Global Warming Is Making Major Marathon Events More Dangerous
In a new study from Climate Central, rising temperatures caused by global warming around the world is making major marathon events more dangerous, and is preventing elite athletes from breaking records, and recreational runners from hitting their goals.
The report analyzed 221 races, and it found that 86% of them were less likely to have optimal racing conditions for runners by 2045. This data includes last week’s New York City Marathon and six other major marathons around the world in London, Berlin, Tokyo, Chicago, Boston, and Sydney.
“We’ve seen time and time again where athletes are passing out from dehydration and heat exhaustion during races and taking months to recover,” Scottish distance runner Mhairi Maclennan told CNN Sports.
“It has really significant impacts on the thickness of your blood, on how quickly your body is able to recover, on your hydration levels for days, and also your ability to train after that kind of experience, which can then delay other achievements and goals that you’re pursuing.”
The study reported that the optimal temperature for elite male marathon runners is 39 degrees Fahrenheit (4 degrees Celsius) and 48 degrees F (9 degrees Celsius) for elite women.
The Tokyo Marathon this year had a 69% chance of optimal race day temperatures for elite men, the study showed, and the odds are expected to decline to 57% within the next 20 years. The Boston Marathon’s odds are also expected to drop from 61% to 53%, and London’s is expected to go from 22% to 17%.
For elite women, the likelihood of optimal conditions is expected to decrease at five of the seven major marathons by 2045.
Copernicus, a climate monitoring agency, released data that showed 2024 was the hottest year on record; 34.88 Fahrenheit (1.6 degrees Celsius) warmer than the period before humans began burning large amounts of fossil fuels.
Higher temperatures cause greater stress to be placed on the body, especially during exercise in high humidity conditions. This makes hydration even more important throughout a marathon.
“Some of the exceptional heat experienced at the 2025 Berlin and Tokyo Marathons pushed temperatures far beyond peak performance conditions,” said Maclennan.
“That’s difficult because at the end of the day, sport is a business, and it generates revenue from spectators, and if spectators are there to see fast performances and that’s not happening because of climate change, that’s an issue for the sector.”
“We have marathons in the spring and in the autumn in the northern hemisphere, because those are the times when we get the good, cool temperatures that you need for good running performance,” Andrew Pershing, who leads the Climate Central science team and worked on the new study, told CNN Sports.
“As the climate warms, if you have a race that happens at the same week every year, that good climate is moving past you and it’s moving away. Those good conditions are becoming less and less frequent.”
Organizers could start scheduling earlier start times for races as a solution. Maclennan then said that the 2028 Olympics in Los Angeles will likely cause athletes from all over the world to acclimatize.
“The same is true for any competition where the environment is different to what you train in. There is consideration to be made into how you adapt and how you train your body to compete in those conditions.”
Eric Mastrota is a Contributing Editor at The National Digest based in New York. A graduate of SUNY New Paltz, he reports on world news, culture, and lifestyle. You can reach him at eric.mastrota@thenationaldigest.com.
