SYLLABUS
GS-3: Conservation, environmental pollution and degradation, environmental impact assessment.
Context: The Copernicus Atmosphere Monitoring Service (CAMS) reported that the Antarctic ozone hole expanded sharply in September 2026, reaching about 25 million sq. km on 12 September, around 5 million sq. km above average for the period.
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• The ozone hole crossed the 15 million sq. km threshold by the end of August, slightly earlier than the long-term average and at a similar stage to 2025. The 15-million-sq.-km area itself is larger than Antarctica.
• During the first half of September, its area expanded rapidly to around 25 million sq. km by September, exceeding Antarctica's area and remaining about 5 million sq. km above the average for that period.
• The rapid expansion coincided with a sudden decrease in minimum stratospheric temperature at about 20 km above the South Pole (50 hPa). However, the minimum ozone-column value and ozone mass deficit remained close to historical averages.
Understanding the Ozone Hole and Ozone Layer
• Ozone Layer: A region of relatively high ozone concentration in the stratosphere that absorbs much of the Sun's harmful ultraviolet (UV) radiation and protects life on Earth.
• Ozone Hole: It is not a physical opening in the atmosphere but a region of severe seasonal depletion of stratospheric ozone, most prominently over Antarctica.
• 220 Dobson Unit (DU) Threshold: CAMS defines the Antarctic ozone-hole area as the region south of 60°S where total-column ozone is below 220 DU. Thus, 220 DU refers to the amount of ozone in the entire atmospheric column above a location, not its concentration at a particular altitude.
- Dobson Unit is a unit used to express the amount of ozone in a vertical column of the atmosphere.
• Why Antarctica? The Antarctic stratosphere becomes extremely cold during winter. The polar vortex helps isolate this cold air, favouring conditions for severe ozone depletion.
• Seasonality: The Antarctic ozone hole develops mainly during the austral late winter and spring, generally from August to November. As temperatures rise later in spring, the polar vortex weakens, and ozone depletion slows.
• Good and Bad Ozone: Stratospheric ozone protects against UV radiation, whereas tropospheric ozone is a harmful air pollutant and a component of photochemical smog.
Why Does the Ozone Hole Vary Each Year?
• Ozone-Depleting Substances (ODSs): CFCs, halons, HCFCs and methyl bromide break down in the stratosphere and release reactive chlorine or bromine, which catalytically destroy ozone.
• Polar Stratospheric Clouds (PSCs): Extremely low temperatures allow PSCs to form. They facilitate the conversion of relatively inactive chlorine and bromine compounds into reactive forms, which rapidly destroy ozone when sunlight returns during Antarctic spring.
• Polar Vortex: The strong Antarctic polar vortex helps maintain cold, isolated stratospheric conditions, favouring PSC formation and concentrated ozone depletion.
• Annual Variability: Changes in stratospheric temperature, winds, polar-vortex strength and atmospheric circulation cause substantial year-to-year variations in the size and duration of the ozone hole.
• 2026 Situation: The rapid September expansion coincided with a sudden fall in minimum stratospheric temperature. Yet near-average ozone-column minimum and ozone mass deficit indicate that the larger area alone does not establish a reversal of long-term ozone recovery.
Global Action and Ozone-Layer Recovery
• Vienna Convention, 1985: Established the international framework for cooperation on research, systematic observations, information exchange and protection of the ozone layer.
• Montreal Protocol, 1987: Controls the production and consumption of ozone-depleting substances. It entered into force in 1989 and, along with the Vienna Convention, achieved universal participation in 2009.
• Multilateral Fund, 1991: Provides financial and technical assistance to developing countries for meeting their obligations under the Montreal Protocol.
• Kigali Amendment, 2016: Provides for the phasedown of hydrofluorocarbons (HFCs). HFCs do not deplete the ozone layer but have high global-warming potential.
• India: India acceded to the Vienna Convention in 1991 and the Montreal Protocol in 1992. It ratified the Kigali Amendment on 27 September 2021. As part of Kigali's Group 2 developing countries, India is scheduled to begin its HFC phase-down in 2032 and reach an 85% reduction by 2047 from its applicable baseline.
• Recovery Trajectory: Continued compliance with the Montreal Protocol is projected to return total-column ozone to 1980 levels around 2040 globally for 60°N–60°S, 2045 in the Arctic and 2066 over Antarctica.
