The Last Ozone-Layer Damaging Chemicals to Be Phased Out Are Finally Falling in the Atmosphere

Since the 1985 discovery of a hole in the ozone layer, countries around the world have united to address this critical issue. 

The most notable of these efforts is the Montreal Protocol on Substances that Deplete the Ozone Layer, widely regarded as the most successful environmental agreement ever devised. 

Ratified by every UN member state and first adopted in 1987, the Montreal Protocol aimed to reduce the release of ozone-depleting substances into the atmosphere, with a particular focus on chlorofluorocarbons (CFCs).

Starting in 1989, the protocol initiated a phased reduction in the global production of CFCs, culminating in a complete phase-out by 2010. 

These substances were banned in equipment such as refrigerators, air-conditioners, and insulating foam. 

This gradual approach allowed countries with less established economies time to transition to alternatives and provided funding to help them comply with the protocol’s regulations. 

Today, household items like refrigerators and aerosol cans use gases like propane, which, although flammable, do not deplete the ozone layer.

However, finding ozone-friendly alternatives for certain products, such as foams used to insulate fridges and buildings, took longer. 

Hydrochlorofluorocarbons (HCFCs) were used as a temporary replacement. 

Unfortunately, HCFCs also destroy ozone, albeit to a lesser extent than CFCs. 

The good news is that levels of HCFCs in the atmosphere have been declining since 2021, marking a major milestone in the recovery of Earth’s ozone layer and a rare success story in humanity’s efforts to tackle climate-warming gases.

HCFCs and CFCs share many similarities, which made HCFCs suitable alternatives initially. Both contain chlorine, the chemical element responsible for ozone depletion. 

However, HCFCs deplete ozone to a much smaller extent than CFCs. Despite this, both are potent greenhouse gases. 

The most commonly used HCFC, HCFC-22, has a global warming potential 1,910 times that of carbon dioxide, but it only lasts for around 12 years in the atmosphere, compared to several centuries for CO₂.

As non-ozone depleting alternatives to HCFCs became available, amendments to the Montreal Protocol were agreed upon in Copenhagen and Beijing in 1992 and 1999, respectively, to phase out HCFCs. 

This phase-out is still underway, with a global target to end most production of HCFCs by 2030, and only minor amounts allowed until 2040. 

Our findings show that levels of HCFCs in the atmosphere have been falling since 2021 – the first decline since measurements began in the late 1970s. 

This milestone underscores the enormous success of the Montreal Protocol in addressing both CFCs and their less destructive successors.

Despite the positive trend in HCFC levels, the phase-out of ozone-depleting substances has not been without challenges. 

In 2019, evidence emerged that CFC-11, a common constituent of foam insulation, was still being used in parts of China despite the global ban on production. 

The United Nations Environment Programme also reported illegal production of HCFCs in 2020. 

In 2023, new research indicated that levels of five more CFCs were increasing in the atmosphere, likely due to a loophole in the Montreal Protocol that allowed CFCs to be produced if used to make other substances, such as plastics or non-ozone depleting alternatives.

Furthermore, some HCFCs at very low levels in the atmosphere have also been shown to be increasing or not falling fast enough, despite few or no known uses. 

Most of these increases are attributed to the production of fluoropolymers, used in non-stick frying pans, or hydrofluorocarbons (HFCs). 

HFCs, developed in the early 1990s to replace HCFCs, are also potent greenhouse gases and are subject to international climate emission reduction treaties such as the Paris Agreement and the Kigali Amendment to the Montreal Protocol.

The search for alternatives to climate-warming HFCs is ongoing. 

While hydrofluoroolefins (HFOs) were initially considered a promising replacement, their environmental impact, particularly in forming trifluoroacetic acid, has raised concerns. 

Despite these issues, HFOs are more energy-efficient refrigerants than older alternatives like propane.

In discovering the fall in atmospheric levels of HCFCs, there is a sense of optimism about the global effort to repair the ozone layer. 

Although there is still a long way to go before it returns to its original state, this decline in HCFCs is a promising sign. 

With policies in place to phase down HFCs, there is hope that environmental agreements and international cooperation can effectively combat climate change.

The decline in HCFCs marks a significant achievement in the global effort to protect the ozone layer. 

It demonstrates the effectiveness of international treaties like the Montreal Protocol and provides a rare beacon of hope in the fight against climate change. 

As we continue to phase out harmful substances, the success of these efforts offers a blueprint for tackling other environmental challenges.