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Evidence for a Medieval Warm Period and Little Ice Age in Central Japan
Adhikari, D.P. and Kumon, F. 2001. Climatic changes during the past 1300 years as deduced from the sediments of Lake Nakatsuna, central Japan. Limnology 2: 157-168.

What was done
Noting that instrumental climate records are insufficient to be used alone in understanding natural climate variability, the authors analyzed the total organic carbon, total nitrogen and sand content of lake sediment cores extracted from Lake Nakatsuna in central Japan (3630'N, 13751'E) to produce a proxy record of climate for this region that covers the past 1300 years.

What was learned
Analysis of the proxy indicators revealed two distinct climatic intervals: the well-known Medieval Warm Period (AD 900-1200), which Adhikari and Kumon say was "warmer than any other period during the last 1300 years," and the Little Ice Age (AD 1200-1950), which was punctuated by three major cold phases: AD 1300-1470, 1700-1760 and 1850-1950.

What it means
The evidence for a global Medieval Warm Period and a global Little Ice Age keeps getting stronger by the day (see both headings in our Subject Index). Clearly, the Intergovernmental Panel on Climate Change should never have abandoned their original climate history of the world - which more accurately depicted these significant climatic excursions (Houghton et al., 1990) - in favor of the flawed "hockey stick" plot of Mann et al. (1998, 1999). And how ironic is it that the location of the international conference where the seeds of this abandonment were sowed - Kyoto - is within a stone's throw (cartographically speaking) of Lake Nakatsuna!

Houghton, J.T., Jenkins, G.J. and Ephraums, J.J. (Eds.) 1990. Climate Change: The IPCC Scientific Assessment. Cambridge University Press, Cambridge, UK.

Mann, M.E., Bradley, R.S. and Hughes, M.K. 1998. Global-scale temperature patterns and climate forcing over the past six centuries. Nature 392: 779-787.

Mann, M.E., Bradley, R.S. and Hughes, M.K. 1999. Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical Research Letters 26: 759-762.

Reviewed 29 March 2006