Ozone Depletion and Protection

 

Introduction

  • What is ozone?
    • Ozone is a naturally occurring molecule made up of three oxygen atoms. It has the chemical formula O3
    • Ozone is found in different levels of the earth’s atmosphere. About 90% of ozone in the atmosphere is concentrated between 15 and 30 kilometres above the earth’s surface (stratospheric ozone).
    • It is also found at ground level in lower concentrations (tropospheric ozone). Here ozone is a pollutant that is a key part of smog over cities
    • The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson.
  • What is the ozone layer?
    • The ozone layer is the common term for the high concentration of ozone that is found in the stratosphere between 15 and 30km above the earth’s surface
    • The ozone layer absorbs 97 to 99 percent of the Sun’s medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which otherwise would potentially damage exposed life forms near the surface

  • Distribution in the stratosphere
    • The thickness of the ozone layer varies worldwide and is generally thinner near the equator and thicker near the poles
    • Thickness refers to how much ozone is in a column over a given area and varies from season to season.
      • The reasons for these variations are due to atmospheric circulation patterns and solar intensity
    • The majority of ozone is produced over the tropics and is transported towards the poles by stratospheric wind patterns
      • When ozone is produced by solar UV radiation in the tropics, it is done so by circulation lifting ozone-poor air out of the troposphere and into the stratosphere where the sun photolyzes oxygen molecules and turns them into ozone. Then, the ozone-rich air is carried to higher latitudes and drops into lower layers of the atmosphere

 

Ozone Depletion

  • Ozone layer depletion is the gradual thinning of the earth’s ozone layer in the upper atmosphere caused due to the release of chemical compounds containing gaseous bromine or chlorine from industries or other human activities.
  • How Ozone Depletion Occurs?
    • When chlorine and bromine atoms come into contact with ozone in the stratosphere, they destroy ozone molecules. One chlorine atom can destroy over 100,000 ozone molecules before it is removed from the stratosphere
    • Some compounds release chlorine or bromine when they are exposed to intense UV light in the stratosphere. These compounds contribute to ozone depletion, and are called ozone-depleting substances (ODS)
      • ODS that release chlorine include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride, and methyl chloroform
      • ODS that release bromine include halons and methyl bromide.
    • The ODS are emitted at the Earth’s surface, they are eventually carried into the stratosphere in a process that can take as long as two to five years.
    • Also the natural processes, such as large volcanic eruptions, can have an indirect effect on ozone levels, with the production of tiny particles called Aerosols
      • These aerosols increase chlorine’s effectiveness at destroying ozone. The aerosols in the stratosphere create a surface on which CFC-based chlorine can destroy ozone. However, the effect from volcanoes is short-lived
    • This severe depletion creates the so-called “ozone hole” that can be seen in images of Antarctic ozone, made using satellite observations.
      • Although ozone losses are less radical in the Northern Hemisphere, significant thinning of the ozone layer is also observed over the Arctic and even over continental Europe.
  • When was the depletion of the ozone layer discovered?
    • In 1974, chemists Mario Molina and Frank Sherwood Rowland discovered a link between CFCs and the breakdown of ozone in the stratosphere
    • In 1985, geophysicist Joe Farman, along with meteorologists Brian G Gardiner and Jon Shanklin published findings of abnormally low ozone concentrations above the Antarctic, which galvanized world-wide action
    • Further, Subsequent laboratory measurements, atmospheric measurements, and atmospheric-modelling studies soon substantiated the importance of their findings. Crutzen, Molina, and Rowland received the Nobel Prize for Chemistry in 1995 for their efforts
  • Effects
    • Effects on Human Health
      • Ozone layer depletion increases the amount of UV that reaches the Earth’s surface. Laboratory and epidemiological studies demonstrate that UV causes non-melanoma skin cancer and plays a major role in malignant melanoma development. In addition, UV has been linked to the development of cataracts, a clouding of the eye’s lens.
    • Effects on Plants
      • UV radiation affects the physiological and developmental processes of plants.
      • Despite mechanisms to reduce or repair these effects and an ability to adapt to increased levels of UV, plant growth can be directly affected by UV radiation
    • Effects on Marine Ecosystems
      • Phytoplankton productivity is limited to the euphotic zone, the upper layer of the water column in which there is sufficient sunlight to support net productivity.
        • Exposure to solar UV radiation has been shown to affect both orientation and motility in phytoplankton, resulting in reduced survival rates for these organisms
      • UV radiation has been found to cause damage to early developmental stages of fish, shrimp, crab, amphibians, and other marine animals.
        • The most severe effects are decreased reproductive capacity and impaired larval development.
        • Small increases in UV exposure could result in population reductions for small marine organisms with implications for the whole marine food chain
    • Effects on Biogeochemical Cycles
      • Increases in UV radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering both sources and sinks of greenhouse and chemically important trace gases (e.g., carbon dioxide, carbon monoxide, carbonyl sulfide, ozone, and possibly other gases).
      • These potential changes would contribute to biosphere-atmosphere feedbacks that mitigate or amplify the atmospheric concentrations of these gases.

