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C40 Cities Climate Leadership Group
FoundedOctober 2005
( London, United Kingdom)
Type International organization
Focus Climate change
Area served
Global member cities
MethodDirect assistance, peer-to-peer exchange, research & communications. What we do for cities. [1]
Steering Committee
Barcelona, Bogotá, Buenos Aires, Dhaka, Dubai, Freetown, Hong Kong, Jakarta, Johannesburg, London, Milan, Montréal, Phoenix, Stockholm, Tokyo [2]
Key people
Mayor Sadiq Khan (Co-Chair)
Mayor Yvonne Aki-Sawyerr (Co-Chair)
Michael Bloomberg (President of the Board of Directors)
President Bill Clinton (Founding Partner)
Mark Watts (Executive Director)

C40 Cities Climate Leadership Group is a group of 96 cities around the world that represents one twelfth of the world's population and one quarter of the global economy. [3] Created and led by cities, C40 is focused on fighting the climate crisis and driving urban action that reduces greenhouse gas emissions and climate risks, while increasing the health, wellbeing and economic opportunities of urban residents.

From 2023, Mayor of London, Sadiq Khan and Mayor of Freetown, Yvonne Aki-Sawyerr serve as C40's Co-Chair, [4] former Mayor of New York City Michael Bloomberg as Board President, and Mark Watts as Executive Director. All four work closely with the 13-member steering committee, the Board of Directors [5] and professional staff. [6] The rotating steering committee of C40 mayors provides strategic direction and governance. [1] Steering committee members include: London, Freetown, Phoenix, Medellin, Copenhagen, Paris, Dhaka North, Nairobi, Tokyo, Rio de Janeiro, Montréal, Milan, Seoul, Oslo and Hong Kong. [7]

Working across multiple sectors and initiative areas, C40 convenes networks [8] of cities providing a suite of services in support of their efforts, including: direct technical assistance; facilitation of peer-to-peer exchange; and research, knowledge management & communications. C40 is also positioning cities as a leading force for climate action around the world, defining and amplifying their call to national governments for greater support and autonomy in creating a sustainable future. [9]


C40 started in October 2005 when London Mayor Ken Livingstone convened representatives from 18 megacities to forge an agreement on cooperatively reducing climate pollution and created the 'C20'. [10] In 2006, Mayor Livingstone and the Clinton Climate Initiative (CCI)—led by the efforts of former U.S. President Bill Clinton—combined to strengthen both organizations, [11] bringing the number of cities in the network to 40 and helping to deliver projects and project management for participating cities to further enhance emissions reductions efforts.

Serving as C40's first chair, Livingstone established the C40 Secretariat in London, set up the C40 Steering Committee, and initiated the use of C40 workshops to exchange best practices amongst participating cities. [10] In 2008, former Mayor of Toronto David Miller took over as C40 chair. Highlights of his tenure included the Copenhagen Climate Summit for Mayors and the C40 Cities Mayors Summit in Seoul, both in 2009, as well as the launch of practical action initiatives for cities, such as the Climate Positive Development Program and the Carbon Finance Capacity Building program. [10]

Three-term Mayor of New York City Michael Bloomberg served as chair from 2010 to 2013. During his three-year tenure, Mayor Bloomberg demonstrated unwavering commitment to building a professional organization and establishing measurable and uniform benchmarks for success, as well as expanding knowledge-sharing between cities and partner organizations with similar priorities. Key milestones during his chairmanship include the full integration of the CCI Cities Program into the C40, and the C40 Mayors Summits in Sao Paulo and Johannesburg. Under Mayor Bloomberg's leadership, C40 grew to include 63 cities.

In December 2013 former Mayor of Rio de Janeiro Eduardo Paes became Chair of C40. During his tenure Mayor Paes oversaw the addition of more than 20 new member cities (particularly those in the Global South) several groundbreaking research reports, successful international events, and thriving global partnerships, all of which are helping cities make real contributions to the reduction of global greenhouse gas emissions and climate risks. He also helped launch the Compact of Mayors (now the Global Covenant of Mayors for Climate & Energy), put in place the C40 Cities Finance Facility, and oversaw the opening of a permanent C40 office in Rio de Janeiro, at the Museum of Tomorrow.

