6.4.9—Montreal Protocol success SL

Montreal Protocol action reduced ODS emissions and prevented the planetary boundary for stratospheric ozone depletion from being crossed, according to the evidence specified by the syllabus.

Evaluate the conclusion with ODS emissions and atmospheric concentrations, ozone-hole area or depth, regional and seasonal ozone measurements, baselines and uncertainty. One good year is not enough.

Declining CFC concentrations alongside long-term ozone recovery supports treaty effectiveness even when polar recovery varies with weather and atmospheric transport.

Boundary avoidance is a monitored long-term trend, not proof that recovery is complete or identical everywhere.

A successful agreement does not remove the need for compliance checks and new substitute assessment.