What led to the Montreal Protocol?

by Jeevan Shemar

The Montreal Protocol on Substances that Deplete the Ozone Layer (1987) [1] is an international treaty [2] that came into effect in 1989 [3]. It aims [4] to protect the ozone layer [5] by regulating the production and consumption of certain chemicals. The Montreal Protocol and (its precursor) the Vienna Convention For The Protection Of The Ozone Layer (1985) [6] became the first [7] treaties to achieve universal participation [8] (meaning that every UN Member State [9] participates in it). The Protocol is widely considered to have succeeded [10] in fulfilling its aim of repairing the ozone layer, and consequently it is judged, by some [11] to be one of the most successful examples of international cooperation in history [12].

What Led To The Montreal Protocol?

What Is The Ozone Layer?

The ozone layer [13] is a thin section in Earth’s stratosphere [14] (the second layer of the atmosphere[15]) that is 10–50km [16] above Earth’s surface. Ozone [17] is a gas [18] composed of three atomically bonded [19] oxygen atoms [20] (O3). The amount of ozone in the atmosphere is measured in Dobson Units [21] (DU) and where fewer than 200 DU of ozone are present in an area, it is called an ozone hole [22].

The ozone layer protects Earth’s surface [23] from harmful [24] ultraviolet (UV) radiation [25], coming from space [26], by absorbing it [27]. This means that most [28] of the UV radiation that passes through the stratosphere is unable to reach Earth. Therefore, the emission of ozone depleting substances reduces the amount of ozone in the atmosphere and consequently increases the risk of UV radiation reaching Earth — radiation that increases the risk [29] of developing skin cancer [30] and eye damage [31].

In 1985 [32], Joseph Farman [33], Brian Gardiner [34] and Jonathan Shanklin [35] discovered the presence of low levels of ozone in the atmosphere [36] around Antarctica [37]. The existence of this ozone hole [38], the discovery of which surprised scientists [39], prompted world leaders to respond [40]. Hence, the creation of the Vienna Convention and the Montreal Protocol.

What Are Chlorofluorocarbons?

A chlorofluorocarbon (CFC) is a type of chemical compound [41] most commonly used [42] in refrigeration equipment, air conditioning units and aerosol products. Before the Montreal Protocol came into force, the emission of CFCs had been increasing each year [43].

When CFCs are released [44] into the atmosphere, they are broken down [45] by UV radiation. The broken down CFCs then react [46] with ozone, which therefore results in ozone being broken down [47]. This breaking down of ozone is called ozone depletion[48] (which explains why CFCs are labelled as ozone depleting substances). If depletion occurs to such an extent that an ozone hole exists, then harmful amounts of UV radiation will be able to reach Earth’s surface. As UV radiation can cause health problems, ozone depletion increases the risk of these problems occurring.

Hence, in light of the discovery of the ozone hole above Antarctica, the Montreal Protocol intended [49] to regulate the emission of CFCs into the atmosphere in order to reduce ozone depletion and, consequently, reduce the amount of UV radiation able to reach Earth’s surface.

Vienna Convention For The Protection Of The Ozone Layer:

Prior to the Montreal Protocol, the Vienna Convention for the Protection of the Ozone Layer (1985) [50] was established. The Vienna Convention is a non-binding [51], multilateral environmental agreement [52] that came into effect in 1988 [53]. The Convention aimed [54] to tackle ozone depletion by encouraging members of the international community [55] to exchange information concerning the effects of human activity [56] on the ozone layer. Despite the aim of the Vienna Convention, to encourage the protection of the ozone layer, the agreement did not require states to take specific forms of action [57] in pursuit of this goal. Hence, the Montreal Protocol was later developed.


