Photo: Unsplash/NASA
15 Sep 2022 Story Climate Action

While the ozone layer is healing, pitfalls remain

In 1987, the world came together to sign the Montreal Protocol, a global agreement to protect the Earth’s ozone layer. The accord was designed to phase out a host of chemicals, such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), that were creating a continent-sized hole in the ozone layer above Antarctica.

Today, the ozone layer is healing, shielding the planet from the potentially devastating effects of ultraviolet radiation.

But while it may have slipped from the headlines, the ozone layer still remains under pressure, said Meg Seki, Executive Secretary of the Ozone Secretariat under the United Nations Environment Programme.

“People tend to assume that the ozone hole is history, that we’ve done our job. Actually, we have a lot of challenges still ahead of us.” 

In the lead up to the International Day for the Preservation of the Ozone Layer, which falls on 16 September, we spoke with Seki about the perils facing the Earth’s sun shield and whether the Montreal Protocol can be a template for fighting climate change.

The Montreal Protocol has been called one of the most successful global environmental agreements in history. Why?

Meg Seki (MS): The Montreal Protocol is so significant because it successfully tackled an emerging environmental catastrophe. When scientists alerted the world that there was a gaping hole in the ozone layer due to man-made chemicals emitted into the atmosphere, political and environmental leaders came together to address the problem. Today, more than 99 per cent of ozone-depleting substances have been phased out and the ozone layer is on a path to recovery.

What is the size of the hole in the ozone layer now compared to 1987?

MS: Because of the annual variability, the size of the hole goes up and down depending on the temperature in the stratosphere.  So, we cannot predict this in advance but there’s a gradual but definite trend towards recovery.

How long until the hole is no more?

MS: Scientists estimate that the hole in the ozone layer will be no more by the 2060s. However, it’s very difficult to talk about complete recovery because the atmosphere itself is very different to what it was when there was no ozone depletion. Greenhouse gases, temperature changes and global warming all affect the dynamics and chemical processes in the atmosphere, impacting the recovery process. In other parts of the stratosphere, the ozone layer recovery is expected to be earlier.

Does climate change threaten to undo some of the progress we’ve made in repairing the ozone layer?

MS: This is a very complex issue. Ozone-depleting substances controlled by the Montreal Protocol are potent greenhouse gases that cause climate change, but we have managed to control and phase out their emissions. Climate change itself is causing changes in atmospheric circulation and temperature, which affect the depletion and recovery of the ozone layer.

The presence of greenhouse gases, such as nitrous oxide, and other pollutants in the stratosphere are also impacting ozone layer depletion. The Scientific Assessment Panel, one of three assessment panels under the Montreal Protocol, is constantly reviewing the state of the ozone layer and monitors the trends of ozone depleting substances and other gases in the atmosphere. The panel also looks into the linkages between stratospheric ozone changes and climate.

There are other challenges, too. The Montreal Protocol includes exemptions for some chemicals that may deplete the ozone layer. Other known ozone-depleting substances, like nitrous oxide, aren’t covered at all. Is it fair to say that the ozone layer isn’t out of the woods yet?

MS: Yes. Because of the Montreal Protocol’s success there’s been a lot of news about the ozone layer healing itself, which is great. But people now assume that the ozone hole is history, that we’ve done our job. Actually, we have a lot of challenges still ahead of us. First and foremost, we have the Kigali Amendment implementation to phase down HFCs and address energy efficiency improvements, especially in the cooling sector. Parties are also phasing out the remaining HCFCs and reducing the exempted uses where they can. Parties have also been looking into the sound destruction of banks of ozone-depleting substances that remain in end-of-life cooling equipment and buildings. Furthermore, although, nitrous oxide is not controlled by the Montreal Protocol parties are interested in understanding the magnitude of its impact on the ozone layer to see if any action needs to be taken. 

How has the Montreal Protocol contributed to biodiversity?

MS: It’s clear that protecting the ozone layer meant protecting all life on Earth: ecosystems, human health, agriculture, wildlife – you name it we protect it. Without the ozone layer, too much harmful UVB radiation would have reached the Earth’s surface. This would have been bad news. Increased exposure to ultraviolet radiation can cause skin cancer and eye cataracts, and damage crops, plants and micro-organisms, affecting ecosystems and food chains.

What lessons from the Montreal Protocol can be applied to tackling climate change?

MS: Ozone depleting substances were widely used in many sectors of our economy – cooling, electronics, firefighting, aerosols, medicine… and as fumigants in agriculture. Innovative measures and mechanisms were needed to ensure that the ozone-depleting substances that had become so essential to human life could be eliminated without disrupting the functioning of society.

To make this happen, all countries, developed and developing, collaborated in a global partnership, also with the full cooperation of industries and other stakeholders, to meet their respective responsibilities. The success of the Montreal Protocol should give us hope and some good lessons learned for tackling other global environmental issues, including climate change and the sustainable development agenda.


For more information, visit the United Nations Environment Programme Ozone Secretariat