Report Warns: Japan Faces 99 Times More Heatwaves with Intensified Global Warming

W. Syaban

March 28, 2025

A recent study shows that global warming might lead to "once-in-a-century" heat waves occurring every year.

Japan might encounter heat waves that occur once every hundred years annually, as cautioned by the nation's weather service.

A report published on Wednesday revealed that if the global average temperature increases by 4°C, "centennial extreme temperatures" – which were historically observed just once every hundred years – could happen as frequently as 99 times each century in Japan. In such a case, these extremely high temperatures would likely exceed those seen before industrialization by almost 6°C.

The report entitled "Climate Change in Japan 2025" was jointly authored by the Japan Meteorological Agency and the Ministry of Education, Culture, Sports, Science, and Technology.

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This research expands upon a comparable study carried out in 2020 and indicates that since 1898 through to 2024, the mean temperature in Japan has been rising at a pace of 1.4 degrees per century.

The document emphasized an increase in what were termed "extremely hot days"—those featuring peak temperatures reaching 35 degrees Celsius—and "real summer days" where the highest temperature surpassed 30 degrees.

Two extreme heat events in Japan, occurring in July 2018 and July 2023, could not have taken place without global warming The report noted, highlighting how global warming influences the frequency and severity of extreme weather occurrences.

The report further indicated that should the global mean temperature rise by 4 degrees, Japan could expect an extra 17.5 extremely hot days annually along with 46.2 fewer instances of minimum temperatures falling below freezing.

Alternatively, if global temperatures remained under the 2-degree Celsius threshold established by the Paris Agreement, Japan could experience approximately three additional extremely hot days each year along with about 16.6 fewer nights where the temperature drops below freezing.

The document also noted that the impacts of global warming would intensify in major cities as a result of urbanization.

It was observed that the current average temperature in Japan stood at 2.5 degrees above the reference level, established as the mean from 1929 to 1958.

In metropolitan regions like Tokyo, Osaka, and Nagoya, the temperature increased to 3.5 degrees.

The report likewise outlined how global warming impacts precipitation patterns, including rainfall and snowfall, as well as tropical cyclones, which could influence Japan.

The prediction indicated that instances of extreme precipitation would grow both in frequency and intensity as a result of global warming. Although overall snowfall was forecasted to decline, significant snowfalls were projected to happen during severe weather events.

The report also indicated that tropical cyclones close to Japan were expected to become more intense.