Medieval Warm Period

The medieval climate optimum or medieval warm period was an unusually warm period in history lasting from about the 10th century to about the 14th century. http://www.wikipedia.org/wiki/Medieval_Warm_Period

http://www.agu.org/revgeophys/mayews01/node5.html

http://www.co2science.org/edit/v5_edit/v5n13edit.htm

http://archive.greenpeace.org/climate/database/records/zgpz0231.html

vikings http://www2.sunysuffolk.edu/mandias/lia/vikings_during_mwp.html