Climatic Change in March Temperature Deduced from Phenological Record for Flowering of Cherry Tree in Tokyo since the Late 18th Century

概要

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The change in spring temperature in Tokyo since the late 18th century was reconstructed using the phenological data of flowering for cherry trees (Prunus jamasakura) from old records. Full flowering dates of cherry trees were closely related to the monthly mean temperatures of March using the DTS method. This method offered accurate estimations of the full flowering dates for P. jamasakura from old documents in the late 19th century, then it was introduced with a reversed procedure, namely monthly temperatures for March were estimated from full flowering dates. The root mean square error of 5-year mean value of March temperature fell within 0.5℃ in the late 19th century. The result showed that there was a cold time from 1810's to 30's with the estimations less than 5℃. This pattern of change in temperature almost synchronizes that in Kyoto. In western and central Japan, it seems that about 2℃ of the large scale climatic warming in spring initiated in the early 19th century, which was the last cold time in the Little Ice Age, and continued to the present.
1998-03-31