By TAKAHIRO TAKENOUCHI/ Staff Writer
August 29, 2023 at 08:00 JST
Kansai International Airport is inundated during Typhoon No. 21 in September 2018. (Asahi Shimbun file photo)
Typhoons will become more damaging because of global warming, with faster winds and heavier rainfall placing a greater human and economic toll, an Environment Ministry model forecasts.
The prediction, released July 21, is based on supercomputer calculations.
Japan is already being battered by heavier storms. Recent typhoons swamped a runway at Kansai International Airport and left parts of Tokyo under water.
A typhoon’s water content originates in the ocean. Higher sea surface temperatures result in higher rates of evaporation. Increased levels of atmospheric water vapor lead to stronger typhoons.
A previous study found that the devastating Typhoon No. 19 of 2019 dumped 11 percent more rainfall because of global warming.
Typhoon No. 19 struck eastern Japan with record rainfall. An embankment collapsed along the Chikumagawa river in Nagano Prefecture, and in Tokyo the Tamagawa river broke its banks, inundating some areas.
With that in mind, the Environment Ministry ran data into a supercomputer for two scenarios: a rise in global temperatures of 2 degrees and 4 degrees from pre-industrial levels.
It found that in a 2-degree scenario, Typhoon No. 19 would have brought 4 percent heavier rainfall to the Kanto and Tohoku regions. Rivers such as the Chikumagawa would have had a 10 percent increase in average peak flow rate, a factor in flooding.
A 4-degree rise would have increased the rainfall by 20 percent and the river peak flow rate by 23 percent.
As for wind velocity, the study looked at Typhoon No. 21 of 2018. That storm is remembered for its record-breaking winds that overturned automobiles in Osaka. It also caused a storm surge that inundated a runway at Kansai International Airport.
The ministry’s simulation predicted that Typhoon No. 21 would have had a 32.4 kph increase in maximum wind speed in a 2-degree scenario. The speed would have been 36 kph faster in a 4-degree world.
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