The Montreal Protocol on Substances that Deplete the Ozone Layer is considered the world’s most successful international environmental treaty. As COP28 wraps up, it’s understandable to feel fairly hopeless. Because of this, I wanted to take a moment to look at a time when things went right, in the belief that they could be successful again.

What is the Montreal protocol?

Under the Montreal Protocol, countries around the world phased out chlorofluorocarbons (CFCs). These were chemicals used as a freezing technology, patented in the 1920s, containing atoms of carbon, chlorine, and fluorine that were used mostly in aerosol sprays, refrigerants, foams and as solvents. Non-toxic, non-flammable and cheap, they were initially seen as a miraculous discovery. However, while CFCs are not toxic to humans, it was discovered that these chemicals were damaging the ozone layer that protects the planet from UV radiation. 

The Montreal Protocol on Substances that Deplete the Ozone Layer was first signed in 1987 and entered into force in 1989, and was a landmark in environmental policy-making; controlling both the production and consumption of various ozone-depleting substances. In 1990 at the second meeting of the Parties to the Montreal Protocol in London, the 80 countries present agreed that the production and consumption of CFCs and halons should be phased out by the year 2000 in developed countries, simultaneously establishing a Multilateral Fund to provide financial assistance to developing countries to meet the cost of phase out. 

Since its entry into force, the Montreal Protocol has phased out over 98% of the world’s consumption of ozone-depleting substances, resulting in a significant, positive impact on the ozone layer.

What is the ozone layer and why was it damaged?

Ozone is rare in the atmosphere, with only 3 molecules of ozone for every ten million air molecules. 90% of the planet’s ozone is in the ozone layer in the lower level of the stratosphere (20-25 kilometres above sea level). Stratospheric ozone filters the sun’s cell-damaging UV radiation, reducing the harmful effects this radiation has on Earth. A damaged ozone layer allows more radiation to reach the Earth’s surface, harming plants and animals while changing the temperature structure of the atmosphere.

While concentrations of ozone in the stratosphere fluctuate naturally due to variations in weather conditions, amounts of energy being released from the Sun, and major volcanic eruptions, in the 1970s scientists realised human activity was affecting the ozone layer. It became clear that man-made emissions of CFCs and other chemicals could cause significant destruction of ozone in the stratosphere, letting more harmful UV radiation pass through.

In 1985, evidence of a large ozone hole was discovered above the continent of Antarctica. As well as allowing more UV radiation to reach the earth, the hole created multiple climate impacts on the Southern Hemisphere. By the 1980s, scientists noted that jet streams were changing. Australia got drier, and the rain increased in parts of Uruguay, Brazil, Paraguay and Argentina. 

The Montreal Protocol

In 1987, the Montreal Protocol on Substances that Deplete the Ozone Layer was signed, which regulated the production and consumption of nearly 100 chemicals, including ozone-depleting CFCs. It was the first global treaty that dealt with the environment and showed what was possible with global cooperation. It’s also the only UN treaty ratified by every country on the planet, adopted by 197 U.N. member states. It only took only 2 years from the discovery of the ozone hole in 1985 for governments to agree to a global ban on the use of CFCs, and a further 2 years for it to come into effect.

Although individual nation states fought for their own national interests throughout the Montreal negotiations, they did ultimately act in the interest of the global commons…

The Montreal Protocol not only binds its signatories to prohibit the use of CFCs in their jurisdictions, it also introduced sanctions that prohibited trade in certain chemicals with non-signatories, creating a significant incentive for countries to sign up. What is striking as well is the effectiveness of the implementation of Montreal Protocol. It is the only global treaty to achieve universal ratification of 197 countries, and has achieved a compliance rate of 98%. As such, Montreal is evidence of the effectiveness of outright bans. Since Montreal, such bans have been harder for governments to contemplate, but the effectiveness of the Protocol shows that governments can and have used their powers to drive rapid transitions away from harmful substances and for the benefit of the environment.


The treaty understood global responsibility, as it facilitated helping poorer countries move away from these chemicals with proper support. These countries were responsible for a comparatively small amount of CFC use, as 80% of CFCs were consumed in industrialised nations. One of the main CFC producers, DuPont, estimated that $135 billion worth of industrial equipment in the US alone was reliant on CFCs in the late 1980s.

