Ozone depletion — MCQs

All questions with answers and explanations

Read the full set here, or use the practice card above to test yourself one question at a time.

1. The ozone layer is located in which layer of the atmosphere?

   • Troposphere
   • Stratosphere (correct answer)
   • Mesosphere
   • Exosphere

   Explanation. The ozone layer sits in the stratosphere, roughly 10 to 50 kilometres above the Earth's surface.

2. Which substances are the primary cause of ozone depletion?

   • Carbon dioxide and methane
   • CFCs and halons (correct answer)
   • Nitrogen and oxygen
   • Water vapour

   Explanation. Chlorofluorocarbons (CFCs) and halons are the primary causes of ozone depletion — they release chlorine and bromine atoms that destroy ozone molecules.

3. Global warming is best defined as:

   • The thinning of the ozone layer
   • The long-term increase in Earth's average surface temperature due to greenhouse gas accumulation (correct answer)
   • A synonym for ozone depletion
   • A decrease in atmospheric CO2

   Explanation. Global warming is the long-term rise in Earth's average surface temperature, caused by the accumulation of greenhouse gases in the atmosphere.

4. Which is the correct relationship between global warming and climate change?

   • They are exact synonyms
   • Global warming is the temperature rise; climate change is the broader set of resulting weather/pattern shifts (correct answer)
   • Climate change causes global warming
   • They are unrelated phenomena

   Explanation. Global warming (the temperature rise) is the primary driver of climate change, which is the broader, downstream set of shifts in weather, rainfall, and sea levels.

5. Which of the following is NOT a greenhouse gas?

   • Carbon dioxide (CO2)
   • Methane (CH4)
   • Chlorofluorocarbons (CFCs)
   • Nitrogen (N2) (correct answer)

   Explanation. Nitrogen (N2) makes up most of the atmosphere but is not a greenhouse gas. Gases such as carbon dioxide and methane trap heat, and CFCs are also strong heat-trapping gases.

6. Increased CO2 absorption by oceans, lowering pH levels and harming corals and shellfish, is called:

   • Ozone depletion
   • Ocean acidification (correct answer)
   • Thermal pollution
   • Eutrophication

   Explanation. Ocean acidification is the process by which increased CO2 absorption by oceans lowers water pH, harming marine life like corals and shellfish.

7. Which international treaty specifically addresses ozone depletion?

   • Paris Agreement
   • Kyoto Protocol
   • Montreal Protocol (correct answer)
   • Ramsar Convention

   Explanation. The Montreal Protocol, 1987 specifically addresses ozone depletion and is widely regarded as a successful treaty, since CFC use fell sharply after its limits applied.

8. Why are ozone depletion and global warming considered linked phenomena?

   • They are actually identical phenomena
   • Some ozone-depleting substances are also potent greenhouse gases (correct answer)
   • Ozone depletion causes greenhouse gases to disappear
   • There is no real connection between them

   Explanation. Some ozone-depleting substances, like certain CFCs, are also potent greenhouse gases — this is the link between the two otherwise distinct phenomena.