze are also affecting rainfall in other ways. Raindrops are becoming smaller and more numerous, triggering less frequent rainfall and longer-lived clouds. One potential consequence is to move precipitation away from populated regions.
A 10 percent reduction in the levels of solar energy hitting the region's oceans in turn reduces the evaporation of the moisture which controls summer rainfall.
Impacts on People
The reduction in sunlight may be having significant impacts on agriculture, the UNEP report said. Research carried out in India indicates that the haze may be reducing the winter rice harvests by as much as 10 percent.
Acids in the haze may, by falling as acid rain, have the potential to damage crops and trees. Ash falling on leaves can aggravate the impacts of reduced sunlight on the Earth's surface.
The pollution that is forming the haze could be leading to "several hundreds of thousands" of premature deaths as a result of higher levels of respiratory diseases, the report suggested.
Studies indicate that the level of fatalities is rising along with the levels of pollution.
Results from seven cities in India alone, including Ahmedabad, Kolkata, Delhi and Mumbai, estimate that some kinds of air pollution were annually responsible for 24,000 fatalities in the early 1990s. By the mid-1990s they resulted in an estimated 37,000 premature fatalities. |
