TOKYO -- Summer heat in the 2060s to 2080s will hit levels where school club activities involving intense exercise should be canceled in 3/4 of areas in Japan, a local research team has announced.

While the National High School Baseball Championship, commonly known as "Koshien," held annually in the height of summer has already introduced a two-part schedule to avoid games during the hottest part of the day, heat countermeasures for outdoor sports other than baseball are also likely to become an issue.

The theme of the research jointly conducted by the National Institute for Environmental Studies and Tokyo's Waseda University is how climate change will affect extracurricular sports activities. The "Wet Bulb Globe Temperature (WBGT)," a heat stress index which serves as the standard for issuing heatstroke alerts, had not previously been projected over the long term or by time of day. The research team analyzed data from 842 locations across Japan, including the time-of-day WBGT, temperature, humidity, wind speed and other factors from the past 12 years.

By combining these data points, the team built a high-accuracy predictive model that enables forecasting within narrow time windows, such as from 3 to 6 p.m., when school sports activities are most common.

They furthermore divided the country into eight regions based on past average WBGT values and created several future scenarios, including one where dependence on fossil fuels continues and another where greenhouse gas emissions are significantly reduced. For each scenario, they predicted what levels the WBGT reaches during club activity hours for at least one day in a week.

In the projections for the 2060s to 2080s, under the scenario where fossil fuel use continues, six out of eight regions are projected to reach a level where intense physical activity should be canceled during school club hours, and four regions may even require all outdoor activities to be suspended. Even in the scenario where emissions are significantly reduced, five regions would still need to restrict intense exercise.

The team also examined the impact of rescheduling club activities to the early morning hours (7-9 a.m.) or moving them indoors, but even with both countermeasures, up to four regions would still need to restrict intense exercise.

The research team stated, "If climate change progresses, continuing club activities in the same way as before will become difficult, and measures such as early morning practices or reducing outdoor training alone will not be sufficient. Fundamental changes, including adjustments to the annual schedules of tournaments and practices as well as the development of indoor training facilities, will also be crucial."

Takahiro Oyama, a researcher in biometeorology at the institute's Center for Climate Change Adaptation, commented on the future of the Koshien championship, "There have been discussions suggesting it should be held in domed stadiums, and as a researcher, I believe such measures are desirable. If it is to continue outdoors, alternatives such as moving the event to autumn may be considered."

(Japanese original by Buntaro Saito, Tokyo City News Department)