How Covid lockdowns triggered record rainfall in China

China’s record-breaking rainfall during summer 2020 was linked to Covid lockdowns, research suggests.

Hundreds of people died and millions were evacuated as unprecedented rains fell over heavily populated regions of eastern China during June and July of 2020.

Now a study, published in Nature Communications, has linked the rapid drop in air pollution to the lower greenhouse gas emissions associated with the Covid shutdown, which contributed to about a third of the extreme rain.

Yang Yang, a professor at Nanjing University of Information Science and Technology, in China, and colleagues modelled the impact that greenhouse emissions and particulates had on rainfall in China over the past four decades.

Increasing air pollution has reduced the amount of rainfall in central and eastern China over this time, with particulates acting as a focal point for droplet formation, resulting in “constipated” clouds.

However, Yang and colleagues found the abrupt cleaning of the skies and drop in greenhouse emissions in 2020 reversed this trend, helping to intensify convection and allow moist air from the ocean to move over land.

The mechanism by which the lockdown changes influenced the weather are complex, but thankfully the researchers believe that more gradual policy-driven reductions in emissions are unlikely to trigger such dramatic events.