Pollution from Northern Hemisphere behind Drought in Africa in 1980s

The Sahel drought that affected millions in Africa in the 1980s was caused by pollution from factories in the Northern Hemisphere, a new study said. 

Coal burning factories in the U.S and Europe released large quantities of aerosols during the 60s and 70s. These aerosols cooled much of Northern Hemisphere and pushed the rain bands south. The rain never reached the Sahel region that's just below the Sahara desert.

Previously it was believed that bad farming practices were behind the drought. However, the latest study shows that global changes in rain patterns driven by pollution were a stronger cause of the drought.

An earlier article by BBC, back in 2002, had said that sulfur dioxide from factories in the west was the reason for this severe drought. Rainfall in the region of Sahel dipped between 20 and 50 percent during the droughts that occurred in 1972, 1975, 1984 and 1985.

In the present study, researchers from New University of Washington and their colleagues used historical data and observations to find whether or not the Sahel drought was related with change in global rainfall pattern. The researchers also used many climate models to determine why the change occurred.

"To some extent, science messed this one up the first time around. People thought that a large part of that drought was due to bad farming practices and desertification. But over the last 20 years or so we've realized that that was quite wrong, and that large-scale ocean and atmosphere patterns are significantly more powerful in terms of shaping where the rains fall," said Dargan Frierson, a UW associate professor of atmospheric sciences and co-author of the study.

In the study, researchers found that cooling of the Northern Hemisphere by sulfur particles was the primary cause of the drought. These sulfur particles are released in the air by dirty burning of carbon. They create reflective, long-lasting clouds.

This cooling of Northern hemisphere was balanced with the warming caused by carbon dioxide, according to a news release.

The rain band over Sahel region shifted back after the U.S and Europe passed the clean-air legislation.

Currently, climate change is affecting the Northern hemisphere more than the Southern Hemisphere, a related study said.

The study is published in the journal Geophysical Research Letters.