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- Using a new computer simulation of the Earth's climate
German scientists say that the Sahara underwent a brutal climate change
about 4,000 years ago. Over three hundred years the climate altered severely.
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- Ten thousand years ago the Sahara, the largest desert
in the world, was covered by grass and low shrubs.
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- But then summer temperatures increased and rainfall almost
ceased. The change devastated many ancient cultures and caused those that
did survive to migrate elsewhere.
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- According to the researchers another, less severe, change
occurred between 6,700 and 5,000 years ago.
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- Scientists at the Potsdam Institute for Climate Research
say that the desertification of the Sahara was one of the most dramatic
changes in climate over the past 11,000 years.
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- 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.
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- Slight climate alterations caused by subtle changes in
the Earth's orbit around the Sun were amplified by a climatic feedback
mechanism.
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- Some 9,000 years ago the tilt of the Earth's axis was
24.14 degrees, today it is 23.45 degrees. Today the Earth is closest to
the Sun in January. Nine thousand years ago the closest to the Sun occurred
at the end of July.
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- 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.
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- The climate model suggests that land use by man was not
an important factor in the creation of the Sahara.
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