Which statement is TRUE regarding the relationship between ozone depletion and climate change?

Question

Which statement is TRUE regarding the relationship between ozone depletion and climate change?

1. A. CFCs destroy ozone and contribute to global warming. (Correct answer)
2. B. Ozone depletion directly causes the greenhouse effect.
3. C. Greenhouse gases directly destroy ozone molecules.
4. D. Reducing CO₂ emissions alone can fully restore the ozone layer.

Correct Answer

Option A — CFCs destroy ozone and contribute to global warming.

Detailed Solution & Explanation

The correct answer is CFCs destroy ozone and contribute to global warming.

Key Points

• Chlorofluorocarbons (CFCs) have a dual effect, which is what makes this statement true:
  • In the stratosphere, ultraviolet radiation splits CFC molecules, releasing chlorine free radicals that destroy ozone catalytically. A single chlorine atom can destroy up to 100,000 ozone molecules.
  • In the troposphere, CFCs are themselves potent greenhouse gases, with global warming potentials thousands of times that of CO₂.
• The catalytic destruction cycle:
  • $CFCl_3 + UV \rightarrow CFCl_2 + Cl\cdot$
  • $Cl\cdot + O_3 \rightarrow ClO + O_2$
  • $ClO + O \rightarrow Cl\cdot + O_2$
• The chlorine radical is regenerated, which is why the damage from a small quantity is so large.

Additional Information

• Why the other statements are wrong:
  • Option B — ozone depletion allows more UV-B to reach the surface; it does not cause the greenhouse effect, which is driven by infrared absorption by CO₂, CH₄, N₂O and water vapour.
  • Option C — greenhouse gases do not directly destroy ozone. In fact, by cooling the stratosphere, rising CO₂ can worsen depletion indirectly by favouring polar stratospheric clouds.
  • Option D — CO₂ reduction addresses warming, not the ozone layer. Ozone recovery depends on eliminating chlorine and bromine compounds.
• The Montreal Protocol (1987) phases out ozone-depleting substances and is the only UN treaty ratified by every country in the world. The Kigali Amendment (2016) extended it to hydrofluorocarbons (HFCs) — which do not deplete ozone but are powerful greenhouse gases.
• The ozone hole over Antarctica forms in the Southern Hemisphere spring (September–October), when polar stratospheric clouds and returning sunlight together activate chlorine.
• World Ozone Day is observed on 16 September.