Future changes in stratospheric ozone and the role of heterogeneous chemistry

Abstract

HETEROGENEOUS chemical reactions on the surfaces of solid or liquid particles present in the lower stratosphere may be an important influence on the levels of ozone depletion resulting from increased concentrations of anthropogenic chlorine compounds in the atmosphere¹. Such processes, occurring on ice particles in polar stratospheric clouds, have been invoked to explain the formation of the springtime ozone hole over Antarctica^2,3. Sulphuric acid aerosols injected into the atmosphere following a volcanic eruption may also provide sites for heterogeneous chemistry leading to ozone depletion⁴. Here we present model calculations that assess the importance of heterogeneous processes in future ozone depletion, assuming that trace-gas concentrations follow the protocol agreed at the recent international convention in London. We find that, even if this protocol is adhered to, reactions on the surface of sulphuric acid aerosol particles could produce significant ozone depletion into the beginning of the next century, especially if a major volcanic eruption (similar to the El Chichón eruption of 1982⁴) takes place.