Blunt talk about the earths future has found a broad audience among people jaded by empty promises and eager to find a climate leader willing to ramp up ambition. Greta Thunberg’s rise coincides with growing scientific concern. A slew of recent reports has warned oceans are heating and the poles melting faster than expected. Last year’s UN Intergovernmental Panel on Climate Change spelled out the dangers of surpassing 1.5C of global warming. To have any chance of avoiding that outcome, it said, emissions must fall rapidly by 2030. That will require far more pressure on politicians – and nobody has proved more effective at that over the past eight months than Thunberg.