There is no doubt what is top of world leaders’ agenda. “It’s the climate, stupid,” to misquote former US president Bill ­Clinton. As some wag commented about this week’s global summit in Switzerland, it should be called Greta 2020, not Davos 2020.

Even Donald Trump claimed to be a “big believer in the environment” and promised to plant trees. But he also told Davos delegates to reject “the perennial prophets of doom” preaching climate apocalypse.