"Tougher Emissions and Efficiency Standards—New standards for cars are becoming a global phenomenon, whether it’s more stringent rules in China, the European Union or the U.S. As the world heads toward two billion vehicles, making sure that these cars emit less pollution—both smog-forming nitrogen oxides and heat-trapping carbon dioxide—will be crucial, whether it is accomplished via more efficient internal combustion engines or better hybrids. Electric cars, including the Chevy Volt, Nissan LEAF or Tesla Model S, can help, too, provided the electricity does not come from burning fossil fuels"