An Africa without desert? Study looks into ancient period of green Africa

African Humid Period closer to being understood with new study

A new study has revealed that Africa has been subject to mass climate change in the past, and may be incredibly vulnerable to it now.

LOS ANGELES, CA (Catholic Online) - An increase in the amount of greenhouse gas in the atmosphere was key to an increase in rainfall in some major regions of Africa thousands of years ago.

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What the current increase in gases will do, is unknown, but its affects could be just as dramatic.

The study by scientists with the National Center for Atmospheric Research (NCAR) in Colorado, published the paper with their findings in the journal Science.

"The future effect of greenhouse gases on rainfall in Africa is a critical socioeconomic issue," said Bette Otto-Bliesner, a scientist with the NCAR. "Africa's climate seems destined to change, with far-reaching implications for water resources and agriculture."

The study was conducted in order to better understand the reasons for the dramatic climate shifts that occurred in Africa about 20,000 years ago.

The catalyst was the retreating of the massive glaciers that had covered much of North American and Europe about 21,000 years ago. This caused a dry spell which lasted nearly 6,000 years.

About 14,700 years ago and ending 5,000 years ago, the amount of rainfall in Africa increased dramatically, turning desert into fertile grassland and savanna. This period, which has long puzzled scientists, was named the African Humid Period (AHP).

Even more puzzling, this climate shift occurred in two wholly separate regions, on either side of the equator.

Previous studies suggested that the AHP in northern Africa was triggered by a change in Earth's orbit which resulted in summertime heating. But Otto-Bliesner said that this pattern was not sufficient to explain the change in southern Africa.

"This study is a step toward solving the puzzle of what triggered abrupt changes in rainfall over southeastern equatorial and northern Africa during early deglaciation," said Anjuli Bamzai, a program director in the National Science Foundation's Division of Atmospheric and Goespace Sciences.

"Through an analysis of proxy records and climate model simulations, the team demonstrated that the recovery of what's called the Atlantic Meridional Overturning Circulation, or AMOC, played a role as the initial trigger to wetter conditions."

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