This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The Antarctic ozone hole in 2025 was one of the smallest in decades—a testament to the continuing success of international action to protect Earth's ozone layer, which shields us from the sun's harmful ultraviolet rays, according to a new report from the World Meteorological Organization (WMO). In welcome news, the WMO Ozone Bulletin said that last year's ozone hole ranked as the fourth or 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 five 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 toward 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, firefighting foam and other common uses. "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 Global Atmosphere Watch (GAW) network provides the critical, high-quality ground-based total column ozone observations required to accurately monitor ozone and ensure that long-term changes can be understood. About 90% of atmospheric ozone resides in the upper stratosphere. If all this ozone were brought down to Earth's surface, the resulting layer of pure ozone would be only approximately 3 millimeters (0.12 inches) thick.
Yet this thin layer blocks nearly all dangerous shortwave 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.
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