Long term variations of summer temperatures in tokyo since 1721

In Japan, summer temperatures are highly correlated with precipitation frequencies. Based on this assumption, we made an attempt to reconstruct summer (July) temperatures in Tokyo for 1721-1995 by using weather records in old diaries in the western suburbs of Tokyo. The results indicate that summer temperatures of Tokyo during the 18th and 19th centuries were estimated to have been 1 to 1.5 degrees lower than today. However, it was rather warm in the early 19th century, and rather cool in the 18th and early 20th centuries. A result of power spectrum analysis reveales several periodicities related to the solar cycle (21 and 10.5 year), ENSO cycle (6.3, 5.0 and 3.2 year) and QBO (2.18 year). Cool episodes in the 1780s, 1830s and 1900s are in accordance with poor rice harvests and severe famines. A comparison with the reconstructed July temperatures in Beijing, China shows opposite trends in the 18th century and similar trends since the late 19th century