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Pollen Can Seed Clouds, Fuel Rainfall, Study Finds

A surge of pollen in spring can affect the formation of clouds and rainfall, according to a new study. The authors say that, as the planet warms, pollen counts are expected to grow, potentially giving rise to more springtime rainfall.

In clouds, water condenses onto bits of dust, sea salt, soot, and even tiny particles of plastic. That water will freeze into ice crystals that eventually fall to the earth, melting into raindrops as they waft toward the ground. Scientists have previously shown in the lab that water will also condense onto pollen, but until now, they had never established a link between pollen and rainfall in the real world.

For the new study, scientists analyzed pollen counts from 50 sites across the U.S. over a decade, finding that a boom in springtime pollen led to an uptick in cloud ice, which was linked to more frequent rainfall. The study was published in Environmental Research Letters.

In light of the findings, the researchers call for incorporating the effect of pollen into climate models. As the planet warms and springs grow longer, pollen counts are edging upwards. More airborne pollen could lead to to more frequent and intense rainfall in the decades to come, said lead author Jan Kretzschmar, of the University of Leipzig in Germany. He added, “If we can correctly simulate the effect of pollen and how it interacts with the climate, we will be able to make more accurate predictions.”