Do we understand the sources of stratospheric sulfur?

Abstract:

In times of quiescent or moderate volcanic activity, sulfur gases released by natural and anthropogenic processes make a significant contribution to the stratospheric aerosol load. To quantify the present flux of non-volcanic sulfur to the stratosphere and to predict future changes, we need to understand troposphere-to-stratosphere transport in general as well as the distribution and cycling of all important sulfur gases in the troposphere.

This keynote will attempt to give an overview of our current understanding of the tropospheric sulfur cycle, and identify key knowledge gaps and possible strategies to fill them. Special focus will be given to the following questions:

• How well do we understand the cycling and budget of OCS in the troposphere, and do current uncertainties impair our ability to estimate the stratospheric flux?
• How much anthropogenic SO₂ reaches the stratosphere?
• What is the role of “minor” species such as DMS, CS₂ and H₂S?