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Researchers Forecast Drier Horn Of Africa As Climate Continues To Warm

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A new study conducted by University of Arizona (UA) researchers has found that the continued warming of the Earth's climate has turned the Horn of Africa, long considered to be the cradle of early human life, into an increasingly arid region at an unprecedented rate.

This African region has also experienced catastrophic droughts every few years over the past several decades.

According to the scientists, if the planet continues to become warmer, the eastern part of the Horn of Africa, which covers the countries of Ethiopia, Djibouti and Somalia, will also continue to receive lessening amounts of rainfall during the traditional "long rains" season in the region, from March until May.

Such a negative trend could result in the exacerbation of tensions in some of the world's most geopolitically unstable nations.

The findings point to the Horn of Africa becoming increasingly drier, which is a direct contradiction to previous international climate models which suggest that the warming of the Earth would bring more rainfall to the African region.

In the study, featured in the journal Science Advances, scientists from Arizona, led by associate professor Jessica Tierney, studied used cores of prehistoric marine sediments collected from the Gulf of Aden in order to reconstruct the levels of aridity and temperature in the region in the last 2,000 years.

They discovered that their own reconstructions were in step with another independent model of temperatures in the Northern Hemisphere that stretches back to A.D. 1. All research data describe the warming and drying of the Horn of Africa in the past century.

Analysis of Ancient Marine Sediments

The layers of prehistoric sediments the researchers retrieved from the Gulf of Aden were well-preserved enough to allow them to study them the samples by decades. Tierney carried out the examinations of the sediments at the Woods Hole Oceanographic Institution and the Lamont-Doherty Earth Observatory at Columbia University.

The core contained samples that date back to 40,000 years ago, which the researchers used to get new insights into the climate of Africa during the time.

In a previous study, Tierney and fellow researcher Peter deMenocal revealed that the Sahara desert, which was once teeming with vegetation because of regular rainfall, suddenly dried out in just one to two centuries around 5,000 years ago. The findings of the UA scientists show that shifts in climates can occur suddenly.

Tierney and her team studied the chemical contents of every layer of the ancient marine core to help them find out the aridity and temperature of the Horn of Africa in the past 2,000 years. Compounds extracted from single-celled marine organisms called archaea, which were capable of changing their chemistry to suit their environment, allowed the scientists to discover the past aridity and temperature of the region.

The team also analyzed samples of fatty acids extracted from the leaves of terrestrial plants to track the past aridity levels of the region. Wax from these leaf litters are often blown into the Gulf of Aden, causing them to end up in the sediment.

During warm and dry climates, the fatty acids found in the leaf wax contain more amounts of condensed hydrogen called deuterium. While the Horn of Africa had a relatively wet period from A.D. 1450 to 1850 in a period known as the Little Ice Age, Tierney and her colleagues discovered increasing levels of deuterium in the past 100 years, suggesting that the climate was indeed beginning to dry.

Based on earlier global-scale models, scientists predict the African region will experience more amounts of rainfall, particularly during the "short rains" season that runs from September to November.

The recent UA study, however, suggests that environmental gains outlined in previous research could be offset by the reduction of rainfall during the long rains season, a period that is crucial to the agriculture of the Horn of Africa.

"It is getting drier right now in the 20th century and we expect it to continue to get dry," Tierney pointed out.

"If we can simulate rainfall in these arid tropical and subtropical regions better, we can understand the future impact of climate change."

Photo: Edward Musiak | Flickr 

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