A hole in the ozone layer three times larger than Brazil has opened up over Antarctica.

Europe’s Copernicus Sentinel-5P satellite shows that the ozone hole is one of the largest on record, according to the European Space Agency (ESA), and measured 26mn square kilometres on September 16, 2023 – roughly three times the size of Brazil.

Satellite data revealed that this year's ozone hole expanded to about twice the size of Antarctica. The eruption of Tonga's underwater volcano in early 2022 is a possible cause for the unusual size of the ozone hole, say scientists.

The ozone layer in Earth's atmosphere is approximately 15 to 30 kilometres above the surface and protects the planet from harmful ultraviolet rays from the sun. Ozone is a type of oxygen molecule with three atoms instead of the usual two that absorbs the sun's radiation.

The discovery of significant ozone holes above Earth's polar regions was made in 1985. Researchers found that chlorofluorocarbons (CFCs), a common chemical used in aerosol cans, packaging materials and refrigerators at the time, were reacting with ozone in the atmosphere, leading to ozone depletion. In response, the international community banned the use of CFCs in 1989, allowing ozone levels to gradually recover.

However, gaps in the ozone layer still appear above the polar regions during each hemisphere's winter months. This occurs when cold air creates polar stratospheric clouds (PSCs), which are exceptionally high clouds composed of tiny ice crystals. These clouds further deplete the already limited amount of ozone above the poles.