The Montreal Protocol on Substances That Deplete 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. Since then, it has undergone nine revisions, in 1990 (London), 1991 (Nairobi), 1992 (Copenhagen), 1993 (Bangkok), 1995 (Vienna), 1997 (Montreal), 1999 (Beijing) and 2016 (Kigali). 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 2040 and 2066. Due to its widespread adoption and implementation, it has been hailed as an example of successful international co-operation. Former UN Secretary-General Kofi Annan stated 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 this case of the ozone depletion challenge, there was global regulation already being installed before a scientific consensus was established. Also, overall public opinion was convinced of possible imminent risks.
Ozone is an inorganic molecule with the chemical formula O
3. It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope O
2, breaking down in the lower atmosphere to O
2 (dioxygen). Ozone is formed from dioxygen by the action of ultraviolet (UV) light and electrical discharges within the Earth's atmosphere. It is present in very low concentrations throughout the atmosphere, with its highest concentration high in the ozone layer of the stratosphere, which absorbs most of the Sun's ultraviolet (UV) radiation.
The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 15 to 35 kilometers (9 to 22 mi) above Earth, although its thickness varies seasonally and geographically.
Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone around Earth's polar regions. The latter phenomenon is referred to as the ozone hole. There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events.
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propane.
Dichloromethane is an organochlorine compound with the formula CH2Cl2. This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with water, it is slightly polar, and miscible with many organic solvents.
A refrigerant is a working fluid used in the refrigeration cycle of air conditioning systems and heat pumps where in most cases they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are heavily regulated because of their toxicity and flammability and the contribution of CFC and HCFC refrigerants to ozone depletion and that of HFC refrigerants to climate change.
Human impact on the environment refers to changes to biophysical environments and to ecosystems, biodiversity, and natural resources caused directly or indirectly by humans. Modifying the environment to fit the needs of society is causing severe effects including global warming, environmental degradation, mass extinction and biodiversity loss, ecological crisis, and ecological collapse. Some human activities that cause damage to the environment on a global scale include population growth, neoliberal economic policies and rapid economic growth, overconsumption, overexploitation, pollution, and deforestation. Some of the problems, including global warming and biodiversity loss, have been proposed as representing catastrophic risks to the survival of the human species.
1,1,1,2-Tetrafluoroethane (also known as norflurane (INN), R-134a, Klea 134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, HFA-134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with thermodynamic properties similar to R-12 (dichlorodifluoromethane) but with insignificant ozone depletion potential and a lower 100-year global warming potential (1,430, compared to R-12's GWP of 10,900). It has the formula CF3CH2F and a boiling point of −26.3 °C (−15.34 °F) at atmospheric pressure. R-134a cylinders are colored light blue. A phaseout and transition to HFO-1234yf and other refrigerants, with GWPs similar to CO2, began in 2012 within the automotive market.
The ozone depletion potential (ODP) of a chemical compound is the relative amount of degradation to the ozone layer it can cause, with trichlorofluoromethane being fixed at an ODP of 1.0. Chlorodifluoromethane (R-22), for example, has an ODP of 0.05. CFC 11, or R-11 has the maximum potential amongst chlorocarbons because of the presence of three chlorine atoms in the molecule.
Trichlorofluoromethane, also called freon-11, CFC-11, or R-11, is a chlorofluorocarbon (CFC). It is a colorless, faintly ethereal, and sweetish-smelling liquid that boils around room temperature. CFC-11 is a Class 1 ozone-depleting substance which damages Earth's protective stratospheric ozone layer. Also R-11 is not flammable at ambient temperature and pressure but it can become very combustible if heated and ignited by a strong ignition source.
Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). This colorless gas is better known as HCFC-22, or R-22, or CHClF
2. It was commonly used as a propellant and refrigerant. These applications were phased out under the Montreal Protocol in developed countries in 2020 due to the compound's ozone depletion potential (ODP) and high global warming potential (GWP), and in developing countries this process will be completed by 2030. R-22 is a versatile intermediate in industrial organofluorine chemistry, e.g. as a precursor to tetrafluoroethylene.
Chlorotrifluoromethane, R-13, CFC-13, or Freon 13, is a non-flammable, non-corrosive, nontoxic chlorofluorocarbon (CFC) and also a mixed halomethane. It is a man-made substance used primarily as a refrigerant. When released into the environment, CFC-13 has a high ozone depletion potential, and long atmospheric lifetime. Only a few other greenhouse gases surpass CFC-13 in global warming potential (GWP). The IPCC AR5 reported that CFC-13's atmospheric lifetime was 640 years.
Design for the environment (DfE) is a design approach to reduce the overall human health and environmental impact of a product, process or service, where impacts are considered across its life cycle. Different software tools have been developed to assist designers in finding optimized products or processes/services. DfE is also the original name of a United States Environmental Protection Agency (EPA) program, created in 1992, that works to prevent pollution, and the risk pollution presents to humans and the environment. The program provides information regarding safer chemical formulations for cleaning and other products. EPA renamed its program "Safer Choice" in 2015.
Dichlorofluoromethane or Freon 21 or R 21 is a halomethane or hydrochlorofluorocarbon with the formula CHCl2F. It is a colorless and odorless gas. It is produced by fluorination of chloroform using a catalyst such as antimony trifluoride:
1-Bromopropane (n-propylbromide or nPB) is an organobromine compound with the chemical formula CH3CH2CH2Br. It is a colorless liquid that is used as a solvent. It has a characteristic hydrocarbon odor. Its industrial applications increased dramatically in the 21st century due to the phasing out of chlorofluorocarbons and chloroalkanes such as 1,1,1-Trichloroethane under the Montreal Protocol.
1-Chloro-1,1-difluoroethane (HCFC-142b) is a haloalkane with the chemical formula CH3CClF2. It belongs to the hydrochlorofluorocarbon (HCFC) family of man-made compounds that contribute significantly to both ozone depletion and global warming when released into the environment. It is primarily used as a refrigerant where it is also known as R-142b and by trade names including Freon-142b.
Stephen Oliver Andersen is the Director of Research at the Institute for Governance & Sustainable Development (IGSD) and former co-chair (1989–2012) of the Montreal Protocol Technology and Economic Assessment Panel (TEAP) where he also chaired and co-chaired Technical Options Committees, Task Forces and Special Reports. He is one of the founders and leading figures in the success of the Montreal Protocol on Substances that Deplete the Ozone Layer that has phased out the chemicals that deplete the stratospheric ozone that protects the Earth against the harmful effects of ultraviolet radiation that causes skin cancer, cataracts, and suppression of the human immune system, destroys agricultural crops and natural ecosystems and deteriorates the built environment. Because ozone-depleting chemicals are also powerful greenhouse gases the Montreal Protocol also protected climate. Dr. Andersen was instrumental in the 2016 Kigali Amendment that will phase down hydrofluorocarbons once necessary to phase out chlorofluorocarbons (CFCs) fast enough to avoid ozone tipping points, but no longer necessary now that environmentally superior replacements are available or soon to be available. For his ambitious campaign saving the ozone layer, Dr. Andersen earned the 2021 Future of Life Award along with Joe Farman and Susan Solomon.
Ozone depletion and climate change are environmental challenges whose connections have been explored and which have been compared and contrasted, for example in terms of global regulation, in various studies and books.
