「中世温暖期(MCA)」と9世紀末の気候的不安定について

概要

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In this study, reconstruction of MCA (Medieval Climate Anomaly) through proxy data was tried to clarify its nature. At first, "prayers for rain" records were collected from "Rikkokushi", six national histories of the ancient Japan, and the climate variation was clarified by their appearance changes. Next, the climate variation of Japan was compared with those from MCAreconstruction studies on many areas in the world. Furthermore, MCA was examined by comparison with its simulation by global circulation model. The main results are as follows: 1) There remain many records on prayers for rain from the end of the first millennium to the beginning of the second millennium, which may show that it was time of warm and dry climate condition. 2) During MCA, there might have been a period of cool and moist condition around 900, specifically from 880 to 910. 3) A prevailing circulation like La Nina on the Pacific Ocean played an important role in MCA. 4) Around the Atlantic Ocean, the North Atlantic Oscillation was usually at its positive mode, and played an important role for the climate there.
2012-10-25