In 2015, as C40 marked its 10th anniversary, [12] cities were crucial voices in shaping and advocating for a strong Paris Agreement—just as city leaders will be crucial in delivering on its ambition going forward. More than 1,000 mayors, local representatives, and community leaders [13] from around the world took part in the Climate Summit for Local Leaders, hosted by Mayor of Paris Anne Hidalgo and the UN Secretary-General's Special Envoy for Cities and Climate Change Michael R. Bloomberg during the 2015 United Nations Climate Change Conference.

In August 2016, Mayor of Paris Anne Hidalgo became C40's first chairwoman after being voted in unanimously by the Steering Committee. [14] Mayor Hidalgo has announced an ambitious agenda for the organization, including plans to focus on securing green financing, supporting compliance with the Global Covenant of Mayors for Climate & Energy, encouraging inclusive and sustainable growth in cities, and recognizing the leadership of women in tackling climate change.

In December 2016, C40 held its sixth biennial Mayors Summit in Mexico City. [15] The Global Summit, hosted by Mayor of Mexico City Miguel Ángel Mancera, was attended by 1,400 people, including representatives from more than 90 cities.

The current chair of C40 Cities is Mayor Sadiq Khan of London, UK.


While C40 originally targeted megacities for their greater capacity to address climate change, C40 now offers three types of membership categories to reflect the diversity of cities taking action to address climate change. The categories consider such characteristics as population size, economic output, environmental leadership, and the length of a city's membership. [16]

1. Megacities

  • Population: City population of 3 million or more, and/or metropolitan area population of 10 million or more, either currently or projected for 2025. OR
  • GDP: One of the top 25 global cities, ranked by current GDP output, at purchasing-power parity (PPP), either currently or projected for 2025.

2. Innovator Cities

  • Cities that do not qualify as Megacities but have shown clear leadership in environmental and climate change work.
  • An Innovator City must be internationally recognized for barrier-breaking climate work, a leader in the field of environmental sustainability, and a regionally recognized “anchor city” for the relevant metropolitan area.

3. Observer Cities

  • A short-term category for new cities applying to join the C40 for the first time; all cities applying for Megacity or Innovator membership will initially be admitted as Observers until they meet C40's year-one participation requirements, for up to one year.
  • A longer-term category for cities that meet Megacity or Innovator City guidelines and participation requirements, but for local regulatory or procedural reasons, are unable to approve participation as a Megacity or Innovator City expeditiously.

Member cities

C40 has 96 member cities across seven geographic regions. [3]

  • Africa:
City Country Member Since
Abidjan   Ivory Coast 2018
Accra   Ghana 2015
Addis Ababa   Ethiopia 2007
Cape Town   South Africa 2014
Dakar   Senegal 2016
Dar es Salaam   Tanzania 2014
Durban   South Africa 2015
Ekurhuleni   South Africa 2020
Freetown   Sierra Leone 2019
Johannesburg   South Africa 2006
Lagos   Nigeria 2007
Nairobi   Kenya 2014
Tshwane   South Africa 2014


Climate Positive

The C40 Cities Climate Leadership Group’s Climate Positive Development Program (Climate Positive) was launched in May 2009 in partnership with the Clinton Climate Initiative and the U.S. Green Building Council. [17] The program brings together leading district-scale new-build and regeneration projects working to achieve "Climate Positive"—or net carbon negative—outcomes in cities around the world. [18] As part of the C40’s Sustainable Communities Initiative, it aims to create a model for large-scale urban communities and to support projects that serve as urban laboratories for cities seeking to grow in ways that are environmentally sustainable, climate resilient, and economically viable. [19]

Climate Positive is an exclusive program, with a competitive application process, and currently comprises 17 global projects that will collectively reduce the emissions impact of more than one million people. [20] The cities in which the Climate Positive projects are located support the implementation process locally and share best practices globally through participation in the C40 Climate Positive Network, [21] [22] The projects are in different stages of development, but share key characteristics like high densities, highly efficient buildings, mixed-use zoning and transit accessibility. [23]



C40 is a member of The People's Vaccine Alliance. [24] Additional partners include: [25]


