Iceland volcano’s eruption shows how sulfur particles influence clouds

The Bardarbunga event was a fissure that emitted sulfur emissions during six months, providing a model for how volcanic or human emissions alter clouds.

It has long been suspected that sulfur emissions can brighten clouds. Water droplets tend to clump around particles of sulfuric acid, causing smaller droplets that form brighter, more reflective clouds.

But while humans have pumped sulfur into Earth’s atmosphere since the Industrial Revolution, it’s been hard to measure how this affects the clouds above. New University of Washington research uses a huge volcanic eruption in Iceland to measure the change.

The new study co-authored by Atmospheric Sciences‘ Dennis Hartmann, to be published in Geophysical Research Letters, a journal of the American Geophysical Union, shows that sulfur emissions do indeed result in smaller cloud droplet size, leading to brighter clouds that reflect significantly more sunlight.

“This eruption is a chance to nail down one of the big uncertainties in climate models,” said first author Daniel McCoy, a UW doctoral student in atmospheric sciences.