---
title: "September’s ozone hole reached 27.4 million square kilometers. We were warned in May"
description: "The Montreal Protocol is still working; the weather over Antarctica simply had other ideas this year"
author: "Tomasz Idle"
published: 2026-09-26T08:44:05.662Z
modified: 2026-09-26T19:00:57Z
url: https://rews.cc/a/september-s-ozone-hole-reached-27-4-million-square-kilometer-8ef264
language: en
tags: ["ozone", "climate", "environment", "monaco", "weather", "science"]
publisher: "Rews (https://rews.cc)"
---

# September’s ozone hole reached 27.4 million square kilometers. We were warned in May

*The Montreal Protocol is still working; the weather over Antarctica simply had other ideas this year*

By Tomasz Idle · September 26, 2026 · https://rews.cc/a/september-s-ozone-hole-reached-27-4-million-square-kilometer-8ef264

## In brief

- The 2026 Antarctic ozone hole peaked at 27.4m sq km in September, the second-largest ever recorded for this time of year
- Researchers predicted a major hole in May after satellites showed atmospheric dynamics priming an unusually cold polar vortex
- Despite its size, the hole is shallower than past large ones; ozone-depleting substances have fallen about a third since 2000
- A prolonged season through October and November is expected, likely ranking 2026 among the 10 most severe ozone seasons on record
- Full recovery is still projected before 2090, though recent holes increasingly linger late into spring

Think of the ozone layer as a patient on the longest course of medication in human history. The prescription was written in 1987, the medicine demonstrably works, and yet every southern spring the patient spikes another fever. This September’s was a doozy.

The Antarctic ozone hole — the annual springtime thinning of the ozone layer over the pole — peaked at more than 27 million square kilometers this month, hitting 27.4 million square kilometers (10.6 million square miles), the second-largest area ever observed at this point in the year, researchers writing in The Conversation reported. Only two holes have been bigger: the 2000 hole briefly topped 28 million square kilometers (10.8 million square miles), and the 2015 hole reached 27.9 million square kilometers (10.8 million square miles) that October.

Nobody here was ambushed. Back in May, satellites watching the atmosphere’s composition picked up the first signs that large-scale air currents were priming the polar vortex — the ring of fierce winds that corrals Antarctica every winter — into something unusually strong and cold. The team went on the record then predicting a “major” ozone hole for September 2026. September has obliged, and unless conditions over the pole shift, the researchers expect the hole to run long, through October and November.

The mechanics are perverse in their elegance. Inside a cold, robust vortex the air gets frigid enough for polar stratospheric clouds to form, and chemical reactions on those rare cloud particles switch dormant ozone-depleting gases into their destructive mode. The destruction then continues for as long as the vortex keeps the polar air bottled up, which is why a strong, cold vortex means a big, long-lived hole. The bracket, in other words, is set by the weather; the chemistry merely shows up to work.

The treaty still deserves its applause. The Montreal Protocol, which phased out ozone-depleting substances, has pushed their stratospheric levels down by about a third since their peak around 2000. And for all its footprint, the 2026 hole is comparatively shallow: by the researchers’ account, it hasn’t plumbed the depths of past giants, so there is less “missing” ozone in total. Wide rather than deep, which in a hole you would prefer to not exist is the right way round.

The wobble is that atmospheric dynamics can prime the vortex months in advance, meaning a recovering layer can still host an outsized hole. The 2020s have supplied a run of them: large, stubborn holes from 2020 through 2023, worsened by smoke from the 2019–20 Australian wildfires and aerosols from the 2021 La Soufrière eruption in the Caribbean, plus an early-starting 2023 season after the 2022 Hunga Tonga–Hunga Haʻapai submarine eruption. The scientists call the decade so far “a unique decade for ozone recovery,” which is a polite way of saying the recovery keeps being interrupted. Their new work aims to quantify exactly how much atmospheric dynamics exacerbated this year’s hole.

The hole is also not merely a chemist’s concern. After a severe season, a climate pattern called the Southern Annular Mode tends to shift into its positive phase: calmer winds and warmer, wetter weather for Aotearoa New Zealand, particularly the west coast, and extra rain along Australia’s southeast coast. The opposite phase brings more extreme wind — like the series of destructive storms that lashed parts of New Zealand in October last year.

The long-range forecast still ends well: full recovery of the Antarctic ozone hole is projected before 2090. But recent holes have developed the habit of lingering late into spring, and the researchers caution that shifting global atmospheric dynamics may be making marathon holes more likely — a behavior the recovery timeline’s models may be missing. For New Zealanders, the hole will keep fiddling with local winds and temperatures for decades yet.

The species, it turns out, is capable of writing itself a prescription and, rarer still, taking the medicine for forty years straight. What it cannot do is tell the weather to hold still while the patient heals.