Reference
Liu, X., Shao, X., Zhao, L., Qin, D., Chen, T. and Ren, J. 2007. Dendroclimatic temperature record derived from tree-ring width and stable carbon isotope chronologies in the Middle Qilian Mountains, China. Arctic, Antarctic, and Alpine Research 39: 651-657.
What was done
Based on ring-width and δ13C data derived from long-lived Qilian juniper (Sabina przewalskii Kom.) trees located in the middle Qilian Mountains of China (37-39°N, ~99-103°E) at the convergence of the Qinghai-Xizang Plateau, the Inner Mongolia-Xinjiang Plateau and the Loess Plateau, the authors reconstructed a 1000-year temperature history of the region. This reconstruction captures approximately 75% of the temperature variance over the calibration period 1960-2000 and correlates extremely well with the Northern Hemisphere temperature reconstruction of Esper et al. (2002).
What was learned
In the words of the authors, the two sets of reconstructed temperature data (theirs and Esper et al.'s) "reveal that the Medieval Warm Period and Little Ice Age were synchronous in China and the Northern Hemisphere." In addition, they note that the two warmest intervals in their temperature reconstruction are 1060-1150 and 1900-2000, with corresponding peaks occurring around 1100 and 1999; and in carefully analyzing the graphical representation of their results, we find that the two peak temperatures are essentially identical, as best we can visually determine. However, their results do not extend as far back in time as those of Esper et al., which rise to their highest level prior to the time that Liu et al.'s history begins. Consequently, Liu et al. conclude that their reconstructed temperature history "has not included all of the Medieval Warm Period and, perhaps, not even its warmest period."
What it means
Contrary to the claims of climate alarmists, new evidence published almost weekly continues to demonstrate that the Medieval Warm Period and Little Ice Age were global in scale and largely synchronous in time, and that the Medieval Warm Period experienced temperatures that were at least as great as, but probably even greater than, those of today. The significance of these observations should be well known to all of our regular readers. For newcomers, we suggest that you visit our Medieval Warm Period Project and read what we have written there.
Reference
Esper, J., Cook, E.R. and Schweingruber, F.H. 2002. Low-frequency signals in long tree-ring chronologies for reconstructing past temperature variability. Science 295: 2250-2253.