Chemical loss of Arctic ozone due to anthropogenic halogens is driven by temperature, with more loss occurring during cold winters favorable for the formation of polar stratospheric clouds (PSCs). A statistically significant rise in the local maxima of PSC formation potential (PFPLM) for cold winters is shown in meteorological data over the past half-century. General Circulation Models (GCMs) also project positive trends in PFPLM from 1950 to 2100, with the highest values at the end of the century for simulations with large increases in radiative forcing from greenhouse gases (GHGs). Combining projections of stratospheric halogen loading and humidity with GCM-based temperature forecasts suggests that conditions favorable for large seasonal Arctic ozone loss could persist or worsen until the end of this century if GHG abundances continue to rise steeply.

Peter von der Gathen, Rigel Kivi, Ingo Wohltmann, Ross J. Salawitch, Markus Rex