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IB ESS SL 6.4 Stratospheric Ozone Questions

Practise IB ESS SL 6.4 by interpreting ozone trends, explaining UV protection and depletion and evaluating Montreal Protocol recovery evidence.

Syllabus
First assessment 2026
Course
ESS SL
Level
SL

Exam points

  • Interpret ozone charts by describing decline, stabilisation and projected recovery against earlier levels.
  • Explain how stratospheric ozone absorbs UV and link depletion to skin, eye and phytoplankton harm.
  • Identify ODS sources and explain how their release disrupts stratospheric ozone.
  • Distinguish ozone depletion from global warming by comparing gases, mechanisms and effects.
  • Compare tropospheric and stratospheric ozone through respiratory harm versus UV protection.
  • Evaluate Montreal Protocol success using ozone-hole data, implementation barriers and recovery projections.
  • Evaluate ODS controls and substitutes against black-market risks, costs and other environmental effects.

Covered syllabus points

6.4.1—Solar radiation spectrum6.4.2—UV radiation danger6.4.3—Stratospheric ozone protection6.4.4—UV radiation impacts6.4.5—Ozone equilibrium6.4.6—Ozone-depleting substances (ODSs)6.4.7—Ozone depletion effects6.4.8—Montreal Protocol6.4.9—Montreal Protocol success

Question 1

[Maximum number: 2]
Tropospheric ozone concentration in Mexico City over time

Figure:Tropospheric ozone concentration in Mexico City over time

Outline why a high concentration of ozone in the troposphere is a direct problem for humans, while in the stratosphere it is a benefit to humans.

Question 2

[Maximum number: 4]

Outline how decreasing stratospheric ozone may impact living organisms.

Question 3

[Maximum number: 7]
Figure 2: Observed and projected changes in global stratospheric ozone

Figure:Observed and projected changes in global stratospheric ozone

Key:
- Annually averaged data
- Average of atmospheric model projections

Question (a)

(a)

Describe the overall trend shown in the recorded annually averaged data in Figure 2.

[ 2 ]

Question (b)

(b)

State one chemical responsible for the trend in the recorded annually averaged data between 1980 and 1990 shown in Figure 2.

[ 1 ]

Question (c)

(c)

Outline one impact of low concentrations of stratospheric ozone on humans.

[ 1 ]

Question (d)

(d)

Identify the year that stratospheric ozone is predicted to return to 1980 levels in Figure 2.

[ 1 ]

Question (e)

(e)

Describe two reasons for the projected change in ozone levels after 2020 in Figure 2.

[ 2 ]
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