City climate leadership in London and New York
Every year, climate leaders gather in both London and New York to share solutions, build partnerships, and set the agenda ahead of major international negotiations. These events bring together mayors, businesses, investors, civil society and activists in the cities where many of the world’s climate decisions are shaped.
C40 mayors use these platforms to showcase what cities are delivering, announce new initiatives, and push for the finance and recognition cities need to scale climate action. The events build momentum in the run-up to COP and provide a space for mayors to connect with partners and each other.
London Climate Action Week 2025
Marking 20 years of C40
London Climate Action Week 2025 marked a milestone moment: 20 years of C40 Cities and a decade since the Paris Agreement. With COP30 on the horizon, mayors used the week to spotlight how cities are stepping up in a time of geopolitical instability, rising disinformation, and growing climate impacts.
Featured C40 events
- Urban futures reimagined: a mayoral exchange on regenerative cities (with Centre for Liveable Cities and Arup)
- Bold cities, brave mayors: governing for a liveable planet (with The Conduit)
- Mayoral masterclass: how to win elections – disarming disinformation (C40 Centre)
- Accelerating climate action through urban planning (with Gensler)
- EVs for everyone: ensuring clean air, good jobs, and access to opportunities for all through electrification (with Uber)
- Sustainable urban regeneration: an opportunity to unlock Europe’s future housing supply (with Arup and Urban Partners)
Climate Week NYC 2025
Ahead of the Local Leaders Forum and C40 World Mayors Summit 2025 in November, C40 mayors used Climate Week NYC to showcase bold, city-led solutions. At a time when global challenges are growing, cities demonstrated what’s possible when action meets ambition: cutting fossil fuels, scaling clean energy, creating good green jobs, and protecting communities.
Key highlights
- C40 and partners explored how port cities can become clean energy hubs
- Climate Mayors convened a leadership forum on local climate capital
- C40 Co-Chair joined events on credible transition planning, climate and health solutions, and disarming disinformation
Featured C40 events
- Cities leading change: unlocking local climate capital (with Raftelis)
- Climate Mayors leadership forum (with Climate Mayors, New York Climate Exchange, Urban Climate Change Research Network)
- Powering the global energy transition: port cities as clean energy hubs (with Arup)
- Advancing local climate leadership through a community of practice (with Building Performance Partnership and Institute for Market Transformation)
Climate Week NYC 2024
Climate Week NYC 2024 took place amid unprecedented global challenges: conflicts and economic crises deepening the effects of the climate emergency. While governments struggled to move away from fossil fuels, C40 mayors used the week to show that cities are championing a just transition and a more secure future.
Key highlights
- C40 Cities and the Rockefeller Foundation announced a partnership to address climate-related health risks
- C40 Co-Chair Mayor Khan, Matt Damon and Gary White of Water.org put water safety and security on the global climate agenda
- C40, The Climate Pledge and development banks announced support for electric freight in Latin America
- Fortaleza won the WRI Ross Center Prize for Cities
Climate Week NYC 2021
In September 2021, C40 hosted “The Urban Energy Transition: Powering green and just cities for the 21st century”, bringing together mayors, climate and energy specialists, finance experts, business leaders and youth activists to accelerate the transition to clean energy in cities.
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