Photo/Illutration The 80-kilometer-wide eye of Typhoon No. 8, 100 km west-northwest of Kumejima island in Okinawa Prefecture, can be seen in this satellite image taken on July 8, 2014. (Provided by the Japan Meteorological Agency)

Typhoons are traveling much slower and causing more damage around the Japanese archipelago in September, a trend that could worsen because of global warming, researchers said.

“With global warming advancing, the combined effects of slower typhoons and strengthened downpours could result in larger-scale devastation,” said Munehiko Yamaguchi, a chief researcher at the Japan Meteorological Agency’s Meteorological Research Institute.

Scientists from the institute and elsewhere studied the speeds of typhoons between 1980 and 2019 by region and month.

The results showed that typhoons passing over the Tokyo metropolitan area in September were 35 percent slower in the last two decades compared with those in the first 20 years of the study.

The speed decline ratios were 33 percent for Osaka Prefecture and 26 percent for Okinawa Prefecture, they said.

The slower speeds prolong the country’s exposure to heavy rain and strong winds from the storms.

One factor cited in the study is that autumn weather is arriving later because of global warming, resulting in weaker prevailing westerly winds that can drive away typhoons.

Computer simulations of the effects of climate change indicate that typhoons reaching Japan will travel slower not only in September but also in October.

Huge storms reported in 2019, such as Typhoon No. 15, which caused heavy damage mainly in Chiba Prefecture, and Typhoon No. 19, which had record rainfalls, were 40 percent slower than in conventional years.

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