The Medieval Warm Period in Kyoto, Japan

Aono and Saito (2010) "investigated documents and diaries from the ninth to the fourteenth centuries to supplement the phenological data series of the flowering of Japanese cherry (Prunus jamasakura) in Kyoto, Japan, to improve and fill gaps in temperature estimates based on previously reported phenological data," after which they "reconstructed a nearly continuous series of March mean temperatures based on 224 years of cherry flowering data, including 51 years of previously unused data, to clarify springtime climate changes." In addition, they estimated still other cherry full-flowering dates "from phenological records of other deciduous species, adding further data for six years in the tenth and eleventh centuries by using the flowering phenology of Japanese wisteria (Wisteria floribunda)."

Aono and Saito report that their temperature reconstruction "showed two warm temperature peaks of 7.6°C and 7.1°C, in the middle of the tenth century and at the beginning of the fourteenth century, respectively," and they say that "the reconstructed tenth century temperatures [AD 900-1000] are somewhat higher than present temperatures after subtracting urban warming effects." Last of all, they add that "the general pattern of change in the reconstructed temperature series in this study is similar to results reported by previous studies, suggesting a warm period in Asia corresponding to the Medieval Warm Period in Europe."

This insightful new study provides a stellar example of both ingenuity and tedious bibliographic sleuthing, as well the significant warmth of the Medieval Warm Period at a specific location, which is said to be typical of what has been learned about the Asian continent in general by the studies of others. In addition, it suggests the importance of considering the presence or absence of urban heat island effects when comparing current and past reconstructed temperatures. And when considered in total, all of these things come together to further strengthen the likelihood that the Medieval Warm Period was truly a global phenomenon, and that its peak warmth was greater than what has been experienced to date in our day.