[SunkenCiv]

Ancient tree rings give climate clues
Wednesday, 28 March, 2001, 19:09 GMT 20:09 UK
http://news.bbc.co.uk/1/hi/sci/tech/1247636.stm

Mystery Of Infamous ‘New England Dark Day’ Solved By Tree Rings
http://www.sciencedaily.com/releases/2008/06/080606145620.htm

Tree-ring reconstructed megadroughts over North America since a.d. 1300
http://www.springerlink.com/content/5478q5t795671806/

[NutCrackerBoy]

Jared Diamond cites man-made environmental problems as the main factor in the failure of past civilizations. But natural disasters are often the real cataclysms, like this possible 540 A.D. comet.