Medieval Warm Period
The Medieval warm period, is an epoch of relatively warm climate which existed in the 10th-13th centuries, following the climatic pessimum of the Great Migration and preceding the so-called Little Ice Age of the 14th-18th centuries. Prior to current theories about man-made global warming - a full 400–700 years before humans began the Industrial revolution - the Medieval warm period's mild winters and relatively warm and even weather allowed for unprecedented crop growth, urban expansion, and the establishment of Scandinavian settlements in Greenland and North America.
Rather than limiting the Medieval warm period to "Europe and neighboring regions or the North Atlantic" as AGW advocate Michael Mann would do, the effects of this period was world-wide. Willie Soon and Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics "found 112 studies containing information about the medieval warm period [in] Russia, the U.S. Corn Belt, Central Plains and Southwest; much of China and Japan; southern Africa; Argentina, Chile and Peru in South America, Australia and Antarctica ... in the Indian Ocean, both central and southern; and in the Central and Western Pacific Ocean. In the Southern Hemisphere, twenty-one of twenty-two studies (95 percent) showed evidence of the Medieval Warming." 
Thomas Gale Moore of the Hoover Institution wrote about the Medieval Warm Period:
|“|| The three centuries beginning with the eleventh, during which the climate became distinctly more benign, witnessed a profound revolution which, by the late 1200s had transformed the landscape into an economy filled with merchants, vibrant towns and great fairs. Crop failures became less frequent; new territories were brought under control. With a more clement climate and a more reliable food supply, the population mushroomed.
The historian Charles Van Doren claimed that: "the ... three centuries, from about 1000 to about 1300, became one of the most optimistic, prosperous, and progressive periods in European history." All across Europe, the population went on an unparalleled building spree, erecting at huge cost spectacular cathedrals and public edifices. Ponderous Romanesque churches gave way to soaring Gothic cathedrals. Virtually all the magnificent religious shrines that we visit in awe today were started by the optimistic populations of the eleventh through the thirteenth centuries, although many remained unfinished for centuries.
Throughout the continent, economic activity blossomed. Banking, insurance, and finance developed; a money economy became well entrenched; manufacturing of textiles expanded to levels never seen before. Farmers in medieval England launched a thriving wine industry. Good wines demand warm springs free of frosts, substantial summer warmth and sunshine without too much rain, and sunny days in the fall. Winters cannot dip below zero Fahrenheit for any significant period. The northern limit for grapes during the Middle Ages was about 300 miles above the current commercial wine areas in France and Germany.
The medieval warm period, which started a century earlier in Asia, benefited the rest of the globe as well. From the ninth through the thirteenth centuries, farming spread into northern portions of Russia. In the Far East, Chinese and Japanese farmers migrated north into Manchuria, the Amur Valley and northern Japan. The Vikings founded colonies in Iceland and Greenland, then actually green. Scandinavian seafarers discovered "Vinland" along the East Coast of North America.
Beginnings of research
Since the 18th century, anecdotal evidence has been used to discuss whether warmer temperatures could have temporarily prevailed in various regions of the North Atlantic in the Middle Ages. The Danish missionary Hans Poulsen Egede (1686-1758), who in 1721 in Greenland sought in vain for inhabited medieval Viking settlements, of which one had heard nothing for 200 years, took climate change into consideration as a possible cause of their disappearance:
- "Were they destroyed by an invasion of the natives ... [or] perished by the inclement of the climate, and the sterility of the soil?"
In the mid-19th century European geologists Bernhard Studer (1847), François Arago (1858), and others interpreted the end of the Greenlandic settlements in the 15th century as evidence of a previously warm climate changed to a cold one, while Conrad Maurer rejected this view and saw the reason in the advance of Inuit. Poul Nørlund, who examined Grænlendingar graves at Herjólfsnes in southwest Greenland, found abundant plant roots which had penetrated the graves under the permafrost and concluded that the summer temperatures had been higher during the Medieval warm period than in the time of his excavations in 1921. Changes in tree boundaries were interpreted partly as an indication of climate change, partly as caused by human intervention. Eduard Brückner pointed out in 1895 that earlier winegrowing in areas such as Northern Germany, where no more occurred around 1900, had been influenced not only by climatic conditions, but also by economic constraints: it was more profitable to collect and sell poor grapes from northern climates than it was to import better grapes from the south.
