The Antarctic ozone hole swelled to its largest extent in ten years in 2026, covering 27.1 million square kilometers on September 18—nearly three times the land area of the United States. Yet the record does not signal a reversal in the ozone layer’s recovery. According to a joint report from NASA and NOAA, an unusually strong polar vortex, not increased pollution, is the culprit.
- Record extent: The hole peaked at 27.1 million square kilometers on September 18, the largest since 2015 and about 90% of the all-time record set on September 9, 2000.
- Meteorological driver: A potent polar vortex kept stratospheric air extremely cold over Antarctica, fueling ozone-destroying clouds; the weather systems that normally break up the vortex were weak in August and September.
- Recovery intact: Scientists stress that the Montreal Protocol continues to work, with stratospheric chlorine down roughly a third from 1980s levels and full recovery expected by the end of the century.
Why the Hole Grew So Large
The expansion stems from atmospheric dynamics rather than chemistry. A particularly strong polar vortex maintained very cold air over the Antarctic, creating ideal conditions for polar stratospheric clouds that catalyze ozone destruction. Amy Butler, a researcher at NOAA, explained that the systems that typically disrupt the vortex were unusually weak in August and September, allowing stronger winds to persist around the South Pole.
The 2026 hole reached about 90% of the largest ever recorded, on September 9, 2000. It contrasts sharply with 2025, which saw the fifth-smallest hole since 1992. That year-to-year variability is precisely what reveals the role of weather: background chemistry barely changes in twelve months, but wind patterns do.
No, the Ozone Layer Is Not Getting Worse
The recovery remains on track, and the Montreal Protocol continues to deliver results. Ozone depletion is initiated by human-made chlorine and bromine compounds, chiefly CFCs. Paul Newman, a senior scientist at the University of Maryland and leader of NASA’s ozone team, estimates that without the reduction of those pollutants, this year’s hole would have been between 2.5 and 5.2 million square kilometers larger.
The ozone hole was discovered in 1985, and in 1987 the Montreal Protocol was adopted to phase out the substances that cause it. According to Stephen Montzka, a senior scientist at NOAA, chlorine in the Antarctic stratosphere has fallen by about one-third compared with 1980s levels, and agencies expect the layer to recover by the end of this century. The finding is a reminder that the stratosphere is fragile and that what we release into the air takes decades to reverse—a concern that also extends to satellites and spacecraft now emerging as new stratospheric pollutants.
“The headline ‘largest hole in a decade’ is frightening, but the data that matters is the other one: the cause being wind rather than pollution confirms that the Montreal Protocol—the most successful global environmental agreement in history—is still doing its job.”
That lesson is uncomfortable for today’s climate debate: the protocol worked because it was binding, universal, and offered a clear industrial alternative to the substances it banned. It is worth remembering as air pollution continues to claim lives through other pathways, with a substantial share of deaths attributed to heat actually caused by atmospheric contamination. The atmosphere can be repaired; we have already done it once.