The C40 Cities Climate Leadership Group (C40) is a network of the world’s megacities committed to addressing climate change.

Acting both locally and collaboratively, C40 Cities are having a meaningful global impact in reducing both greenhouse gas emissions and climate risks. C40 brings together a unique set of assets and creates a shared sense of purpose. C40 offers cities an effective forum where they can collaborate, share knowledge and drive meaningful, measurable and sustainable action on climate change.

Explore an interactive list of the C40 Cities and our Networks and Research connecting them.

C40 Cities: Showing the Way Forward

Take a ride with us through five of our cities to see actions and progress.

See the C40 like never before in this short video that takes you on a journey through member cities London, Johannesburg, Jakarta, Rio de Janeiro and New York. 

Meet the C40 Cities taking action.

C40 & Climate Week NYC 2014

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With crucial climate talks looming in Paris next year, member city New York will host a pivotal series of meetings and events.

C40 Chair, Mayor of Rio de Janeiro, Eduardo Paes and all of C40 welcome member cities and partners to this pivotal moment. Together, under the spotlight of Climate Week, we will help to demonstrate the growing demand for — and promise of — a global agreement on climate action through important events and meetings such as the C40 & Siemens City Climate Leadership Awards and the UN Climate Summit. The leadership role of cities is now clear -- and C40 will release a series of new research findings and publications to inform that leadership, including a special report from UN Secretary-General's Special Envoy for Cities and Climate Change and President of the C40 Board of Directors, Mayor Michael R. Bloomberg.