What will happen if America’s president-elect follows through on pledges to tear up environmental laws

“LIKE ice water through the veins.” That is how a UN official, in Marrakesh for the UN climate summit that ended on November 18th, described the effect of Donald Trump’s electoral victory. Her trepidation was widely shared at the two-week event—and justified. In a tweet in 2012 Mr Trump called anthropogenic warming a “hoax”. On the campaign trail he said he would abolish America’s Environmental Protection Agency (EPA) and “cancel” the UN agreement to curb greenhouse-gas emissions adopted by 190-odd countries in Paris last year. But in an interview this week with the New York Times, he seemed to waver. Gathered in the ancient Berber city, representatives of those countries pondered whether America is about to forfeit the leadership on climate change it belatedly showed when Barack Obama helped bring about the Paris accord. 

That deal, which came into force earlier this month, includes a...