Nearly 1 billion people live in C40 cities. Mayors see firsthand the challenges people face and the solutions that can make a difference.
The Urban 20 (U20) brings together cities to develop shared recommendations that push for action on city priorities and needs in G20 discussions.
Over 30 cities came together for this year’s U20, co-hosted by Los Angeles and New York, to identify shared priorities, asks, and opportunities for action on some of the world’s most pressing challenges.
When a city succeeds, we know there is potential for all cities to succeed.
Mayor of New York City, Zohran Mamdani
Cities are stronger when they work together
The first day of U20 focused on collaboration and highlighted how mayors are working together to address the key priorities of this year’s cycle:
- Affordable housing
- Climate action
- Sustainability
- Resilience
- Protecting immigrant communities and human mobility
C40 Co-Chair and Mayor of Freetown, Yvonne Aki-Sawyerr, shared the work of C40 mayors, how they are implementing bold climate action and highlighted where greater co-operation can help them go further.
Mayors came to New York from different countries and different circumstances, but the pressures facing our residents are remarkably similar: rising costs, extreme heat, housing insecurity and displacement.
C40 Co-Chair and Mayor of Freetown, Yvonne Aki-Sawyerr
C40’s Executive Director, Mark Watts, spoke about the urgency of the moment and the need for collective action across cities, governments, and civil society, and mayors set out what they need to deliver more for their residents – including stronger partnerships, better policies and greater support from national governments.
For all of us, what binds us, whether Rome or Freetown or Mexico City, we know that oftentimes it is mayors and it is cities that have to deal with the crises of people most directly. And we believe that cities also have many of the answers.
Mayor of New York City, Zohran Mamdani
Cutting costs, creating jobs and strengthening local economies
City leaders also explored how the clean-energy transition can cut costs, create good jobs and bring new investment into communities.
The Mayor of Paris, Emmanuel Grégoire, the Mayor of Amsterdam, Femke Halsema and the Governor of Jakarta, Pramono Anung, shared how their cities are ensuring the benefits of the clean-energy transition reach everyone and what a just urban transition looks like in practice.
Showcasing urban climate action that improves residents’ lives
Hosted by C40, the Mayor of Helsinki, Daniel Sazonov, the Mayor of Miami, Eileen Higgins and the Mayor of The Hague, Jan van Zanen, explored how cities can leverage the clean-energy transition to build stronger economies, lower costs and create good jobs.
The conversation centred on making sure the tangible benefits of climate investment reach the communities facing the greatest economic and environmental inequality.
For us it’s crucial, if we don’t have the people with us, then we will never get the government with us.
Mayor of Miami, Eileen Higgins
If you want the people with you, you need to make them part of the process – not the audience.
Mayor of The Hague, Jan van Zanen
NYC Chief Climate Officer Louise Yeung closed the session by reflecting on what cities can learn from each other as they work toward a fairer, cleaner future: “We are more powerful when we work together. Climate change is borderless and unrelenting. In turn, we must be unrelenting in our response.”
City leadership needs support at every level of government
Cities can move faster when national governments work with them.
UN-Habitat Executive Director Anacláudia Rossbach joined national representatives to respond to the commitments made by mayors and consider how stronger collaboration between cities, national governments and global institutions can help turn local solutions into broader action.
The communiqué sets out action across three priorities:
- Climate and energy: Accelerate a clean and just energy transition that lowers costs, creates good jobs and improves health, while giving cities greater access to climate finance and the tools to protect residents from extreme heat, flooding, wildfire and other worsening climate impacts. Mayors call for better access to climate and health data to expand and accelerate the roll-out of early warning systems.
- Housing: Expand access to affordable, resilient homes, protect tenants, and tackle homelessness. Mayors call for greater local authority over housing and better access to public and international finance for locally led solutions.
- Migration: Support newcomers while maintaining strong public services and social cohesion for all residents. Cities call for a greater role in migration policy and direct funding for reception, integration and essential services.
This communiqué turns that shared experience into a shared agenda for action. Cities are ready to deliver. Give us the tools and resources to act, and we will.
C40 Co-Chair and Mayor of Freetown, Yvonne Aki-Sawyerr
related
Find out more about C40’s announcements and activities at the United Nations General Assembly and Climate Week NYC, taking place in New York City from 20-27 September 2026
A city-led platform ensuring city priorities are reflected in G20 discussions and global policy decisions.
Commitments by C40 cities to drive ambitious climate results and halve fossil fuel use by 2030.
