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Little Ice Age (“LIA”)

Filed under: — group @ 28 November 2004 - (Français)

Term originally introduced in the late 1930s by Matthes (1939) to describe a broad interval of the late Holocene during which significant glacial advances were observed. In the climatological literature the LIA has now come to be used to characterize a more recent, shorter recent interval from around A.D. 1300 to 1450 until A.D. 1850 to 1900 during which regional evidence in Europe and elsewhere suggest generally cold conditions. Variations in the literature abound with regard to the precise definition, and the term is often used by paleoclimatologists and glaciologists without formal dates attached. The attribution of the term at regional scales is complicated by significant regional variations in temperature changes due to the the influence of modes of climate variability such as the North Atlantic Oscillation and the El Nino/Southern Oscillation. Indeed, the utility of the term in describing past climate changes at regional scales has been questioned [see e.g. Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, 42, RG2002, doi: 10.1029/2003RG000143, 2004 and references therein.] A number of myths or exaggerations can still be found in the literature with regard to the details of this climate period [see Jones and Mann, 2004]. These include the citation of frost fairs on the River Thames as evidence of extreme cold conditions in England. Thames freeze-overs (and sometimes frost fairs) only occurred 22 times between 1408 and 1814 [Lamb, 1977] when the old London Bridge constricted flow through its multiple piers and restricted the tide with a weir. After the Bridge was replaced in the 1830s the tide came further upstream and freezes no longer occurred, despite a number of exceptionally cold winters. Winter 1962/3, for example, was the third coldest winter recorded in instrumental records extending back to 1659, yet the river only froze upstream of the present tidal limit. It is also sometimes claimed that the extreme cold of the “Little Ice Age” impeded the navigation of a Northwest Passage in the Canadian Arctic during the early 19th century. However, an exhaustive study of 19th century explorer logs for the region yields no evidence of conditions that would be considered unusually cold by modern standards.

See also “Medieval Warm Period”.

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