In August 2006, President Clinton launched the Clinton Climate Inititative  a project dedicated to making a difference in the fight against climate change in practical, measurable, and significant ways. In its first phase, CCI is serving as the exclusive implementing partner of the C40 Large Cities Climate Leadership Group, an association of large cities that have pledged to accelerate their efforts to reduce greenhouse gas emissions. CCI is assisting its partner cities to develop and implement large scale programs that directly result in substantial greenhouse gas emissions reductions.

The C40 Large Cities Climate Leadership Group consists of the following cities: Addis Ababa, Athens, Bangkok, Beijing, Berlin, Bogota, Buenos Aires, Cairo, Caracas, Chicago, Delhi, Dhaka, Hanoi, Hong Kong, Houston, Istanbul, Jakarta, Johannesburg, Karachi, Lagos, Lima, London, Los Angeles, Madrid, Melbourne, Mexico City, Moscow, Mumbai, New York, Paris, Philadelphia, Rio de Janeiro, Rome, Sao Paulo, Seoul, Shanghai, Sydney, Toronto, Tokyo, and Warsaw.