A report published on June 30, 2016, in the journal Science indicates that the hole in the ozone layer above Antarctica shows signs of beginning to heal. Since its discovery in 1985 the ozone hole has grown bigger each Spring, reaching a size of 10.9 million square miles in 2015.
The main cause of the hole is man-made chemicals known as CFCs (chlorofluorocarbons), which were widely used as propellants, refrigerants and solvents until they were banned by an international treatment in 1987 – use of CFCs had to be phased out by 1996. However, CFCs in the atmosphere are long-lived, so it will be decades, possibly centuries, before the ozone layer can fully repair itself. Naturally-released sulphur gases, for example, from volcanic eruptions can also affect the ozone layer, acting to slow its recovery.