C40's work is made possible by three strategic funders: Bloomberg Philanthropies, Children's Investment Fund Foundation and Realdania. [27] [25]

Additional funding comes from: [27] [25] [28]

See also


  1. ^ a b "What We Do For Cities". 24 August 2015. Archived from the original on 7 August 2015.
  2. ^ "Our Cities - C40 Cities". Retrieved 14 August 2022.
  3. ^ a b "The Power of C40 Cities". Retrieved 17 July 2019.
  4. ^ "The C40 Co-Chairs - Leadership". C40 Cities. Retrieved 2024-04-25.
  5. ^ "Board of Directors Archives". C40 Cities. Retrieved 2022-10-07.
  6. ^ "Our Team". C40 Cities. Retrieved 2022-10-07.
  7. ^ "Steering Committee". C40 Cities. Retrieved 2024-04-25.
  8. ^ "Networks". C40 Cities. Retrieved 2022-10-07.
  9. ^ Schlossberg, Tatiana (December 16, 2016). "As Trump Signals Climate Action Pullback, Local Leaders Push Forward". The New York Times. Archived from the original on 2 January 2017. Retrieved 27 February 2017.
  10. ^ a b c "About C40". C40 Cities. Retrieved 2022-10-07.
  11. ^ "President Clinton launches a climate initiative" (Press Release). Clinton Foundation. 1 August 2006.
  12. ^ 10th anniversary
  13. ^ C40 Cities (2015-12-05), The Climate Summit for Local Leaders, 2015 1, retrieved 2022-10-07{{ citation}}: CS1 maint: numeric names: authors list ( link)
  14. ^ "Press Release: Paris Mayor Anne Hidalgo Elected as New Chair of the C40 Cities Climate Leadership Group". C40 Cities. Retrieved 2022-10-07.
  15. ^ "Mayors Agree To Bold And Concrete Actions To Meet Paris Agreement". C40 Cities. Retrieved 2022-10-07.
  16. ^ "C40 Announces New Guidelines for Membership Categories" (Press Release). 3 October 2012.
  17. ^ Clinton Climate Initiative and USGBC Show the World How to Go Climate Positive with 16 Demonstration Projects in 10 Countries, U.S. Green Building Council,, accessed 2013-07-18
  18. ^ The Launch of Climate Positive, Archived 2013-03-15 at the Wayback Machine, accessed 2013-07-18
  19. ^ London’s Evening Standard recognizes coming of Climate Positive Development Project in Elephant & Castle, C40 Blog, [1], accessed 2013-07-17
  20. ^ Clinton Climate Initiative to Demonstrate Model for Sustainable Urban Growth with Projects in 10 Countries on Six Continents, U.S. Green Building Council,, accessed 2013-07-18
  21. ^ Branson2013-07-18T06:00:00+01:00, Adam. "Interview: Pascal Mittermaier, Lend Lease". Building. Retrieved 2022-10-07.{{ cite web}}: CS1 maint: numeric names: authors list ( link)
  22. ^ Spotlight on the C40 Climate Positive Development Program,, accessed 2013-07-18
  23. ^ Lorinc, John (2009-05-26). "Building 'Climate Positive' Communities". Green Blog. Retrieved 2022-10-07.
  24. ^ "Who We Are". People's Vaccine. Archived from the original on 2022-08-25. Retrieved 2023-09-02.
  25. ^ a b c "Partners". C40 Cities. Archived from the original on 2021-05-29. Retrieved 2021-05-23.{{ cite web}}: CS1 maint: unfit URL ( link)
  26. ^ Dasgupta, Ani (April 2022). "Annual Report 2021" (PDF). World Resources Institute. Archived (PDF) from the original on 2022-07-30. Retrieved 2023-09-01.
  27. ^ a b Garcetti, Eric; Watts, Mark (2021-04-16). "C40 Annual Report 2020" (PDF). C40 Cities Climate Leadership Group. Archived (PDF) from the original on 2021-05-15. Retrieved 2023-09-02.
  28. ^ "Funders & Partners". C40 Cities. Archived from the original on 2023-08-23. Retrieved 2023-09-02.

This is the roadmap and what they want to do.