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A Georgia Tech atmospheric scientist and a former colleague have reported a new and potentially important mechanism by which chemical emissions from ocean phytoplankton may influence the formation of clouds that reflect sunlight away from our planet.
Discovery of the new link between clouds and the biosphere grew out of efforts to explain increased cloud cover observed over an area of the Southern Ocean where a large bloom of phytoplankton was occurring.
Based on satellite data, Athanasios Nenes of Georgia Tech and Nicholas Meskhidze, formerly at the Institute but now at North Carolina State University, hypothesized that airborne particles produced by oxidation of the chemical isoprene — which is emitted by the phytoplankton — may have contributed to a doubling of cloud droplet concentrations seen over a large area of ocean off the eastern coast of South America.
Using complex numerical models, they estimated that the resulting increase in cloudiness reduced the absorption of sunlight by an amount comparable to what has been measured in highly polluted areas of the globe. If confirmed by field studies, this connection between clouds and biological activity could add a critical new component to global climate models. Many environmental scientists believe that increased cloud cover may be partially countering the effects of global warming by reducing the amount of energy the planet absorbs from the sun.
"Studies like this one may help reshape the way we think about how the biosphere interacts with clouds and climate," said Nenes, an assistant professor in the School of Earth and Atmospheric Sciences and School of Chemical and Biomolecular Engineering. "One of the largest uncertainties right now in climate models is the ability to predict how clouds would respond to changing particle levels — whether they originate from humans with air pollution or from biological activity. We can now see very strongly the influence of marine biology on oceanic clouds."
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