Using direct satellite observations of the Antarctic ozone layer, NASA scientists have been able to link the 20 percent decrease in ozone depletion from 2005 to 2016 with the decline of stratospheric chlorine (chlorine loading) during that period, resulting itself from the ODS (Ozone Depleting Substances) phase-out resulting from the Montreal Protocol.
Satellite data were analyzed for the dark southern winter, when the stratospheric weather is quiet and temperatures are low and stable. During this period, as Antarctic temperatures are always very low, the rate of ozone destruction depends mainly from the chlorine concentration, differently from the summer period, when ozone depletion is strongly influenced by the low stratosphere circulation.
Earlier estimates of the ozone hole recovery were based on a statistical analysis of the variable size of the yearly ozone hole area. This study is the first to link ozone depletion with the decrease of ODS concentrations in the stratosphere resulting from the Montreal protocol.