Increased stratospheric greenhouse gases could delay recovery of the ozone hole and of ozone loss at southern mid-latitudes

Stratospheric H2O is increasing, and may be responsible for a large part of the observed cooling of the lower stratosphere. Further cooling will lead to more PSCs in the edge of the Antarctic stratospheric vortex in spring, though not in the vortex core which already becomes cold enough for near-continuous PSCs. A new diagnostic of mixing, plus measurements of H2O, show that the vortex edge is weakly mixed with the core until late in the spring. This isolation will allow any increase in PSCs to result in continued severe ozone loss, despite reduced chlorine due to the Montreal Protocol. The isolated edge region is half the area of the ozone hole. It frequently passes over southern South America late enough in the spring for major UV damage, and in summer the broken-up ozone hole contributes to significant hemisphere-wide ozone loss. (C) 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.