Ozone hole recovery accelerates: 2025 size among lowest in decades, NASA reports

The hole this year was the fifth smallest since 1992, the year a landmark international agreement to phase out ozone-depleting chemicals began to take effect, read the NASA website.

At the height of this year’s depletion season from Sept. 7 through Oct. 13, the average extent of the ozone hole was about 7.23 million square miles (18.71 million square kilometers) — that’s twice the area of the contiguous United States. The 2025 ozone hole is already breaking up, nearly three weeks earlier than usual during the past decade.

The hole reached its greatest one-day extent for the year on Sept. 9 at 8.83 million square miles (22.86 million square kilometers). It was about 30% smaller than the largest hole ever observed, which occurred in 2006, and had an average area of 10.27 million square miles (26.60 million square kilometers).

“As predicted, we’re seeing ozone holes trending smaller in area than they were in the early 2000s,” said Paul Newman, a senior scientist with the University of Maryland, Baltimore County, and leader of the ozone research team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “They’re forming later in the season and breaking up earlier. But we still have a long way to go before it recovers to 1980s levels.”

NASA and NOAA scientists say this year’s monitoring showed that controls on ozone-depleting chemical compounds established by the Montreal Protocol and subsequent amendments are driving the gradual recovery of the ozone layer in the stratosphere, which remains on track to recover fully later this century.

The ozone-rich layer acts as a planetary sunscreen that helps shield life from harmful ultraviolet (UV) radiation from the Sun. It is located in the stratosphere, which is found between 7 and 31 miles above the Earth’s surface. Reduced ozone allows more UV rays to reach the surface, resulting in crop damage as well as increased cases of skin cancer and cataracts, among other adverse health impacts.

The ozone depletion process starts when human-made compounds containing chlorine and bromine rise high into the stratosphere miles above Earth’s surface. Freed from their molecular bonds by the more intense UV radiation, the chlorine and bromine-containing molecules then participate in reactions that destroy ozone molecules. Chlorofluorocarbons and other ozone-depleting compounds were once widely used in aerosol sprays, foams, air conditioners, and refrigerators. The chlorine and bromine from these compounds can linger in the atmosphere for decades to centuries.

“Since peaking around the year 2000, levels of ozone-depleting substances in the Antarctic stratosphere have declined by about a third, relative to pre-ozone-hole levels,” said Stephen Montzka, a senior scientist with NOAA’s Global Monitoring Laboratory.

As part of the 1987 Montreal Protocol, countries agreed to replace ozone-depleting substances with less harmful alternatives.

“This year’s hole would have been more than one million square miles larger if there was still as much chlorine in the stratosphere as there was 25 years ago,” Newman said.

Still, the now-banned chemicals persist in old products like building insulation and in landfills. As emissions from those legacy uses taper off over time, projections show the ozone hole over the Antarctic recovering around the late 2060s.

NASA and NOAA previously ranked ozone hole severity using a time frame dating back to 1979, when scientists began tracking Antarctic ozone levels with satellites. Using that longer record, this year’s hole area ranked 14th smallest over 46 years of observations.

Factors like temperature, weather, and the strength of the wind encircling Antarctica known as the polar vortex also influence ozone levels from year to year. A weaker-than-normal polar vortex this August helped keep temperatures above average and likely contributed to a smaller ozone hole, said Laura Ciasto, a meteorologist with NOAA’s Climate Prediction Center.

Researchers monitor the ozone layer around the world using instruments on NASA’s Aura satellite, the NOAA-20 and NOAA-21 satellites, and the Suomi National Polar-orbiting Partnership satellite, jointly operated by NASA and NOAA.

NOAA scientists also use instruments carried on weather balloons and upward-looking surface-based instruments to measure stratospheric ozone directly above the South Pole Atmospheric Baseline Observatory. Balloon data showed that the ozone concentration reached its lowest value of 147 Dobson Units this year on Oct. 6. The lowest value ever recorded over the South Pole was 92 Dobson Units in October 2006.