With the world continuing to fear the impact of climate change new data has found the world’s most concerning  hole in the ozone layer is shrinking.

The World Meteorological Organization (WMO) has published its latest research which found the Antarctic ozone hole in 2025 was one of the smallest in decades – testimony to the continuing success of international action to protect the Earth’s ozone layer which shields it against the sun’s harmful ultraviolet rays.

As the planet marked World Ozone Day the WMO issued a bulletin which said that last year’s ozone hole ranked as the fourth to fifth smallest since severe depletion patterns were observed in 1992. This is the second consecutive year that both the depth and extent of the ozone hole were significantly below the 1990–2010 average.

Year-to-year fluctuations are influenced by large-scale meteorological transport conditions which drive springtime ozone depletion almost every austral winter above Antarctica and every 5 to 10 years in the northern hemisphere.

In the Northern Hemisphere, total column ozone in 2025 was below average (negative anomalies) in a large region extending from Greenland and Europe to Central Asia, northern Japan and the Kamchatka Peninsula in the Russian Federation.

These variations occur within the long-term trend towards the healing of the ozone layer, reflecting the success of the Montreal Protocol on Substances that Deplete the Ozone Layer, which phased out chemicals such as chlorofluorocarbons once found in refrigeration, fire-fighting foam and other common uses.

The 1987 Montreal Protocol, successfully phased out ozone-depleting substances. This year marks the tenth anniversary of the Kigali Amendment, which expanded the scope of the Montreal Protocol.

The 2016 Kigali Amendment provides for a phase down of hydrofluorocarbons (HFCs), potent greenhouse gases that are used to replace ozone depleting substances. These chemicals are widely used in everyday cooling technologies such as refrigerators, air conditioners, insulating foams, and some medical and industrial equipment.
Whilst they do not deplete the ozone layer, some HFCs trap thousands of times more heat than carbon dioxide, even though they remain in the atmosphere for a much shorter time.
“This is an environmental success story. Since 2000, the ozone layer has been recovering, and we can expect full recovery within several decades,” said WMO secretary-general Celeste Saulo.

The WMO explained about 90% of atmospheric ozone resides in the upper-level stratosphere. If all this ozone were brought down to the Earth’s surface, the resulting layer of pure ozone would be only approximately 3 millimetres thick. Yet, this thin layer blocks nearly all dangerous short-wave ultraviolet (UV) radiation from the Sun and protects life on Earth.

While substantial progress has been made in addressing ozone depletion, measurements over the past decades show a significant increase in the number of days with high UV index values. The UV index was developed to track the depletion of the ozone layer and now serves as an international health standard for UV protection.

Since the mid-1990s, UV radiation has increased by as much as 20% in some parts of Europe. Ground-based measurements show that this has been driven primarily by a reduction in cloud cover and an accompanying increase in annual sunshine duration. Higher UV exposure means a greater risk of skin cancer and other UV-related diseases among exposed populations.

“In light of this trend, targeted and effective UV protection measures are of paramount importance,” the Bulletin stated.