C40 is a network of nearly 100 cities working to deliver the urgent action needed right now to confront the climate crisis. Mayors of C40 cities are committed to using a science-based and collaborative approach to help the world limit global heating to 1.5°C and build healthy, equitable and resilient communities.


The C40 member cities earn their membership through action. C40’s most distinguishing feature is that it operates on performance-based requirements. Members are approved by C40’s Steering Committee of mayors, who set minimum membership criteria and ensure the integrity of C40 as a network of climate leaders. Member cities must meet these requirements or leave C40. In conjunction with working in a peer group of world-leading cities taking ambitious and innovative climate action, this approach creates positive competition, encouraging C40 cities to go even further in their efforts to tackle the climate crisis.


C40’s mission is to halve the collective carbon emissions of its member cities within a decade, while improving resilience and equity and creating the conditions for everyone everywhere to thrive. The climate crisis, compounded by the COVID-19 pandemic, requires an unprecedented global response. Cities know what needs to be done to limit global heating to 1.5° Celsius, and they know that achieving this climate-safe future is only possible if we act now and in collaboration with other levels of government, businesses, civil society, and citizens.


C40’s aim is to assist its cities as they implement their robust, science-based climate action plans which are aligned with the 1.5°C target of the Paris Agreement and prioritize increasing climate resilience and equity. That is why C40 will closely follow the COP26 summit. If this is achieved, C40 cities will see emissions reductions consistent with halving their collective emissions by 2030.

In the coming years, C40 will shift its in-depth regional resources to focus on the highest priority and highest impact climate actions in each region. When providing assistance, it will concentrate on its unique ability to support mayors to make the case for and enact ambitious and sometimes difficult policies, by building coalitions of support and facilitating peer-to-peer knowledge exchange.

Above all, C40 will help its mayors use their strong track record domestically to bring hope, energy, best practice, and a uniting vision to others.