The size of the 2015 Antarctic Ozone Hole was the third largest on record in the 1991-2014 period, and lasted an extra two weeks in October.
It started rather late and reached a size of 28.2 million km2 on October 2nd, 2015, close to the maximum observed of 28.75 million km2.
This large and persistent ozone hole was due to unusually low stratospheric temperatures that instead of increasing after the polar night – suddenly dropped down to 181.9 K on October 3rd, about 8 K lower than the 1979-2014 average, and remained close to the long term minimum values for weeks. These very low temperatures are themselves explained by the persistence of a very stable vortex, which would prevent warmer air to enter the stratosphere above the pole.
The 2015 NOAA Ozone Depleting Gas Index (ODGI) presents a continuous decrease since 2002 for the Antarctic atmosphere, and still projects the recovery of the ozone layer to occur around 2070 in the Antarctic and in mid-latitudes around 2045.