How Air Pollution Makes Floods Worse

A better understanding of how aerosols interact with weather could lead to better flood forecasts, fewer floods

Air Pollution
George Hammerstein/Corbis

It’s common knowledge that air pollution can affect health — the World Health Organization estimates that it caused 3.7 million premature deaths worldwide in 2012 alone. But now, reports Science’s Roland Pease, air pollution is being blamed for something else: flooding.

Pease writes that an atmospheric science named Jiwen Fan was inspired to study air pollution’s role in flooding after she watched catastrophic floods rush through Sichuan, China in 2013. Fan, who is an air pollution expert, wondered whether air quality played a role in the valley’s disaster, which occurred when nearly 2.5 feet of rain fell in just five days.

Together with a team of atmospheric scientists, Fan conducted simulations of how air pollution particles interact with weather. They discovered that in some geographic regions, aerosols absorb heat from the sun, suppressing the chance of rain during the day and stabilizing the atmosphere. It’s another story at night: the warmed, rising air is transported to mountainous areas before it heads higher up into the atmosphere. This causes massive precipitation that can actually make flooding worse.

The team calls their discovery “aerosol-enhanced conditional instability,” and its flipside is that reducing pollution in places like Sichuan can actually reduce floods. There’s another upside to a better understanding of how pollution particles worsen flooding, says the team in a release: it could help future weather forecasters predict floods.

“We were amazed at the scale the effect of the pollution had,” Fan told Pease. Perhaps her new research will help prompt people worldwide to commit to reducing air pollution.

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