As the treaty turns 35 on Ozone Day, we will remember how the Montreal Protocol ended one of the biggest threats ever to face humanity as a whole: the depletion of the ozone layer. When the world found out that ozone-depleting gases used in aerosols and cooling were creating a hole in the sky, they came together. They showed that multilateralism and effective global cooperation worked and they phased out these gases. Now the ozone layer is healing, allowing it once again to shield humanity from the sun’s ultraviolet radiation.
Background
A number of commonly used chemicals have been found to be extremely damaging to the ozone layer. Halocarbons are chemicals in which one or more carbon atoms are linked to one or more halogen atoms (fluorine, chlorine, bromine or iodine). Halocarbons containing bromine usually have much higher ozone-depleting potential (ODP) than those containing chlorine. The man-made chemicals that have provided most of the chlorine and bromine for ozone depletion are methyl bromide, methyl chloroform, carbon tetrachloride and families of chemicals known as halons, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).
