Particulate pollution has been shown to ‘choke’ clouds, preventing them from condensing into rain as they pass over mountain ranges, which normally triggers rainfall.

Comparing over 50 years of rainfall and visibility data from a meteorological station on Mount Hua in the north-west of China showed rainfall decreased by up to 50% on days when particle pollution, as indicated by lower visibility, was high.

“This is the first time a direct link between increasing pollution and decreasing precipitation has been observed. The finding is important since precipitation is one of the main sources of water in northern China,” said Daniel Rosenfeld from the Hebrew University of Jerusalem who led the research.

Since the 1950s, when the oldest measurements date back to, average precipitation over the mountain has fallen by 20%.

A similar comparison made for a lowland area showed no such correlation. This is due to the distinct ways in which raindrops are formed over mountains and on plains.

In a country where clean water is becoming increasingly scarce due to pollution, land use changes and global warming, the

Particulate pollution from cars, agriculture and power plants has been rising steadily and causing considerable damage to people’s health and affecting crop production, as well as – it now turns out – aggravating the droughts parts of the country are regularly subjected to.

The phenomenon observed in China is very likely to affect other parts of the world, the researchers said.

Goska Romanowicz

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