Industrial plumes seed snow

The influence of industrial pollution on clouds has long interested scientists like Velle Toll , a climate physicist at the University of Tartu. He uses satellite data to study how aerosols—microscopic solid and liquid particles—emitted by human activities affect clouds. While parsing thousands of satellite images, Toll started noticing something strange: holes in the wintertime cloud cover near industrial factories ( Science 2024, DOI: 10.1126/science.adl0303 ). Once Toll recognized the pattern, it took some time to determine what caused the holes. “We detected snowfall in the same areas where we saw these holes,” he explains, and realized that the water in the clouds was condensing into snow and falling to the earth, leaving behind reduced cloud cover. Interestingly, the pattern of snowfall appeared to follow the path of each industrial site’s pollution plume. With temperatures at the sites between 0 and –36 °C, the supercooled water droplets required ice-nucleateing particles