The hole in the ozone layer has now been consistently shrinking for years. Without the protocol, it’s estimated that ozone-depleting substances could have destroyed two-thirds of the stratospheric ozone layer by 2065. While CFCs can remain in the atmosphere for 70 years, without the release of CFCs this cycle will eventually stop, and scientists believe the ozone layer can recover to 1980 levels.

The changing wind patterns that caused climate impacts in the Southern Hemisphere also paused around the year 2000, approximately when the Montreal Protocol began to take effect. In 2020, researchers from NOAA’s Chemical Sciences Laboratory documented that declining atmospheric concentrations of ozone-depleting chemicals were responsible.

Why was the Montreal Protocol successful?

There was widespread public understanding of the dangers that CFCs posed, and what their continued use would do to the environment. Public support for change drove industry to change and seek out alternatives. This proved the power of public pressure, cooperation and collaboration, and the relevance of the concept of the Overton Window.

Environmental organisations coalesced around the issue of CFCs – and through inventive public campaigns managed to spur changes in consumer behaviour, including widespread boycotts of products and companies that used CFCs. Consumer pressure forced action by some US-based companies even before the government introduced bans on the use of CFCs. By the time the ban was in place, the market for CFCs had dwindled, making their phase out more feasible.


Scientists as advocates were also key. The scientific community communicated powerfully on the dangers posed by ozone depletion, making the message accessible enough so ordinary people could understand both the threat and the action required to mitigate it.

A diverse coalition – including environmental organizations, scientists, and the public – lobbied for further research and the eventual Protocol. Non-governmental organizations (NGOs) were essential to the consumer awareness campaign to ban aerosol products in the 1970s and helped educate the public and pressure politicians on ozone depletion the following decade. NGOs also turned to the courts when the administration refused to act: when officials first disputed the data in 1984, EPA staffers leaked an internal report to the Natural Resources Defense Council, which sued the government under the Clean Air Act. The suit’s eventual resolution, which included negotiation with CFC producers, included a “Stratospheric Ozone Protection Plan” requiring continued EPA research and cooperation with the UNEP. 


There was also a role for business, which is where this specific situation differs from wider fossil fuel phase-out. Unlike major fossil fuel producers, CFCs were limited to a smaller number of businesses, who had more motivation to change. It’s important to also note these differences, to understand where tactics must vary for future climate justice work.

The limited number of business actors involved also made it relatively easy to reach an agreement. Eighteen chemical companies accounted for most of the world’s production of CFCs in the early 1980s – mostly concentrated in the US, UK, France and Japan. DuPont was the most important player, producing around 1/4 of the global output. This meant that once DuPont acted as the industry leader in the global negotiations, and once the company’s agreement for a ban was secured, the rest of the industry followed suit. Also important was the fact that, although the CFC market was important, it was not truly ‘big business’ – CFCs accounted for 3% of DuPont’s total sales.



CFCs deplete the ozone layer, but scientists have also learned that they are also potent greenhouse gases. Controlling CFCs helped reduce greenhouse gas emissions worldwide, an important climate justice outcome. 

However, scientists now know that some of the alternatives used cause other issues. While hydrofluorocarbons (HFCs) cause considerably less damage to the ozone layer, they are also powerful greenhouse gases. Fortunately, the Montreal Protocol is designed to be flexible, so new pollutants can still be added to the ban list. There have been numerous amendments over the years since it was first written, helping to incorporate new research findings. In 2016, the Kigali Amendment was adopted to phase down future global production and consumption of HFCs. Its implementation should prevent the emissions of up to 105 billion tonnes of CO2 equivalent, helping to avoid up to 0.5 degree of warming.

The final deal divided the world economies into three groups, each with a target phasedown date. The richest countries, including the United States and those in the European Union, will reduce the production and consumption of HFCs from 2019. Much of the rest of the world, including China, Brazil and all of Africa, will freeze the use of HFCs by 2024. A small group of the world’s hottest countries such as Bahrain, India, Iran, Iraq, Kuwait, Oman, Pakistan, Qatar, Saudi Arabia, and the United Arab Emirates have the most lenient schedule and will freeze HFCs use by 2028.


Ultimately, the Montreal Protocol was a unique set of circumstances that have been hard to replicate, as evidenced by the lack of meaningful climate action from successive COPs. It’s not a set of tactics that can be perfectly copied and pasted on to the current climate justice movement, however it does provide hope. We know that, when things work together, this kind of international collaboration can be achieved. It’s going to be hard work, and it is people power and international solidarity that will likely achieve this, but it can be done again.