As the Vienna Convention for the Protection of the Ozone Layer celebrates its 40th anniversary this year, protective stratospheric ozone layer is healing. Delegates to the 37th Meeting of the Parties (MOP 37) to the Montreal Protocol on Substances that Deplete the Ozone Layer addressed some of the challenges still facing its health.

Widely regarded as “the most effective environmental treaty in history,” the Montreal Protocol “has sheltered humanity from most of the dire consequences of ozone layer depletion and increased ultraviolet radiation,” the Earth Negotiations Bulletin (ENB) analysis of the meeting notes. In addition, “the Protocol’s original measures are estimated to avert up to 1°C of global warming by 2050, with the subsequent Kigali Amendment projected to avoid another 0.3-0.5°C [of] warming by 2100.”

The ENB summary report highlights that one of the more contentious issues on the MOP 37 agenda had to do with discrepancies between atmospheric monitoring and reporting of emissions of hydrofluorocarbons (HFCs) – potent greenhouse gases (GHGs) covered under the Protocol’s Kigali Amendment. Related discussions focused on areas of the world lacking atmospheric monitoring of substances controlled under the Protocol and on how to fill in the gaps.

“Another issue facing many developing countries is how to find medium- and long-term solutions to the significant accumulation of inventories of refrigerant gases nearing the end of their life cycles,” ENB further flags.

Administrative matters delegates addressed to allow the Protocol to continue its work include:

• Terms of reference for the study on the 2027-2029 replenishment of the Multilateral Fund (MLF) for the Implementation of the Montreal Protocol;
• Technology and Economic Assessment Panel (TEAP) organizational issues;
• Adoption of the budget of the Trust Fund for the Montreal Protocol for 2026; and
• Ensuring the viability of Montreal Protocol operations.

The ENB report notes that delegates adopted 20 decisions, but postponed those on controlled substances used as feedstocks, further strengthening Montreal Protocol institutions, and Technology and Economic Assessment Panel (TEAP) organizational issues.

Described by ENB as “otherwise successful,” the meeting was held up because of a dispute over a nomination to represent the Eastern European States regional group on the Protocol’s Implementation Committee.

MOP 37 convened in Nairobi, Kenya, from 3-7 November 2025. [ENB Coverage of MOP 37]