History of the C40

Johannesburg

Johannesburg, South Africa. Host of the Fifth C40 Mayors Summit in 2014.

Photo credit: Dimitri Nenkov

The C40 Mission

C40 is a global network of large cities taking action to address climate change by developing and implementing policies and programs that generate measurable reductions in both greenhouse gas emissions and climate risks.

Working together since 2005

In October 2005, then Mayor of London Ken Livingstone convened representatives from 18 megacities to pursue action and cooperation on reducing greenhouse gas emissions. The meeting resulted in an agreement to cooperate on reducing climate emissions by taking decisive and immediate action on a number of points, most notably the creation of procurement policies and alliances to accelerate the uptake of climate-friendly technologies and influence the market place. This was the start of the network.

In 2006, Mayor Livingstone invited the Clinton Climate Initiative (CCI) to become its delivery partner, greatly strengthening both organisations with a shared sense of purpose and an efficient support network for delivering world-class projects that optimise emissions reductions. The network at this point had grown to 40 cities, and thus the name C40 was born. Serving as C40’s first Chair, Mayor 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 C40 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 C40-CCI Climate Positive Development Programme and the Carbon Finance Capacity Building programme.

In November 2010, New York City Mayor Michael R. Bloomberg began his tenure as C40 Chair. Key milestones in 2011 include the full integration of C40 with the CCI Cities Program by which C40 executives and staff are working in unison with CCI City Directors and programmatic teams to support climate action in cities.

The work that the C40 Cities accomplishes is critical for reducing carbon emissions worldwide, but there is far more to be done, as President of the C40 Board, former C40 Chair, and 108th Mayor of New York City Mayor Bloomberg explains.

While international negotiations continue to make incremental progress, C40 Cities are forging ahead. Collectively they have taken more than 4,700 actions to tackle climate change, and the will to do more is stronger than ever. As innovators and practitioners, our cities are at the forefront of this issue – arguably the greatest challenge of our time. Mayor Michael R. Bloomberg

Another highlight of 2011 was the C40 Cities Mayors Summit in Sao Paulo, where C40 announced new partnerships with the World Bank and ICLEI—Local Governments for Sustainability—to accelerate climate action in cities through streamlined financing, greenhouse gas accounting and uniform reporting. The release of two reports developed in collaboration with Carbon Disclosure Project (CDP) and ARUP, respectively, emphasized the critical role of measurement and transparency in tackling climate change in megacities.

Rio de Janeiro Mayor Eduardo Paes began his tenure as C40 Chair in December 2013.

Leading the Way

We’re proud of what cities have accomplished since 2005, and we continue to lead the way on mitigating the risks of climate change with our innovative and effective approach.

Learn more about our networks , research , and communications platform .