University of Manchester scientists, writing in the journal
Nature Geoscience, have shown that natural emissions and manmade pollutants can
both have an unexpected cooling effect on the world’s climate by making clouds
brighter.
Clouds are made of water droplets, condensed on to tiny
particles suspended in the air. When the air is humid enough, the particles
swell into cloud droplets. It has been known for some decades that the number
of these particles and their size control how bright the clouds appear from the
top, controlling the efficiency with which clouds scatter sunlight back into
space. A major challenge for climate science is to understand and quantify
these effects which have a major impact in polluted regions.