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A 2000-Year Tibetan Temperature History
Reference
Yao, T., Thompson, L.G., Duan, K., Xu, B., Wang, N., Pu, J., Tian, L., Sun, W., Kang, S. and Qin, X. 2002. Temperature and methane records over the last 2 ka in Dasuopu ice core. Science in China (Series D) 45: 1068-1074.

What was done
Among other things, the authors derived a 2000-year proxy temperature (18O) history from an ice core retrieved from Dasuopu glacier (2823'N, 8543'E), which is located in the central Himalayas, Tibet.

What was learned
In the words of the authors, temperature in the first century A.D. "was low and [was] followed by a significant increase until 730 A.D.," whereupon it "reached its maximum during 730-950 A.D., then it lowered again, which persisted until 1850 A.D.," after which "temperature has increased gradually to its present levels."

What it means
These intervals correspond, respectively, to the Dark Ages Cold Period, the Medieval Warm Period, the Little Ice Age and, near the very end of the record, the Modern Warm Period, which distinctive climatic regimes are evident in the records of many sites from all around the world. They demonstrate the reality of a millennial-scale climate cycle that operates independently of changes in the air's CO2 content. In addition, the Dasuopu temperature record demonstrates the importance of considering more than just the past thousand years when attempting to gain an appreciation for the degree of natural climate variability one must consider when attempting to assign a cause to the temperature increase of the past century and a half. In the words of the authors, "if we just analyse temperature changes in [the most] recent 1 ka, we may draw a wrong conclusion that [the] temperature recorded in [the] Dasuopu ice core goes beyond the natural variability range [near its end]."


Reviewed 19 March 2003