We?re accustomed to seeing the faces of pitiful, starving African children staring out at us from advertisements. They?re emaciated, standing on parched and cracked earth, and appealing to us for aid. Now it turns out we may be the cause of their problem.
Emissions spewed out by power stations and factories in North America and Europe may have started the severe droughts that have afflicted regions of Africa. These droughts have been among the worst the world has ever seen, and led to the famines that killed thousands in countries such as Ethiopia in the 1980s.
The cause appears to be the sulfur, soot, carbon, ammonium and nitrate produced when fossil fuels are burnt. As these are belched out of factory chimneys in the First World, the wind takes them to Africa, where they create aerosols that affect cloud formation, altering the temperature of the Earth's surface and leading to dramatic shifts in regional weather patterns.
In the past thirty to forty years, the Sahel, an area in Africa south of the Sahara that includes parts of Ethiopia and Guinea, has had the worst droughts in any part of the world since record-keeping began, with precipitation falling by between 20 and 50 per cent. During the worst years, between 1972 and 1975, and 1984 and 1985, a million people starved to death.
Now Leon Rotstayn of CSIRO, Australia's national research agency, thinks he knows what caused them. Rotstayn and Ulrike Lohmann of Dalhousie University in Halifax, Nova Scotia, ran a computer simulation of the global climate that studied the relationship between sulfur dioxide emissions and cloud formation. Sulfur dioxide creates sulfate aerosols that become the nuclei around which clouds form. With more of these nuclei available, clouds condense from smaller droplets than usual, and are more efficient at reflecting solar radiation, cooling the Earth below.
When the researchers included the huge sulfur emissions emitted from the northern hemisphere during the 1980s in their model, the Earth's surface in the north became much cooler than the south, driving the tropical rain belt south and causing droughts in the Sahel. "It's the first time we've seen a connection between pollution in the mid-latitudes and climate in the tropics," says Johann Feichter of the Max Planck Institute for Meteorology in Germany. Feichter believes that even if the droughts were due to happen anyway, the sulfur emissions made them worse.
During the past few years, African droughts have become less severe. Rotstayn thinks this is because of stricter pollution emissions standards in North America and Europe. We didn?t reduce sulfur emissions out of concern for Africa, however?we reduced them because of our own problems with acid rain.
Climate researchers around the world are beginning to study other types of air pollution, such as the clouds of black soot and sulfate being emitted in India and China, where industry is still expanding (and where a lot of U.S. and European manufacturing has gone). The pollution in those areas may be affecting the weather. For instance, northern China has had unusually dry summers in the past few years, while it has been unusually wet in the south.
Those ads showing children with skinny limbs and swollen bellies used to always fill us with guilt. Now it turns out that was the right way to feel.
Don?t feel guilty about global warming?there are small but important things that each of us can do to make things better. To find out what they are, read ?The Coming Global Superstorm,? now only $9.95 for a hardcover signed by Whitley Strieber, click here.
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