Introduction
Many students preparing for IB Environmental Systems and Societies (ESS) ask: “Do I still need to study the ozone layer for the 2026 first assessment?” The answer is yes—but with a focus on stratospheric ozone depletion rather than climate change.
While climate change dominates the ESS syllabus, the ozone layer remains relevant because it shows how human activities can disrupt atmospheric systems and how international cooperation can solve global environmental problems. Understanding the ozone story also helps students see the difference between ozone depletion and the greenhouse effect, which are often confused in exams.
Quick Start Checklist for ESS Students
When revising the ozone layer, make sure you can:
- Define the ozone layer and its role in filtering UV radiation.
- Explain the causes of ozone depletion (CFCs, halons).
- Describe the environmental and health impacts of ozone thinning.
- Outline the Montreal Protocol as a case study in international cooperation.
- Distinguish clearly between ozone depletion and climate change.
The Ozone Layer in ESS
- Located in the stratosphere, the ozone layer absorbs harmful UV-B radiation.
- Without it, humans and ecosystems would face much higher exposure to UV radiation.
Causes of Ozone Depletion
- Chlorofluorocarbons (CFCs): once used in refrigerators, aerosols, air conditioners.
- Halons: used in fire extinguishers.
- Nitrous oxide (N₂O): agriculture and combustion, emerging as a concern.
CFCs release chlorine atoms when broken down by UV light, which destroy ozone molecules.
Impacts of Ozone Depletion
Environmental
- Reduced phytoplankton productivity in oceans.
- Damage to plant tissues and reduced crop yields.
Health
- Increased skin cancers and cataracts.
- Weakened human immune systems.
Economic
- Loss of agricultural productivity.
- Increased healthcare costs.
The Montreal Protocol: A Success Story
- Signed in 1987, the Montreal Protocol banned ozone-depleting substances (ODS).
- It is widely seen as the most successful environmental treaty.
- Evidence shows the ozone layer is recovering, with predictions of near-full repair by mid-21st century.
This case study demonstrates effective global cooperation—a contrast to the challenges of addressing climate change.
Ozone Depletion vs. Climate Change
ESS examiners often test your ability to distinguish the two:
- Ozone depletion = thinning of the stratospheric ozone layer, caused by CFCs.
- Climate change = warming of Earth’s surface due to enhanced greenhouse effect.
They are separate issues, though both involve human impacts on the atmosphere.
How the Ozone Layer Appears in ESS Exams
Paper 1
You may see data on ozone concentration, UV radiation levels, or global trends.
Paper 2
Typical essay questions include:
- “Discuss the environmental and health impacts of ozone depletion.”
- “Evaluate the effectiveness of the Montreal Protocol.”
Exam Tips
- Don’t confuse ozone depletion with global warming. Examiners mark this mistake harshly.
- Use the Montreal Protocol as a case study. It’s a perfect example of international cooperation.
- Keep it focused. The ozone layer is not as broad as climate change—learn the essentials.
FAQs
1. Is the ozone layer still in the syllabus?
Yes, but the focus is on stratospheric ozone depletion and its management, not tropospheric ozone or smog.
2. How detailed do I need to be about CFCs?
Know what they are, where they came from, and how they break down ozone. Chemical equations are not required.
3. Could the ozone layer appear in Paper 1?
Yes. Expect graphs of ozone concentration or maps of the Antarctic ozone hole.
Conclusion
The ozone layer remains an important part of the ESS syllabus for 2026 because it shows how human activity can damage atmospheric systems—and how international policy can repair them. By focusing on causes, impacts, and the Montreal Protocol, while avoiding confusion with climate change, you’ll be prepared for any exam question on this topic.
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