Arctic ozone loss and Antarctic ozone hole
First proposed by Molina and Rowland in early 1970s (Rowland and Molina won Nobel prize for Chemistry in 1995 along with Paul Crutzen), Stratospheric ozone hole in the Antarctic region due to chemical destruction involving halogen compounds is very well known.
Ozone hole has resulted in significant changes in southern hemispheric climate in the past decades (Gillett and Thompson, 2003; Thompson et al., 2011). It resulted in the enactment of an international treaty, popularly known as Montreal Protocol, adopted on September 16, 1987 in Montreal. It aimed to protect the ozone layer by controlling the global emissions of ozone depleting substances (ODS), known as chlorofluorocarbons (CFC).
Due to the decrease in atmospheric loading of ODSs which has peaked around 2000 (Velders et al., 2007), the Antarctic ozone hole is expected to be on the mend since 2000. A number of studies have already reported the early signs of the healing of ozone hole (Solomon et al., 2016; Kuttippurath et al., 2017). However, there has not been any study reporting the healing in saturation layers. Ozone hole saturation layers are the atmospheric layers in the lower stratosphere (13-21 km from the sea level) where the complete destruction of ozone occurs.
A few of the studies have suggested the beginning of ozone saturation in 1991 (Jiang et al., 1996; Yang et al., 2008) but there have been references of the same occuring at McMurdo in 1987 (Hofmann et al., 1993; Gardiner et al., 1988).