Dimming cities

Lest we think there are simple answers and explanations for massive problems with even more massive ramifications.
Atmospheric brown clouds over China

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...

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 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.

Now that's a vicious cycle if I ever heard of one.