The group of cities, whose members include Berlin, Beijing, Hong Kong, Johannesburg, London, Paris, Sao Paulo, New York and Toronto, pledged to fight climate change by taking measures ranging from promoting renewable energy to introducing new building regulations designed to reduce the consumption of natural resources including water.

David Miller, Toronto Mayor and Chairman of the C40 group, said that city mayors from around the world were every day taking important actions to reduce energy consumption and the carbon emission. "The focus of the Tokyo conference is on measures that support adapting to climate change that is already occurring," the mayor from Canada added.

Members from the C40 group put forward ideas to prevent the "urban heat island effect," in which temperatures tend to rise in crowded metropolitan areas. The ideas include expanding green space in urban areas and building corridors to allow more wind and water to come into cities. The city planners also pledged to look into renewable energies such as solar power and to introduce water retentive pavements. The widespread use of concrete is a key reason that cities absorb heat more than rural areas.

The C40 group is an initiative started by former London Mayor Ken Livingstone in 2005. Then representatives from 18 cities met in London to discuss joining forces to tackle global warming and climate change. In August 2006, the initiative was strengthened when former President Clinton and Ken Livingstone announced a partnership between the Clinton Climate Initiative and the Large Cities Climate Leadership Group. This new partnership pledged to reduce carbon emissions and increase energy efficiency in large cities across the world.