Observations of a substantial cloud-aerosol indirect effect during the 2014–2015 Bárðarbunga-Veiðivötn fissure eruption in Iceland

The Bárðarbunga-Veiðivötn fissure eruption lasted from 31 August 2014 to 28 February 2015, during which its sulfur emissions dwarfed anthropogenic emissions from Europe. This natural experiment offers an excellent opportunity to investigate the aerosol indirect effect and the effect of effusive volcanic eruptions on climate. During the eruption cloud droplet effective radius (re) over the region surrounding Iceland was at the lowest value in the 14 year Moderate Imaging Spectroradiometer data record during September and October 2014. The change in reflected solar radiation due to increased cloud reflectivity during September and October is estimated to exceed 2 W m
2 over the region surrounding Iceland, with increases of 1 W m
2 extending as far south as the Açores. The strength of the aerosol indirect effect diagnosed here reaffirms the ability of volcanic aerosols to affect cloud properties and ultimately the planetary albedo.