The 2018 WMO/UNEP Scientific Assessment of Ozone Depletion, has confirmed that the ozone “hole” is beginning to close as a result of measures taken under the Montreal Protocol to phase-out ozone depleting substances.
Chemical reactions in the stratosphere involving chlorine and bromine from ozone depleting substances cause ozone in the southern polar region to be destroyed. This depleted region is known as the “ozone hole”. The stratospheric temperature and the amount of sunlight reaching the south polar region control the depth and size of the Antarctic ozone hole. This year, the stratosphere over Antarctica was slightly colder than the previous few years, so the ozone hole was larger, but the overall trend is showing a reduction.