Measuring the impact of city climate action

What is a high-impact accelerator?

A High-Impact Accelerator is a framework developed by C40 to support cities in taking urgent climate action. Accelerators help cities prioritise critical sectors and implement science-based solutions that address climate challenges while creating more equitable and resilient communities.

Why do cities join high-impact accelerators?

Cities and mayors join accelerators to demonstrate their commitment to tackling the climate crisis and to access support in delivering impactful climate action. By joining, cities and mayors benefit from C40’s unique insights, expertise and network that facilitates peer-to-peer sharing. Cities collaborate to show how they are progressing towards their goals, sharing their achievements and the challenges they encounter.

What is the impact of C40’s accelerators?

Since 2017, 74 C40 cities have committed to taking action by joining one or more of C40’s High-Impact Accelerators. Among the cities signed up to an accelerator, this has prompted city-led climate action across various sectors, including:

  • Electrifying public transport: Seoul deployed over 1,000 electric buses and 27 hydrogen fuel cell buses by 2023. Since 2021, the city only buys zero-emission buses.
  • Energy consumption: Paris implemented an energy-saving plan for city buildings, reducing heating temperatures, delaying winter heating by a month, and cutting ornamental lighting. This led to a 6.7% energy reduction by winter 2023.
  • Urban nature and resilience: Chennai restored eight parks and 32 water bodies, developed vertical gardens, and has plans to develop 57 sponge parks to mitigate flooding.
  • Engaging city residents: Freetown established two-way communication channels between the city council and communities, with plans to integrate a youth council for climate governance.
  • Accessible public spaces and transport: Buenos Aires designed bus stops with people’s needs and gender considerations in mind, making them more comfortable and placing them in accessible locations.
  • Investing in green infrastructure: New York City launched its Ten-Year Capital Strategy, including plans to invest US$ 1.3 billion in green infrastructure and stormwater management on streets, parks, playgrounds, and New York City Housing Authority campuses.

2023 Accelerator Progress Reports

Following the expansion of C40’s High-Impact Accelerators, in 2023, cities reported on three new accelerators and the Pathway Towards Zero Waste for the first time since signing.

A summary of the progress, achievements and impact of taking science-based, inclusive climate action can be accessed in the central report, C40 Accelerator Progress Report 2023 [also in French and Portuguese].

Alternatively, access the detailed progress reports for each accelerator below:

Translated versions of the reports will be available soon.


2021/2022 Accelerator Progress Reports

In 2021, C40 completed the first reporting process to asses how cities delivered on their accelerator commitments. Cities were also encouraged to report on their Equity Pledges. This was followed by further selected reporting in 2022.

Access the 2021/2022 progress reports: