A city. PHOTO; pexels
A new global coalition of cities has pledged urgent action to confront one of the most dangerous and fastest-growing threats of the climate crisis: extreme heat.
Unveiled on the opening day of the C40 World Mayors Summit in Rio de Janeiro, the Cool Cities Accelerator will equip mayors and city leaders to protect residents, safeguard economies, and redesign urban environments for a hotter, more unpredictable future.
The initiative brings together 33 founding cities representing over 145 million people across every region of the world, from Austin, Boston, Buenos Aires, and Freetown to Nairobi, Paris, Singapore, and London, all united by a shared goal: to make cities cooler, greener, and safer by 2030.
The Accelerator was established by C40 Cities with the support of The Rockefeller Foundation, and implementation backing from the ClimateWorks Foundation, Robert Wood Johnson Foundation, Z Zurich Foundation, and the Danish Ministry of Foreign Affairs.
Extreme heat is already the world’s deadliest weather hazard, claiming nearly half a million lives each year.
Without decisive action, the number of people exposed to life-threatening urban heat could increase fivefold by 2050. But city leaders say this future can be changed.
“Extreme heat is no longer a distant threat; it’s a daily reality affecting the lives and livelihoods of millions around the world. Local leaders are not just responding to the climate crisis today, they’re redesigning urban life to protect people, strengthen economies, and build a cooler, safer future for all,” said Elizabeth Yee, Executive Vice President of The Rockefeller Foundation.
The Cool Cities Accelerator offers a science-based roadmap for immediate and long-term action.
Cities will strengthen early warning systems, create cooling access plans for emergencies within two years, and within five years expand tree cover, enhance building standards, and future-proof infrastructure against extreme heat.
It directly supports the UN Secretary-General’s call to action on extreme heat and the COP30 “Beat the Heat” agenda, helping cities and national governments scale sustainable cooling solutions.
“Extreme heat is a silent killer and an increasingly urgent global threat. The number of days that major capitals experience temperatures above 35°C has increased by 54% over the past twenty years. Cities are showing real leadership by taking practical steps to protect communities, safeguard economies, and create more livable urban environments,” said Mark Watts, Executive Director of C40 Cities.
Among the 33 cities, Athens stands out as one of Europe’s most heat-affected capitals.
“Athens is one of the most severely heat-impacted cities in Europe, with the number of heatwave days expected to double by 2050,” said Haris Doukas, the city’s mayor.
“In response to this crisis, Athens is leading a comprehensive, cross-agency effort built on awareness, preparedness, and redesign. Over the next five years, we will continue to transform Athens in alignment with the Accelerator and make it cooler, greener, and safer, especially for those who need it the most.”
As part of its support, The Rockefeller Foundation is providing a USD 1 million grant to help cities set measurable targets for heat adaptation and implement life-saving solutions.
C40 and its partners are already providing technical assistance to over a dozen cities, including Accra, Austin, Bengaluru, Durban (Ethekwini), Freetown, Jakarta, London, Milan, Nairobi, New York City, Quezon City, Rio de Janeiro, and Tshwane, helping them achieve the resilience goals of the Accelerator.
Jessica Brown, Senior Director of Adaptation & Resilience at the ClimateWorks Foundation, highlighted the importance of local leadership.
“Extreme heat is becoming a more intense challenge for people’s health and their economic security. We are proud to have mobilized funding for people facing extreme heat and other climate risks, and we are thrilled to help transform cities through the Cool Cities Accelerator. Local and community organizations hold the trust and insight needed to drive meaningful change and chart a more resilient future.”
Together, these efforts form part of a global movement to save lives and strengthen resilience.
As cities share strategies and scale proven cooling solutions, they are collectively reshaping how the world’s urban areas confront the realities of climate change, proving that the future of cities can be cooler, greener, and more livable for generations to come.
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