New data reveal one of the smallest ozone holes in decades

This year’s ozone hole over Antarctica ranked among the smallest since the early 1990s, reflecting steady progress from decades of global action under the Montreal Protocol.

Declining chlorine levels and warmer stratospheric temperatures helped limit ozone destruction. Scientists say the layer remains on track to recover later this century.

Scientists from National Oceanic and Atmospheric Administration (NOAA) and National Aeronautics and Space Administration (NASA) report that this year’s ozone hole over Antarctica is the fifth smallest seen since 1992, the year that the Montreal Protocol, a landmark international agreement to phase out ozone-depleting chemicals, began to take effect.

During the peak of the 2025 ozone depletion season, from September 7 to October 13, the ozone hole covered an average of about 7.23 million square miles (18.71 million square kilometres).

It is already breaking apart almost three weeks earlier than the typical timing over the past ten years.

“As predicted, we’re seeing ozone holes trending smaller in area than they were in the early 2000s,” said Paul Newman, a senior scientist at the University of Maryland system and longtime leader of NASA’s ozone research team.

“They’re forming later in the season and breaking up earlier.”

PEAK SIZE

On September 9, the ozone hole reached its largest single-day size for 2025, spanning 8.83 million square miles (22.86 million square kilometres).

That area is roughly 30 per cent smaller than the largest ozone hole on record in 2006, which had an average size of 10.27 million square miles (26.60 million square kilometres).

In earlier assessments, NASA and NOAA rated ozone hole severity using records that extend back to 1979, when satellites first began tracking ozone levels above Antarctica.

Using this longer 46 year record, the 2025 ozone hole ranks as the 14th smallest in terms of area.

WHY OZONE LAYER MATTERS

Earth’s ozone-rich layer functions like a global sunscreen that protects living things from harmful ultraviolet (UV) radiation from the sun. This layer resides in the stratosphere, which lies between seven and 31 miles above Earth’s surface.

When ozone levels drop, more UV rays reach the ground, increasing the risk of crop damage and contributing to higher rates of skin cancer and cataracts, along with other negative health effects.

Ozone depletion begins when certain chlorine- and bromine-containing compounds reach the stratosphere, where intense UV radiation breaks them apart and releases reactive forms of chlorine and bromine. These reactive substances then interact with ozone molecules and destroy them.

For many years, compounds such as Chlorofluorocarbons (CFCs) and other ozone-depleting substances were widely used in aerosol sprays, foam products, air conditioners and refrigerators, and the chlorine and bromine in these chemicals can remain in the atmosphere for long periods.

Although these chemicals are now banned, many still linger in older materials such as building insulation and in landfills. As emissions from these legacy sources gradually diminish, scientists expect the ozone hole over Antarctica to recover (get smaller) by around the late 2060s.

Laura Ciasto, a meteorologist with NOAA’s Climate Prediction Center and a member of the ozone research team, noted that conditions such as temperature, overall weather patterns and the strength of the band of winds circling Antarctica known as the polar vortex also affect ozone levels and the size of the ozone hole from year to year.

“A weaker-than-normal polar vortex this past August helped keep temperatures above average and likely contributed to a smaller ozone hole,” said Ciasto.

Keeping an eye on the ozone layer takes a team of observing systems spread across the globe. Scientists monitor ozone using instruments aboard NASA’s Aura satellite, the NOAA-20 and NOAA-21 satellites, and the Suomi National Polar-orbiting Partnership satellite that is jointly operated by NASA and NOAA.

NOAA scientists also rely on instruments carried by weather balloons, along with upward-looking surface-based instruments, to directly measure stratospheric ozone above the South Pole Atmospheric Baseline Observatory.

– ANI