The Vienna Convention for the Protection of Ozone Layer was adopted in the year 1985 and entered into force in 1988. It acts as a framework for the international efforts to protect the ozone layer. However, it does not include legally binding reduction goal for the use of ozone-depleting substances (ODS).
The Vienna Convention and its Montreal Protocol are the most widely ratified treaties in the history of United Nations, with 197 parties. United Nations Environment Programme (UNEP) provides secretarial assistance to the Convention.
The Montreal Protocol on Substances that Deplete the Ozone Layer was designed to reduce the production and consumption of ozone-depleting substances in order to reduce their abundance in the atmosphere and thereby protect the earth's fragile ozone layer. The treaty was opened for signature in 1987 and entered into force in 1989. The first follow up meeting under the protocol was held in Helsinki in 1989. Since then, it has undergone multiple revisions:
- London, 1990
- Nairobi, 1991
- Copenhagen, 1992
- Bangkok, 1993
- Vienna, 1995
- Montreal, 1997
- Beijing, 1999
- Kigali, 2016
The protocol sets a mandatory timetable for the phase-out of ozone-depleting substances which was reviewed periodically. The developed, as well as developing countries, come under binding progressive phase-out obligations for all the major ozone-depleting substances, including chlorofluorocarbons (CFCs), halons, and the less damaging transitional chemicals such as hydrochlorofluorocarbons (HCFCs). The Multilateral Fund was the first international treaty-based finance mechanism designed to help the developing countries achieve their phase-out obligations by providing them with financial assistance.
The protocol targets 96 chemicals which are used in over 240 industrial processes/sectors. Under the Multilateral Fund, more than $2.5 billion was provided as financial assistance to help developing countries phase-out the production and consumption of ozone-depleting substances. The protocol is considered to be one of the most successful environmental treaties because it has helped in not only stopping the depletion of ozone layer but also in reversing the damage which was reflected in the shrinking of the ozone hole that was formed over Antarctica. Other significant environmental benefits of the protocol include the delay of climate forcing by up to 12 years.