AFP: Mayors from some of the world’s major cities on Friday vowed to do their part in curbing the carbon emissions blamed for global warming, ahead of a major UN climate meeting later this month. Mayors from New York, Johannesburg and Toronto — part of the “C40” group — were among those in Hong Kong discussing ways to tackle the problem, including making buildings energy efficient and putting more electric-powered vehicles on roads. The “C40”, launched in 2005, is an initiative of more than 40…