The extraordinary severe winters in which it was so cold that the river Yodo froze at Osaka (34°39'N, 135°32'E) and its vicinity had been successively occurred around A. D. 1820, where the eustatic curve established by Van Veen proves its minimum point during the recent 250 years. (Fig. 1)
The great famines in the period of recorded history in Japan had been occurred in the epochs of Tenmei (A. D. 1782-A. D. 1787) and Tenpo (A. D. 1833-A. D. 1839), holding the severe period of winters between them.
The secular rising trend of winter and summer temperatures in the recent instrumental age in Japan. (Fig. 2) is considered to be connected with the trend of warming from so called “Little Ice Age” in the beginning of the 19th century in Japan, in which the climate is generally characterized by the predominance of cold and snowy winters and of cooler and pluvial summers in Japan.
It must be noticed that the amount of precipitations seems to have been changing with the opposite tendency in the Pacific side of Japan and in the northern part of Japan Island, that is to say, Hokkaido and Korea. (Fig. 3)
By analogical reasonings and synthetic estimations, the following presumable conclusions are derived on the climatic conditions in the historical age of Japan.
(i) The climate around A. D. 700 is concluded to be colder in winters and cooler and more rainy in summers than at present.
(ii) “Little Climatic Optimum” is presumed centering around the 9th century, in which the climate was generally warmer and drier in the central and south-western part of Japan, but probably more rainy in Hokkaido districts than today.
(iii) Corresponding to the PARIA Emergence of the eustatic curve of Fairbridge, the significant deterioration of the climate appears to have set in towards the 15th century, in which it was presumed to be severe in Japan and dry in summer in Korea.
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