Of 221 global marathon races analyzed, 86% will see a decline in odds of optimal running conditions by 2045, including all seven World Marathon Majors, a new Climate Central analysis concluded.
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Marathon runners will have less chances of racing in optimal conditions as the planet continues to heat up, according to new research published just weeks after Berlin Marathon runners struggled in unusual heat.
The study by independent climate research group Climate Central looked at the impact of rising temperatures on 221 global marathon races, including all seven so-called World Majors, which form a championship-style competition for marathon runners. It concluded that 190 of them (86%), including all Majors, will see a decline in odds of optimal running conditions by 2045.
Optimal running conditions vary between women and men, with women at elite level running faster at warmer temperatures (10C/50F) and men at elive level running best in cooler conditions (4C/39F). Optimal running temperatures are slightly lower for recreational female runners and slighly higher for recreational male runners.
With human-made climate change increasing temperatures around the world, the chances of running in these ideal conditions are shrinking, the study concluded. Already this year, the average temperature at the Tokyo Marathon in March was 15.2C – about 8.2C warmer than usual. And in Berlin last month, the average temperature was a whopping 6.7C warmer than normal at 20.7C. In both cases, the abnormal warmth was made more likely by climate change, Climate Central found.
Earlier Start Times
Starting races earlier could reduce the impact of climate change-driven warming on race performance at some locations, according to the study. For marathons in London, Tokyo, and Boston, for example, elite male runners would benefit significantly from an earlier start, with chances of peak conditions in 2045 increasing by 44%, 31%, and 27%, respectively.
Since elite women perform better in warmer temperatures, earlier starts in Tokyo and Boston would actually decrease their chances of optimal conditions – by 41% and 18%, respectively. In Berlin and Sydney, which have the lowest probability of optimal temperatures on race days among all seven Majors, an earlier start would be beneficial for female elite athletes, too.
Ultimately, however, protecting runners and the future of marathon requires meaningful action to curb fossil fuel pollution, the study concluded.
Climate Change Increasingly Disrupting Sports
As global temperatures continue to rise and extreme weather events become more frequent and intense, the sporting world faces an array of challenges that threaten individual events and athletes but also the very future of the industry.
Just last month, extreme heat disrupted the Athletics World Championships in Tokyo and the world’s top tennis athletes competing in the Shanghai Masters in China, who described the baking weather as “very challenging physically”. Other major events worldwide, like last year’s Paris Olympics, now face higher risk of cancellations, delays and adjustments brought about by extreme, unpredictable weather.
Venues are also under threat from weather-related climate risks.
A recent report warned that 14 of the 16 World Cup venues are already exceeding “safe-play thresholds” for extreme heat, unplayable rainfall, and flooding. By mid-century, nearly 90% of host stadiums will face unsafe extreme heat conditions and 11 stadiums will experience unplayable heat.
The “safe-play” benchmark for extreme heat is 35C (95F), which represents the limit of human adaptability to extreme heat. Once this threshold is reached, the body’s natural cooling system begins to fail, heightening the risk of heatstroke and dehydration, both for players and spectators.
According to the report, several of the 2026 World Cup locations are already recording temperatures at or above this threshold.
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