WMO Bulletin finds ozone hole in 2024 was smaller than in recent years.
Global action under Montreal Protocol has phased out 99% of ozone-depleting substances.
Ozone layer projected to return to 1980 levels by mid-century.
Recovery already visible, with delayed onset and faster healing over Antarctica.
Scientists warn continued monitoring remains vital.
The Earth’s protective ozone layer is healing, according to a new report from the World Meteorological Organization (WMO). The ozone hole in 2024 was smaller than in recent years and is now on track to return to 1980 levels by the middle of this century.
The WMO’s Ozone Bulletin, released on World Ozone Day on September 16, highlighted that the long-term positive trend is the result of coordinated international action through the Vienna Convention and the Montreal Protocol, which phased out the vast majority of ozone-depleting substances. The convention recognised stratospheric ozone depletion as a global problem and provided the framework for mobilising international cooperation in ozone research, systematic observations and scientific assessments.
“The Vienna Convention and its Montreal Protocol became a landmark of multilateral success. Today, the ozone layer is healing. This achievement reminds us that when nations heed the warnings of science, progress is possible,” United Nations secretary general António Guterres said in a statement.
According to the bulletin, the ozone hole over Antarctica in 2024 was smaller than the large holes recorded between 2020 and 2023. The maximum ozone mass deficit was 46.1 million tonnes on September 29, 2024, below the 1990-2020 average. Its onset was relatively slow, and depletion was delayed through September, followed by a rapid recovery. This later onset has been identified as “a robust indication of initial recovery of the Antarctic ozone hole,” the WMO said.
According to the most recent global scientific assessment, issued in 2022, the ozone layer is projected to recover to 1980 levels by 2066 over Antarctica, by 2045 over the Arctic and by 2040 across the rest of the world — if current policies remain in place. The next assessment will be published in 2026.
The recovery of the ozone layer cuts risks of skin cancer, cataracts and damage to ecosystems from harmful ultraviolet radiation.
Celeste Saulo, WMO’s secretary general, said the recovery demonstrated the value of “trust, international collaboration and commitment to free data exchange — all cornerstones of the world’s most successful environmental agreement.”
The Montreal Protocol, agreed in 1987, has already eliminated more than 99 per cent of controlled ozone-depleting substances once used in refrigeration, air conditioning, firefighting foam and hairsprays.
The report also emphasised the importance of continued monitoring of both stratospheric ozone and replacement substances. “Despite the great success of the Montreal Protocol in the intervening decades, this work is not yet finished,” said Matt Tully, chair of WMO’s Scientific Advisory Group on Ozone and Solar UV Radiation.
The Bulletin traced progress under the Montreal Protocol and its Kigali Amendment, which commits countries to phasing down hydrofluorocarbons, powerful greenhouse gases. Ratified by 164 parties, the amendment is expected to prevent up to 0.5 degrees Celsius of global warming by the end of the century.