WMO Ozone and UV Bulletin No. 4 – September 2026
- 2025 Antarctic ozone hole was one of smallest in recent decades
- Annual fluctuations occur despite long-term recovery trend
- World Ozone Day celebrates Montreal Protocol success
- UV radiation remains a threat to health
- Atmospheric monitoring is essential to inform policy
The depth and overall extent of the 2025 Antarctic ozone hole were significantly smaller than the 1990–2010 average. The 2025 ozone depletion cycle was one of the least severe in over two decades, with the 2025 ozone hole ranking as the fourth to fifth weakest since severe depletion patterns were observed in 1992 (Newman et al., 2026). The maximum ozone mass deficit (OMD) was 36.7 million tons on 29 September, more than 25% less than the 1990–2010 mean of 50.1 million tons.
The daily development of the 2025 ozone hole began normally in mid-July. A relatively early onset of ozone depletion was observed in late August, while peak ozone depletion rates were observed at the start of September, much earlier in the season than in previous years. In fact, OMD values in October – when peaks are usually observed – were well below the 1990–2010 historical envelope.
About the WMO Ozone and UV Bulletin series
The WMO Ozone and UV Bulletin is an annually issued scientific update that assesses the health of the ozone layer and UV radiation trends, highlighting recovery progress, challenges posed by extreme events, and the crucial need for continued monitoring and policy action.
