What happened
Bounded success. By the 2022 assessment, controlled ozone-depleting substances were declining and ozone recovery was progressing. Unexpected CFC-11 emissions showed that agreed phase-outs had not eliminated noncompliance. Subsequent declines were encouraging, but observing-network gaps and emissions from stored chemicals continued to complicate judgments about complete compliance and recovery timing.
- Article 10 establishes financial and technical cooperation, including a Multilateral Fund covering agreed incremental costs for eligible parties. Montreal Protocol Article 10: Financial mechanism
- Atmospheric measurements showed declining controlled ozone-depleting substances and progress toward ozone recovery. Scientific Assessment of Ozone Depletion 2022: Executive Summary
- Unexpected CFC-11 emissions triggered investigations and subsequently declined, while gaps in monitoring left uncertainty about emissions elsewhere. Scientific Assessment of Ozone Depletion 2022: Executive Summary
What might explain it
Plausible
Financial assistance plausibly made compliance more feasible and politically acceptable where transition costs otherwise threatened participation. Montreal Protocol Article 10: Financial mechanism
Alternative explanation: Available substitutes, commercial incentives, and domestic regulation also supported phase-outs; the financial mechanism operated alongside these changes.
Supported in case
Independent atmospheric measurement allowed the regime to detect problems that production reports alone could miss. Scientific Assessment of Ozone Depletion 2022: Executive Summary
Alternative explanation: Detection does not by itself explain subsequent reductions; enforcement, publicity, and producer decisions may have jointly contributed.
Questions to take into practice
- Shared obligations became more feasible when the agreement also addressed eligible countries' transition costs.
- Atmospheric measurements provided a check beyond countries' production reports.
- Unexpected emissions required investigation and response after the treaty was already operating; signing an agreement was not the end of coordination.
What remains uncertain
- Observing-network gaps leave uncertainty about the location and scale of some emissions.
- Stored chemicals can continue to leak after new production is controlled, so phase-out dates and atmospheric recovery dates need not coincide.
- The relative contributions of finance, substitutes, commercial incentives, and domestic enforcement remain difficult to separate.