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The "little" Medieval Warm Period in Southeast Tibet

09 Nov 2022 | Science Notes

From the CO2Science Archive: Climate alarmists have long worked to convince the world that late 20th-century temperatures were unprecedented over the past one to two millennia, attempting to discredit the climate-realist contention that the Medieval Warm Period of a thousand or so years ago was equally as warm as, or even warmer than, it has been recently. In doing so, however, both sides of the debate have neglected to focus attention on a much shorter period of time in the early 1400s that a number of studies have also identified as being anomalously warm; and we here review another study that finds strong evidence for its existence.

Paper reviewed: Yang, B., Kang, X., Brauning, A., Liu, J., Qin, C. and Liu, J. 2010. A 622-year regional temperature history of southeast Tibet derived from tree rings. The Holocene 20: 181-190.

What was done
The authors developed a tree ring-width history spanning the time interval AD 1377-1998 from Tibetan juniper (Cupressus gigantea) trees growing at a site just north of the deep gorge of the Yarlung Tsangbo River of southeast Tibet, from which they developed a linear regression model between ring-width and mean January-June temperature that accounts for 35% of the variance of this parameter over the period 1961-1998.

What was learned
Yang et al. identified a number of relatively warmer and cooler intervals throughout their 622-year record, among the former of which were several that exceeded late 20th-century warmth. The two most striking of these short-term warm periods were those of 1443-1466 and 1482-1501; and as best we can determine from their graphical representations of the data, annual temperatures during the second of these two warm periods exceeded those of the late 20th century by as much as 0.75 degC, while 11-year smoothed temperatures of the first of the two warm periods exceed those of the late 20th century by as much as 0.3 degC.

What it means
Evidence continues to accumulate for periods of warmth in the AD 1400s that significantly exceeded late 20th-century warmth. For more examples of this warmer-than-late-20th-century warm period, see the materials we have archived in the CO2Science Subject Index under the heading of Little Medieval Warm Period.

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