Greenhouse gases may spell wet future for Africa

Historic damp periods linked to boosts in planet-warming emissions

the Serengeti in Tanzania

STORMY FORECAST  By studying a wet period in Africa's distant past, researchers have found that current increases in atmospheric greenhouse gases may spell a rainy future for certain parts of the continent, such as northern Tanzania (shown).

Colin J. McMechan/FLICKR (CC BY-SA 2.0)

A flood of greenhouse gases into the atmosphere may trigger downpours in certain parts of Africa.

By examining a historic African rainy spell, scientists determined that greenhouse gases play a large role in boosting rainfall in northern and southeastern areas of the continent. The finding, appearing in the Dec. 5 Science, may portend how climate change will alter access to a critical resource —water —plus help scientists understand other climate data that predict surges in African rainfall.

Between around 21,000 and 14,700 years ago, parts of Africa experienced a soggy era, marked by brimming lakes. The soaked sectors included a northern belt across the width of the continent, spanning the bottom of the Sahara to savanna territory, and a southeastern region around northern Tanzania.

Using a computer simulation to re-create that period, researchers led by Bette Otto-Bliesner at the National Center for Atmospheric Research in Boulder, Colo., individually added and removed variables that could have spurred the showers. These factors include an uptick in greenhouse gases noted during that time frame and changes to the Earth’s tilt and orbit, which alter the amount of sunlight that reaches the planet’s surface.

Increases in greenhouse gases — to levels nearly those seen in pre-industrial times — was behind much of the northern region’s extra moisture and nearly all of that of the southeastern region, the researchers conclude.

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