Is the ozone layer changing as expected?
TOMS Observations from 1978 to the present show strong secular trends in decreasing ozone both at midlatitudes and at the polar regions, Although the Antarctic ozone hole growth has slowed, very significant ozone depletions have occurred in the Arctic . As a result of international agreements, tropospheric chlorofluorocarbons concentrations have begun to decrease. UARS data shows a flattening in the stratospheric chlorine reservoir concentrations although an unambiguous decrease has not been detected. A decrease in chlorine should lead to recovery of the ozone layer, but this recovery may be delayed by increases in greenhouse gases which would cool the stratosphere giving rise to more frequent and persistent polar stratospheric clouds and/or increase the water vapor in the stratosphere by warming the tropical tropopause. In fact, stratospheric water vapor does appear to be increasing faster than can be accounted for by the secular trend in methane. As a result of the uncertainty in str
