Clouds of Pollution Block Sunlight

The sun is fading above cities around the world as thick clouds of pollution prevent its rays from reaching the ground, says a new report by the United Nations Environment Programme (UNEP).  The dirty brown haze, sometimes three-kilometers thick, stretches from the Arabian Peninsula to China and the western Pacific Ocean.

The clouds have blocked up to 25 percent of sunlight in Karachi, New Delhi, Shanghai and Beijing.  Guangzhou, in southern China, is among several cities to have recorded a more than 20 percent reduction in sunlight since the 1970s, says the Atmospheric Brown Clouds (ABC) report.

Other megacities threatened by brown clouds include Bangkok, Beijing, Cairo, Dhaka, Karachi, Kolkata, Lagos, Mumbai, New Delhi, Seoul, Shanghai, Shenzhen and Tehran.   The clouds are also found in parts of Europe and on the Eastern seaboard of the United States but are less dangerous because winter rains and snow wash them away.

The giant brown haze comes from a mix of ozone, black carbon and soot particles released by coal-fired power plants, wood-burning stoves, burning fields and vehicles on the road.  It contains a variety of aerosols, carcinogens and tiny particles that have been linked to respiratory diseases and cardio-vascular problems.   According to the UN report, the toxic material could kill 340,000 people n China and India every year.

The toxic clouds also threaten the massive Hindu Kush-Himalaya-Tibetan glaciers.  “If the current rate of retreat continues unabated, these glaciers and snow packs are expected to shrink by as much as 75 percent before the year 2050,” says the report.

China’s glaciers have already shrunk five percent since the 1950s.  Some in India retreat at a rate of 10 to 25 meters each year.  One explanation is that the snow and ice on the glaciers reflect less solar radiation because they are exposed to black carbon from the brown clouds.

And the glaciers’ disappearance could threaten water supplies to millions of people who depend on rivers to drink and irrigate their crops.  The Ganges River basin in India, for instance, is home to over 400 million people and irrigates 40 percent of the country’s croplands.  The clouds are also reducing rainfall which could aggravate the recent rise in food prices.

The team of scientists commissioned by UNEP to study the “atmospheric brown clouds” has been doing so since 2002 and do not pretend to have found all the answers to this environmental nightmare.  “The science of ABCs, woven with the science of greenhouse gases, is not simple and may be behind some highly complex warming and cooling patterns witnessed on continents and in different regions of specific countries,” they write in the report.

In fact, the brown clouds may alter the traditional climate change scenario. On the one hand, they are filled with black carbon and soot particles that absorb sunlight and heat the air and other gases.   On the other hand, they contain other particles, such as sulfates, that reflect sunlight and cool the earth’s surface.  In effect, the clouds may be dampening the rise in global temperatures by 20 to 80 percent, say the scientists.

By including “atmospheric brown clouds” in the mix of reasons why climate change is taking place so rapidly on Earth, scientists have provided more reason to combat the origins of air pollution.  They have also highlighted that air pollutants do not just hover above their point of origin.  Clouds glide with the wind and masses of toxic particles can just as easily move across continents in three to four days, says the Associated Press.  Enough time to convince anyone that hiding in a bubble is no longer an available option on planet Earth.

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