Ozone Layer [UPSC Environment & Ecology Notes]

The ozone layer or ozone shield is a region of the Earth’s stratosphere that absorbs most of the Sun’s Ultraviolet (UV) radiation. It is important to know facts about the Ozone layer as in July 2020, the Montreal Protocol mid-year meeting took place virtually where delegates discussed the action plans on ozone layer recovery and HFCs. 

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What is the Ozone Layer?

  • It is a layer in the earth’s stratosphere that contains high levels of ozone. 
  • This layer protects the earth from the Sun’s harmful UV radiation. It absorbs 97 – 99% of the UV radiation from the Sun. 
  • In the absence of the ozone layer, millions of people would be affected by skin diseases including cancer and weakened immune systems. 
  • UV radiation would also affect the environment adversely leading to decreased productivity. 
  • Fauna on earth is also adversely affected by the ozone layer depletion.

Good Ozone and Bad Ozone

IAS aspirants should know the difference between the good ozone and bad ozone. The fact is that ozone is found in two layers of the atmosphere. The ozone found in the troposphere is near the earth’s surface and is harmful to life (causes breathing issues in humans) and plants (damages crops and plants.) Urban smog comprises the bad ozone. The good ozone is found in the stratosphere which also hosts the ozone layer. It is called good as it absorbs the sun’s harmful ultraviolet radiation.

Facts about the Ozone Layer

  • One atom of chlorine can destroy more than 100,000 ozone molecules, according to the U.S. Environmental Protection Agency, eradicating ozone much more quickly than it can be replaced.
  • Ozone (O3) is a highly reactive gas whose molecules are comprised of three oxygen atoms. Its concentration in the atmosphere naturally fluctuates depending on seasons and latitudes, but it generally was stable when global measurements began in 1957.
  • Ozone in the stratosphere absorbs most of the ultraviolet radiation from the Sun. Without ozone, the Sun’s intense UV radiation would sterilize the Earth’s surface. Ozone screens all of the most energetic, UV-c, radiation, and most of the UV-b radiation

World Ozone Day

  • September 16th is observed as the World Ozone Day. It is the day that marks the signing of the Montreal Protocol.

Ozone Layer Depletion

Ozone Layer (O3) - Ozone Layer Depletion

Ozone layer depletion refers to the thinning of the protective ozone layer in the atmosphere. 

  • This happens when certain chemicals come into contact with ozone and destroy it.
  • Chemical compounds that cause ozone layer depletion are called Ozone Depleting Substances (ODSs).
  • Examples of ODSs are chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride, methyl chloroform, hydrobromofluorocarbons, halons, etc.
    • Chlorofluorocarbons (CFC): The use of CFCs is one of the main reasons for the depletion of the layer. They are usually used as a coolant in refrigerators and air conditioners used in cars, etc. It is also used as an industrial solvent, in foam products and hospital sterilization equipment.
    • Methyl chloroform: Finds its applications usually in industries for chemical processing, etc.
    • Carbon tetrachloride: Normally used as a solvent.
  • Chlorofluorocarbons are the most abundant ODS.
  • The indiscriminate use of these chemicals causes ozone layer depletion.
  • These ODSs are also powerful Green-House Gases (GHGs) and have a long life as well.
  • There are a few natural causes also which cause ozone depletion such as volcanic eruptions, sunspots and stratospheric winds. However, these do not cause more than 1 – 2% of the ozone depletion.

Ozone Layer Preservation Depletion

The depletion of the Ozone Layer is a serious issue and various programmes have been launched by the government of various countries to prevent it. But, steps should be taken at the individual level as well.

  • The IMO (International Maritime Organisation) mandated that cargo ships must not use fuel that has sulphur content any higher than 0.5%. 
    • This will be implemented from 1st January 2020 as this is one of the many environmental-related issues that is associated with the shipping industry.
  • The Vienna Convention for the Protection of the Ozone Layer was signed in 1985 under which UN member countries recognized the importance of curbing damage to the ozone layer. 
    • As per the Convention’s provisions, countries agreed to adopt the Montreal Protocol to further the goals of the Vienna Convention.
  • The Montreal Protocol was signed in 1987 and entered into force in January 1989.
    • The protocol gives provisions to reduce the production and consumption of ODSs in order to protect the ozone layer.
  • Efforts on an Individual level can be as follows:
Avoid Using Pesticides Minimise the Use of Vehicles
Use Eco-friendly Cleaning Products The Use of Nitrous Oxide should be Prohibited

Updates on ozone later make an important part of current affairs and general knowledge. These are a crucial part of UPSC IAS Prelims as well as Mains examination. Environment and ecology is a very important segment of the UPSC Syllabus. What makes it interesting is that it is intertwined with current affairs immensely. It also has an overlap with other subjects such as geography, economy, and social issues for the IAS exam. Every year, several questions are asked from this section in the UPSC Prelims.

Ozone Layer UPSC Notes:- Download PDF Here

Related Links
 UPSC MCQ On Environment UPSC MCQs on Science & Technology
NCERT Notes for UPSC PIB Summary
UPSC Current Affairs Climate Change In India



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