The
Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the
Vienna Convention for the Protection of the Ozone Layer) is an international
treaty designed to protect the
ozone layer by phasing out the production of numerous substances that are responsible for
ozone depletion. It was agreed on 16 September 1987, and entered into force on 1 January 1989, followed by a first meeting in
Helsinki, May 1989. Since then, it has undergone eight revisions, in 1990 (
London), 1991 (
Nairobi), 1992 (
Copenhagen), 1993 (
Bangkok), 1995 (
Vienna), 1997 (
Montreal), 1998 (
Australia), 1999 (
Beijing) and 2007 (
Montreal). As a result of the international agreement, the ozone hole in Antarctica is slowly recovering. Climate projections indicate that the ozone layer will return to 1980 levels between 2050 and 2070. Due to its widespread adoption and implementation it has been hailed as an example of exceptional international co-operation, with
Kofi Annan quoted as saying that "perhaps the single most successful international agreement to date has been the Montreal Protocol". In comparison, effective burden sharing and solution proposals mitigating regional conflicts of interest have been among the success factors for the
Ozone depletion challenge, where global regulation based on the
Kyoto Protocol has failed to do so. In case of the ozone depletion challenge, there was global regulation already being installed before a scientific consensus was established. As well in comparison, lay people and public opinion were more convinced about possible imminent risks.