The 2026 Antarctic ozone hole reached about 25 million square kilometres on September 12, roughly five million square kilometres above average

CAMS says the hole’s surface area grew rapidly, but other measurements remain close to historical averages

BONN — CLIMATE NEWS — September 16, 2026 — The Antarctic ozone hole expanded more quickly than usual during the first half of September, reaching an estimated 25 million square kilometres by September 12.

That is about five million square kilometres larger than the average for this point in the season, according to the European Union’s Copernicus Atmosphere Monitoring Service, known as CAMS.

The update was released as the world marks the United Nations International Day for the Preservation of the Ozone Layer on September 16.

While the size of the ozone hole is drawing attention, scientists say the wider picture is more complicated. Other measurements—including the lowest ozone level recorded inside the hole and the total amount of missing ozone—remained close to their historical averages.

Ozone Hole Reached 15 Million Square Kilometres Early

The 2026 Antarctic ozone hole began developing at a generally typical rate during the second half of August.

By the end of August, it had grown to approximately 15 million square kilometres. That is larger than Antarctica itself, which covers about 14.2 million square kilometres.

The hole crossed that threshold slightly earlier than average and at about the same point as it did in 2025.

The area then increased sharply during the first half of September, reaching an estimated 25 million square kilometres on September 12. CAMS forecasts indicated it could continue growing through the middle of the month.

For comparison, the largest ozone-hole area measured since satellite monitoring began reached 29.6 million square kilometres on September 9, 2006.

What Is the Ozone Hole?

The ozone hole is not an empty opening in the atmosphere.

Scientists define it as an area where the total amount of ozone in a vertical column of the atmosphere falls below 220 Dobson Units. A Dobson Unit is the standard measurement used to describe the amount of ozone above a location.

The ozone layer is located in the stratosphere, well above the weather systems experienced at ground level. It absorbs much of the Sun’s harmful ultraviolet radiation.

Too much ultraviolet exposure can increase the risk of skin cancer and eye damage while also affecting plants, wildlife and marine ecosystems.

Ozone levels over Antarctica fall each year during the Southern Hemisphere’s spring, generally between August and November.

Cold Stratospheric Temperatures Help Drive Depletion

The rapid expansion observed in early September coincided with a sharp temperature drop approximately 20 kilometres above the South Pole.

Very cold stratospheric conditions allow polar stratospheric clouds to form. Chemical reactions on these clouds help activate chlorine and bromine compounds that destroy ozone when sunlight returns to Antarctica in the spring.

Many of those compounds came from human-produced ozone-depleting chemicals once widely used in refrigeration, air conditioning, aerosol products and industrial applications.

The size and duration of the annual ozone hole are also influenced by atmospheric circulation, the strength of the Antarctic polar vortex and year-to-year weather conditions in the stratosphere.

This means a large ozone-hole area during one part of a season does not, by itself, establish whether the ozone layer’s long-term recovery is advancing or reversing.

Size Is Only One Measurement

CAMS monitors several indicators when assessing the Antarctic ozone hole.

The first is its geographical area. The second is the minimum amount of ozone measured within that area. The third is the ozone mass deficit—the amount of ozone that would have to be restored to bring the affected region back to the 220-Dobson-Unit threshold.

In 2026, the hole’s area was well above average by September 12. However, its minimum ozone level and ozone mass deficit remained close to average.

CAMS Director Laurence Rouil said the findings demonstrate why continuous monitoring is important. The ozone hole can vary considerably from one year to the next because of the interaction between atmospheric conditions, natural variability and human-produced chemicals.

Current conditions therefore deserve attention, but the large area should not be interpreted as evidence that decades of international ozone-protection work have failed.

Is This Connected to Climate Change?

Ozone depletion and climate change are different environmental problems, although they interact.

Climate change is mainly driven by greenhouse gases trapping additional heat in the lower atmosphere. Ozone depletion is caused primarily by chemicals that release chlorine and bromine in the stratosphere.

Warming near Earth’s surface can be accompanied by cooling higher in the stratosphere. Colder stratospheric temperatures can support the formation of the polar clouds involved in ozone-destroying reactions.

Scientists must consider both human-produced chemicals and changing atmospheric conditions when studying the annual ozone hole.

Recovery Remains a Long-Term Process

The Montreal Protocol, adopted in 1987, led countries to phase out many of the chemicals responsible for ozone depletion.

Because these substances can remain in the atmosphere for decades, repairing the ozone layer is a slow process. Annual changes can still be substantial, even while the concentration of many ozone-depleting chemicals gradually declines.

Recent years have included smaller and shorter-lived ozone holes. CAMS reported that the 2025 Antarctic ozone hole was the smallest and shortest-lived in five years.

The larger area observed early in the 2026 season shows why continued satellite measurements, ground observations and atmospheric forecasting remain necessary.

Why the Ozone Layer Matters in Canada

The annual Antarctic ozone hole is centred far from Northwestern Ontario, but protection of the ozone layer remains a global concern.

Ozone-depleting substances circulate through the atmosphere and do not remain within the country where they were released. International cooperation was essential to reducing their production and use.

The ozone layer protects people everywhere from damaging ultraviolet radiation. Canadians should continue following local UV forecasts and using sun protection when the UV index is elevated, regardless of what is happening over Antarctica.

CAMS will continue monitoring the 2026 ozone hole as it develops through the Southern Hemisphere spring. The hole normally begins shrinking as temperatures rise and the Antarctic polar vortex breaks down later in the season.

Readers can follow the latest observations through the CAMS ozone-layer monitoring service.

Source: Copernicus Atmosphere Monitoring Service and the European Centre for Medium-Range Weather Forecasts.