Colorado air quality officials on Thursday launched a push ordered by Gov. John Hickenlooper to ensure ever-more-efficient gas-powered vehicles — calculated to cut heat-trapping greenhouse pollution by 2 million tons a year of carbon dioxide. Then the state air commissioners went a step further and committed to consider requirements on the auto industry aimed at accelerating a shift toward zero-emission electric vehicles. This means new cars Coloradans buy likely will have to cover more miles per gallon in the future — even as the Trump administration freezes federal fuel-efficiency standards.