How Volcanic Aerosols Globally Inhibit Precipitation

Observations and models have indicated a reduction in global mean precipitation during the years following major volcanic eruptions, yet why this occurs has not been rigorously established. Here we apply an energy budget framework to identify the mechanisms behind reduced post-eruption precipitation. Volcanic aerosols alter the atmosphere’s energy balance, with a precipitation (latent heating) response being one pathway that returns the atmosphere towards equilibrium. Using global climate model simulations, we demonstrate that post-eruption precipitation reduction is primarily a consequence of Earth’s surface and troposphere cooling in response to reflection of sunlight by volcanic aerosols. Additionally, these aerosols directly add energy to the atmosphere by absorbing outgoing longwave radiation, which causes much of the precipitation decline in the first post-eruption year. We further identify mechanisms that limit the post-eruption decline, most prominently the influence of a warmer stratosphere. Lastly, we demonstrate that our results are robust across climate models.