Washington DC [US], December 21 (HBTV): 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, and scientists say the ozone layer remains on track to recover later this century.
Scientists from National Oceanic and Atmospheric Administration (NOAA) and NASA reported that this year’s ozone hole was the fifth smallest observed since 1992, when the Montreal Protocol began to take effect.
During the peak of the 2025 ozone depletion season, from September 7 through October 13, the ozone hole covered an average of about 7.23 million square miles (18.71 million square kilometres). It is breaking apart nearly three weeks earlier than the average timing recorded over the past decade.
‘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.’
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 figure is about 30 per cent smaller than the record 2006 ozone hole, which averaged 10.27 million square miles (26.60 million square kilometres).
Using satellite records dating back to 1979, when ozone monitoring above Antarctica began, the 2025 ozone hole ranks as the 14th smallest in the 46-year record.
According to NOAA and NASA scientists, the findings reinforce evidence that restrictions on ozone-depleting substances under the Montreal Protocol and its amendments are supporting gradual recovery of the ozone layer. The layer is expected to return to pre-ozone hole conditions later this century as countries continue replacing harmful chemicals with safer alternatives.
‘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, senior scientist with NOAA’s Global Monitoring Laboratory.
‘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 added.
Weather balloon observations showed that in 2025, the ozone layer directly over the South Pole dropped to a minimum of 147 Dobson Units on October 6. The lowest value ever recorded over the South Pole was 92 Dobson Units in October 2006.
The ozone-rich layer in the stratosphere acts as a protective shield against harmful ultraviolet (UV) radiation from the sun. When ozone levels decline, more UV radiation reaches the Earth’s surface, increasing the risk of crop damage, skin cancer, cataracts and other health issues.
Ozone depletion occurs when chlorine- and bromine-containing compounds reach the stratosphere and break down under UV radiation, releasing reactive substances that destroy ozone molecules. For decades, chemicals such as chlorofluorocarbons were widely used in aerosol sprays, foam products, air conditioners and refrigerators. These substances can persist in the atmosphere for long periods.
Although most ozone-depleting chemicals are now banned, many remain in older materials such as building insulation and landfills. As emissions from these legacy sources decline, scientists project that the Antarctic ozone hole could recover by the late 2060s.
Laura Ciasto, a meteorologist with NOAA’s Climate Prediction Center and a member of the ozone research team, said weather conditions also influence ozone levels each year.
‘A weaker-than-normal polar vortex this past August helped keep temperatures above average and likely contributed to a smaller ozone hole,’ Ciasto said.
Scientists continue to monitor ozone levels using instruments aboard 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. Ground-based instruments and weather balloons are also used to measure stratospheric ozone above the South Pole Atmospheric Baseline Observatory.
(ANI)