1970-85 Famine Blamed on Pollution
by Joseph B. Verrengia | July 21, 2002
( Associated Press )
Nearly two decades after one of the world's most devastating famines in
Africa, scientists are pointing a finger at pollution from industrial nations
as one of the possible causes.
Now, a group of scientists in Australia and Canada say that drought
may have been triggered by tiny particles of sulfur dioxide spewed by
factories and power plants thousands of miles away in North America,
Europe and Asia.
The short-lived pollution particles, known as aerosols, didn't have to
travel to Africa to do their dirty work. Instead, they were able to alter
the physics of cloud formation miles away and reduce rainfall in Africa
as much as 50 percent, say the researchers, who used a computer to
simulate the atmospheric conditions.
The process, known as teleconnection, continues in the atmosphere
today. Some scientists suspect it might help explain the drought gripping
parts of the United States, although that question has not been
specifically examined.
And while pollution may affect the behavior of rain clouds, scientists
stopped short of solely blaming industry's effluent for the famine and
starvation that wracked the region of Africa called the Sahel.
"It's more subtle than that," said atmospheric scientist Leon Rotstayn,
lead author of the study on the subject.
"The Sahelian drought may be due to a combination of natural variability
and atmospheric aerosols," said Rotstayn, of the Commonwealth
Scientific and Industrial Research Organization, a government research
agency in Australia. The CSIRO study will be published in the August
Journal of Climate.
Over the years, the disastrous lack of rainfall over the Sahel has been
blamed on everything from overgrazing to El Nino. Many scientists still
argue those are chief culprits.
One interesting clue: In the 1990s, rain returned to the Sahel. During the
same period, emissions laws in the industrialized West reduced aerosol
pollution. A coincidence? Scientists don't think so.
"Cleaner air in the future will mean greater rainfall in the region,"
Rotstayn said.
Some researchers say the CSIRO study is intriguing, but that the
computer simulation is too simple to solve the mystery by itself.
"It is quite a plausible argument," said atmospheric scientist V.
Ramanathan of Scripps Institute of Oceanography in La Jolla, Calif.
Last year, Ramanathan co-authored a global pollution study examining
an industrial haze that covered nearly 4 million square miles and upset
the water cycle over the Asian subcontinent.
He said similar processes appeared to be at work over the Sahel, but the
CSIRO model must be sharpened to prove it.
Until then, "I would be cautious about overextending these conclusions,"
Ramanathan said.
Other scientists were even more guarded. Teleconnection is a
reasonable, but complicated, explanation, they said.
"Rotstayn focuses on an indirect effect of aerosols that is really hard to
quantify," said Philip Rasch, senior scientist at the National Center for
Atmospheric Research in Boulder, Colo.
Some scientists complained that the global rainfall pattern simulated by
the computer model does not match up with actual rainfall observed at
weather stations around the world during the drought. This lack of a
neat correlation makes the study's Sahel conclusions "highly
speculative," they said.
For example, the real weather observations and those generated by the
computer model correspond for the Sahel, Senegal and parts of Brazil,
said Yogesh Sud, senior research meteorologist at NASA's Goddard
Space Flight Center in Greenbelt, Md.
"But in India and Australia, there is absolutely no match" between
recorded rainfall and the simulated conditions, Sud said.
Nations share the same atmosphere and, increasingly, the same pollution.
Pollution is known to alter temperature and precipitation patterns near its
source. Recent studies suggest that one country's pollution can become
a problem for other countries, too.
Over the desolate North African Sahel, the influence of global pollution
is less direct. Normally, this harsh land receives patchy summer rainfall.
Soil studies show that milder droughts came in the 1680s, the 1750s,
the mid-1800s and the early 20th century.
Rotstayn believes industrial smokestacks are the smoking guns for the
more recent, more intense drought.
The sulfur dioxide pollution particles, which can remain in the air 5 to
20 days, probably drifted over the North Atlantic where they created
more condensation nuclei for cloud formation, the scientists theorize.
The additional nuclei remained suspended in clouds rather than growing
into fewer, larger droplets and falling as rain.
In addition, these clouds were brighter than normal, in part because of
the added nuclei, and they reflected more of the Sun's energy into space.
This cooled the surface of the North Atlantic, which reduced the normal
evaporation rate from the ocean and further hampered the moisture
cycle.
South of the Sahel, the sea surface remained warm and evaporation
increased so more rain fell to the south, Rotstayn said.
Leon Rotstayn: http://www.dar.csiro.au/profile/rotstayn.html
Source
by Joseph B. Verrengia | July 21, 2002
( Associated Press )
Nearly two decades after one of the world's most devastating famines in
Africa, scientists are pointing a finger at pollution from industrial nations
as one of the possible causes.
