With net zero policies under attack from elected far-right populists as well as autocratic petrostates, and another summer of record-breaking temperatures in Europe, the failure to decarbonise the world’s power supply is as gravely concerning as ever. But the UN secretary general, António Guterres, struck an optimistic note in a recent speech in New York. The world, he said, “is on the cusp of a new era … The sun is rising on a clean energy age.” Pointing to falls in the cost of onshore wind and solar, and the risk of further gas-price shocks in future, he called on big technology companies – whose datacentres are one reason