As global warming intensifies, a lot of cities will become too hot to hold the summer Olympics. A new study in The Lancet has concluded that in the northern hemisphere, only 33 cities of a plausible Olympic size are reasonably likely to be cool enough—and half of those will be in Britain.
To come to this conclusion, Kirk Smith of the University of California at Berkeley and his colleagues assumed that the standard of whether a city can host the Games is whether athletes can run the marathon, a key event of the modern Olympics. In the US Olympic team trials this year in Los Angeles, where peak temperatures reached 25.6 °C (78.1 °F), only about 70% of the elite athletes taking part finished their race.
To assess whether a city is too hot, the researchers used something called the wet-bulb globe temperature. It’s a measure of the heat stress that an athlete might suffer, taking into account factors such as temperature, humidity, and wind speed. Smith and his team posited that any city that has a more than 10% chance of having a wet-bulb globe temperature of more than 26 °C in the shade during the summer months will not be a viable venue for the marathon.
Smith’s team analyzed only cities in the northern hemisphere (because it has 90% of the world’s population), and only those with populations larger than 600,000 (because that’s been the threshold for host cities since World War Two). Of those, only 33 them met the temperature criterion.
The list contains three cities in North America (San Francisco, Vancouver, and Calgary), two in Asia (Bishkek and Ulaanbaatar), three in eastern Europe (St Petersburg, Riga, and Krasnoyarsk), and 25 in western Europe: The Hague, Amsterdam, Rotterdam, Copenhagen, Oslo, Stockholm, Gothenburg, Helsinki, Malmo, Dublin, plus 15 cities in the UK, which include, Belfast, Birmingham, Bristol, Coventry, Edinburgh, Glasgow, Leeds, Leicester, London, Liverpool, Manchester, Newcastle, Nottingham, Sheffield, and Southampton.
The UK leads the charts because it’s among the most populous of the top 10 countries considered least vulnerable to climate change, according to an index developed by the University of Notre Dame. Other northern hemisphere countries among the top 10 are Norway, Denmark, Finland, and Sweden, which all have one or more cities in the list of viable host cities for the Olympics. (It seems Switzerland, Germany, and Singapore, which are also in the top 10 list, are too warm according to the analysis.)
Of course, the marathon is only one event in the summer Olympics, and the Games could adapt to changing conditions. But the team’s analysis is a good proxy for understanding how livable cities will be when global warming’s effects become more severe in the decades ahead.
And, if this happens to the summer Olympics, things can only get worse for the winter Olympics too. A 2014 study showed that, by 2080, only six out of 19 former host cities will be cold enough to host the winter games.