 

Ozone Protection

  • World governments agreed in the late 1980s to protect the Earth’s ozone layer by phasing out ozone-depleting substances emitted by human activities, the actions of which are as follows:
    • The Montreal Protocol
      • In 1987, to address the destruction of the ozone layer, the international community established the Montreal Protocol on ozone-depleting substances.
      • It was the first international treaty to be signed by all countries of the world and is considered the greatest environmental success story in the history of the United Nations
      • The Montreal Protocol’s objective is to cut down the production and consumption of ozone-depleting substances, in order to reduce their presence in the atmosphere and thus protect the Earth’s ozone layer.
      • Under the original Montreal Protocol agreement (1987), 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
      • Further, The Parties to the Montreal Protocol have amended the Protocol to enable
        • the control of new chemicals and
        • the creation of a financial mechanism to enable developing countries to comply
      • Amendments to the Montreal Protocol
        • The London Amendment (1990) changed the ODS emission schedule by requiring the complete phaseout of CFCs, halons, and carbon tetrachloride by 2000 in developed countries, and by 2010 in developing countries. Methyl chloroform was also added to the list of controlled ODSs, with phaseout in developed countries targeted in 2005, and in 2015 for developing countries.
        • The Copenhagen Amendment (1992) significantly accelerated the phaseout of ODSs and incorporated an hydrochlorofluorocarbons (HCFC) phaseout for developed countries, beginning in 2004. Under this agreement, CFCs, halons, carbon tetrachloride, and methyl chloroform were targeted for complete phaseout in 1996 in developed countries. In addition, methyl bromide consumption of methyl bromide was capped at 1991 levels
        • The Montreal Amendment (1997) included the phaseout of HCFCs in developing countries, as well as the phaseout of methyl bromide in developed and developing countries in 2005 and 2015, respectively
        • The Beijing Amendment (1999) included tightened controls on the production and trade of HCFCs. Bromochloromethane was also added to the list of controlled substances with phaseout targeted for 2004
        • The Kigali Amendment (2016) extended controls to phase down the production and consumption of hydrofluorocarbons (HFCs) because these substances were adopted by industries in moving away from ozone-depleting substances and they are potent greenhouse gases damaging to the earth’s climate.
    • The Vienna Convention
      • Adopted in 1985, The Vienna Convention for the Protection of the Ozone Layer is the precursor to the Montreal Protocol.
      • The Vienna Convention is often called a framework convention, because it served as a framework for efforts to protect the globe’s ozone layer.
      • The Vienna Convention did not require countries to take concrete actions to control ozone depleting substances.
      • Instead, in accordance with the provisions of the Convention, the countries of the world agreed the Montreal Protocol on Substances that Deplete the Ozone Layer under the Convention, to advance that goal

 

