Chapter 18, Problem 1CR

To determine

The nature, origin, and harmful effects of the massive South Asian Brown Clouds.

Answer to Problem 1CR

The South Asian Brown Clouds represent the enormous, dark brown clouds of pollution observed by the UN satellite images, and they were observed to be stretching across India, Bangladesh, China, and the Pacific. They are capable of blanketing the entire Earth in two weeks. They generally consist of smoke, dust, and ash generated as a result of drought and clearing and burning of forest for cultivation. The constituents in the South Asian Brown Clouds may be also produced from diesel engine exhausts, coal-burning power plants, metal smelters, and incinerators. Atmospheric warming and the Himalayan glacier melting are some of the identified effects of these clouds. Nevertheless, in addition to warming, they might also initiate a global cooling of the planet sometimes. This is due to the difference in the ability of various components present within the clouds to reflect or absorb the solar insolation.

Explanation of Solution

Air pollution cannot be considered as a regional urban issue any more. Recent research performed by the UNEP (United Nations Environment Programme) and annual satellite images revealed the presence of large, dark brown clouds of pollution extending across most parts of India, Bangladesh, and the industrial center of China, as well as parts of the western Pacific Ocean. These are known as the South Asian Brown Clouds.

In most of the years, this 3-kilometer thick set of clouds occupy a region of almost the size of the continental U.S. The clouds consist of small particles of smoke, dust, and ash produced as a result of drought and clearing and burning of forest for cultivation. They also include 1) soot particles that are mostly generated from diesel engine exhaust and from the combustion of biomass such as animal dung and wood, 2) acidic compounds resulting from coal-burning power plant emissions and vehicle exhaust, and 3) particles of toxic metals such as mercury and lead, formed generally by combustion of coal and from metal smelters, and waste incinerators. Rather than blue skies, a lot of people residing under this cloud observe brown or gray polluted skies during most part of the year.

Those massive thick pollution clouds are able to drift across the Asian continent in 3 to 4 days, and satellites have traced the spreading of those clouds from northern China across the Pacific Ocean to the western coast of the U.S. On account of the measurements done by atmospheric scientists, the United States Environmental Protection Agency has assessed that on some days, almost 25 percent of the particulate matter, 77 percent of the black carbon (soot), and 33 percent of the poisonous mercury in the skies above Los Angeles of California can be tracked to the coal-fired power plants, wood and dung fires, smelters, diesel trucks, and deforested regions of China.

Based upon satellite measurements, it is inferred that these and other air pollutants with high residence time from China, India, the U.S., or anywhere else on the Earth can encircle the entire planet in almost two weeks. Therefore, air pollution links all the humans.

Some scientists have sited the South Asian Brown Clouds as a cause of slow melting of the Himalayan glaciers that form the source of water for most of the main rivers of Asia. Researchers have assumed that soot along with certain other particles within the brown clouds absorb sun rays and cause heating of the air on top of the glaciers. Black soot falling on the glacier’s shiny surface also reduces the albedo effect of the glaciers. As the glaciers absorb more solar radiations, the air above them become more hot and, thus, triggers the increased melting of the glaciers. Melting is taken as an indicator of atmospheric warming and global climate change. Several health issues such as bronchitis, lung cancer, and many other respiratory disorders can be also caused due to pollution from these kind of clouds.

However, apart from contributing to atmospheric warming, the South Asian Brown Clouds can sometimes initiate a cooling effect also on the planet as some types of particles within the clouds reflect certain incoming solar radiations back into the space. The overall effect of the South Asian Brown Clouds is that during this century, they have aided in slowing down the atmospheric warming and the subsequent expected climate change. Meanwhile, this serious case of air pollution has had many adverse effects on food supplies and water in Asia and is directly related to the deaths of at least 380,000 people in China and India annually.