"Lake sediments in western Greenland confirm that abrupt climate change brought cold conditions to the region just before the collapse of the Norse settlements."
"Now, new research by U.S. and British scientists led by geologist William D'Andrea at Brown University, Providence, RI, reconstructs 5,600 years of climate history buried in lake sediments of West Greenland that links temperatures and three human migrations in the region, including the Norse. Their study was just published in the Proceedings of the National Academy of Sciences."

http://news.discovery.com/earth/shifting-climes-in-greenland-110601.html