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The Medieval Warm Period on Maui
Reference
Pau, S., MacDonald, G.M. and Gillespie, T.W. 2012. A dynamic history of climate change and human impact on the environment from Kealia Pond, Maui, Hawaiian Islands. Annals of the Association of American Geographers 102: 748-762.

Background
As many other researchers have expressed before them with respect to other locations around the world, the authors write that "the response of the tropical Pacific to climate variability such as the Medieval Climate Anomaly (also known as the Medieval Warm Period) ... is an important analogy for understanding projected future climate change." And so they set out to see what they could learn about the well-known global phenomenon on the Hawaiian Island of Maui.

What was done
Based on "high-resolution palynological, charcoal, and sedimentological analysis of a sediment core from Kealia Pond, Maui, coupled with archaeological and historical records," as they describe it, Pau et al. developed "a detailed chronology of vegetation and climate change since before human arrival."

What was learned
Most pertinent was the three researchers' finding that "a shift from dry to wet climate conditions marked the beginning of the Medieval Climate Anomaly (MCA) as evidenced by a precipitation reconstruction based on a pollen abundance index." They note, for example, that over the 2500 years of their record "there have been two major climatic events: first the MCA (AD 800-1300), followed by the Little Ice Age (AD 1400-1850)." And with respect to this finding, they indicate that "increased rainfall during the MCA in Hawai'i supports the evidence that climate dynamics during the MCA was consistent with decreasing El Nino frequency or a persistent La Nina-like state," as espoused by Crowley (2000), Bradley et al. (2003), Cobb et al. (2003) and Mann et al. (2005).

What it means
In the case of the early inhabitants of Maui, Pau et al. write that "an increase in forest resources during this wet climate interval coincided with rapid Polynesian population growth," which suggests that the Medieval Warm Period was a time of prosperity for them, especially when compared with the Dark Ages Cold Period and Little Ice Age that preceded and followed it, much as has also been found for many other places around the world. See, in this regard, various reviews archived under Medieval Warm Period in our Subject Index.

References
Bradley, R.S., Hughes, M.K. and Diaz, H.F. 2003. Climate in medieval time. Science 302: 404-405.

Cobb, K.M., Charles, C.D., Cheng, H. and Edwards, R.L. 2003. El Nino/Southern Oscillation and tropical Pacific climate during the last millennium. Nature 424: 271-276.

Crowley, TJ. 2000. Causes of climate change over the past 1000 years. Science 289: 270-277.

Mann, M.E., Cane, M.A., Zebiak, S.E. and Clement, A. 2005. Volcanic and solar forcing of the tropical Pacific over the past 1000 years. Journal of Climate 18: 447-456.

Reviewed 16 January 2013