[1] https://www.britannica.com/event/Montreal-Protocol
[2] https://www.britannica.com/topic/treaty
[3] https://treaties.un.org/Pages/ViewDetails.aspx?src=IND&mtdsg_no=XXVII-2-a&chapter=27&clang=_en
[4] https://www.environment.gov.au/protection/ozone/montreal-protocol
[5] https://www.nationalgeographic.org/encyclopedia/ozone-layer/
[6] https://www.britannica.com/topic/Vienna-Convention-for-the-Protection-of-the-Ozone-Layer
[7] https://www.unenvironment.org/news-and-stories/press-release/kigali-amendment-hits-milestone-100th-ratification-boosting-climate
[8] https://treaties.un.org/pages/ViewDetails.aspx?src=TREATY&mtdsg_no=XXVII-2-a&chapter=27&lang=en
[9] https://www.un.org/en/member-states/
[10] https://www.unenvironment.org/news-and-stories/story/thirty-years-what-montreal-protocol-doing-protect-ozone1
[11] https://www.unenvironment.org/news-and-stories/story/montreal-protocol-triumph-treaty
[12] https://theconversation.com/saving-the-ozone-layer-why-the-montreal-protocol-worked-9249
[13] https://www.britannica.com/science/ozone-layer
[14] https://www.britannica.com/science/stratosphere
[15] https://www.britannica.com/science/atmosphere
[16] https://www.nasa.gov/mission_pages/sunearth/science/atmosphere-layers2.html
[17] https://uk-air.defra.gov.uk/research/ozone-uv/ozone-concerns
[18] https://www.britannica.com/science/gas-state-of-matter
[19] https://www.britannica.com/science/atom/Atomic-bonds
[20] https://www.britannica.com/science/oxygen
[21] https://www.oxfordreference.com/view/10.1093/oi/authority.20110803095724169
[22] https://public.wmo.int/en/media/news/2020-antarctic-ozone-hole-large-and-deep
[23] https://terra.nasa.gov/science/earths-surface-interior
[24] https://www.who.int/uv/health/uv_health2/en/
[25] https://www.britannica.com/science/ultraviolet-radiation
[26] https://science.nasa.gov/ems/10_ultravioletwaves
[27] https://earthobservatory.nasa.gov/features/Ozone/ozone_2.php
[28] http://butane.chem.uiuc.edu/pshapley/GenChem2/A2/1.html
[29] https://stanfordhealthcare.org/medical-conditions/cancer/skin-cancer/causes-skin-cancer/uv-exposure-categories.html
[30] https://www.wcrf.org/int/blog/articles/2019/06/how-does-sun-cause-skin-cancer
[31] https://eye.keckmedicine.org/harmful-uv-light-can-cause-eye-damage-blindness/
[32] https://www.history.com/this-day-in-history/discovery-of-antarctic-ozone-hole-announced
[33] https://www.bl.uk/voices-of-science/interviewees/joseph-farman#
[34] https://www.independent.co.uk/news/obituaries/joe-farman-scientist-who-first-uncovered-hole-ozone-layer-8624438.html
[35] https://legacy.bas.ac.uk/met/jds/
[36] https://www.bas.ac.uk/data/our-data/publication/the-ozone-layer/
[37] https://www.britannica.com/place/Antarctica
[38] https://discoveringantarctica.org.uk/oceans-atmosphere-landscape/atmosphere-weather-and-climate/the-ozone-hole/
[39] https://www.smithsonianmag.com/science-nature/ozone-hole-was-super-scary-what-happened-it-180957775/
[40] https://www.sciencehistory.org/distillations/podcast/whatever-happened-to-the-ozone-hole
[41] https://www.britannica.com/science/chemical-compound
[42] https://www.esrl.noaa.gov/gmd/hats/publictn/elkins/cfcs.html
[43] https://ourworldindata.org/ozone-layer
[44] https://uk-air.defra.gov.uk/research/ozone-uv/moreinfo?view=cfc-stratosphere
[45] https://ozone.unep.org/ozone-and-you
[46] https://www.britannica.com/science/chemical-reaction
[47] https://www.britannica.com/science/ozone-depletion
[48] https://www.nationalgeographic.com/environment/global-warming/ozone-depletion/
[49] https://www.canada.ca/en/environment-climate-change/corporate/international-affairs/partnerships-organizations/ozone-layer-depletion-montreal-convention.html
[50] https://ozone.unep.org/treaties/vienna-convention
[51] https://www.britannica.com/topic/international-law
[52] https://www.eac.int/environment/multilateral-environmental-agreements
[53] http://publications.europa.eu/resource/cellar/607feb06-39d3-11ea-ba6e-01aa75ed71a1.0001.02/DOC_1
[54] https://www.bafu.admin.ch/bafu/en/home/topics/chemicals/info-specialists/international-affairs–chemicals/vienna-convention-and-the-montreal-protocol.html
[55] https://www.un.org/en/observances/decade-people-african-descent/international-community
[56] https://www.eea.europa.eu/publications/92-827-5122-8/page011.html
[57] https://ozone.unep.org/treaties/vienna-convention/vienna-convention-protection-ozone-layer
Categories International Policy/Key Terms and Agreements

Tell us what you think!

This site uses Akismet to reduce spam. Learn how your comment data is processed.