Beijing has cut PM2.5 pollution by nearly 70% since 2013, and you can feel and see the difference. More people outdoors, more cycling and running, more green spaces. Climate action woven into everyday life looks just like this.

As climate risks accelerate, investment in resilience is essential - and cities are on the front lines. C40 Cities' new report confirms what cities have known all along: that well-designed adaptation projects deliver clear economic and financial value.

Heidi Sørensen, who passed away on 25 April after living with cancer for years, was a pioneer in the global climate movement. At C40 Cities, we remember Heidi as a tenacious innovator who proved that cities must lead the way in solving the climate crisis.

Cities are showing that a future beyond fossil fuels is possible - and already underway. From cutting demand to scaling clean energy, mayors and local leaders are turning ambition into delivery. The task now is to ensure that the transition is just, coordinated, and irreversible.

“Global events demonstrate there’s not a moment to waste in our drive for clean power”. observer.co.uk/news/opinion...

To all the incredible women leading the way towards a fairer, cleaner, climate-safe future - including the 70% of @c40cities.bsky.social colleagues who are female & our amazing co-Chair, Yvonne Aki-Sawyerr, Happy International Women’s Day!

A commentary in @nature.com argues the 1.5°C temperature limit has “outlived its usefulness” because we’re headed towards overshoot and should be replaced by a “clean-energy shift” metric. That’s the wrong diagnosis. Here is why. www.nature.com/articles/d41...

Great to meet with New York’s new Chief Climate Officer, Louise Yeung and other colleagues from across the NYC city government. New York has long been a climate leader. As one of the first members of C40 Cities, it has always set the pace for bold and practical action.

A standout moment at the #WMS25: youth activists declaring, "We do this for our today, we do this for our tomorrow, and we will do this together.” This new Hot Takes episode from the Cities 1.5 podcast brings the young voices we heard to even more people - an absolute must-listen: lnk.to/HotTakes2

A $10B fraud. 2 whistleblowers. On Cities 1.5, David Miller, Managing Director of the C40 Centre and former Mayor of Toronto, speaks with Lindsay Gulden about exposing Exxon’s fraudulent ways and the disinformation playbook behind it all. https://c40.me/3OwZpHT

How 2 people helped expose a $10B Exxon scandal. I highly recommend the latest episode of Cities 1.5, where Lindsey Gulden sheds light on how Exxon’s shocking overvaluation was protected by disinformation and silence. The fossil fuel industry’s culture of deception must be stopped. lnk.to/S6E3

“One city does something and a hundred of us then will take it to scale. I find hope in the fact that cities can make this work” - inspiring words for difficult times from the Mayor of Austin, Kirk Watson, in the latest episode of the Cities 1.5 podcast: lnk.to/S6E2

Privileged to accompany @london.gov.uk to welcome United Nations Secretary General, Antonio Guterres, to London today. Inspired by his leadership on climate & so much else & motivated by his message that we must up the pressure to shift off polluting fossil fuels

We must end the fossil fuel era. UN Secretary-General, António Guterres, knows this better than anyone. I want to thank him for his steadfast climate leadership and his commitment to phasing out fossil fuels. A pleasure to meet today together with C40 Cities Co-Chair, Mayor of London Sadiq Khan.

My comment on the #COP30 outcome: Multilateralism needed a boost in Belém, and instead it got a bandage. The COP process needs to take a long, hard look at itself.

As we wait for the official outcome of #COP30, here’s a time capsule of its last day: the outrage, the optimism, the urgency, and the sheer human effort that goes into trying to land a deal. The latest episode of @outrageoptimism.bsky.social featuring C40’s Eric Garcetti & @mark--watts.bsky.social:

🚨BREAKING: C40 Cities reacts to the disappointing draft outcome of #COP30 @mark--watts.bsky.social, C40 Cities Executive Director, on the draft of the Belém Political Package: “The draft texts we've seen this morning in Belém suggest several parties are trying to leave the global mutirão in ashes.

How are cities and subnational leaders turning negotiation into action? This #COP30 booklet captures the crucial role cities play in tackling the climate crisis, and lays out our COP30 asks. To deliver climate action at the speed required, subnational inclusion at COPs cannot be overlooked.

We start the final week of #COP30 with strong momentum behind our push for greater inclusion of cities as key partners in the delivery of these critical climate negotiations. A thread 👇 (1/7)

#Disinformation is a core topic at #COP30. C40's @mark--watts.bsky.social on how mayors are tackling it: "C40 supports the importance @lulaoficialbluesky.bsky.social has placed on information integrity and tackling disinformation. Cities can play a critical role in making this the ‘COP of Truth’.

In case you missed it: Yesterday, I joined the COP30 Briefing Room and spoke with @projectsyndicate.bsky.social about climate disinformation, how local leaders are driving progress and our yearly offers of action. www.youtube.com/watch?v=7NaY...

It’s time to move from promises and negotiations at #COP30 to delivering climate action. To unlock progress, we should focus on where the decisions are really made: cities. Read my op-ed in @politico.com with Jader Barbalho Filho, Minister of Cities, Brazil. www.politico.eu/sponsored-co...

🚨BREAKING: #COP30 President André Corrêa do Lago opens COP highlighting the role of cities 🏙️ "Subnational entities play a central role in implementing the decisions made at COPs. To stop climate change, multilateralism is unquestionably the way forward.”

This week, I’m at @cop30brazil.bsky.social in Belém where cities are backing the COP30 Presidency's call in moving from negotiation to implementation. Here’s what to expect from C40 Cities over the next two weeks ⬇️

"Mayors, we get the job done" ⭐ Meet the local leaders taking real climate action, defying populist governments who dismiss and deny science.

