This is from a paper published in a China Science Bulletin:
Abstract with my highlights:
Amplitudes, rates, periodicities, causes and future trends of temperature variations based on tree rings for the past 2485 years on the central-eastern Tibetan Plateau were analyzed. The results showed that extreme climatic events on the Plateau, such as the Medieval Warm Period, Little Ice Age and 20th Century Warming appeared synchronously with those in other places worldwide. The largest amplitude and rate of temperature change occurred during the Eastern Jin Event 343–425 AD, and not in the late 20th century. There were significant cycles of 1324 a, 800 a, 199 a, 110 a and 2–3 a in the 2485-year temperature series. The 1324 a, 800 a, 199 a and 110 a cycles are associated with solar activity, which greatly affects the Earth surface temperature. The long-term trends >1000 a of temperature were controlled by the millennium-scale cycle, and amplitudes were dominated by multi-century cycles. Moreover, cold intervals corresponded to sunspot minimums. The prediction indicated that the temperature will decrease in the future until to 2068 AD and then increase again.
While the forecast may be speculation, climate history has been a better predictor that climate models.
via New Paper “Amplitudes, Rates, Periodicities And Causes Of Temperature Variations In The Past 2485 Years And Future Trends Over The Central-Eastern Tibetan Plateau” By Liu Et Al 2011 | Climate Science: Roger Pielke Sr..