The ozone layer is on the path to recovery: Here's how the world made it happen

This article has been updated.

Good news. The hole in the ozone layer that stretched unchecked above the Antarctic in the 1980s is continuing to shrink - and scientists now believe it could recover completely by 2066.

The problem was originally caused by gases known as chlorofluorocarbons (CFCs), which were silently tearing a giant hole in the ozone layer above the South Pole. CFCs were found in aerosol cans, as well as air-conditioning units and refrigerators.

But since 1987, when countries unanimously agreed to regulate nearly 100 ozone-depleting substances, the hole has been getting smaller. As World Ozone Day, or the International Day for the Preservation of the Ozone Layer, continues to be marked every year on 16 September, let’s head out into space for a closer look at what’s happening.

The ozone layer is part of the stratosphere, which lies 10-50 kilometres above the surface of the Earth. As NASA explains: “Ozone is a gas made up of three oxygen atoms.” As you can see in the infographic below, the ozone layer is fairly low down in the atmosphere.

For a simple gas, ozone plays a major role in the functioning of the Earth’s ecosystems. “Ozone protects life on Earth from the sun’s ultraviolet (UV) radiation,” says NASA. “Ozone in the stratosphere absorbs most of the ultraviolet radiation from the sun. Without ozone, the sun’s intense UV radiation would sterilize the Earth’s surface.” A depleted ozone layer can cause skin cancer and vision impairment.

There isn't a literal hole in the ozone layer, explains NASA. It's a way for scientists to describe an area where ozone concentrations have dropped below 220 Dobson Units, a measurement that indicates the amount of ozone in a vertical column of air above the Earth's surface.

Scientists from NASA and the US National Oceanic and Atmospheric Administration recently reported that the hole in the ozone layer "was relatively small in 2024 compared to other years". The hole lies above Antarctica, and between 7 September and 13 October this year, it ranked the seventh smallest since recovery began in 1992.

Scientists have confirmed that the shrinking of the ozone hole has continued a positive trend in recent decades.

“The 2024 Antarctic hole is smaller than ozone holes seen in the early 2000s,” said Paul Newman, leader of NASA’s ozone research team and chief scientist for Earth sciences at NASA’s Goddard Space Flight Center. “The gradual improvement we’ve seen in the past two decades shows that international efforts that curbed ozone-destroying chemicals are working.”

While human-caused ozone depletion may be under control, the eruption of the Hunga Tonga-Hunga Ha’apai volcano in 2022 unexpectedly caused a 30% reduction in ozone concentrations. Conversely, in 2019, unusual weather patterns over Antarctica dramatically reduced ozone depletion.

The discovery of the ozone layer hole prompted urgent international efforts to reverse the damage. In 1987, countries around the world came together to sign the Montreal Protocol, which formalized the mission to protect and repair the ozone layer by rapidly reducing the volume of ozone-depleting gases being released into the atmosphere. It’s the only UN treaty that all 198 UN member states have ratified.

The chart above shows that CFCs have almost been completely phased out, while the use of other ozone-depleting gases has been reduced significantly, and work is underway to go further.

To fulfil its obligations under the Montreal Protocol, the European Union brought into operation its EU Ozone Regulation in March 2024, which prohibits the production, supply and use, as well as the import or export, of ozone-depleting substances, with a few exceptional circumstances.

If the Montreal Protocol is fully implemented, the ozone layer is projected to recover completely.

In January 2023, an UN-backed scientific panel published its latest assessment report. It confirms that 99% of ozone-depleting gases have been phased out. Projections from the United Nations Environment Programme (UNEP) suggest the Antarctic ozone layer will recover to 1980 levels by around 2066, with recovery in the rest of the world between 2040 and 2045.

UNEP says international action to restore the ozone layer has protected millions of people from cancer: “Without this treaty, ozone depletion would have increased tenfold by 2050 compared to current levels, and resulted in millions of additional cases of melanoma, other cancers and eye cataracts. It has been estimated, for example, that the Montreal Protocol is saving an estimated 2 million people annually by 2030 from skin cancer.”

It's a positive and reassuring example of how the international community can come together to resolve a global environmental challenge. But on the wider issue of the climate crisis, the world is still "massively off track to limiting global warming to 1.5°C," warns the UN. And power plants run on fossil fuels account for around 14% of global population exposure to particle pollution and ozone, according to the World Economic Forum's Clean Air Actions in Cities report. Addressing the issue can not only improve health outcomes, it says, but also enable progress towards the world's climate goals.