This year’s ozone hole over Antarctica has turned out to be one of the smallest seen in decades, with new measurements from NOAA and NASA showing a clear continuation of the gradual recovery that began after the global restrictions introduced under the Montreal Protocol. Scientists attribute the smaller size primarily to declining chlorine in the stratosphere and to warmer conditions aloft, both of which limited ozone destruction during the 2025 season.

According to the latest data, the Antarctic ozone hole averaged about 7.23 million square miles between September 7 and October 13, placing it among the five smallest since 1992. Researchers also note that the hole is breaking apart almost three weeks earlier than it typically has over the past ten years. On September 9, the hole reached its single largest extent for the year at roughly 8.83 million square miles. Even at that peak, it remained about 30 percent smaller than the record 2006 season, when the average size reached 10.27 million square miles. Long-term satellite records dating back to 1979 place the 2025 ozone hole as the 14th smallest over the entire 46-year dataset.

The figures reinforce what scientists have been expecting: steady recovery driven by the global phase-out of ozone-depleting chemicals. Researchers highlight that levels of these harmful substances have fallen by about one-third since their peak around 2000. NASA experts estimate that without this decline, the 2025 hole would have been more than one million square miles larger. Balloon-based observations over the South Pole recorded a minimum of 147 Dobson Units on October 6. While this is still low, it remains well above the all-time minimum of 92 Dobson Units measured in 2006.

The ozone layer, positioned high in the stratosphere, acts as Earth’s shield against dangerous ultraviolet radiation. When ozone thins, more UV rays reach the surface, raising risks for agriculture and human health, including skin cancer and cataracts. Ozone depletion occurs when compounds containing chlorine or bromine—traditionally found in products such as aerosols, foams, refrigerators and air conditioners—break apart in the upper atmosphere and trigger chemical reactions that destroy ozone molecules. Despite bans on these substances, many persist in older materials such as insulation or remain in landfills, meaning their gradual release continues to influence ozone levels. Scientists expect a full return to pre-depletion conditions around the late 2060s.

Short-term variations still depend heavily on weather. This year, a weaker-than-normal polar vortex in August helped keep temperatures higher than average, which likely contributed to the smaller ozone hole. NOAA researchers also point out that broader atmospheric patterns, temperature profiles and the strength of circumpolar winds all shape how the ozone layer behaves each year.

Monitoring the state of the ozone layer remains a global effort. NASA’s Aura satellite, NOAA-20 and NOAA-21, and the joint Suomi National Polar-orbiting Partnership mission all collect data from space, while ground-based instruments and weather balloons provide direct measurements from the South Pole Observatory. Together, these systems allow scientists to track how the ozone layer is evolving as the effects of international action continue to play out over time.