The California Air Resources Board says it will require new cars to display labels indicating how much smog-forming and global warming pollutants they will emit compared with other vehicles in the same model year.

Each label will carry a score for global warming pollution and another for smog-forming pollution. On a 10-point scale, average vehicles will receive five points, the dirtiest vehicles will receive a one, and the cleanest a 10.

Officials said some automobile dealerships might introduce the labels as early as next month.

"For most people in California, driving a car is the No. 1 way they pollute," said Spencer Quong, a senior vehicles analyst with the Union of Concerned Scientists. "These labels are simple and straightforward and will make identifying a greener car easier than ever."

He said the labels will cut through industry "greenwashing" by making automakers accountable.