- The starvation brought on by the
1970-85 drought that stretched from
Senegal to Ethiopia captured the
world's attention with searing
images: skeletal mothers staring
vacantly, children with bloated
bellies lying in the sand, vultures
lurking nearby. Before rains finally
returned, 1.2 million people had died.
Now, a group of scientists in Australia and Canada say that drought
may have been triggered by tiny particles of sulfur dioxide spewed by
factories and power plants thousands of miles away in North America,
Europe and Asia.
The short-lived pollution particles, known as aerosols, didn't have to
travel to Africa to do their dirty work. Instead, they were able to alter
the physics of cloud formation miles away and reduce rainfall in Africa
as much as 50 percent, say the researchers, who used a computer to
simulate the atmospheric conditions.
The process, known as teleconnection, continues in the atmosphere
today. Some scientists suspect it might help explain the drought gripping
parts of the United States, although that question has not been
specifically examined.
And while pollution may affect the behavior of rain clouds, scientists
stopped short of solely blaming industry's effluent for the famine and
starvation that wracked the region of Africa called the Sahel.
"It's more subtle than that," said atmospheric scientist Leon Rotstayn,
lead author of the study on the subject.
"The Sahelian drought may be due to a combination of natural variability
and atmospheric aerosols," said Rotstayn, of the Commonwealth
Scientific and Industrial Research Organization, a government research
agency in Australia. The CSIRO study will be published in the August
Journal of Climate.
Over the years, the disastrous lack of rainfall over the Sahel has been
blamed on everything from overgrazing to El Nino. Many scientists still
argue those are chief culprits.
One interesting clue: In the 1990s, rain returned to the Sahel. During the
same period, emissions laws in the industrialized West reduced aerosol
pollution. A coincidence? Scientists don't think so.
"Cleaner air in the future will mean greater rainfall in the region,"
Rotstayn said.
Some researchers say the CSIRO study is intriguing, but that the
computer simulation is too simple to solve the mystery by itself.
"It is quite a plausible argument," said atmospheric scientist V.
Ramanathan of Scripps Institute of Oceanography in La Jolla, Calif.
Last year, Ramanathan co-authored a global pollution study examining
an industrial haze that covered nearly 4 million square miles and upset
the water cycle over the Asian subcontinent.
He said similar processes appeared to be at work over the Sahel, but the
CSIRO model must be sharpened to prove it.
Until then, "I would be cautious about overextending these conclusions,"
Ramanathan said.
Other scientists were even more guarded. Teleconnection is a
reasonable, but complicated, explanation, they said.
"Rotstayn focuses on an indirect effect of aerosols that is really hard to
quantify," said Philip Rasch, senior scientist at the National Center for
Atmospheric Research in Boulder, Colo.
Some scientists complained that the global rainfall pattern simulated by
the computer model does not match up with actual rainfall observed at
weather stations around the world during the drought. This lack of a
neat correlation makes the study's Sahel conclusions "highly
speculative," they said.
For example, the real weather observations and those generated by the
computer model correspond for the Sahel, Senegal and parts of Brazil,
said Yogesh Sud, senior research meteorologist at NASA's Goddard
Space Flight Center in Greenbelt, Md.
"But in India and Australia, there is absolutely no match" between
recorded rainfall and the simulated conditions, Sud said.
Nations share the same atmosphere and, increasingly, the same pollution.
Pollution is known to alter temperature and precipitation patterns near its
source. Recent studies suggest that one country's pollution can become
a problem for other countries, too.
Over the desolate North African Sahel, the influence of global pollution
is less direct. Normally, this harsh land receives patchy summer rainfall.
Soil studies show that milder droughts came in the 1680s, the 1750s,
the mid-1800s and the early 20th century.
Rotstayn believes industrial smokestacks are the smoking guns for the
more recent, more intense drought.
The sulfur dioxide pollution particles, which can remain in the air 5 to
20 days, probably drifted over the North Atlantic where they created
more condensation nuclei for cloud formation, the scientists theorize.
The additional nuclei remained suspended in clouds rather than growing
into fewer, larger droplets and falling as rain.
In addition, these clouds were brighter than normal, in part because of
the added nuclei, and they reflected more of the Sun's energy into space.
This cooled the surface of the North Atlantic, which reduced the normal
evaporation rate from the ocean and further hampered the moisture
cycle.
South of the Sahel, the sea surface remained warm and evaporation
increased so more rain fell to the south, Rotstayn said.
Leon Rotstayn: http://www.dar.csiro.au/profile/rotstayn.html
Source
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