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News: Scientists Confirm Historic Massive Flood in Climate Change
http://www.giss.nasa.gov/research/news/20060228/
 
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THE SAHARA

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Author Topic: THE SAHARA  (Read 4036 times)
Bianca
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« Reply #15 on: May 17, 2009, 08:45:22 am »












Written by
Graham Chandler
Saudiaramcoworld.com


Three reddish-brown giraffe images watch over Nick Brooks as he struggles, hunched over, to shovel sand from the rock shelter’s floor. Some 150 meters (500') above a sweeping, flat and desolate Western Sahara landscape, the burly environmental scientist is hoping these cliffs of Bou Dheir will reveal just when those animals roamed the plains. Three thousand years ago? Four thousand? Five thousand?

 
Today, only traces remain of the seasonal watercourse that until 5500 to 6000 years ago supported a landscape whose rich hunting we deduce from the abundance of animals in the area’s rock art.


Pinning down dates like these is essential to the study of human response to drastic alterations in climate. While many scientists believe climate change was responsible for the decline of such civilizations as the Mayan, a growing number, including Brooks, believes there’s also evidence that earlier global climate shifts actually spurred the beginnings of the world’s first civilizations.

For all of Earth’s history, the only constant about global climate has been its changes. For those climate-change episodes severe enough (and recent enough) to affect human survival, the response, in most cases, must have been to migrate and continue life in a new place, to adapt to new resources—or perish.

But one climatic episode in particular, a massive change during the fourth and early third millennium BC, shifted global rainfall patterns in many subtropical and temperate northern-hemisphere regions and caused severe desertification. Only that change—not any of the earlier ones—was immediately followed by the new human social arrangement we call “civilization.” Was that because the affected humans were larger groups that were forced to share limited resources, since they were boxed into refuges with no other place to go?
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