September 16 is the International Day for Preservation of the Ozone Layer. Date back on 16th September 1987, Montreal Protocol was signed. Twenty four countries met in Montreal and announced to the world that the time had come to stop depleting the ozone layer. On December 19, 1994, the UN General Assembly proclaimed September 16 to be the International Day for Preservation of the Ozone Layer, commemorating the date when the Montreal Protocol was signed. As on to date 197 countries have signed on to one of the most widely recognized international agreement. The day is mainly intended to spread awareness of the depletion of the Ozone Layer and search for solutions to preserve it. People from all over the world gather in Montreal on September 16th of every year to join the talks and Seminars. The Montreal Protocol has so far been successful in meeting some of its targets on phasing out ozone-depleting substances. As a result, the abundance of ozone-depleting substances in the atmosphere is declining and the ozone layer is expected to recover within few decades. The phase out or controlled uses of ozone depleting substances have not only helped protect the ozone layer but have also contributed significantly to global efforts to address climate change; furthermore, it has protected human health and ecosystems by limiting the harmful ultraviolet radiation from reaching the earth.
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Ozone layer is a deep layer in earth’s atmosphere that contains ozone gas (O3) which is a naturally occurring molecule containing three oxygen atoms. An essential property of ozone molecule is its ability to block ultraviolet radiations that are dangerous for most living beings. Otherwise, UV radiation could injure or kill life on Earth. Ultraviolet (UV) light is a solar radiation that may cause long term devastating effects on human beings as well as plants and animals. Increased penetration of solar UV-B radiation is likely to have profound impact on human health with potential risks of eye diseases, i.e, damage of cornea and lens, skin cancer and adversely affecting the immune system that may cause other infectious diseases. In forests and grasslands increased UV-B radiation is likely to result in changes in species composition thus altering the bio-diversity in different ecosystems. It can have adverse impacts on the productivity of aquatic systems. High levels of exposure in tropics and subtropics may affect the distribution of phytoplanktons which form the foundation of aquatic food webs. UV-B can also cause damage to early development stages of fish, shrimp, crab, amphibians and other animals, the most severe effects being decreased reproductive capacity and impaired larval development. It could affect terrestrial and aquatic bio-geo-chemical cycles. Reduction of stratospheric ozone and increased penetration of UV-B radiation result in higher photo dissociation rates of key trace gases that control the chemical reactivity of the troposphere and thus affects on air quality. And at the most it has a great effect in climate change.
The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure stratospheric ozone from the ground. On the other hand the photochemical mechanisms that give rise to the ozone layer were discovered by the British physicist Sydney Chapman in 1930. The production of ozone in the stratosphere results primarily from the breaking of the chemical bonds within oxygen molecules (O2) by high-energy solar photons. This process is called photo-dissociation, which results in the release of single oxygen atoms and subsequently joins with intact oxygen molecules to form ozone (O3) and build up in Earth’s atmosphere. Later, it gradually leads to the formation of an Ozone shield in the stratosphere. Scientists believe that the formation of the ozone layer played an important role in the development of life on Earth by screening out lethal levels of UVB radiation and thus facilitating the migration of life-forms from the oceans to land.
But, over the course of last several decades, human activities substantially altered the ozone layer. Ozone depletion, the global decrease in stratospheric ozone was observed since 1970s, which is well correlated with the increase of chlorine and bromine in the stratosphere. These chemicals, once freed by UV radiation from the chlorofluorocarbons (CFCs) and other halocarbons (carbon-halogen compounds) that contain them, destroy ozone by stripping away single oxygen atoms from ozone molecules. Depletion is so extensive that so-called ozone holes (regions of severely reduced ozone coverage) over the poles are noticed. The largest such hole—which has spanned more than 20.7 million square km on a consistent basis since 1992—appears annually over Antarctica between September and November. Ozone layer has been found to be affected by certain natural phenomena such as Sun-spots and stratospheric winds. But this has been found to cause not more than 1-2% depletion of the ozone layer. Man-made compounds such as chlorofluorocarbons (CFCs), halons, CH3CCl3 (Methyl chloroform), CCl4 (Carbon tetrachloride), HCFCs (hydro-chlorofluorocarbons), hydrobromofluorocarbons and methyl bromide are found to have direct impact on the depletion of the ozone layer. Chlorine and bromine demolish ozone at an alarming rate, by stripping an atom from the ozone molecule. A single molecule of chlorine can break apart thousands of molecules of ozone. These are categorized as ozone-depleting substances (ODS). Chlorofluorocarbons are released into the atmosphere due to: Cleaning Agents, Coolants in refrigerators, Packaging material, Air conditioning, Aerosol spray cans etc. The problem with the Ozone-Depleting Substances (ODS) is that they are not washed back in the form of rain on the earth and in-fact remain in the atmosphere for quite a long time.
Under the auspices of United Nations Environmental Programme (UNEP), Nations including United States have cooperatively taken action to stop ozone depletion with “The Montreal Protocol (1987) on substances that deplete the ozone layer”. There is need to maintain programs to ensure that ozone-depleting substances are not released and ongoing vigilance is required to this effect.
India became Party to the Vienna Convention for the Protection of the Ozone Layer on 18th March 1991 and the Montreal Protocol on Substances that Deplete the Ozone Layer on 19th June, 1992. In accordance with the National Strategy for ODS phase-out, the MoEF&CC, Government of India, has notified Ozone Depleting Substances (Regulation & Control) Rules, 2000 in the Gazette of India on 19th July, 2000, covering various aspects viz. production, consumption, export and import of ODSs. These Rules prohibit the use of CFCs in manufacturing various products beyond 1st January’2003 except in MDIs and for other medical purposes.
The theme for World Ozone Day 2024 is “Montreal Protocol: Advancing Climate Actions” reflecting the Montreal Protocol's crucial role in both protecting the ozone layer and driving broader climate action initiatives globally. The Montreal Protocol is rightly hailed as a multilateralism success story. It united the world to phase out ozone-depleting substances putting the ozone layer on the path to recovery and protecting all life on Earth. On this World Ozone Day, we also celebrate its climate action. Phasing out ozone-depleting substances has proven to be a powerful tool for climate action that has helped slow global warming, for example, postponing the first ice-free Arctic summer by up to 15 years.