Study Reveals Unexpected Cooling Effect from Cleaner Clouds
A new study has found that cleaner clouds, resulting from reduced dust levels in the atmosphere, are helping to slow the rate of global heating. This previously unidentified effect is not accounted for in current climate models, which may overestimate the projected pace of global warming.
Researchers analyzed satellite observations of high clouds in the northern hemisphere from 2008 to 2018, assessing the ratio of ice crystals to liquid droplets. Their findings, published in Geophysical Research Letters, show that clouds have become less icy over that period.
Dust Levels Decline Due to Weaker Winds
Weakening surface winds, driven by climate change, have resulted in less dust being lifted into the atmosphere over the last two decades. Dust particles typically help seed ice crystals, so lower dust levels lead to fewer ice crystals in clouds. This effect is not observed in southern hemisphere clouds, where dust levels are already much lower.
Increased Cloud Reflectivity Offsets Heating
Liquid droplets reflect more sunlight than ice crystals, making less icy clouds more reflective. According to the study, this extra reflectivity offsets about a quarter of the heating caused by other changes, such as an increase in high clouds that trap more heat. The findings suggest global warming may not occur as rapidly as current models predict, though researchers caution against complacency.
