Research results have shown that air pollutants emitted from factories in Asian countries had the effect of suppressing the occurrence of typhoons around Japan and the Philippines.
It is said that the number of typhoons will decrease as global warming progresses, but experts point out that the pace of typhoons decreasing may slow down due to the progress of environmental measures.
NOAA = National Oceanic and Atmospheric Administration, Researcher Hiroyuki Murakami of the Geophysical Fluid Dynamics Research Institute investigated how the number of tropical cyclones such as typhoons and hurricanes has changed in the world.
Regional differences in the increase and decrease of tropical cyclones
From 2001 to 2020, compared to 1980 to 2000, ▽
decreased by 13.8% in the "northwest Pacific" around Japan and the Philippines,
▽ decreased by 15.9% in the "Southern Hemisphere" around Australia, and
▽ in the United States. In the "North Atlantic" around the east coast, it increased by 33.6%.
"Aerosol" has the effect of blocking sunlight
In order to investigate the differences between regions, we simulated over the past 40 years, taking into account changes in the atmosphere and ocean, as well as the conditions of air pollutants emitted from factories, etc., in the "Northwest Pacific" and "Southern Hemisphere". It was confirmed that the decrease in tropical cyclones such as typhoons and the increase in the "North Atlantic" were related to the increase and decrease of air pollutants.
Small particles such as air pollutants "aerosol" have an effect like a "typhoon" that blocks sunlight, so the increase in air pollutants in China and India makes it harder for the surrounding land to warm up than the sea. It is said that the wind from the west, which is necessary for the generation of typhoons and tropical cyclones, has been suppressed.
In addition, it seems that the decrease in air pollutants in Europe and the United States has changed the flow of wind over the North Atlantic Ocean, making it easier for hurricanes to occur.
The decline in the Southern Hemisphere is a reaction to that.
The pace of decrease in the number of typhoons may slow down
Efforts to reduce air pollutants are underway worldwide.
According to many research results, tropical cyclones such as typhoons are expected to decrease while increasing as global warming progresses, but Murakami said that the pace of decrease will increase as aerosols in Asia are reduced in the future. It may be dull.
Researcher Murakami said, "Reducing air pollutants is very beneficial to health, but for the first time it has been found that there are side effects that alleviate the reduction of typhoons. It is necessary to take these side effects into consideration and proceed with future disaster prevention measures. I'm talking.
Expert "Achievements that attract a great deal of attention both socially and academically"
Regarding this research, Associate Professor Yoshiaki Miyamoto of Keio University, who specializes in meteorology and is familiar with the mechanism of typhoons and cumulonimbus clouds, said, "A study focusing on the relationship between artificially discharged aerosols and the ease of typhoons. This is the first time for us to receive a great deal of attention both socially and academically. Further research is expected in the future, such as what the future impact will be. "