6.4.3—Stratospheric ozone protection
- Syllabus
- First assessment 2026
- Objective
- 6.4.3
- Level
- SL
Treat Ozone as a Dynamic UV Shield
Stratospheric ozone absorbs damaging UV, reducing the dose that reaches surface organisms while being continually formed and destroyed.
Ozone forms when UV splits O₂ and oxygen atoms combine with O₂; other reactions destroy it. Location matters: stratospheric ozone shields, near-surface ozone is a pollutant.
A temporary fall in stratospheric ozone can raise surface UV even if total atmospheric oxygen is unchanged.
It must be present in the stratosphere where it intercepts relevant UV before it reaches the surface.
‘Ozone’ is not always beneficial; location and concentration determine whether it shields or harms.