Air pollution is a killer. But cleaning it up could have deadly consequences. A study shows that by the end of the century, cleaner air may bring stronger heatwaves.

It has long been known air pollution has been helping to prevent even greater global heating. Sulphate particles reflect heat back into space and other pollutants encourage cloud formation. But until now, it has not been clear where and when warming will occur if we clean up our skies.

Alcide Zhao and colleagues from Edinburgh University used a climate model to explore this question. With emissions remaining at current levels, they show that by the end of the century, heatwaves will be an average of 2.4C warmer and 17 days longer compared with today. On top of this, improved air quality will make heatwaves 25% hotter, 12% more likely and 41% longer.

Regions that currently have the most polluted skies will feel the greatest effect. During the second half of this century, cleaner skies will increase the chances of a record-breaking European heatwave every year from 45%, through greenhouse gases alone, to 74%. Similar effects are seen over China. Zhao said: “It all adds urgency to reducing greenhouse gases simultaneously with air pollution.”