Measuring the impact of city-led climate action
Cities are demonstrating what ambitious climate action looks like in practice. Through C40 Accelerators, mayors are turning climate commitments into measurable results, transforming how cities cut emissions, improve health, and build fairer, more resilient communities.
Why cities join C40 Accelerators
C40 Accelerators provide a shared framework for delivery backed by data, collaboration, and technical expertise, which helps cities design strong policies, attract investment, and scale proven climate solutions.
By joining C40’s Accelerators, mayors gain access to a global network of cities facing similar challenges that allows them to exchange what works, create solutions, and hold each other accountable. This collective drive keeps ambition high and ensures climate action translates into visible, equitable change for residents.
Cities are turning ambition into impact
Since 2017, 96 cities have committed to taking action by joining one or more of C40’s Accelerators. Signatory cities are leading on actions across sectors, from clean air and safer streets to green jobs and climate resilience.
Saving lives and protecting communities
- Through the C40 Clean Air Accelerator, cities have saved more than 21,000 lives by cutting air pollution
- Through the C40 Water Safe Cities Accelerator, 59% of signatory cities are making progress towards establishing early warning systems, with over half improving emergency response measures
- Launched in November 2025, the C40 Cool Cities Accelerator helps cities adapt to rising temperatures by protecting residents from extreme heat
- 79% of C40 Urban Nature Accelerator signatories are delivering large-scale greening projects to bring nature back into cities and strengthen climate resilience
Driving investment and green growth
- Cities have saved USD47 billion by cutting air pollution and improving public health through the C40 Clean Air Accelerator
- The C40 Clean Investment Accelerator has redirected nearly USD11 billion more pension fund investment into green and impact-driven funds since 2023
- The C40 and UN-Habitat Urban Planning Accelerator supports cities to adopt a climate-responsive urban planning model that prioritises people, the planet, and shared prosperity
Reducing emissions and waste
- 62.5% of C40 Clean Construction Accelerator cities now have an approved pilot for net-zero operational and low embodied emissions.
- By achieving the commitments, signatory cities of the C40 Sustainable Waste Systems Accelerator can collectively prevent one million tonnes of methane emissions each year.
- 86% of C40 Towards Zero Waste Accelerator cities now have food collection schemes in place to tackle food waste.
Improving procurement
- More than half of the C40 Green and Healthy Streets Accelerator signatory cities are now procuring exclusively zero-emission buses, with a fleet of more than 12,700 zero-emission buses across all cities.
- Through the C40 Good Food Cities Accelerator, cities are cutting food-related emissions by 16% on average, largely through shifting procurement towards more climate-friendly foods.
- The C40 Thriving Food Systems Accelerator, launched in late 2025, addresses food and nutrition insecurity and creates thriving food economies within planetary boundaries.
Switching to clean energy
- In signatory cities of the C40 Net Zero Carbon Buildings Accelerator, 1.3 million square metres have been built in the last two years across new net-zero carbon buildings.
- More than a third of 15 signatory cities of the C40 Renewable Energy Accelerator are 100% reliant on renewable energy sources for their municipal electricity consumption.
Tracking progress together
Nearly a decade after the first C40 Accelerator was launched, cities have made 342 commitments to C40 Accelerators, together shaping a global model for fair, science-based climate action.
2025 Accelerator Progress Report
The 2025 Accelerator Progress Report showcases the C40 Accelerators and the collective progress of their signatory cities.
Explore individual 2025 C40 Accelerator Progress reports
Access detailed reports focused on progress for each of the individual C40 Accelerators:
- Clean Air [English]
- Clean Construction [English]
- Clean Investment [English]
- Good Food Cities [English]
- Green and Healthy Streets [English]
- Net Zero Carbon Buildings [English]
- Renewable Energy [English]
- Sustainable Waste Systems [English]
- Towards Zero Waste [English]
- Urban Nature [English]
- Water Safe Cities [English]
C40 Accelerators launched in 2025
In 2025, C40 launched three new Accelerators, expanding support for cities in priority areas of climate action.
Read our additional C40 Accelerator reports launched this year: Clean Air Full Report, Cool Cities Launch Report
Translated versions of the reports will be available soon.
Previous reports
2023 Accelerator Progress Reports
Following the expansion of C40’s High-Impact Accelerators, in 2023, cities reported on three new accelerators, as well as the Pathway Towards Zero Waste, for the first time since signing.
A summary of the progress, achievements and impact of science-based, inclusive climate action is available in the C40 Accelerator Progress Report 2023 (also in French, Portuguese and Spanish).
Explore Individual 2023 C40 Accelerator Progress Reports
- Clean Air [English, French, Portuguese, Spanish]
- Clean Construction [English, Spanish]
- Divesting from Fossil Fuels, Investing in a Sustainable Future [English]
- Green and Healthy Streets [English, Spanish]
- Good Food Cities [English]
- Net Zero Carbon Buildings [English, Spanish]
- Renewable Energy [English, French, Spanish]
- Towards Zero Waste [English, French]
- Pathway Towards Zero Waste [English, Portuguese, Spanish]
- Urban Nature [English, Portuguese, Spanish]
2021-2022 Accelerator Progress Reports
In 2021, C40 completed the first reporting process to assess how cities were delivering on their Accelerator commitments. Cities were also encouraged to report on their Equity Pledges, followed by further selected reporting in 2022.
Explore the 2021-2022 C40 Accelerator Progress Reports:
- Clean Air [2022: English; 2021: English, Spanish]
- Good Food Cities [English]
- Green and Healthy Streets [English, Spanish]
- Net Zero Carbon Buildings [English]
- Renewable Energy [English, French, Spanish]
- Towards Zero Waste [English]
C40 Accelerators
At the 2025 C40 World Mayors Summit, three new Accelerators were launched: the Cool Cities Accelerator, the Thriving Food Systems Accelerator, and the C40 & UN-Habitat Urban Planning Accelerator.
So far, 49 cities have signed one or more of the new Accelerators, and 78 cities reported on their progress since becoming a signatory city and since the last reporting cycle.
Together, these cities are advancing strategic climate initiatives that phase out fossil fuels, expand equitable access to good, green jobs, and strengthen resilience through increased climate finance and inclusive planning.
Related
Supporting cities to create ambitious climate strategies that deliver meaningful community benefits.
Cities worldwide are proving that climate action is most successful when equity and fairness are at the heart of every decision.
How C40 helps cities access the evidence and insight they need to accelerate climate action and create local opportunity.
