History Files
 

 

Prehistoric Africa

Sahara Desert Born 4,000 Years Ago

by Dr David Whitehouse, 9 July 1999. Updated 22 April 2017

Using a new computer simulation of Earth's climate, German scientists in 1999 announced the finding that the Sahara underwent a brutal climate change around 2000 BC.

Over a very short time scale - possibly as short as three hundred years - it went from grassland with low shrubs to the desert we are familiar with today. Summer temperatures increased rapidly and rainfall almost ceased. The change devastated many ancient cultures and caused those that did survive to migrate elsewhere.

Scientists at the Potsdam Institute for Climate Research said that the desertification of the Sahara was one of the most dramatic changes in climate over the past 11,000 years.

The loss of agricultural land to the desert may have been one of the reasons why early civilisations developed along the valleys of the Nile, the Tigris, and the Euphrates. This was a period known as the Priora oscillation, a dry period from circa 3200-2900 BC which marked the end of a long, wetter, warmer climate period from about 9,000 to 5,000 years ago, called the Holocene climatic optimum.

Feedback mechanism

Slight climate alterations caused by subtle changes in the Earth's orbit around the sun were amplified by a climatic feedback mechanism. Around 7000 BC, the tilt of the Earth's axis was 24.14 degrees; today it is 23.45 degrees. Today, Earth is closest to the sun in January. Nine thousand years ago, our planet was closest to the sun at the end of July.

The changes in the tilt of the Earth occur gradually. However, the interplay of atmosphere, ocean, and landmass can react to these changes in abrupt and severe ways. This particular climate model suggested that land use by man was not an important factor in the creation of the Sahara. They were simply victims of extreme climate change.

 

 

     
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