TOKYO - Organisers of next year's Tokyo Olympics are testing a number of measures to counter the expected scorching heat next summer when outdoor track events are held.

So far, at least one test has failed to protect endurance athletes from the effects of climate change, a global problem that could have even greater ramifications for future Summer Games.

With climate researchers warning that marathon runners in the 2020 Olympics would face unprecedented heat levels, some runners may decide to sit out the prestigious event.

As part of a test event held on Aug 15 in the Odaiba district of Tokyo, the women's triathlon started at 7.30am. The overnight low had not fallen under 25 deg C, a common occurrence during the hot and humid Tokyo summers.

Despite the early morning start, the temperature in central Tokyo was 29.1 deg C when the starter's gun went off.

Cassandre Beaugrand, a competitor from France, began feeling uncomfortable after completing the 1.5km swim and 40km bicycle portion of the event. She completed the 5km run and finished 19th.

Race organisers had shortened the run portion by half because of the heat.

Still, Beaugrand complained of abdominal pain after the race and was taken to a hospital where she was diagnosed with dehydration. Doctors immediately began an IV drip to help her replenish liquids.

The Odaiba area was cloudy when the triathlon began. But in central Tokyo, the high temperature that day was 32.6 deg C with an average humidity of 83 per cent.

Stephanie Deanaz, the French team coach who was in Tokyo that day, said the competitors would have been in an even more serious situation if the skies had been clear and the race had not been shortened.

She said the start of the event during the Tokyo Olympics should be pushed back to 6.30am.

The Tokyo Olympics will begin on July 24.

Statistics support the rising concerns both in Japan and abroad about holding the sports events during the hot Tokyo summer.

According to the Japan Meteorological Agency, over the 10-year period between 2010 and 2019, the high temperature in Tokyo between July and August was, on average, 31.3 deg C, with average humidity of 75.5 per cent.

The Tokyo Medical Examiner's Office said there have been five years over the past decade, including 2019, when the number of deaths caused by heatstroke in Tokyo's 23 wards exceeded 100.

The summer of 2018 was an especially hot one. In July alone, 1,032 people around Japan died from heatstroke, a record figure for a single month.

The Meteorological Research Institute analysed the extent to which global warming caused temperatures to soar in summer 2018 and concluded that the torrid heat would not have occurred without global warming.

"There is a high possibility of hot summers occurring at an unprecedented frequency in the future," Yukiko Imada, a senior researcher at the institute, said.

THREAT TO FUTURE SUMMER GAMES

Global warming has become a threat not only to the 2020 Tokyo Games but also to all future Summer Olympics.

A research team at the University of California at Berkeley published a report in August 2016 in Lancet, the British medical journal. One conclusion reached was that the number of cities capable of hosting the Summer Games would drastically decrease because of rising temperatures worldwide.

The team estimated temperatures and humidity in July and August 2085 if nothing is done to combat global warming.

It forecast that of the 645 cities in the Northern Hemisphere with the necessary populations and geographical conditions to host a Summer Olympics, only 33 would be able to hold a marathon race with no problems.

In Asia, the only cities meeting those conditions were Ulaanbaatar in Mongolia and Bishkek in the Kyrgyz Republic.

Referring to future Summer Olympics, the article said: "The Games might be run entirely indoors, in winter, or without the marathon and other heat-sensitive endurance events."

Some athletes have already decided not to focus on the marathon in the Tokyo Olympics.

The Marathon Grand Championship was held in Tokyo on Sept 15 as a qualifying race for Japanese runners seeking berths in next year's Olympic marathon.

But Yuki Kawauchi, who won the 2018 Boston Marathon, did not enter the race.

Kawauchi, who has not hidden his concerns about running in the Tokyo heat, said he was instead setting his sights on the marathon at the world track championships that will be held on Oct 5 in Doha.

Yuko Arimori battled against the heat when she won the silver medal in the marathon at the 1992 Barcelona Olympics and the bronze at the 1996 Atlanta Olympics. She said a number of top-ranked runners from abroad decided to sit out those races because of their own concerns about the heat.

"Even with the prestige associated with the Olympics, it would not be surprising if some professional marathon runners decided not to take part if they judged the risks of doing so as being too high," Arimori said.

Eliud Kipchoge of Kenya is the current men's marathon record-holder with a time of 2 hr 1 min 39 sec. In response to questions from The Asahi Shimbun, he expressed no concerns about running next year in Tokyo.

"Tokyo's heat is a different sort of heat from Kenya's, but I don't worry about it," he said. "Every athlete has to cope with it, so I am not the only one who has to adapt to it."

However, Stephen Ole Marai, a Kenyan coach who has developed many Olympic runners, appeared worried about what some Kenyan runners would have to face in the Japanese capital.

Noting that many Kenyan marathoners train at high altitudes where the daily highs do not exceed 30 deg C and humidity is low, he said the Tokyo marathon would prove a gruelling event for many runners.

He added that some athletes might worsen their physical condition if they trained in the high temperatures and humidity of Japan just before the event.

The Tokyo Olympics will be held in the middle of summer because of conditions set by the International Olympic Committee. When seeking prospective hosts, the IOC states that the Games should be held in a window between July 15 and Aug 31.

The 1964 Tokyo Olympics were held in October, but that month is now in the middle of the season for many popular professional sports in North America and Europe.

When submitting its proposal for hosting the 2020 Olympics, the Tokyo committee said weather conditions for the period between July 24 and Aug 9 were "ideal" because there were many sunny days with warm temperatures.

But even the IOC has been forced to take action over the many concerns now being raised about Tokyo's hot summers.

In August, it released a pamphlet titled "Beat the Heat" that outlines various measures that could be taken to deal with the high temperatures. For example, it recommends that athletes acclimate their bodies to the Tokyo heat by training for about two weeks before the Olympics in weather conditions similar to those of a Tokyo summer.

The Tokyo Olympic organising committee has also taken a number of steps, such as starting the marathon an hour earlier, covering part of the marathon route with a heat-blocking agent to reduce surface temperatures and distributing ice-packed bags at water distribution points for the race.

Arimori said it would be ideal to allow each host city to hold the Summer Games under their best climate conditions.

But since it is not possible to change the dates for the Tokyo Olympics, she said: "While I hope the organising committee will take as many measures as possible right up until the holding of the Games, I also want athletes and spectators to be aware that they are the only ones capable of doing anything to protect their own bodies."

This story originally appeared in The Asahi Shimbun. It is republished here as part of The Straits Times' partnership with Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.