Africa’s developing economies are particularly susceptible the changes in climate which can quickly and significantly impact agriculture. A recent study led by the National Center for Atmospheric Research (NCAR) examined historic Co2 levels in an effort to determine what could happen as the Earth warms and glaciers and ice caps recede. Specifically, the researchers looked at the African Humid Period (AHP) which lasted from approximately 14,700 until about 5,000 years ago.

As the last ice age came to an end and the ice sheets that covered North America and Europe receded, Africa’s rainfall responded with a considerable increase. The increase in moisture was so significant and long lasting that deserts turned into grasslands and savannas.

Although the reasons for it are not well understood, the most significant increases in rainfall occurred in two well-seperated regions.

According to samples and climate models, as the last ice age ended there was a significant increase in atmospheric levels of Co2, methane and other greenhouse gasses. By 11,000 years ago these levels rivaled those of the pre-industrial age. It was the last naturally occurring period of significant global warming.

At the same time, there was a dramatic influx of fresh water into the oceans as a result of retreating ice sheets. The increase interrupted a circulation pattern in the Atlantic Ocean which drove heat and salinity northward. As a result, African precipitation shifted southward and was suppressed in other parts of the continent. When the melting of the ice sheets slowed, precipitation returned more strongly to the rest of the continent, triggering the AHP.

For the study, which is published in the journal Science, the researchers examined fossil polling, historic lake levels and other indications of past moisture. This data was combined with simulations based on the Community Climate System Model using supercomputers at the Oak Ridge National Laboratory. The past moisture evidence and simulations agreed on the researchers explanation for the AHP.

With greenhouse gasses on the rise again and fresh water pouring into the oceans from melting glaciers and ice caps the information should help Africa prepare for the future.

“The future impact of greenhouse gases on rainfall in Africa is a critical socioeconomic issue. Africa’s climate seems destined to change, with far-reaching implications for water resources and agriculture,” said Bette Otto-Bliesner, NCAR scientist and lead author of the research in a statement.