Liu, Y., An, Z.S., Linderholm, H.W., Chen, D.L., Song, M.H., Cai, Q.F., Sun, J.S. and Tian, H. 2009. Annual temperatures during the last 2485 years in the mid-eastern Tibetan Plateau inferred from tree rings. Science in China Series D Earth Science 52: 348-359.
Based on Qilian juniper (Sabina przewalskii) tree-ring width chronologies obtained from both living trees and archaeological wood located in the mid-eastern Tibetan Plateau and centered at approximately 36.4°N, 98.5°E (which data were calibrated against measured air temperatures for the period AD 1958-2000), Liu et al. obtained a mean annual temperature history of the region spanning the 2,485-year period 484 BC - AD 2000. This record, which they demonstrated to be well correlated with other Northern Hemisphere temperature histories, indicates that the 40-year running-mean of annual temperatures centered at approximately AD 875 and AD 980 was about 0.2°C greater than the similarly averaged temperature at the end of the record (see the authors' Figure 4). A similar approximate 0.2°C temperature difference is also noted when comparing the peak reconstructed value (no time averaging) at AD 880 and AD 1990, suggesting once again that the Medieval Warm Period at this location was warmer than the Current Warm Period by about 0.2°C.