6.4.6—Ozone-depleting substances (ODSs)
- Syllabus
- First assessment 2026
- Objective
- 6.4.6
- Level
- HL
Separate Ozone-Depleting and Warming Pathways
An ozone-depleting substance changes stratospheric chemistry; CO₂-driven warming changes infrared energy balance. Some gases can affect both, but mechanisms differ.
CFCs release chlorine radicals that catalytically destroy ozone and also have high greenhouse potential. CO₂ does not deplete ozone through that chlorine cycle.
Replacing CFCs protects ozone; reducing CO₂ addresses long-wave forcing. One policy can help both only if the substance and mechanism overlap.
Ozone chemistry and greenhouse forcing are different problems, even when a refrigerant policy affects both.
‘Atmospheric chemical’ does not mean every gas has the same target, lifetime or impact.