U.S. pollution behind African drought
By Gary Wilson
The African drought from 1970 to 1985 killed 1.2 million
people in one of the most devastating famines ever known. A new
study by scientists from Australia and Canada has concluded
that the cause was sulfur dioxide spewed out by factories and
power plants in the United States, Canada and Western
Europe.
The pollution of North America and Europe disrupted weather
patterns, dramatically changing the temperature of the Earth's
surface. This led to a reduction in rainfall by as much as 50
percent in the Sahel region of Africa that stretches from
Senegal to Ethiopia.
Tiny airborne particles called sulfate aerosols, which are
found only in the highly industrialized countries, boost the
number of small droplets in clouds; researchers have found that
this extends the lifetime of clouds. Some suspect that the
particles also make clouds reflect more sunlight, cooling
Earth's surface below, reducing evaporation, and ultimately
decreasing rainfall.
"Global climate change is not solely being caused by rising
levels of greenhouse gases. Atmospheric pollution is also
having an effect," says Leon Rotstayn, the Australian scientist
who headed the study.
According to Rotstayn, the sulfate aerosol pollution
concentrations are far greater in the Northern Hemisphere,
cooling the atmosphere there more than in the Southern
Hemisphere. It is this imbalance that affects the tropical rain
belt. As a result, the tropical rain belt, which migrates
northwards and southwards with the seasonal movement of the
sun, is weakened in the Northern Hemisphere and does not move
as far north.
The New Scientist magazine quotes another scientific
researcher, David Roberts:
"It's an effect of the thermal balance between the two
hemispheres. There has to be a rough balance between the north
and south hemispheres--you can't have spare energy in one place
or the other. If the Earth was completely symmetrical, then the
point of thermal equilibrium, where the total energy on either
side of a line was equal, would be the Equator. But because the
Northern Hemisphere isn't the same as the south [because of the
vast energy reservoir of the Pacific, which retains energy more
efficiently than land] we find that the Northern Hemisphere is
warmer than the South."
However, the cooling of the Northern Hemisphere by aerosol
pollution pushes the point of thermal equilibrium south--and
with it go the rain clouds that had covered the Sahel. It may
also explain the flooding rains that are now sweeping southern
Africa.
One change that the researchers cite in the study occurred
in the 1980s. At that time, improvements in anti-pollution laws
meant that sulfur emissions dropped because they were blamed
for acid rain. Following that change, the droughts in Africa
became less severe.
With the new understanding of the connection between sulfate
aerosol pollution and rainfall, the position taken by
Washington administrations from George W. Bush to Bill Clinton
can no longer be sustained. Washington had claimed that nothing
needed to be done about global warming because the aerosol
pollution cools the Earth. Now it has been shown that this kind
of cooling contributes to changing weather patterns in ways
that are disastrous for millions of people, just as are the
rising sea levels caused by global warming.
Reprinted from the Aug. 29, 2002, issue of
Workers World newspaper
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