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US Clean Air Legislation Helped End the '80s African Mega-Drought

What's good for us is also good for the world.
Photo: Thure Johnson/Flickr

The starvation-inducing 1980s drought across the Sahel in Africa, once blamed on bad agricultural practices and overgrazing, really was caused by all the coal being burnt across the Northern Hemisphere, a new report in Geophysical Research Letters shows.

From the 1960s through the 1980s, prior to air pollution laws taking effect in the United States and Europe, all the sulfate emissions from coal-fired power plants cooled the atmosphere across the Northern Hemisphere to such a degree that it both masked the warming caused by all the carbon emissions it produced, as well as causing bands of rain to shift south far enough that the Sahel was plunged into drought.

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Looking at rain gauges around the world, precipitation patterns were shifted south by air pollution in the north around the globe. Northern India and parts of South America also experienced drier-than-normal conditions at the time, but places just to the south, northeastern Brazil and the Great Lakes region of Africa were wetter than usual. The map below shows the shifts in precipitation that occurred at the time.

Image: University of Washington

Sulfate particles, unlike their cousins in particulate air pollution, black carbon, both reflect sunlight directly and help create hazy cloud conditions that also reflect the sun. During the 1980s, as today, coal-fired power plants are the main source of this pollution, which ultimately masks some of the warming that would otherwise be created by the greenhouse effect, furthered by the carbon emissions of burning coal.

It's this same principle that geoengineering advocates propose deploying by injecting sulfate particles into the atmosphere to help slow global warming.

Other recent research, from UC Berkeley, shows that the difference in warming between the Northern and Southern Hemispheres will significantly alter tropical rainfall, creating drier conditions in some places and wetter places in others—especially along the Intertropical Convergence Zone.

Report co-author Andrew Friedman explains,

It really is these borderline regions that will be most affected, which, not coincidentally, are some the most vulnerable places: Areas like the Sahel where rainfall is variable from year-to-year and the people tend to be dependent on subsistence agriculture. We are making major climate changes to the planet and to expect that rainfall patterns will stay the same is very naive.

These historical rainfall patterns still include significant short-term drought, but the catastrophic long-term drought was alleviated by the reduction of air pollution in the North.

What helped reverse the African drought (which, in case your pop culture history fails you, also spawned the charity pop singer feel good record album genre, viz We Are the WorldDo They Know It's Christmas?, etc.) was the US Clean Air Act and similar legislation in Europe.

By reducing particulate emissions from power plants these laws both cleaned up the air, saving hundreds of thousands of lives in the US alone, as well as help revive historical rainfall patterns at the northern edge of the tropics.   And really, it shouldn't come as much of a surprise, as the atmosphere doesn't stop mixing at national boundaries. Still, it's interesting to see the point made clear that what's good for us is also good for the world.