From the 1970s to the 1990s a severe drought impacted Africa, leading to a massive famine and hundreds of thousands of deaths.
A new study published April 24 in the journal Geophysical Research Letters revealed critical information about Africa’s most severe drought: that it was caused not by overgrazing and poor land use, but rather by the West’s pollution.
From the 1970s to the 1990s a severe drought impacted Africa, leading to a massive famine and hundreds of thousands of deaths. Understanding what caused the dry spell is critical as scientists look for ways to prevent it from happening again.
To understand the Sahel drought better, a team of researchers looked at the rainfall records from the 1930s to the 1990s for the area and then used the 26 climate models utilized by the Intergovernmental Panel on Climate Change to analyze what was causing the rainfall patterns. All of the models confirmed that sulfate aerosol pollution from the Northern Hemisphere (primarily Europe and North America) caused the changes.
The study makes it clear that pollution has an impact on climate change worldwide, study co-author Dargan Frierson told LiveScience.
In the study, Frierson and his colleagues tracked the Intertropical Convergence Zone, which is a wide band of rainfall that occurs naturally. It wandered back and forth across the equator from the 1930s to the 1950s, but in the 1960s it began to shift downward and dry out central Africa and parts of South America and South Asia.
Pollution triggered this shift; as aerosols cooled the Northern Hemisphere, the rain band moved southward. Coal burning plants emitted the tiny particles of sulfide, called aerosols, into the atmosphere, RedOrbit explains.
The cooling effect was previously overlooked due to a focus on the overall warming of the climate. Eventually, clean air legislation caused the pollution to decrease, allowing the band to move back up and ease the drought in Africa.
One strategy that the team used was to zoom out and look for larger patterns, doctoral student and study co-author Yen-Ting Hwang noted, according to RedOrbit. By zooming out, the team was able to observe what was happening in other regions of the world at the same time as the drought was occurring in Africa.
People should understand that pollution impacts climate not only locally but in remote areas as well, Hwang said. The team is now researching the effects of aerosol pollution emitted in Asia, a timely study because of the large amount of pollution occurring in the area. As this study shows, that pollution is likely to have far-reaching impacts around the world.
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