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The Summer Olympics
Global warming

Increasing heat may dash dreams of
Kuala Lumpur, Jakarta, Seoul/Pyongyang,
Baku, Rome, Chicago and New York


The International Olympic Committee’s decision to move the marathon and race walking events at this summer’s Tokyo Games to cooler Sapporo -- over 1,000 km to the north -- left the organizers and some athletes dismayed. This is only the beginning. A combination of rising temperatures and broadcasting considerations threatens the future of the Summer Olympics as we know them.

section.1 Global warming is likely to remove 60% of possible cities from contention, while making Southeast Asia completely unfit.

By August 2050, much of Asia will be too hot for Summer Olympics
(Unsuitable areas, based on simulated heat stress index)

Alert level
  • Severe warning
  • Warning
  • Caution
  • Low risk

Number of cities ill-suited to holding Olympic Games in August

122 /193cities worldwide
Southeast Asia
East Asia
Middle East
South Asia
North and Central America

Including cities at southern high latitudes where sun sets early in July and August, those at elevations of over 1,500 meters

Climate change will create a plethora of challenges, one of which will be finding a place that is not too hot to handle the Olympics. When Nikkei ran major climate simulations on 193 cities around the world, we found that more than 60% of possible locations are likely to become unsuitable to host the games in August due to extreme heat and other conditions. This is up from about 40% before 2000. And as we will explore later, solving the problem by holding the games at another time of year is more complicated than it sounds.

In Southeast Asia, home to fast-growing economies that hope to bring the games to their shores, there is unlikely to be a single appropriate Summer Olympic venue.

Heat stress index used to determine risk of heatstroke

Heat stress index

(air temperature,
solar radiation,

Heat stress index alert level (International Institute for Race Medicine)

Heat stress indexAlert level
>28Severe warning
<18Low risk

Heat stress index alert level by event/organization

Heat stress
MarathonTennisSoccerTriathlonJapan Sport
32Additional rest
31Exercise should be
avoided in principle
30Very high risk
Additional rest
High riskSevere warning

First, we put together a list of 193 possible hosts using certain criteria: a population of 1 million or more; a place in the top 300 cities by the latest economic growth indicators compiled by the Brookings Institution; and prior Olympic bids. We then examined a range of climate analyses based on satellite data along with major climate simulations for each area. In addition, we considered the heat island effect and included population and energy consumption data in our model.

Since the IOC plans to pay more attention to climate factors in choosing future hosts, we looked at the Wet Bulb Globe Temperature (WBGT) index, a composite widely used in sports science to estimate heat stress. The WBGT takes into account temperature, humidity, wind and other weather conditions that impact athletes to help determine whether an event should be canceled or suspended.

Of all the Olympic sports, marathon running is one of the most physically demanding. It also attracts large crowds. So it has a significant bearing on IOC decisions.

“A WBGT reading of 28 is one key threshold for marathons,” said Yuri Hosokawa, an assistant professor at Waseda University and an expert involved in developing international heat safety guidelines for sports. World Athletics’ Dr. Stephane Bermon agrees that extreme caution is advised when competing under a WBGT level of 28.

That number is important for spectators and volunteers too. The Japan Sports Association’s guidelines say an estimated WBGT of 28 or higher requires a “Severe Warning” because, above this level, heatstroke cases increase sharply among both athletes and spectators.

Cities located at high latitudes, where the sun sets early, and those located 1,500 meters above sea level or higher were included in our unsuitable city list because it is already difficult to hold the Olympics in such places.

Number of Asian cities ill-suited to
hosting Olympic Games in August
1970-2000 August
2050 August
2050 October
Alert level
  • Severe warning
  • Warning
  • Caution
  • Low risk

Until 2000, Malaysia’s Kuala Lumpur, Indonesia’s Bandung, Semarang and Surabaya were barely cool enough to host the Summer Games. By 2050, they will likely be too hot. Both Seoul and Pyongyang -- often mentioned as possible, richly symbolic joint hosts -- are also projected to drop off the list of candidates by then. Although Jakarta plans to bid to host the 2032 Summer Olympics, its heat stress index was already a little above 28 in 2000. Up to 2050, the gap between ideal and actual climate conditions will only widen.

