Outright bans can sometimes be a good way to fight climate change

WHEN SET against the grave threat posed by climate change, the green policies favoured by economists can seem convoluted. Carbon prices, beloved of wonks, require governments to estimate the social cost of carbon emissions, a nebulous concept. Green subsidies put politicians in the position of picking promising innovators and praying that bets with taxpayers’ money pay off. Faced with these fiddly alternatives, you might ask, would simply banning the offending technologies be so bad? In fact a growing number of governments are bowing to this logic. More than a dozen countries say they will prohibit sales of petrol-fuelled cars by a certain date. On September 23rd Gavin Newsom, California’s governor, pledged to end sales of non-electric cars by 2035. Such bans may look like window-dressing, and that could yet in some instances prove to be the case. But in the right circumstances, they can be both effective and efficient at cutting carbon.