Beware the Brown Cloud

November 20th, 2008 | Sources: Wall Street Journal

Man-made Atmospheric Brown Clouds (ABCs or simply, brown clouds) are darkening Asian megacities from Tehran to Shanghai, reducing crop yields and killing hundreds of thousands of people each year, according to a report released last week by the United Nations Environment Program.

The report was compiled by a scientific team with research bases in China, India, Europe and the US.

Brown clouds are 2-mile thick layers of soot, black carbon, sulfates, toxic aerosols and carcinogens that result from burning fossil fuels and biomass. Coal-stoked power plants are the single biggest contributor.

Half the world’s population resides under one or another of the world’s 5 major regional brown clouds blanketing:
– East Asia, including eastern China
– South Asia including Pakistan, India, Bangladesh and Myanmar
– Southeast Asia including Cambodia, Indonesia, Thailand, and Vietnam
– Southern Africa from sub-Saharan Africa to Zimbabwe
– South America’s Amazon basin

Brown clouds reflect and absorb sunlight and have thus dimmed the skies over Tehran, Karachi, Beijing, Hanoi, Bangkok and hundreds of other major cities by 10-25% in just 30 years.

They also adversely affect food production, according to the UN report. In addition to the lost photosynthetic potential caused by dimming, brown clouds cut crop yields by 10-40% by trapping ground level ozone. Annual economic losses from crop damage exceed $5 billion in China, Japan and the Republic of Korea. 

In addition, the toxic components of brown clouds cause respiratory and cardiovascular disease. The UN report attributes 340,000 excess deaths per year in China and India to brown clouds, and estimates economic losses due to illness and disability at 3.6% of GDP in China and 2.2% in India.

And that’s not the half of it. It turns out that getting rid of the toxic clouds may accelerate global warming. Stay tuned for a post on this matter.


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