The Great Drying of Africa

Martin P. Hoerling and Jon K. Eischeid
NOAA/ESRL Physical Sciences Division

Science Writer: Barb DeLuisi
NOAA/ESRL Physical Sciences Division 		African Mother & Child

Introduction

Located just south of the scorching sands of the Sahara Desert is an expansive, semi-arid region of Africa called the Sahel. This sparsely vegetated area receives an average of four to eight inches of rainfall per year during its July to September monsoon season. During this warm time of year, summer rains are usually abundant with the heating of the sun. However, the Sahel experienced a severe drying trend during the last half of the 20th century that led to devastating drought during the 1970s and 1980s, and resulted in widespread famine and the loss of more than 1,000,000 human lives.

Researchers Martin Hoerling and Jon Eischeid of the NOAA Physical Sciences Division (PSD), and James Hurrell of the National Center for Atmospheric Research (NCAR)wanted to find out the reasons for the drying. Learning the cause would not only permit a better understanding of the climate risks in this vulnerable region, but could also lead to improved projections of 21st Century Sahelian rainfall. They would attempt to simulate the African climate including its variations and trends of the 20th century.

"We judged from climate simulations that the ocean was a material factor for the drying over the Sahel," says Hoerling. "And that the oceans also played a leading role in drying of other parts of Africa including an increased incidence of drought over southern Africa during austral summer."

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