The Azerbaijani capital of Baku looks destined to be unsuitable, too, much to the chagrin of autocratic President Ilham Aliyev, who has staged a spirited diplomatic campaign to bring the games to his oil-rich country.

section.2 Doha offers a frightening preview of a fast-warming world.

Climate change and its side effects are advancing at an alarming rate, forcing sports organizations to adapt. The 2019 World Athletics Championships in Doha offered a preview of what could happen when they do not adjust quickly enough.

The championships in the Qatari capital were marred by scenes of exhausted, collapsing athletes being carted away in wheelchairs due to the searing heat.

The organizers were well-aware of the risk. They poured money into a powerful air-conditioning system for the stadium. They moved the event to September and October, from August. And in a particularly unusual move, the marathon was started at midnight to avoid brutal daytime temperatures. That was the only time the WBGT was predicted to be below 28, based on an analysis of data for the past 30-plus years by researchers for the World Athletics.

The actual conditions were far worse. The temperature ranged from 30 C to 32.7 C, with 73% humidity, resulting in a WBGT reading of about 30 -- higher than the maximum of 28. Twenty-eight of the 68 runners who entered the marathon failed to finish.

The IOC fears a similar situation could unfold at the 2020 Games, damaging its reputation. The disaster in Doha spurred the decision to move the endurance events to Sapporo. The larger lesson is that climate criteria for the Summer Games need to be much stricter than in the past.

Weather conditions during World Athletics Championships 2019 in Doha, Qatar

Source: Reports by Stephane Bermon of World Athletics, et al in Frontiers. Heat stress index calculated based on highest temperatures during World Athletics Championships held from 1980 to 2016

Comparison between Doha, Tokyo and Sapporo

Tokyo measurement taken on Aug. 3, 2018; half-hourly course-wide average
Source: Data released by Chukyo University professor Takaaki Matsumoto and others, Japan’s Environment Ministry, World Athletics

Despite the risks, the IOC’s abrupt decision to relocate the races took the Tokyo Organizing Committee and Japanese officials by surprise. When the two sides had discussed measures to cope with the summer heat, a venue change was not among the options. The Japanese had the impression the IOC would be satisfied with their plans to hold events in the early morning or in the evening.

But the Tokyo organizers now concede that hotter summers are rendering long-term climate data obsolete, and that the extraordinary circumstances may call for extraordinary measures. Takao Akama, a medical director for the organizing committee, said the body now uses data for the past several years to assess health hazards.

According to NASA, the 2010s were the hottest decade in history, and 2019 was the second-warmest year on record.

section.3 Commercialism and U.S. clout sway Olympic decision-making.

A logical solution might be to hold the games in cooler months. The IOC has the power to decide the timing and has promised to be more flexible for the sake of the athletes. In reality, however, the power structure behind the Olympic machine limits that flexibility.

Breakdown of the IOC’s revenue sources in 2018

Chronological changes in the IOC’s revenue from broadcast rights

Number of markets where Summer Games were broadcast

Source: IOC

For decades, U.S. media giant NBC Universal has held the exclusive Olympic broadcasting rights in the U.S., the biggest market. In 2011, NBC agreed to a $4.38 billion contract with the IOC to show the games through 2020. In 2014, it added a $7.65 billion deal for the rights from 2021 to 2032.

The media unit of cable operator Comcast has been a reliable source of big money for the IOC. The North American media industry supplied more than a third of the committee’s total income. This gives the broadcaster quite a bit of power, and it strongly prefers to have the Summer Games in July and August, when the domestic U.S. sports scene is relatively quiet.

How Olympic schedules have changed

*Denotes a high-latitude city in Southern Hemisphere; games held mainly in autumn or later due to early sunset. Dates of 2028 Olympics are not yet fixed.

Total numbers of viewers in the U.S. for Olympics held outside the U.S.

The 2000 Summer Olympics, held in Sydney from Sept. 15 to Oct. 1, showed the downside of scheduling the games outside the July-August window. They were held later because the sun sets early in August, the Australian winter, and broadcasting outdoor events in the dark would not have been cost-efficient. But the shift came at a cost for NBC: low ratings. The average total viewership for Sydney was 30% below the 2012 London Games, which attracted the most eyeballs for an Olympics outside the U.S.

It was not as if holding the event late was unprecedented.

In the early years of the modern Olympics, the games were stretched out over nearly six months. The current format centered on July and August started with the 1932 Games in Los Angeles.

