Global volcanic aerosol properties and volcanic forcing of global climate change since 1990

Abstract:

To quantify the impacts of man-made climate change and the effectiveness of mitigation strategies it is essential to accurately attribute changes of surface temperature over recent and future decades not only to anthropogenic, but also to natural climate forcing agents such as volcanic eruptions. Here we present a new time series of global volcanic aerosol properties and volcanic aerosol forcing since the year 1990 by using a volcanic sulfur dioxide (SO₂) emissions inventory in a state-of-the-art climate model (CESM1) with detailed sulfur chemistry and a prognostic stratospheric aerosol scheme (WACCM-MAM). Based on our model simulations, we calculate a time-mean global-mean volcanic forcing of ‑0.10 W m^-2 during 2005-2015 relative to the 1999-2002 time-mean, which can be attributed to a high frequency of small-to-moderate magnitude eruptions after the year 2005. Based on a statistical analysis of the recurrence frequencies of eruptions of different magnitude, we suggest that near-term warming projections are overestimated when assuming volcanically quiescent conditions, which are statistically rarer than periods of frequent small-to-moderate magnitude eruptions.