Strong constraints on aerosol-cloud interactions from volcanic eruptions

• Published in: Nature
• Main Authors: Malavelle, Florent F., Haywood, Jim M., Jones, Andy, Gettelman, Andrew, Clarisse, Lieven, Bauduin, Sophie, Allan, Richard P., Karset, Inger Helene H., Oreopoulos, Lazaros, Cho, Nayeong, Lee, Dongmin, Bellouin, Nicolas, Boucher, Olivier, Grosvenor, Daniel P., Carslaw, Ken S., Dhomse, Sandip, Mann, Graham W., Schmidt, Anja, Coe, Hugh, Hartley, Margaret E., Dalvi, Mohit, Hill, Adrian A., Johnson, Ben T., Johnson, Colin E., Knight, Jeff R., O'Connor, Fiona M., Partridge, Daniel G., Stier, Philip, Myhre, Gunnar, Platnick, Steven, Stephens, Graeme L., Takahashi, Hanii, Thordarson, Thorvaldur
• Other Authors: Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU]Sciences of the Universe [physics]; Holuhraun; Iceland
• Online Access: https://insu.hal.science/insu-03727061; https://doi.org/10.1038/nature22974

International audience Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol-cloud interactions. Here we show that the massive 2014-2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets—consistent with expectations—but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around -0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response.