The Tokyo Olympics in 1964 started in October, however, as the summer was considered too hot even then, noted Takaaki Matsumoto, an expert on heatstroke in sports at Chukyo University. “Holding the Olympics in July and August is unreasonable,” he said.

NBC says it would strive to maximize viewers regardless of where and when the games are held. “Our goal is always to showcase the Olympics to the widest possible audience, whenever the IOC and the host city decide to stage them,” said Chris McCloskey, vice president of communications for NBC Sports Group.

But the 2024 Paris Olympics and 2028 Los Angeles Games have already been slated for late July through early August, and for NBC, truly maximizing viewers would require sticking to that time frame at least through 2032. Within the IOC itself, power "lies securely in the hands of Europeans, who occupy 40% of member seats," noted Robert Barney, a professor at Western University in Canada.

It is not only NBC that likes the status quo. July and August are also convenient for organizing committees because it is easier to recruit volunteers during summer vacations, which can help to keep costs in check.

Hosting hopefuls in Southeast Asia, on the other hand, would only be suitable if the games were held in winter -- right in the thick of the U.S. professional football, basketball and hockey seasons.

section.4 The Olympic Movement is losing momentum.

Olympic bids in decline

  • Cities that withdrew bids
  • Cities in developed countries or cities with Olympic hosting experience
  • Cities in emerging economies

Source: IOC, Games Bids

Some experts suggest the answer is to confine the Olympics to colder cities, which are concentrated in advanced countries. Trouble is, fewer and fewer of them want the games. Time and again, hosts have vowed to limit costs by using existing facilities as much as possible, only to end up with overruns and a heavy financial burden.

A number of bidders have withdrawn from the running due to opposition from their residents: Barcelona, Boston, Budapest, Davos, Hamburg, Krakow, Munich, Oslo, Rome, Stockholm and Toronto, among others.

All this has already badly damaged the Olympic brand and shaken the IOC, said Bent Flyvbjerg, a professor at Oxford University and expert on the economics of the games.

“The most important thing that the IOC could do is to help manage down the costs of the games to a level where more countries can afford them and would therefore bid … and then choose countries with a conducive climate,” Flyvbjerg said. Another way to cap the costs would be to hold the Olympics at “one appropriate location” every time, he added.

Athens, the city where the modern Olympics began, might seem like a good candidate. But, again, climate data suggests the Greek capital would be too hot to host the games by 2050.

The same problem applies to emerging countries that might otherwise be ambitious, enthusiastic hosts.

Until 2008, North America generated more than 60% of the IOC’s broadcasting revenue. That has changed as other markets have grown: North America’s ratio fell to 50% between 2013 and 2016. Stephen Greyser, a branding expert at Harvard Business School, said, “Although hosting Olympics is always a big loss, for emerging countries like Saudi Arabia sports events are a really big thing as an image builder. They are keen on following the Beijing Olympic model.” Western control over the Olympics has long been a sore spot for countries like Indonesia, and as economic fortunes change, new players will surely have more influence.

Regional breakdown of IOC broadcast rights income for the IOC

Composition of IOC members by region

Yet, the fact remains that many would-be hosts will be taken out of contention by global warming.

Cities in emerging countries could conceivably team up with colder partners to share the events, but this seems like headaches waiting to happen. Overcoming conflicting interests and ensuring local enthusiasm would be tough.

This much is clear: Climate change is endangering the Summer Olympics.

The WBGT heat index factors in temperature, humidity, airflow and solar radiation data. Forecasts for 2050 were calculated by averaging four high-resolution sets of the latest comparable data (CMIP6), derived from global climate change prediction models developed by meteorological agencies in each country. Temperature data was adjusted for the heat island effect to improve accuracy in urban areas, on the advice of Manabu Kanda, an expert in urban meteorology at the Tokyo Institute of Technology, and other professors. For comparison, we used annual averages for 1970-2000 on WorldClim, a weather database compiled by researchers at the University of California. The data is used by the United Nations, among others. The standard for determining it would be "difficult to hold" the Olympics was based on international standards for marathons. The heatstroke risk to audience members and volunteers was also considered.

Yuichiro Kanematsu and Francesca Regalado
Hiroshi Kunou
Takeshi Sato
Hiroyuki Miyashita

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