In just a decade, the world has slashed super-polluting chemicals used in air-conditioners and fridges. Experts say the pact offers a model for cooperation on warming.

The Antarctic ozone hole reached its largest area in two decades during September 2026, covering over 27 million square kilometres. This unprecedented size was preceded by early warning signs observed in May 2026, when scientists detected changes in atmospheric circulation patterns. The ozone hole's growth was driven by a strong polar vortex and unusually cold temperatures over Antarctica, creating ideal conditions for ozone depletion. While the 2026 ozone hole is the second-largest recorded for September, it has not yet reached the extreme depths seen in previous record years. The Montreal Protocol, which has successfully phased out ozone-depleting substances since its inception in 1987, continues to show positive results, with stratospheric levels of these chemicals dropping by approximately one-third since their peak around 2000. The 2026 ozone hole began forming earlier than usual in August, with low stratospheric temperatures accelerating its development. By September, it had rapidly expanded to 27.4 million square kilometres, surpassing all but two previous records. Scientists predict the hole will persist through October and November, potentially ranking among the top ten most severe ozone holes in recorded history. This year's event follows a pattern of increasingly severe ozone depletion since 2020, with factors including the 2019-20 Australian wildfires and the 2021 La Soufrière volcanic eruption contributing to worsened ozone depletion in previous years. The ozone hole significantly impacts Southern Hemisphere weather patterns, influencing the Southern Annular Mode which affects wind and precipitation patterns across New Zealand and Australia. While the ozone layer is projected to fully recover before 2090, recent trends suggest longer-lasting ozone holes may become more common, potentially altering the timeline for complete recovery. The ongoing research by scientists at the University of Otago and Earth Sciences New Zealand continues to improve understanding of the complex relationship between atmospheric dynamics and ozone depletion.