[eschaton]

Originally Posted by James Bond Agent 007

I have an even more radical idea: Dredge giant canals and create vast new seas in the lower-elevation parts of the Sahara Desert. This will let the Atlantic Ocean spread into the newly-created seas, helping to lower sea levels worldwide. The dredgings from the operations can be used to create new mountain ranges in nothern Africa between the new seas, hopefully creating some orthographic precipitation, which in turn can make thew new mountainous areas more habitable.

This actually was a real plan bandied about since the 19th century. Though the actual area which could be flooded (below sea level) is far more limited than you intimate.