PARIS, June 12: A swathe of countries south of the Sahara suffered crippling drought for decades because of pollution by power stations and factories in North America and Europe, a team of climate experts say.
A band of nations, from Guinea in western Africa to Ethiopia in the east, were hit by the worst and most prolonged droughts since weather records began, with precipitation falling by 20-50 percent for 30 to 40 years.
During the worst years, 1972-75 and 1984-85, up to a million people starved to death.
The reason, say Australian and Canadian researchers, is that rich countries unwittingly hijacked the clouds that should have provided rain for the Sahel.
They blame emissions of sulphur dioxide (SO2) belched out by burning coal and other fossil fuels by the industrialised north, the British weekly New Scientist says in next Saturday’s issue.
Drifting high in the atmosphere, the SO2 forms sulphate aerosols that provide a handy core around which moisture molecules form and develop into a cloud.
These clouds are made from fine, misty droplets, which means they are also highly efficient at reflecting radiation from the sun and so cool the earth and seas beneath them.
The team ran a computer model that simulated the huge pollution of SO2 disgorged in the northern hemisphere during the 1980s.
They found that Europe and North America were cooler relative to the southern hemisphere and this had a big effect on climate across central Africa.
The tropical rainbelt moved south, depriving the Sahel countries of their precipitation.
The research, by Leon Rotstayn at Australia’s national research agency CSIRO and Ulrike Lohmann of Dalhousie University in Halifax, Nova Scotia, is to be published shortly in a specialist review, Journal of Climate, New Scientist says.
The SO2 pollution in the North has greatly eased because of tough laws in the 1980s to combat “acid rain”, which attacked northern pine forests.
As a consequence, the scientists say, the Sahel droughts have eased.
However, the suffering in those countries will continue for years because land gets stripped of vegetation during a drought and this in turn causes the fertile topsoil to be washed away when the rains return.
Aerosols — a category that includes soot and dust — are becoming a keenly-researched area in climate science.
China and India are huge producers of aerosols because of their high use of coal and there is much interest in whether this may be causing disruption to local weather patterns.—AFP