Medieval Warm Period

The Medieval Warm Period (MWP) or Medieval Climate Optimum 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 (LIA), a period of cooling that lasted until the 19th century when the current period of global warming began.

Initial research on the MWP and LIA 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].

For more on the topic of the MWP in various IPCC reports, see MWP and LIA in IPCC reports.

See also the 1000 y temperature reconstruction of Mann et al [2]. The IPCC TAR says of the MWP that the posited Medieval Warm Period appears to have been less distinct, more moderate in amplitude, and somewhat different in timing at the hemispheric scale than is typically inferred for the conventionally-defined European epoch. The Northern Hemisphere mean temperature estimates of Jones et al. (1998), Mann et al. (1999), and Crowley and Lowery (2000) show temperatures from the 11th to 14th centuries to be 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, Soon & Baliunas don't disagree altogether with Mann because Soon & Baliunas state in their table 1 that Mann shows a widespread Little Ice Age). However, the Soon and Baliunas report itself has been extensively criticised [3].

For further discussion of regional and global temperature variations see Temperature record of the past 1000 years.

External links and references

• Vikings During the Medieval Warm Period
• The Little Ice Age and Medieval Warm Period
• American Heritage Dictionary- "The period from about 1000 to 1400 in which global temperatures are thought to have been a few degrees above those of the preceding and following periods. The climatic effects of this period were confined primarily to Europe and North America. Also called Medieval Warm Epoch." (American Heritage Dictionary)
• The "Medieval Warm Period"- Greenpeace article citing journal article: (M.K. Hughes and H.F. Diaz, "Was there a 'Medieval Warm Period?", Climatic Change, v.26, p.109-142, March 1994).
• John L. Daly's graphs - evidence that the Medieval Warm Period may have been global in character (this is an opinion piece - highly controversial)