04/11/2024
Montreal Protocol on Substances that Deplete the Ozone Layer
When scientists discovered a hole in the ozone layer over Antarctica in 1985, the world was struck with fear. Reaction was swift. Public health experts immediately warned that rising intensity of ultraviolet (UV) radiation may greatly increase the incidence of skin cancer and cataracts as well as significantly damage global crops and the marine food chain.
Scientists became aware that manmade chemicals could be destroying the ozone layer in the early 1970s and began calling for action even before the Antarctic ozone hole captured global attention. The United Nations Environment Programme (UNEP) initially responded by calling for further research and later for the negotiation of an international treaty. In fact, the resulting 1985 Vienna Convention for the Protection of the Ozone Layer and the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer are often seen as the most effective environmental treaties in the world, having slowed down and started to reverse ozone depletion. Furthermore, the Montreal Protocol has become part of the global response to climate change by addressing potent greenh
The protection of the ozone layer is one of multilateralism’s great success stories. But as parties to the Vienna Convention and the Montreal Protocol gather in Bangkok in late October 2024, they still have their work cut out for them to address the continuing threats to the Earth’s ozone layer and climate system.
Why is the ozone layer important?
Ozone is a pungent, slightly bluish gas composed of three oxygen atoms (O3). Nearly 90% of naturally occurring ozone resides in the stratosphere, the portion of the atmosphere ten to fifty kilometers (six to thirty miles) above the Earth. By absorbing the most dangerous UV-B radiation in the stratosphere, the ozone layer prevents harmful levels of this radiation from reaching Earth’s surface.
Increased exposure to UV radiation can cause skin cancer, cataracts, and weakened immune systems in humans. It can damage aquatic food chains, and cause direct damage to crustaceans and fish eggs, threatening fisheries and other aquatic resources that contribute to the global food supply. Furthermore, even a 10% reduction in stratospheric ozone could reduce plant production by about 6%, reducing global crop production. Ozone depletion also threatens plants, animals and microbes that provide important ecosystem services that the planet relies on for clean air and clean water, and the absorption of carbon dioxide.
Concern about ozone depletion
Created in the 1920s to replace flammable and noxious refrigerants, chlorofluorocarbons (CFCs) are inert, nonflammable, nontoxic, colorless, and odorless chemicals that are adaptable to a wide variety of uses. By the mid-1970s, CFCs had become the chemical of choice for coolants in air-conditioning and refrigeration systems, propellants in aerosol sprays, solvents in the cleaning of electronic components, and the blowing agent for the manufacture of flexible and rigid foam.
In 1974, scientists Mario Molina and F. Sherwood Rowland published a report showcasing their research suggesting that long-lived organic halogen compounds, such as CFCs, could reach the stratosphere where they would be dissociated by UV light, releasing chlorine atoms. These chlorine atoms would then act as a catalyst in the destruction of ozone molecules. Furthermore, they found CFCs can live for decades in the stratosphere. In fact, according to the US Environmental Protection Agency, one chlorine molecule can destroy over 100,000 ozone molecules before it is removed from the stratosphere.
“The years following the publication of our paper were hectic,” said Molina, “as we had decided to communicate the CFC–ozone issue not only to other scientists, but also to policy makers and to the news media; we realized this was the only way to ensure that society would take some measures to alleviate the problem.”
Molina and Rowland’s research, which was awarded the 1995 Nobel Prize in Chemistry—along with the confirmation of an ozone hole above the Antarctic by British scientists Joseph Farman, Brian Gardiner and Jonathan Shanklin in 1985—catalyzed the international community to coordinate an effective response to this shared crisis.
In 1975, the World Meteorological Organization (WMO) issued a scientific statement warning of the danger to the ozone layer and set the stage for an intergovernmental response. In 1976, UNEP called for "an examination of the need and justification for recommending any national and international controls over the release of man-made chemicals". UNEP and WMO convened an expert meeting in early 1977 in Washington, DC. WMO distributed an 80-page "Survey of the state of knowledge of the ozone layer" with a series of scientific and monitoring proposals. UNEP laid the foundation for international action. T
What are the Vienna Convention and the Montreal Protocol?
The UNEP Governing Council set the political process in action in 1981 by adopting a decision to draft a global framework convention on stratospheric ozone protection. This ultimately led to the adoption of the Vienna Convention for the Protection of the Ozone Layer in 1985.
The Vienna Convention was a dramatic step forward. Often called a “framework convention” because it serves as a framework for efforts to protect the Earth's ozone layer, it focused on research, cooperation and monitoring. However, spurred on by the discovery of the Antarctic ozone hole, just two years later in 1987, the Montreal Protocol on Substances that Deplete the Ozone Layer was adopted and included control measures for certain CFCs and halons, a class of chemicals commonly used as fire extinguishing agents.
The Montreal Protocol mandated that industrialized countries freeze and then reduce by 50% their production and use of the five most widely used CFCs by the year 2000. Production of three key halons would be frozen on the same terms. Developing countries were given ten extra years to meet each obligation, allowing them to increase their use of these chemicals before taking on commitments. This grace period was necessary to get developing countries on board, especially since they argued they deserved access to these important chemicals for their economic development and that industrialized countries had emitted almost all of the CFCs in the atmosphere to that point.
This grace period reflects the principle of common but differentiated responsibilities, which has since become a mainstay of global environmental politics. The principle states that all countries have a common responsibility to address global environmental issues but that some countries have the responsibility to act first or enact more measures because of their contribution to the problem or their access to greater financial and technological resources to address it.
The Protocol also included provisions establishing scientific and technological assessment panels to provide parties with independent and authoritative information, requiring parties to report on their ozone depleting substance (ODS) production and use, banning trade in CFCs and halons with countries that did not ratify the agreement, creating provisions for reviewing the effectiveness of the regime, and strengthening controls through amendments and adjustments by a decision of the Meeting of the Parties (MOP).
The Vienna Convention and the Montreal Protocol have 198 parties, representing universal ratification.
