There is an old joke about an economist and an engineer stranded on a desert island, who find a case full of cans of beans washed up on the beach. After the engineer has tried various ways to open a can, without success, the economist steps up: “It’s easy! Assume we have a can-opener … ” Much of the debate about how the world can minimise the risk of the worst effects of climate change has a similar flavour: we may be on a worrying trajectory today, but we can assume that amazing new technologies will emerge to enable steep cuts in greenhouse gas emissions. An interesting report,from a team led by Daniel Yergin of IHS Markit and former US energy secretary Ernest Moniz, this week tried to set out an approach for developing those technologies that goes beyond simple wishful thinking. To extend the analogy, they are making a plan for lighting some torches and trying really hard to find a can-opener, or several.