The Montreal Protocol on Substances that Deplete the Ozone Layer

The Montreal Protocol on Substances that Deplete the Ozone Layer is a global agreement to protect the Earth’s ozone layer by phasing out the chemicals that deplete it. This phase-out plan includes both the production and consumption of ozone-depleting substances. The landmark agreement was signed in 1987 and entered into force in 1989.

The parties to the Protocol meet once a year to make decisions aimed at ensuring the successful implementation of the agreement. These include adjusting or amending the Protocol, which has been done six times since its creation. The most recent amendment, the Kigali Amendment, called for the phase-down of hydrofluorocarbons (HFCs) in 2016. These HFCs were used as replacements for a batch of ozone-depleting substances eliminated by the original Montreal Protocol. Although they do not deplete the ozone layer, they are known to be powerful greenhouse gases and, thus, contributors to climate change.

The Montreal Protocol provided a set of practical, actionable tasks that were universally agreed on. The Protocol has successfully met its objectives thus far and continues to safeguard the ozone layer today. Thanks to the collaborative effort of nations around the world, the ozone layer is well on its way to recovery.

Decision XXVII/7: Investigation of carbon tetrachloride discrepancies

Reiterating its concern about the discrepancy between observed atmospheric concentrations and data on carbon tetrachloride reported in the 2014 assessment reports of the Technology and Economic Assessment Panel and the Scientific Assessment Panel, indicating that the mismatch between bottom-up inventories and global top-down estimates of carbon tetrachloride remains unresolved,

Noting with concern that derived emissions of carbon tetrachloride, based on its estimated lifetime and its accurately measured atmospheric abundances, have become much larger over the last decade than those from reported production and usage, notwithstanding that some of the discrepancy could be explained by additional sources unrelated to reported production, such as contaminated soils and industrial waste, and that additional explanations could include underreported releases to the atmosphere and incorrect partial lifetimes (stratosphere, ocean or soil),

Recalling decisions IV/12, X/12, XVI/14, XVIII/10, XXI/8 and XXIII/8,

  1. To request the Technology and Economic Assessment Panel and the Scientific Assessment Panel to continue their analysis of the discrepancies between observed atmospheric concentrations and reported data on carbon tetrachloride and to report and provide an update on their findings to the Twenty-Eighth Meeting of the Parties;