Scientists have discovered extraordinarily precise data on rainfall in the Mediterranean region from 200 B.C. to 1100 A.D. which suggests that the fall of the Roman and Byzantine empires may have been partly caused by climate change.

It is not likely to end the debate among historians, some of whom believe the fall was more of a transformation than a collapse, but it is a tantalizing bit of evidence.

http://abcnews.go.com/Technology/JustOneThing/story?id=6428550&page=1