Climate change is reducing the chances of breaking records in the world’s top marathons, according to a new study released ahead of Sunday’s New York Marathon.
Concerned elite athletes say rising temperatures are transforming the sport, with some urban marathons affected more than others. Last month’s Berlin event was run in unusual temperatures of 24°C.
A report from Climate Central, a US-based non-profit organization, reveals that 86% of the 221 global marathons analyzed for their 2025 dates are expected to experience a decrease in the probability of reaching optimal running conditions by 2045, including the seven Abbott World Marathon Majors.
Mhairi Maclennan, the fastest British finisher of the 2024 London Marathon, said the findings reflect a growing challenge for elite runners.
“At the elite level, conditions determine the success or failure of a performance,” Maclennan said. “We train day after day for years and manage every aspect of our lives to compete at our best, only for that elusive goal to become further and further away as ideal temperatures become scarcer.”
Climate change isn’t just about racing getting harder; it’s about knowing that breaking records could soon be impossible if conditions continue to escalate.
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Heat waves make marathons difficult
The report identifies an optimal temperature point for the marathon that favors maximum performance. For elite runners, men perform better in colder conditions (on average, 4 degrees Celsius or 39 degrees Fahrenheit) and women in warmer temperatures (10°C, 50°F).
However, the report warns that global warming is becoming more difficult to find those conditions.
Tokyo currently offers the highest probability of ideal temperatures for elite men’s runners (69%), but is also projected to experience the largest decline by 2045.
The 2025 Berlin and Tokyo marathons were cited as examples of how heat waves have already raised race-day temperatures above maximum performance thresholds, although starting races earlier may slightly improve conditions.
Former world record holder Catherine Ndereba said the sport was already adapting.
“Climate change has altered “Marathon,” said Kenyan Ndereba, a two-time world champion and four-time Boston winner.
“Dehydration is a real risk, and a simple miscalculation can end a race before it begins. Every step now sends a message: if we don’t take care of our planet, even our strongest steps will fall short.”
Ibrahim Hussein, the first Kenyan to win the New York and Boston marathons, echoed this sentiment.
“The weather is part of the journey now,” Hussein said. “If we don’t protect it, future records and enjoyment for all will become less and less likely.”
With information from Reuters
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