When will it be socially unacceptable to drive a car with a tailpipe? Twitter poll results

Exhaust emissions from tailpipe [photo: Simone Ramella, 2005, used under Creative Commons 2.0]At Green Car Reports, we've developed something of a tradition for Earth Day. Back in 2014, we formulated the question: "When will we start to see tailpipes on cars as morally wrong?" The question came originally from a friend who works in advocacy in public health, who likened CO2 emissions from tailpipes to smoking cigarettes, which has now been...