You don't know how emissions should be regulated, but somehow you know the regulations aren't working b/c they are too lenient? My hypothesis is that all of th

You don't know how emissions should be regulated, but somehow you know the regulations aren't working b/c they are too lenient? My hypothesis is that all of the diesel-powered cars sold in the past 20 years in the US could vanish tonight, and there would be no significant change in the planet's climate vs. had people continued to drive them. The real motivation for strictly regulating diesels is their predilection to produce oxides of nitrogen and particulates, which contribute to smog and respiratory distress. While one has to make allowances for the climate and traffic in a particular place (the LA basin is always going to be smog-prone, and probably should be able to set its own regs for mobile pollution sources), the point of diminishing returns for adding more pollution controls to cars probably past at least 15 years ago.