A new study uses satellite data over the Southern Hemisphere to understand the makeup of global clouds since the Industrial Revolution. This research tackles one of the largest uncertainties in today’s climate models — the long-term effect of tiny atmospheric particles on climate change.
Research led by the University of Washington and the University of Leeds in the United Kingdom uses remote, pristine parts of the Southern Hemisphere as a window into the early-industrial atmosphere.
The team compared satellite measurements of cloud droplet concentration in the atmosphere over the Northern Hemisphere — now heavily polluted with today’s industrial aerosols — and over the relatively pristine Southern Ocean. They used this to measure how particles from pollution may have affected Earth’s temperature since 1850.
The results, published the week of July 27 in the Proceedings of the National Academy of Sciences, suggest that early industrial aerosol concentrations and cloud droplet numbers were much higher than many global climate models estimate. This could mean that human-generated atmospheric aerosols, or particulate pollution, is not damping the warming from carbon dioxide as much as some climate models estimate. The study suggests that the cooling effect of pollution is likely to be more moderate.
“One of the biggest surprises for us was how high the concentration of cloud droplets is in Southern Ocean clouds,” said co-lead author Isabel McCoy, a UW doctoral student in Atmospheric Sciences.
The Southern Ocean surrounding Antarctica has few aerosol particles from human activity, but the cloud droplet concentration remains high, especially in summer.
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