C40 Cities

A network of city mayors delivering urgent climate solutions.

Protecting the people and places we love. 🌳🌍🌆💚

[Sadiq Khan @SadiqKhan]

We know early warning systems save lives.

Speaking at the World Leaders Summit at #COP31 - at an event convened by the @UN Secretary-General, I highlighted London’s world-leading action on heat and air quality alerts.

As co-chair of @c40cities - I committed to all our member cities – home to almost a billion people - having early warning systems in place by the end of next year.

[C40 Cities @c40cities]

“Negotiations matter – but success must be measured on the ground.” - @antonioguterres @UN at COP31

And cities are already delivering.

Mayors are turning climate commitments into real results.

[C40 Cities @c40cities]

Mayors achieve many of the climate actions that help deliver national commitments.

At #COP31, they’re coming together to share solutions and successes.

C40 Cities Co-Chair & @MayorofLondon, @SadiqKhan highlighted the Yearly Offer of Action: https://t.co/aX89tFe1p6

[Sadiq Khan @SadiqKhan]

Great to be at #COP31.

This year has been another stark reminder of the devastating impacts of climate change, including the extreme heat experienced in London.

We must go further and faster to tackle the climate emergency. The time for action is now - delay is not an option.

[C40 Cities @c40cities]

Cities are ready to do more on climate - but they need national governments alongside them.

At #COP31, the CHAMP Subnational Advisory Council brought city and regional leaders together to strengthen partnerships, unlock finance and accelerate climate progress.

[C40 Cities @c40cities]

Is your city on the map?

See how 69 mayors are taking climate action through the Yearly Offer of Action, from early warning systems and extreme weather protection to affordable electric transport for all.

Explore the map ➡️ https://t.co/ejZ4wg2isJ

[C40 Cities @c40cities]

We're at #COP31.

Here’s why cities need to be part of the conversation ➡️

[C40 Cities @c40cities]

⭐ The Yearly Offer of Action is back, and more mayors are involved than ever before.

From cleaner energy to greener public spaces, C40 and @Mayors4Climate cities are turning climate targets into real results, year after year.

https://t.co/XrQq8d7uiW

[C40 Cities @c40cities]

Brazil is showing what climate action looks like 🇧🇷

Cities are bringing climate action into public budgets and building on the momentum of COP30.

https://t.co/VyGzvOlibo

[C40 Cities @c40cities]

Huge opportunities await businesses investing in green tech and infrastructure.

In @ClimateHome, @LordMayorMelb Nick Reece & Mayor of Renca @cn_castro detail why C40 cities are generating a green investment boom.

https://t.co/9GBisbtreI

[C40 Cities @c40cities]

Mayor Sadiq Khan's transformation of Oxford Street shows what is possible when mayors put people at the heart of their cities.

[C40 Cities @c40cities]

Londonmaxxing at its finest.

Under the leadership of C40 Co-Chair and @MayorofLondon, one of the world's most famous shopping streets is putting people first.

@SadiqKhan

[C40 Cities @c40cities]

Water = life 💧

By introducing clean drinking water kiosks in underserved communities, C40 Co-Chair and Mayor of Freetown @yakisawyerr is tackling climate challenges, creating new jobs and protecting people from unsafe water.

@FCC_Freetown

[C40 Cities @c40cities]

More trees, cooler streets and a city better prepared for extreme heat. 🌳

Through ‘Freetown the Treetown’, C40 Co-Chair @yakisawyerr is showing how a simple solution can make a big difference in the fight against rising temperatures in Freetown, Sierra Leone.

@FCC_Freetown

[C40 Cities @c40cities]

Transforming the Seine River and making it clean and swimmable was one of the boldest moves Paris took to tackle the climate crisis.

Hear from the Mayor of Paris, Emmanuel Gregoire, about how restoring the Seine is future-proofing the city for generations to come.

[C40 Cities @c40cities]

🇲🇾 Kuala Lumpur is helping communities stay cool as temperatures rise.

🇮🇳 Bengaluru is turning rooftops into a major source of clean energy.

Explore the progress and learn more about the data in our 2025 annual report: https://t.co/arCNj8raxf

[C40 Cities @c40cities]

GOOD NEWS: Cities are taking bigger, bolder steps to tackle the climate crisis.

Across C40 cities, climate action is already delivering real results. From cleaner air and greener transport to cooler neighbourhoods and more renewable energy ⬇️🧵

[C40 Cities @c40cities]

🇨🇳 Shenzhen is making global shipping greener with cleaner energy at ports.

🇧🇷 Curitiba is improving waste services six years ahead of its target timeline.

🇺🇸 New York City is cutting food emissions by serving more plant-based meals across hospitals.

[C40 Cities @c40cities]

Cities are already feeling the impact of a hotter, more unforgiving climate.

From opening public areas 24/7 for people to cool down to creating more shade and green spaces, cities like Paris are finding practical ways to protect residents from extreme heat.

@egregoire