Ozone is a gas comprised of three oxygen atoms and is essential in protecting humans and the environment from harmful ultraviolet light from the sun. The stratospheric ozone layer is threatened by gases such as chlorofluorocarbons (CFCs) which destroy ozone and cause the ozone hole over Antarctica. However, a recent United Nations (UN) report shows that emissions of ozone-depleting substances (ODS), such as CFCs, have significantly decreased over the past 30 years, which bodes well for the recovery of the stratospheric ozone layer. The UN report is released every four years to assess progress on the Montreal Protocol on Substances that Deplete the Ozone Layer, an agreement among UN member nations to reduce the production and consumption of man-made ODS and some hydrofluorocarbons (HFCs).
While a reduction in ODS emissions is beneficial for the climate, as many ODS are also greenhouse gases, their overall impact on the climate is generally less than other greenhouse gases such as carbon dioxide and methane. It will still take many years for the ozone layer to recover and be restored to average 1980 levels by 2040. Some ODS can persist in the stratosphere for a long time after being emitted and still be present in old appliances, which can continue to emit ozone-depleting substances into the future. A depleted ozone layer increases the risk of skin cancer, cataracts, and harm to marine life and crops due to the harmful ultraviolet rays that reach the Earth's surface.
The reason for the recovery of the ozone layer is due to the decrease in emissions of ODS and the natural chemical reactions in the stratosphere, referred to as the Chapman Cycle, which can restore ozone levels to normal, historical levels. A 2018 scientific paper showed that CFCs were not decreasing in the atmosphere as expected, likely due to illegal emissions from factories in eastern China. The Chinese government quickly cracked down on these emissions and the ozone layer is now recovering. The ozone layer is a remarkable story of global cooperation to successfully tackle an environmental problem and serves as a positive example of what can be achieved through international collaboration.Source: Futurity