The systematic investigation of a possible medieval climate anomaly - especially in Europe - was initially the field of historical climatology. Long before the beginning of instrumental measurements, a record of climate change could be drawn from historical documents and archaeological finds, leading to conclusions on climatic conditions and their consequences. Thus, for the period from about 1300, there are reasonably complete historical reports of summer and winter weather. It was the pioneering work in this field, such as the British climatologist Hubert Lamb or the French historian Emmanuel Le Roy Ladurie, the first comprehensive overviews of higher temperatures and social contexts for the North Atlantic and here especially Europe delivered.
The term "medieval warm period" was then primarily influenced by the work of Lamb in the 1960s, and later adopted by other fields of research. Lamb called this a global warming, which he stated regionally with up to 1-2° C (1.8–3.6° F) and whose peak he suspected between the years 1000 and 1300. Lamb found evidence of such warming, especially around the North Atlantic, while there were indications of relatively low temperatures for the North Pacific at about the same time. As a cause, he assumed displacements of the Arctic polar vortex.
- Anthony G. Martin. A thorough examination of Climategate evidence, examiner.com, December 13, 2009.
- Warmer is Richer by Thomas Gale Moore, Hoover Institution, Stanford University
- Egede, pg. xi
- Egede, Hans. A Description of Greenland; T. and J. Allman, London (1818) 
- Coherent High- and Low-Latitude Climate Variability During the Holocene Warm Period (Science, vol. 288. no. 5474, pp. 2198 – 2202, 23 June 2000) - Peter deMenocal, Joseph Ortiz, Tom Guilderson, Michael Sarnthein
- Evidence for a 'Medieval Warm Period' in a 1,100 year tree-ring reconstruction of past austral summer temperatures in New Zealand (Geophysical Research Letters, vol. 29, no. 14, pp. 12–1 to 12-4. 15 July 2002) - E. R. Cook, J. G. Palmer, R. D'Arrigo
- Evidence for the existence of the medieval warm period in China (Climatic Change, vol. 26, nos. 2-3, March, 1994) - De'Er Zhang
- Glacial geological evidence for the medieval warm period (Climatic Change, vol. 26, nos. 2-3, March, 1994) - Jean M. Grove, Roy Switsur
- Medieval climate warming and aridity as indicated by multiproxy evidence from the Kola Peninsula, Russia (Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 209, issues 1-4, pp. 113–125, 6 July 2004) - K. V. Kremenetski, T. Boettger, G. M. MacDonald, T. Vaschalova, L. Sulerzhitsky, A. Hiller
- Medieval Warm Period, Little Ice Age and 20th century temperature variability from Chesapeake Bay (Global and Planetary Change, vol. 36, issues 1-2, March 2003, Pages 17–29) - T. M. Cronin, G. S. Dwyer, T. Kamiya, S. Schwede, D. A. Willard
- Nørlund, Poul. Buried Norsemen at Herjólfsnes: An Archæological and Historical Study; C.A. Rietzel (1924)
- The Little Ice Age and Medieval Warm Period in the Sargasso Sea (Science, vol. 274. no. 5292, pp. 1503 – 1508, 29 November 1996) - Lloyd D. Keigwin
- The Little Ice Age and Medieval Warming in South Africa (South African Journal of Science 96: 121-126, 2000) - P. D. Tyson, W. Karlén, K. Holmgren and G. A. Heiss
- The 'Mediaeval Warm Period' drought recorded in Lake Huguangyan, tropical South China (Holocene, vol. 12, no. 5, pp. 511–516, 2002) - Guoqiang Chu, Jiaqi Liu, Qing Sun, Houyuan Lu, Zhaoyan Gu, Wenyuan Wang, Tungsheng Liu
- The Medieval Warm Period in the Daihai Area (Journal of Lake Sciences, vol. 14, no. 3, pp. 209–216, September 2002) - Z. Jin, J. Shen, S. Wang, E. Zhang
- Tree-ring and glacial evidence for the medieval warm epoch and the little ice age in southern South America (Climatic Change, vol. 26, nos. 2-3, March, 1994) - Ricardo Villalba