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“International Agreements on Climate Change and the Condition of the Ozone Layer – a short analysis”

Dr. Nandini Chattopadhaya – Vice Principal AW S


Introduction – Ozone is present only in small amounts of Earth’s atmosphere. Most of which resides in the upper part of the atmosphere. This region, called the stratosphere, is more than 10 kilometres (6 miles) above Earth’s surface and extends up to about 50

kilometres (31 miles) altitude. In the mid-1970s it was discovered that some human-produced chemicals could lead to depletion of the ozone layer. Following the discovery of this environmental issue, researchers sought a better understanding of this threat to the ozone layer, which revealed an abundance of ozone-depleting substances (ODSs) and the existence of a hole in the ozone layer. This article attempts to analyse the efficacy of the International Agreements on Climate change with respect to the Ozone layer.


Location of the Ozone Layer – The ozone layer resides in the stratosphere surrounding the entire Earth. UV-B radiation (280- to 315- nanometer (nm) wave- length) from the Sun is strongly absorbed in this layer. As a result, the amount of UV-B reaching Earth’s surface is greatly reduced. Human exposure to UV-B radiation increases the risks of skin cancer, cataracts, and a suppressed immune system. UV-B radiation exposure can also damage terrestrial plant life, single-cell organisms, and aquatic ecosystems.


The Ozone Hole – In 1984 British Antarctic Survey scientists, Joesph Farman, Brian Gardiner, and Jonathan Shanklin, discovered a recurring springtime Antarctic ozone hole. Their paper was published in Nature, May 1985, showing that ozone levels had dropped to 10% below normal January levels for Antarctica. The ozone “hole” is really a reduction in concentrations of ozone high above the earth in the stratosphere. The word ‘hole’ isn’t literal as no place is empty of ozone. Scientists use the word hole as a metaphor for the area in which ozone concentrations drop below the historical threshold of 220 Dobson Units. The ozone hole is defined geographically as the area wherein the total ozone amount is less than 220 Dobson Units. This has steadily grown in size (up to 27 million sq. km.) and length of existence (from August through early December) over the past two decades.


International Agreements and the Ozone Hole – The ozone hole opened the world’s eyes to the global effects of human activity on the atmosphere. The global recognition of CFCs’ destructive potential, led to the 1989 Montreal Protocol, banning the production of ozone-

depleting chemicals. 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. It stipulates that the production and consumption of compounds that deplete ozone in the stratosphere– chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform–are to be phased out by 2000 (2005 for methyl chloroform). Scientific theory and evidence suggested its capacity to wreak havoc on the stratospheric ozone layer, which shields the planet from damaging UV-B radiation. This was the first step in international efforts to protect stratospheric ozone. Under the Montreal Protocol agreement, developed countries were required to begin phasing out CFCs in 1993 and achieve a 20% reduction relative to 1986 consumption levels by 1994 and a 50% reduction by 1998. Additionally, developed countries were required to freeze their production and consumption of halons

relative to their 1986 levels. After the Montreal Protocol was signed, new data showed worse- than-expected damage to the ozone layer (United States Environmental Protection Agency, n.d).

A drastic fall in chlorine and bromine levels have been observed since the mid-1990s. However, the long lifetimes of CFCs in the atmosphere mean it may take until the middle of the 21st century as the abundances of these gases decline in the stratosphere and the chlorine content to go back to values like those of the 1960s.

Fig 1: Antarctic ozone hole Shrinks to new records


Long-term observations reveal that Earth’s ozone has been strengthening following international agreements to protect this vital layer of the atmosphere. According to the ozone sensor on Europe’s Metop weather satellite, the hole over Antarctica has shrunk as can be seen above.

Source: Antarctic ozone hole Shrinks to new records. Retrieved from –

Conclusion – But though there has been progress, there’s still a long way to go. The Antarctic ozone hole, where protective ozone thins dramatically to create a “hole,” is still reappearing annually though the extent of the hole has decreased to a great extent. The UN-backed Scientific Assessment Panel to the Montreal Protocol on Ozone Depleting Substances quadrennial assessment report, published every four years, confirms the phase out of nearly 99% of banned ozone-depleting substances. The Montreal Protocol has thus succeeded in safeguarding the ozone layer, leading to notable recovery of the ozone layer in the upper stratosphere and decreased human exposure to harmful ultraviolet (UV) rays from the sun.

Thus, Ozone action sets a precedent for climate action. The success in phasing out ozone- depleting compounds is a glowing example of cooperation amongst nations and inspires us to believe that we can battle climate change and emerge victorious.

References –

  1. European Space (2013). Observing the Earth. Retrieved from the_road_t o_recovery
  2. Agis (2012).Wordless Tech. Antarctic ozone hole Shrinks to new records. Retrieved from: records/
  3. Fahey, D.W. & Hegglin, M.I. (2010). Twenty Questions and Answers About the Ozone Layer: 2010 Update. Retrieved from: P-2010- FAQs-update.pdf
  4. NASA: Goddard Earth Sciences Data and Information Services (n.d).Ozone. Retrieved from: ozone/ozone_cycle.shtml
  5. Ozone Secretariat, UNEP. (n.d).THE MONTREAL PROTOCOL ON SUBSTANCES THAT DEPLETE THE OZONE LAYER. Retrieved from decisions/montreal-protocol-substances- deplete-ozone-layer
  6. United States Environmental Protection Agency. (n.d). Ozone Layer Protection. Retrieved from treaties-and-cooperation