Ozone layer recovery

  • Global consumption of ozone-depleting substances has been reduced by some 98% since countries began taking action under the Montreal Protocol.
    • As a result, the atmospheric concentration of the most aggressive types of ozone-depleting substances is falling and the ozone layer is showing the first signs of recovery.
  • During the early 2000s, scientists expected that stratospheric ozone levels would continue to rise slowly over subsequent decades.
    • However, the size of the Antarctic ozone hole reached its greatest extent in 2000, when it spanned 29.9 million square km (11.5 million square miles); by 2021 its area had shrunk to 24.8 million square km (9.6 million square miles).
  • A 2018 United Nations report estimated that the Antarctic ozone hole would close slowly and stratospheric ozone concentrations would return to 1980 values by the 2060s
    • Above the Arctic, ozone levels are expected to return to 1980 values by the mid-2030

 

Ozone Protection: India

  • The Government of India has entrusted the work relating to the ozone layer protection and implementation of the Montreal Protocol on Substances the Ozone Layer to the Ministry of Environment, Forest and Climate Change (MoEF&CC)
    • The Ministry has established an Empowered Steering Committee (ESC) Chaired by Secretary (EF&CC), which is supported by two standing committees viz. Technology and Finance Standing Committee (TFSC) and the Standing Committee on Monitoring
    • The ESC is overall responsible for implementation of the Montreal Protocol provisions, review of various policies including implementation options, project approvals and monitoring.
    • The Ministry has set up an Ozone Cell as a National Ozone Unit (NOU) to render necessary services for effective and timely implementation of the Montreal Protocol and its ODS phase-out program in India
  • India had prepared a detailed Country Program (CP) in 1993 for the phase-out of ODSs in accordance with its National Industrial Development Strategy by accessing funds from financial mechanism of the Montreal Protocol
    • India has proactively phased out the production and consumption of CFCs except use in Metered Dose Inhalers (MDIs) used for treatment of Asthma and Chronic Obstructive Pulmonary Disease (COPD) ailments from 1st August, 2008.
    • Subsequently, the use of CFCs in MDIs has been phased out from December, 2012.
    • India has also completely phased out production and consumption of halons as of 1st January, 2010.
  • Currently, the Ozone Cell is engaged in phase-out of production and consumption of next category of chemicals, Hydrochlorofluorocarbons (HCFCs) with an accelerated phase-out schedule as per the Montreal Protocol. The Ozone Cell, MoEF&CC in association with the implementing agencies and in close cooperation with the stakeholders in the country has been implementing following projects :
    • Accelerated CFC Production Sector Phase-out Project
    • National CTC Phase-out Plan
    • National Strategy for Transition to Non-CFC MDIs and Plan for Phase-out of CFCs in the Manufacture of Pharmaceutical MDIs
    • HCFC Phase-out Management Plan (HPMP) – Stage-I
      • Foam Manufacturing Sector
      • Systems House
      • Refrigeration and Air-Conditioning Servicing Sector
    • HCFC Phase-out Management Plan (HPMP) – Stage-II
  • In India, nearly 50 % of the consumption of ozone depleting chemicals in the country was attributable to HCFC-141 b in the foam sector
    • In the year 2020, India has successfully achieved the complete phase out of Hydrochlorofluorocarbon (HCFC)-141 b, which is a chemical used by foam manufacturing enterprises and one of the most potent ozone depleting chemical after Chlorofluorocarbons (CFCs)

 

More Actions needed

  • Actions required globally to continue the recovery of the ozone layer are:
    • Ensuring that existing restrictions on ozone-depleting substances are properly implemented and global use of ozone-depleting substances continue to be reduced.
    • Ensuring that banks of ozone-depleting substances (both in storage and contained in existing equipment) are dealt with in an environmentally-friendly manner and are replaced with climate-friendly alternatives.
    • Ensuring that permitted uses of ozone-depleting substances are not diverted to illegal uses.
    • Reducing use of ozone-depleting substances in applications that are not considered as consumption under the Montreal Protocol.
    • Ensuring that no new chemicals or technologies emerge that could pose new threats to the ozone layer (e.g. very short-lived substances).