Climate Variations in Tokyo Since the Edo Period

Abstract

This chapter discusses climate variations in Tokyo, based on the reconstructed summer temperatures since the eighteenth century and instrumental meteorological data from the nineteenth century to the present. During the Little Ice Age, especially in the eighteenth century, remarkable cool episodes occurred in the 1730s, the 1780s, and the 1830s. These cool conditions could be a significant reason for the severe famines that occurred during the Edo period. Around the 1840s and 1850s, near the end of the Edo period, it was rather warm, which could correspond to the end of the Little Ice Age in Japan. Although there was a low-temperature period in the 1900s, a long-term warming trend could be seen, especially in winter temperatures and daily minimum temperatures, throughout the twentieth century. While annual precipitation has been increasing during the last 30 years, relative humidity has been decreasing since the late nineteenth century. This could be the result of saturated vapor pressure rise due to warming and a loss of water bodies due to urbanization. During the last century, both warmer and wetter conditions in summer and autumn, and drier conditions in winter and spring, were documented by analyzing hythergraphs.