A study explores the role of solar geoengineering focused on reducing incoming sunlight in protecting against the effects of greenhouse gases on stratocumulus cloud cover. Solar geoengineering aims to mitigate climate change by reducing incoming solar radiation. Such efforts, however, are largely focused on the incoming and outgoing energy balance at the upper layers of the atmosphere. Tapio Schneider and colleagues modeled the effects of geoengineering and warming scenarios on high-resolution idealized cloud simulations. Because subtropical stratocumulus clouds depend on longwave radiative cooling to sustain air and moisture flow and because elevated atmospheric carbon dioxide and water vapor weaken longwave radiative cooling, a rise in greenhouse gas emissions can thin and dissipate clouds. Modeling results suggested that subtropical stratocumulus clouds thin under increasing greenhouse gas concentrations and may eventually break up at atmospheric carbon dioxide concentrations higher than 1,700 parts per million, with an accompanying strong global warming of around 5 °C, despite solar geoengineering. According to the authors, the results suggest that solar geoengineering alone may not be sufficient to prevent climate hazards amid rising greenhouse gas concentrations.
Article #20-03730: "Solar geoengineering may not prevent strong warming from direct effects of CO2 on stratocumulus cloud cover," by Tapio Schneider, Colleen M. Kaul, and Kyle G. Pressel.
MEDIA CONTACT: Tapio Schneider, California Institute of Technology, Pasadena, CA; e-mail: tapio@caltech.edu
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Proceedings of the National Academy of Sciences