Cities' policies may reduce carbon emissions 8 gigatons by 2050

Cities have the potential to reduce annual greenhouse-gas emissions by 8 gigatons by 2050, the equivalent of cutting global coal use by more than half, through better energy-management at the local level, according to the C40 Cities Climate Leadership Group.

Cities can implement new policies faster than nations in areas including transportation, energy efficiency and waste management, the group said in a statement today. C40 includes leaders of large cities around the world working to curb climate change.

"Mayors are not waiting to take decisive action to combat global climate change," Eduardo Paes, chairman of C40 and the mayor of Rio de Janeiro, said in the statement. "Leading mayors are setting the example for the rest of the world, and this research shows what could be achieved."

C40 announced its findings -- the first time cities' potential to reduce global emissions has been quantified -- at the United Nations' Climate Summit in New York City.