A proposed volcanic sulfur dioxide index (VSI)

This paper proposes a volcanic SO 2 index (VSI), on the basis of a 15‐year satellite sampling of volcanic eruptions. This index is scaled to be compatible with the commonly cited volcanic explosivity index (VEI) used to compare explosive volcanic eruptions. A range of SO 2 for each VEI level is proposed so that estimates of SO 2 emission can be made from the historic VEI database. Volcanic SO 2 from large eruptions can be routinely measured by satellite instruments, and for the smaller eruptions, where the sensitivity of satellite remote sensing is not sufficient, ground‐based measurements are becoming more available. At the present time we do not think SO 2 can be used to define an accurate climate‐perturbation index, as we have both insufficient data on volcanic SO 2 and understanding of the volcano‐climate relationship.