Carbon pollution would have to be cut by 45 per cent by 2030 – compared with a 20 per cent cut under the 2C pathway – and come down to zero by 2050, compared with 2075 for 2C. This would require carbon prices that are three to four times higher than for a 2C target. But the costs of doing nothing would be far higher.

Rising arctic temperatures mean we face a future of ‘extreme extremes’ where sunny days become heatwaves and rain becomes floods, study says.