Ceasing or reducing to acceptable levels emissions of fluorocarbons and other halocarbons used as aerosol propellants, blowing agents in foam production, solvents and refrigerants, nitrous oxide emissions from both organic and inorganic nitrogen fertilizers, aircraft exhaust emissions and other. Collectively known sources of ozone depleting substances (ODS): the principal ones being chlorofluorocarbons (CFCs), other halons (compounds of chlorine, bromine and fluorine), carbon tetrachloride, methyl chloroform and nitrous oxide.
Stratospheric ozone in the so called ozone layer plays a vital ecological role by filtering out most biologically harmful ultraviolet radiation (UV-B). Since the discovery of an ozone hole over Antarctica in 1985, ozone depletion has been recorded over other parts of the world, including a reduction by more than 14% between 1969/70 and 1993 over continental parts of the northern middle latitudes. Resulting biological damage that has been linked to or established as a result of ozone depletion include skin infections and skin cancer, eye damage, reduced vitality of the immune system in animals including humans, adversely affected cultivated plants and forested plant species (typically resulting in reduced biomass), as well as damaging aquatic ecosystems, particularly single-celled algae and plankton, which are at the start of the aquatic food chain. Furthermore, it has been estimated that a one percent decrease in stratospheric ozone increases UV-B radiation at Earth's surface by two percent, whilst only a one percent reduction in total ozone produces a two to four percent increase in biological effects, and a one percent decrease in the ozone layer could result in a four to six percent increase in certain kinds of skin cancer. Changes in the ozone layer can also change the climate and the circulation of the atmosphere. Ozone depletion and increasing aerosol concentrations in the lower stratosphere and troposphere have a cooling effect, which may be partially offsetting and masking the full extent of the greenhouse effect.
This strategy features in the framework of Agenda 21 as formulated at UNCED (Rio de Janeiro, 1992), now coordinated by the United Nations Commission on Sustainable Development and implemented through national and local authorities.
In 1977, the USA Congress banned CFCs in aerosols.
During the 1980s progressively more ambitious agreements were reached, culminating in 1990 with a binding agreement to phase out the consumption of CFCs and related chemicals in industrial countries by 2000. The Montreal Protocol on Substances that Deplete the Ozone Layer was signed in 1987. The protocol aims to control consumption and hence emissions of CFCs and related substances that deplete ozone, and called for a 50% reduction in CFC production in the 24 signature countries by 1997. Since then, the protocol has been revised twice following increasing evidence that the ozone layer was thinning more rapidly than previously thought and that less damaging processes could be developed more quickly and less expensively. In 1990, the treaty's signatories met again under the London Amendment to adopt a deadline for phasing out the most damaging chemicals by 2000. The Interim Multilateral Fund, involving UNEP, UNDP and the World Bank, was established to help developing countries meet the cost of complying with the Montreal Protocol and provide the necessary transfer of technology. In 1992, under the Copenhagen Amendment, the signatories (now 87 nations) agreed to the transition of the Fund from its interim to permanent status, and speeding up of the phase-out deadlines as follows: 1994 for halons, CFCs for 1996, and hydrochlorofluorocarbons for 2030. It was further agreed to limit methyl bromide 1995 production to 1991 levels. As of January 1993, there were over 100 parties to the Protocol. As of 28 November 1994, there are 148 parties to the Protocol, 100 parties to the London Amendment, and 37 parties to the Copenhagen Amendment. However, many countries have not signed the Protocol. The Montreal Protocol is often viewed as an example of what can be achieved through international cooperation.
International agencies under the Protocol include: UNEP Industry and Environment (IE) Programmes, and UNEP Ozone Secretariat; UN Development Programme (UNDP); UN Industrial Development Organization (UNIDO); the World Bank (IBRD). As one of the implementing agencies of the Protocol, UNEP and its Industry and Environment Programme Activity Centre (UNEP IE/PAC) assists countries to prepare Country Programmes which lay the groundwork for the phase-out of ozone depleting substances. The setting up of Country Programmes enable developing countries to obtain technical and financial support. 12 Country Programmes have been completed (meeting Protocol phase-out requirements), and Country Programmes under UNEP are being prepared for nearly 40 countries. UNEP's Executive Committee in December 1994, approved 144 activities in 40 countries costing over US$73 million. UNEP is also assisting non-Party countries in preparing Country Programmes. UNEP IE also organizes workshops, training courses, and meetings concerned with ozone protection. In the latter half of 1994, the World Bank has negotiated and signed ozone destroying substances (ODS) phase-out project Grant Agreements with Thailand ($40 million), the Philippines ($15 million), Tunisia ($1.79 million), and India ($1.252 million). The total value of Protocol investment projects presented by the World Bank to the December 1994 UNEP Executive Committee (EC) Meeting has been more than US$70 million. UNDP is submitting 60 projects in 14 countries to the December 1994 UNEP EEC/EU Meeting, with project budgets amounting to $24.5 million, and for a volume of 3,267 ODS tonnes to be phased out annually. China (18) and Malaysia (8) have the largest number of UNDP projects. As of end October 1994, UNDP has disbursed $17.3 million and has phased out 427 ODS tonnes per annum. UNIDO has submitted 10 investment projects in the refrigeration and halon sectors in Algeria, China, Egypt, Syria and Vietnam for a total of $18 million.
One measure of the Protocol's success is that the ozone layer is now expected to recover to pre-1980 levels by the year 2050. Without the Protocol, levels of ODS would have been five times higher then than they are today, and surface UV-B radiation levels would have doubled at mid-latitudes in the northern hemisphere (UNEP 1999).
At the country level, examples include among others: a commitment by Canada to reduce its methyl bromide consumption by 75% of 1991 levels in 1998; a New Zealand government approved policy recommending HCFC imports be capped at an amount of 75% of that allowed under the Montreal Protocol. By the year 2000, HCFC imports will be reduced to only 50%, and by 2015 will be completely phased-out.
Realistic and cheap alternatives to ozone depleting substances have yet to be found, and many users of refrigeration and fire-fighting equipment have found repair and maintenance increasingly expensive. Foremost, however, is the combined effort that should spare the Earth serious environmental damage, and many more millions of people from the increased risk of contracting cancer due to increased exposure to ultraviolet radiation.
While the potential impact of stratospheric ozone depletion means there is no room for complacency, the cooperative measures that followed the identification of the problem remain an outstanding and encouraging example of the ability of the international community to act in unison in protecting the global environment.