An attempt to evaluate the contributions of year-specific climate anomaly, long-term climate change, and urban warming to hot summers in Japan

Abstract

The contributions of year-specific climate anomaly and long-term climate changes to hot summers in Japan during the past 100 years were evaluated using surface observation data of the JMA. A number of indices were defined to indicate the severity of summer heat for each year. The time series of each index was divided into a year-specific component and a temporally smoothed component, which was divided into a nationwide non-urban component and an urban component. The non-urban component began to increase after the 1990s, whereas urban warming in cities became apparent since the 1960s although it slowed in recent decades.