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.
During this time wine grapes were grown in Europe up to 300 miles north of their present northerly growing limit. Also during this time, the Vikings took advantage of ice-free seas to colonize Greenland and other outlying lands of the far north. The period was followed by the Little Ice Age, a period of cooling that lasted until the 18th century when the current period of global warming began.
Initial research on the MWP was largely done in Europe, where the phenomenon was most obvious, and it was assumed that this period was global. However, more recently this view has been revised, and the 2001 IPCC report says: "...current evidence does not support globally synchronous periods of anomalous cold or warmth over this timeframe, and the conventional terms of 'Little Ice Age' and 'Medieval Warm Period' appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries." [1]. See also the 1000 y temperature reconstruction of Mann et al [1]. The IPCC says of the MWP that temperatures from the 11th to 14th centuries [were] about 0.2°C warmer than those from the 15th to 19th centuries, but rather below mid-20th century temperatures. A paper by Soon and Baliunas disagrees with the IPCC and Mann and states that those warm and cold periods were indeed widespread climatic anomalies (amusingly enough, it doesn't: because it states (their table 1) than Mann shows a widespread Little Ice Age). However, the Soon and Baliunas report itself has been extensively criticised [1], [1].
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