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The Little Ice Age: Its Relevance for Interpreting Modern Warming
Reference
Bakke, J., Trachsel, M., Kvisvik, B.C., Nesje, A. and Lysa, A. 2013. Numerical analyses of a multi-proxy data set from a distal glacier-fed lake, Sorsendalsvatn, western Norway. Quaternary Science Reviews 73: 182-195.

What was done
Working with what they describe as a lacustrine sediment record derived from three c. 3.5-m-long sediment cores recovered from the distal glacier-fed lake Nedre Sorsendalsvatn located 35 km inland from the coast downstream of Blabreen in Nordfjord, western Norway, the authors developed a Holocene record of glacier variability based on a multi-proxy data set consisting of sedimentological, physical and geochemical data.

What was learned
Bakke et al. report that their reconstruction accords with "glacier variability reconstructed from other sites in western Norway, including the termination of the deglaciation at approximately 10,000 cal yr BP, the 8.2 ka BP (Finse) event, the Holocene thermal optimum between ~8000 and 5500 cal yr BP, and the onset of the Neoglacial at 5500 cal yr BP," while further noting that "the largest glacial extent during the Neoglacial time period took place during the 'Little Ice Age'." They additionally indicate that these several findings are "in accordance with all glacier reconstructions available for western Norway (e.g., Nesje et al., 2001; Nesje, 2009; Vasskog et al., 2012), northern Norway (e.g., Bakke et al., 2010) and ... with glacier fluctuations in Iceland (Geirsdottir et al., 2009) and in the European Alps (e.g. Holzhauser, 2007)."

What it means
These facts clearly demonstrate that the most recent warming of the globe - which brought the earth to its current state of warmth (which is still far less than levels that were reached at earlier times in the Holocene) - began at the very coldest point of the current interglacial. Thus, there is no reason to think it out of the ordinary that the planet would subsequently experience a strong warming, or that the latter portion of that warming would be in any way unusual, unnatural or unprecedented (especially since it actually ceased over a decade and a half ago). In fact, it was no more unnatural than the cooling that had brought the plane's temperature down to that earlier and truly unique cold point in time. We should be thankful for what 20th-century warming has done for both us and the rest of the biosphere in rescuing us from the extreme cold of the Little Ice Age.

References
Bakke, J., Dahl, S.O., Paasche, O., Simonsen, J., Kvisvik, B., Bakke, K. and Nesje, A. 2010. A complete record of Holocene glacier variability at Austre Okstindbreen, northern Norway: an integrated approach. Quaternary Science Reviews 29: 1246-1262.

Geirsdottir, A., Miller, G.H., Axford, Y. and Olafsdottir, S. 2009. Holocene and latest Pleistocene climate and glacier fluctuations in Iceland. Quaternary Science Reviews 28: 2107-2118.

Holzhauser, H. 2007. Holocene glacier fluctuations in the Swiss Alps. In: Mordant, C., Richard, H. and Magny, M. (Eds.). Enironnements et cultures a l'Age du Bronze en Europe occidentale. Comite des travaux historiques et scientifiques (CTHS), Paris, France, pp. 29-43.

Nesje, A. 2009. Latest Pleistocene and Holocene alpine glacier fluctuations in Scandinavia. Quaternary Science Reviews 28: 2119-2136.

Nesje, A., Matthews, J.A., Dahl, S.O., Berrisford, M.S. and Andersson, C. 2001. Holocene glacier fluctuations of Flatebreen and winter-precipitation changes in the Jostedalsbreen region, western Norway: evidence from pro-glacial lacustrine sediment records. The Holocene 11: 267-280.

Vasskog, K., Paasche, O., Nesje, A., Boyle, J.F. and Birks, H.J.B. 2012. A new approach for reconstructing glacier variability based on lake sediments recording input from more than one glacier. Quaternary Research 77: 192-204.

Reviewed 23 October 2013