Aono, Y. and Saito, S. 2010. Clarifying springtime temperature reconstructions of the medieval period by gap-filling the cherry blossom phenological data series at Kyoto, Japan. International Journal of Biometeorology 54: 211-219.
The authors investigated documents and diaries from the ninth to the fourteenth centuries to supplement phenological data series pertaining to the flowering of Japanese cherry trees 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." The resulting 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 are somewhat higher than present temperatures after subtracting urban warming effects." Quantitatively, that difference during the 10th century was determined to be as high as 0.5°C.