C40 Cities Climate Leadership Group is a group of 96 cities that represents more than ten percent of the world's population and 23 percent of the global economy. 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, 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 and professional staff. The rotating steering committee of C40 mayors provides strategic direction and governance. Steering committee members include: London, Freetown, Melbourne, Jakarta, Abidjan, Phoenix, Medellin, Copenhagen, Nairobi, Tokyo, Curitiba, Boston, Milan, Seoul, Oslo and Hong Kong.
Working across multiple sectors and initiative areas, C40 convenes networks 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 sharing & 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.
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History
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'. 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, 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. 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.
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 São 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.
Membership
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.
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.
Affiliations
Partners
C40 is a member of The People's Vaccine Alliance. Additional partners include:
Clinton Foundation
Institute for Transportation and Development Policy (ITDP)
International Council for Local Environmental Initiatives (ICLEI)
International Council on Clean Transportation (ICCT)
United Cities and Local Governments (UCLG)
World Bank
World Resources Institute (WRI)
Funding
C40's work is made possible by three strategic funders: Bloomberg Philanthropies, Children's Investment Fund Foundation and Realdania.
Additional funding comes from: