• Choose a category
• All
• Classic-Fiction

By Root 814 0

1,200 new cars and trucks are added to the capital’s roads each day, deadly particulates known as PM 10s average around three times the WHO standard.5 Rich countries are affected too, though to a much lesser extent: In the U.K. the Parliamentary Environmental Audit Committee recently concluded that up to 50,000 people could be dying prematurely each year due to air pollution,6 while for the U.S., the American Lung Association’s State of the Air 2010 report states that “over 175 million people—roughly 58 percent—still suffer pollution levels that are too often dangerous to breathe.”7 Children are particularly vulnerable to traffic-exhaust emissions, with impacts ranging from respiratory ailments like asthma and chronic bronchitis to abnormal lung development and even cancer. Yet studies show that a third of U.S. schools are located within 400 meters of major roads, well within the traffic pollution danger zone.8

Because of their global distribution and effects on solar-heat absorption and distribution, atmospheric aerosols are having major impacts on the Earth’s hydrological cycle. Pollution from Northern Hemisphere smokestacks is thought to have played a significant role in triggering the terrible decades-long drought that struck the Sahel region of Africa in the 1970s and 1980s, which led to regional famines with death tolls in the millions.9 As sulfur and soot darkened the atmosphere above the North Atlantic Ocean, they pulled life-giving rains away from North Africa, allowing the desert to spread south as precipitation levels declined by 40 percent.10 Thanks to pollution controls, the trend has now reversed, and rainfall over the Sahel largely recovered.11 The reduction in “global dimming” that helped prevent the Sahel turning into permanent desert has in fact increased rainfall across the globe, with an upward trend of more than 30 mm measured between 1986 and 2000.12

Using sophisticated models run on powerful supercomputers, scientists have begun to work out the ways aerosol emissions are affecting the Indian monsoon. First, it seems, a 10 percent drop in sunshine reaching the ocean lowers the level of evaporation, reducing the moisture available for rainfall. Second, the Asian brown cloud—thickest over the densely populated landmass of India—also reduces the temperature difference between land and sea that is the main engine of the monsoon. The differing impacts on the northern and southern Indian Oceans—where the northern half cools, and the southern half, which remains under relatively clean air, warms—also hampers the monsoon circulation.13 Over much of India, Bangladesh, Burma, and Thailand summer monsoon rainfall has been declining as brown-cloud aerosols weaken circulation patterns that sustain the food production and livelihoods of over a billion people across the subcontinent.14 In China, aerosols have split the country in half, bringing drought to the north and floods to the south by displacing the usual annual progression of the East Asian monsoon.15

Like toxics, atmospheric pollutants tend to concentrate in the frigid, stable atmosphere of the Arctic, where as long ago as the 1950s air pilots noticed a whitish haze obscuring the horizon. So-called “Arctic haze” has since become recognized as a well-established phenomenon, one that may be making a significant contribution to atmospheric warming.16 Likely sources are industry and coal-burning in Eurasia, plus occasional fierce wildfires like those that swept Russia in the summer of 2010.17 As the soot from the haze layer gets gradually deposited on the snow, it darkens the surface and adds to springtime melt. One study suggests that sooty deposits in Northern Hemisphere snow add a fifth to the melt-rate and are a major contributor to Arctic warming.18 The effect has been observed too on the other side of the world, where smoke from the burning Amazon rain forests is darkening the snow over faraway Antarctica.19

In the Himalaya, jammed between the world’s two largest sources of soot—India and China—the glaciers that cloak the world’s highest mountains are