As with the economy, government intervention can have unintended consequences. In Europe, the push to go green actually endangered lives through noxious air pollution. London, Paris and European governments “aggressively promoted diesel vehicles,” The Washington Post reported on Dec. 20. Why? For the environment, of course. Governments used policy to steer people away from carbon-dioxide emissions and toward diesel as the better choice. But the attempt to go green backfired as nitrogen dioxide emissions from diesel vehicles are shortening lives and clogging lungs, according to the Post’s London bureau chief Griff Witte. London has become the “global leader” in nitrogen...