A blockbuster Chinese study of Tibetan tree rings by Lui et al 2011 shows, with detail, that the modern era is a dog-standard normal climate when compared to the last 2,500 years. The temperature, the rate of change — it's all been seen before. Nothing about the current period is "abnormal", indeed the current warming period in Tibet can be produced through calculation of cycles. Lui et al do a Fourier analysis on the underlying cycles and do brave predictions as well.
In Tibet, it was about the same temperature on at least four occasions — back in late Roman times (those chariots!), then again in the dark ages (blame the collapse of industry), then in the middle ages (the Vikings?), then in modern times (blame the rise of industry).