Thirty years ago, 28 parties decided to start preservingthe ozone layer,a shield that protects us and the environment from harmful radiation from the sun. A hole in the ozone layer had been detected over Antarctica in 1985.

Thirty years later, 197 parties are celebrating the results of their efforts to control chemicals that have been destroyingthe ozone layer. And today, there is scientific evidence that the ozone layer is healing itself and is expected to recover by the middle of this century.

The Vienna Convention for the Protection of the Ozone Layer and its Montreal Protocol on Substances that Deplete the Ozone Layer have so far led to a 98 per cent reduction globally of the historic baseline levels of the produced and consumed chemicals that destroy the ozone layer. They are therefore widely recognized as the most successful environmental treaties in history.