Thirty-five years ago, in Montreal, Canada, world leaders came together to make a landmark agreement to protect the ozone layer.
The Montreal Protocol on Substances that Deplete the Ozone Layer is now considered the most successful international environmental treaty ever, and an inspiring example of global cooperation to protect life on Earth.
Protecting life on Earth
The ozone layer sits at about 15–30 kilometres up in the atmosphere and stops too much harmful ultraviolet (UV) radiation getting down to the ground. UV radiation damages human health, the natural environment and agricultural productivity. Less ozone up in the atmosphere means more UV radiation at ground level.
The ozone layer is a shield that has stopped life on earth from getting too much sun for over half a billion years. All the world's ecosystems rely on its protection – we can't live without it.
The ozone problem
In the 1970s and 80s, scientists discovered the ozone layer was being destroyed by a group of manufactured chemicals, now called ozone depleting substances.
Chlorofluorocarbons (CFCs) were causing the most damage. And at that time, CFCs were used everywhere – in fridges, air conditioners, fire extinguishers, aerosol cans and asthma inhalers. They were also used to produce synthetic foam found in many products, from building insulation to running shoes.
The ozone layer is thinnest at the southern end of the globe in springtime. Where the ozone layer is thinner, more people get skin cancer, cataract blindness and other diseases linked to the damage caused by UV radiation. This means it is people in the southern hemisphere, including parts of Australia and New Zealand, who face the biggest risks from ozone depletion.
In 1985, British scientists reported an alarming decline in ozone levels above Antarctica. The ozone layer was thinning at an alarming rate but there was a solution. Scientists found that less environmentally harmful alternatives could be used instead of CFCs – but implementing this would require unprecedented global cooperation.
Video without sound. This series of images of the stratospheric ozone layer captured by NASA shows the size of the ozone hole over Antarctica each year from 1979 to 2019.
Scientists use the word hole as a metaphor for the area in which ozone concentrations drop below the historical threshold of 220 Dobson Units (DU).
The maximum depth of the hole in 1979 was 194 DU. The deepest ozone hole occurred in 1994, when concentrations fell to 73 DU.
In the early years of the 21st century, annual ozone holes roughly stabilised.
The Montreal Protocol
Countries came together in 1985 to agree to the Vienna Convention for the Protection of the Ozone Layer as a framework to investigate the problem and its solutions.
Just 2 years later, on 16 September 1987, the countries of the United Nations agreed to a plan to phase out ozone depleting substances – the Montreal Protocol. This date is now marked every year as World Ozone Day.
Australia ratified the Montreal Protocol in 1989, the year it came into force. Eventually all 198 United Nations member states signed on, making the Montreal Protocol the first environmental treaty signed by all countries.
Perhaps the single most successful international environmental agreement to date has been the Montreal Protocol.Kofi Annan, former Secretary General of the United Nations.
Under the treaty, countries committed to phase out the chemicals that were known to damage the ozone layer.
The negotiation and cooperation that began in the 1980s has continued. The Montreal Protocol now covers about 100 ozone depleting substances. Most of these are also greenhouse gases. Unfortunately, so are some of the alternatives.
Around the world, hydrofluorocarbons (HFCs) replaced ozone depleting chemicals in many uses. While HFCs are not damaging to the ozone layer, they are potent greenhouse gases that contribute to climate change (although not as much as the ozone depleting substances they have replaced).
In recognition of this, parties agreed to the Kigali Amendment to the Montreal Protocol, to phase down HFCs too.
Adopting an ambitious amendment to phase down the use and production of [HFCs] is likely the single most important step that we could take at this moment to limit the warming of our planet and protect the planet for future generations to come.John Kerry, US Secretary of State (2016)
The treaty now controls 18 HFCs, which do not harm the ozone layer but do contribute to climate change – another global threat requiring global cooperation to solve.
The Montreal Protocol has built in scientific and technological reviews every 4 years. Controls have been tightened, and chemicals added as new scientific information and technological solutions have become available.
Australian scientists play an important role in the global assessment of ozone depletion and recovery, and monitoring the progress of the Montreal Protocol.
Australia has often moved faster than our Montreal Protocol obligations to phase out ozone depleting substances.
Our approach relies on partnership between industry, community, scientists and all levels of government to manage the whole-of-life use of these substances. We track and manage their use from when they are imported, through the supply chain and while in use, and manage collection or destruction at end-of-life.
When you have a fridge or air conditioner installed, serviced or removed, a trained and licensed technician will safely handle refrigerants so they’re not released into the atmosphere.
The good news
International efforts to protect the ozone layer are working.
Recent research confirms that while the ozone layer has been seriously harmed by human actions, it can recover.
The ozone layer is estimated to reach full recovery by the middle of the century. This will only happen with continued global cooperation and all countries continuing to meet their obligations to the Montreal Protocol.
Global action under the Montreal Protocol will continue to be an important part of addressing the climate challenge. And that is something we can all be proud of.
Find out more about the Montreal Protocol.