The wet, hospitable Sahara It’s a little hard to believe, looking at images like this one, of

The wet, hospitable SaharaIt’s a little hard to believe, looking at images like this one, of a dust storm whipping up sand and fine grained particles over the coast of Libya and out into the Mediterranean sea, that only a few thousand years ago, the Sahara was nothing like what it is today.Paintings from early humans in what is today the Sahara record images of elephants and hippopotami visiting watering holes and streams in the area, a far cry from the dust and sand of today. Records of this period are abundant, from the rocks to the soil to the sediment; only 5,000 years ago, the Sahara was a much more hospitable place.One worry for modern humans is that what happened to the Sahara could happen elsewhere. We’ve seen droughts of scales large enough that they could indicate creeping desertification, such as the infamous Dust Bowl of the 1930’s in the U.S. or the ongoing drought in the Sahel region of Africa, just south of the Sahara. But, converting any of these areas into another Sahara would be a huge change, the kind people might consider unprecedented.So, how big of an environmental change struck the Sahara when it dried up 5,000 years ago? Researchers led by David McGee of MIT took sediment cores off of the coast of North Africa, using the abundance of this exact kind of dust as a proxy for how dry the area was.At some points over the last 30,000 years, the dust abundance was even greater than today, meaning North Africa can be even drier than currently seen. But 6,000 years ago, the dust abundance was miniscule, only 1/5 as much dust appearing in the sediments off the African coast as is deposited today.These results suggest that Africa’s climate has been even more volatile than generally believed over the past few thousand years. The area we see as a massive desert today has sometimes been even larger, and sometimes been downright pleasant.What does this mean for today? The swings in climate seen in Africa associated with the end of the last glacial period are enormous. Humanity has built cities and civilizations in areas where supplies and water are available, even in the countries surrounding the Sahara, so we count on the presence of a stable climate. The Sahara is clearly an incredibly unstable area, where even greater desertification is possible. That may be one of the messages that the Saharan records tell, that changes we might think of as impossible and unprecedented are surprisingly common, and the stable climate of the last few thousand years is the exception, not the rule.-JBBImage:http://www.earthobservatory.nasa.gov/IOTD/view.php?id=80799Science Daily article:http://phys.org/news/2013-04-abrupt-widespread-climate-shift-sahara.htmlSahel drought:http://en.wikipedia.org/wiki/Sahel_drought -- source link
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