Bristol, Jun 12 – The discovery of a hole in the ozone layer in 1985 led to international efforts to mitigate its damage, most notably through the Montreal Protocol on Substances that Deplete the Ozone Layer. This treaty, widely regarded as the most successful environmental agreement, aimed to reduce the release of ozone-depleting substances such as chlorofluorocarbons (CFCs).
First adopted in 1987 and ratified by every UN member state, the Montreal Protocol phased out the global production of CFCs by 2010, banning their use in refrigerators, air conditioners, and insulating foams. This gradual phase-out allowed countries with less established economies to transition to alternatives with the support of international funding.
Today, substances like propane have replaced CFCs in many applications, such as in refrigerators and aerosol cans, as they do not deplete the ozone layer. However, finding ozone-friendly alternatives for some products, such as certain insulating foams, took longer. In the interim, hydrochlorofluorocarbons (HCFCs) were used, though these too were found to damage the ozone layer.
The good news is that atmospheric levels of HCFCs have been falling since 2021, marking a significant milestone in the recovery of the ozone layer. Research I led with colleagues indicates this decline, demonstrating the success of the Montreal Protocol in addressing both the original CFCs and their HCFC successors.
HCFCs were initially chosen as alternatives to CFCs due to their similar properties but caused less ozone depletion. However, they are potent greenhouse gases. For example, HCFC-22 has a global warming potential 1,910 times that of carbon dioxide but remains in the atmosphere for only about 12 years, compared to several centuries for CO₂.
As non-ozone depleting alternatives became available, amendments to the Montreal Protocol in 1992 and 1999 set a timeline to phase out HCFCs. This phase-out is ongoing, with a target to end most HCFC production by 2030 and only minor amounts allowed until 2040.
Our findings of declining HCFC levels since 2021 reflect the effectiveness of these measures. The milestone is particularly notable as it shows the protocol’s success not only in tackling CFCs but also in addressing HCFCs, contributing to the ozone layer’s recovery. Predictions made in 2022 suggested that HCFC levels would not fall until 2026, making this an encouraging development.
Despite this progress, challenges remain. In 2019, evidence emerged that CFC-11 was still being used in parts of China, and the United Nations Environment Programme reported illegal HCFC production in 2020. Additionally, levels of five more CFCs have been increasing, likely due to a loophole in the Montreal Protocol allowing their production for specific uses.
Furthermore, HCFCs used in fluoropolymer production and hydrofluorocarbons (HFCs) as alternatives have their environmental issues. HFCs, although ozone-friendly, are potent greenhouse gases and are subject to international climate agreements such as the Paris Agreement and the Kigali Amendment to the Montreal Protocol. Hydrofluoroolefins (HFOs), the next potential alternative, pose environmental risks due to the formation of trifluoroacetic acid, which does not break down in the environment.
The decline in HCFC levels provides hope for the future. Although the ozone layer’s full recovery is still distant, the decrease in these gases since 2021 offers optimism. It demonstrates that environmental agreements and international cooperation can be effective in combating climate change and protecting the ozone layer.
