CNN: City mayors from all over the world will be attending the World Mayors Summit on Climate in Mexico City later this month to pledge their commitment to combating global warming. The centerpiece of the one-day summit will be the signing of “The Mexico City Pact” — formally known as the Global Cities Covenant on Climate — which will recognize the strategic importance cities need to play in reducing carbon emissions. Convened by the World Mayors Council on Climate Change (WMCCC), ICLEI — Local…