If you’ve ever opened your IB ESS notes at 11:47 pm and thought, “Wait… are we still doing the ozone layer in 2026?”, you’re in good company. The ozone story feels like an older headline compared to climate change. But that’s exactly why it shows up in exams: it’s a clean, testable example of how human systems can break an atmospheric balance, and how policy can actually fix something.
So yes -- for IB ESS (first assessment 2026), you still need the ozone layer. The focus is stratospheric ozone depletion and management, not a vague “ozone is important” paragraph.
What to know for IB ESS 2026 (fast checklist)
If you can do the items below, you’re covered for most IB ESS ozone questions:
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Define the ozone layer and locate it in the stratosphere.
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Explain the cause of depletion (CFCs, halons; and know N₂O is an emerging concern).
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Describe impacts (UV-B increases, health, ecosystems, economics).
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Use the Montreal Protocol (1987) as your go-to treaty case study.
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Separate ozone depletion vs enhanced greenhouse effect clearly in exam language.
For syllabus-aligned support, start with the Topic 6 hub: Topic 6: Atmosphere and climate change.
Where the ozone layer sits in IB ESS
In IB ESS, ozone usually appears as part of atmospheric structure and global environmental management.
The key point: the ozone layer is mainly in the stratosphere (roughly 15--35 km up) where it absorbs harmful UV radiation, especially UV-B. That “shield” framing matters because it links directly to impacts questions.
If your basics are shaky, revise atmospheric layers here: 6.1 Introduction to the atmosphere.
Causes of stratospheric ozone depletion (what examiners want)
Examiners don’t need you to be a chemist. They want you to explain the chain of reasoning like a system:
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CFCs (old refrigerants, aerosols, some industrial uses) reach the stratosphere.
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UV breaks them down, releasing chlorine radicals.
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Those radicals catalytically destroy ozone molecules, reducing ozone concentration.
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Depletion can be especially dramatic over Antarctica (the “ozone hole”).
Also know:
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Halons (fire suppression) contribute via bromine.
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Nitrous oxide (N₂O) is increasingly discussed as a contributor through atmospheric chemistry pathways.
If you want a crisp, syllabus-specific explanation, use: ESS 6.4B Ozone notes.
Impacts: environment, health, and the “so what?” paragraph
In IB ESS, impacts are where marks stack up because you can connect science to society.
Environmental impacts
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Reduced phytoplankton productivity (base of marine food webs).
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Damage to plant tissues and reduced crop yields.
Human health impacts
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Higher rates of skin cancers and cataracts.
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Immune system effects from increased UV exposure.
Economic impacts
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Healthcare costs rise.
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Agriculture and fisheries can be affected through ecosystem disruption.
A strong IB ESS response ties at least two categories together (example: phytoplankton decline -- food webs -- fisheries -- livelihoods).
The Montreal Protocol: your highest-return case study in IB ESS
The ozone layer is also a story about competence: the world noticed a problem, agreed on rules, and followed through.
The Montreal Protocol (1987) is widely considered the most successful environmental treaty because it:
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Regulated production and trade of ozone-depleting substances.
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Achieved near-universal participation.
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Was updated as science improved.
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Is linked to recovery projections for stratospheric ozone by mid-century.
Build your case-study paragraphs using RevisionDojo’s treaty notes: 6.4C The Montreal Protocol notes.
Ozone depletion vs climate change (the mistake that costs marks)
This is a classic IB ESS trap: both are “atmosphere problems,” but they’re not the same.
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Ozone depletion: thinning of stratospheric ozone, mostly from CFCs/halons, leading to more UV-B reaching Earth.
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Climate change: warming driven by the enhanced greenhouse effect, mainly from CO₂, CH₄, etc., trapping infrared radiation.
Examiners reward students who state the distinction cleanly before they elaborate.
How ozone shows up in IB ESS exams
You’ll see ozone in both skill types:
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Data-response questions (trend graphs, maps of ozone concentration, UV index changes)
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Extended responses (impacts, evaluate effectiveness of international agreements)
To practice in the right style, use RevisionDojo’s exam practice: Stratospheric ozone Questionbank. And if you want to tighten overall exam technique, this pairs well with: How to revise efficiently for ESS Paper 1 and Paper 2.
The simplest answer (and what to do next)
For IB ESS 2026, you do need the ozone layer. Learn the essentials: what it does, why it thins, what it changes (UV impacts), and why the Montreal Protocol matters. Then practise separating ozone depletion from climate change in one crisp sentence, because that single distinction protects a lot of marks.
If you want everything in one place, RevisionDojo is built for this exact moment: use the Study Notes for clarity, Flashcards for active recall, the Questionbank for exam-style practice, and AI Chat when you need a quick explanation that doesn’t waste your time. Add Mock Exams, Predicted Papers, and Grading tools near exam season, and you’ll walk into IB ESS feeling prepared instead of panicked.
Explore more IB ESS support here: All IB ESS blog posts.