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The Medieval Warm Period in Southern Tibet
Reference
Zhu, L.-p., Zhang, P.-z., Xia, W.-l., Li, B.-y. and Chen, L.  2003.  1400-year cold/warm fluctuations reflected by environmental magnetism of a lake sediment core from the Chen Co, southern Tibet, China.  Journal of Paleolimnology 29: 391-401.

What was done
A sediment core was extracted from lake Chen Co in the Yamzhog Yum Co drainage basin of southern Tibet in the delta of the Kaluxiong River.  The core was dated by comparing sedimentary rates measured by 210Pb and absolute time horizons measured by 137Cs (Wan 1997, 1999; Benoit and Rozan, 2001), after which several environmentally-related magnetic properties of sections of the core were measured and analyzed.

What was learned
The authors report that "the 'Middle Ages Warm-period' (around ca. 1120-1370 AD) was demonstrated by recent studies in China (Zhang, 1993)," and for this same time period, they say that their newest data reveal "a warm-humid stage."  This period was followed by what they call "an intensively cold stage during ca. 1550-1690 AD, a cold-humid stage from ca. 1690-1900 AD and a warm-dry stage since ca. 1900 AD."  However, Zhu et al. note that the warm period of the past century is not as warm as the earlier 250-year warm period of the Middle Ages.

What it means
Once again, we have a demonstration of the Medieval Warm Period in Asia out-performing the Modern Warm Period in terms of both high temperatures and longevity of warmth [see Medieval Warm Period (Regional - Asia) in our Subject Index], which findings contradict the climate-alarmist claim that the Medieval Warm Period was but a barely-detectable phenomenon restricted to countries bordering the North Atlantic Ocean.

References
Benoit, G. and Rozan, T.F.  2001.  210Pb and 137Cs dating methods in lakes: a retrospective study.  Journal of Paleoliminology 25: 455-465.

Wan, G.-J.  1997.  The 210Pb dating to modern deposits.  Journal of Quaternary Science 17: 230-239.

Wan, G.-J.  1999.  The 137Cs dating with annual resolution to modern deposits - a case study in Er hai and Hongfeng Lake in Yunnan.  Journal of Quaternary Science 19: 73-80.

Zhang, D.-E.  1993.  The preliminary inferring of the "Warm Period of Middle Ages" in China.  Journal of Quaternary Science 13: 7-15.


Reviewed 24 March 2004