redOrbit: New York City, Denver and Las Vegas are among 21 U.S. cities that will measure their carbon footprints in an effort to reduced climate-warming emissions. The cities will employ the same system in use by some 1,300 companies. “If you don’t measure these emissions, you cannot manage them,” said Paul Dickinson, CEO of UK- based Carbon Disclosure Project (CDP), in an interview with Reuters. The CDP, which represents 385 global institutional investors that together manage …