During #WMS25 @outrageoptimism.bsky.social spoke with mayors about how they are turning ambition into action. Listen to interviews with the mayors of Paris, Freetown, and Portland about how cities are cutting emissions, investing in resilience, and driving progress.

At the city-business roundtable, @mark--watts.bsky.social and María Mendiluce @wemeanbusiness.bsky.social spoke to how local partnerships can lead to real progress. The mayors of Tshwane and Oslo shared how working with businesses drives tangible results in the places where people live and work.

The @ec.europa.eu announced today that the European Union has officially endorsed CHAMP – the Coalition for High Ambition Multilevel Partnerships – and in doing so, committed to continue working with cities and regions to deliver stronger climate action. climate.ec.europa.eu/news-other-r...

It was fantastic to join the #WMS25 session on South-South cooperation hosted jointly by CPAFFC & C40 Cities. I talked about how inspired I always am by the speed and scale of progress of the green transition in China, which I recently visited. Some of my thoughts here: www.c40.org/news/theres-...

Rio is a real leader in tackling extreme heat: a huge priority for @cop30brazil.bsky.social & @c40cities.bsky.social. Its Extreme Heat Response Protocol provides inspiration & learnings for cities worldwide. Thank you @eduardopaesoficial.bsky.social for hosting the Local Leaders Forum here in Rio!

The World Mayors Summit 2025 opened with a powerful call: move negotiation to implementation. 20 years ago, a small group of forward-thinking mayors created this organisation because they feared no one else would act.

C40 Executive Director @mark--watts.bsky.social celebrated cities' progress and said what must come next to reach 2030 targets. “Thanks to the tremendous leadership in this room and efforts by city residents, emissions across C40 cities are now falling despite growing populations and economies.”

Fantastic interview with @london.gov.uk on eve of C40 Summit www.theguardian.com/environment/...

I’m in Rio de Janeiro for the @c40cities.bsky.social World Mayors Summit ahead of COP30 in Belem. This COP is the most critical since Paris in 2015. Mayors showing that cities are leading the way. While others talk, mayors are delivering tangible, measurable progress that builds a fairer future.

Congratulations @eduardopaesoficial.bsky.social for being one of TIME’s 100 most influential climate leaders of 2025. Great news ahead of Rio de Janeiro welcoming 300+ mayors from all over the world to discuss city climate action at World Mayors Summit, part of COP30 Local Leaders Forum. #WMS25

How do we build cities that prioritise health for all of their residents? That’s the question we’re tackling with partners like Novo Nordisk – a Gold Sponsor of next week’s C40 World Mayors Summit in Rio.

For 200+ years, fossil fuels have been at the heart of the global shipping industry. The 21st century must be a time of change: port cities can unlock billions in investment, create new green jobs, and deliver cleaner air by transforming into clean energy hubs. From @c40cities.bsky.social & Arup:

Last week, I attended the UN NDC Summit during Climate Week NYC, which was an unexpectedly positive week for climate action. My top highlights:

I remember being told that it would take 193 years to reach legal limits for nitrogen dioxide. I decided this was unacceptable. Thanks to the bold policies we put in place, we've managed to do it in nine years - 184 years earlier than expected.

Climate Week NYC ✅ Next stop 📍 World Mayors Summit and COP30

Over the past decade, local governments have shown that they can deliver some of the most effective and rapid climate solutions. Cities are not waiting for international agreements, they are taking action. @c40cities.bsky.social @mayors4climate.bsky.social www.linkedin.com/pulse/turnin...

At #ClimateWeekNYC, mayors from around the world proved how cities are stepping up on climate action and standing together to protect the people and places we love.

Great to meet with the @cop30brazil.bsky.social High-Level Champion Dan Ioschpe who has made huge progress on consolidating the the action agenda to ensure it can deliver on the goals of the Paris Agreement. #ClimateWeekNYC

C40 Cities Co-Chair and Mayor of Freetown, Yvonne Aki-Sawyerr, implored national governments and financial institutions to match cities’ climate ambition. Showcasing Freetown’s tree-planting campaign, she called for global action: cities are delivering, now it’s time for the world to back them.

“We are united by a common purpose: to ensure that the energy systems of our cities are not just functional, but transformative, providing reliable power, fostering economic growth, and creating opportunities for every citizen.” - C40 Co-Chair, Mayor Aki-Sawyerr at Climate Week NYC.

Great to see Søren Staugaard Nielsen and Michael Simmelsgaard at Climate Week NYC. Ramboll's unrestricted funding to @c40cities.bsky.social is an example of great leadership in the sector and a vote of confidence in resilient cities where communities and nature thrive.

It’s great to be in New York for Climate Week NYC. Mayors are on the ground showing that local leaders are delivering real solutions in the face of rising climate threats. @annehidalgo.bsky.social, @valplante.bsky.social, @mayorofchicago.bsky.social, @mayorgallego.bsky.social

New York Climate Week is an essential moment for global climate action on the road to COP30. The work C40 mayors are doing to create green jobs, transition to clean energy, and build liveable cities is proof that climate action is not only possible but politically popular and economically smart.

Great to be marching in London today to Make Polluters Pay

The U20 Summit in Johannesburg closed with one clear message: cities are key to a renewed global push for a fairer, climate-safe future for all. The momentum to empower cities and unlock direct climate finance must move forward into the G20, into COP30, and beyond: c40.me/4gphstr