WMO report finds Antarctic ozone hole shrinking; global recovery on track but risks remain
World Meteorological Organization says 2024 saw higher stratospheric ozone across much of the globe and a below‑average Antarctic ozone hole, but scientists urge continued monitoring and caution over remaining threats
The World Meteorological Organization reported that the ozone layer showed signs of recovery in 2024, with total stratospheric ozone cover higher over much of the globe and the seasonal ozone hole over Antarctica well below the 1990–2020 average.
The WMO said the Antarctic ozone hole reached a maximum ozone mass deficit of 46.1 million tonnes on Sept. 29, 2024, noting a relatively slow onset, delayed ozone depletion through September and a relatively rapid recovery after the deficit peaked. The below‑average level of ozone loss persisted through mid‑November, the agency said.
United Nations Secretary‑General António Guterres called the findings “proof that when nations heed the warnings of science, progress is possible,” reflecting assessments that international action under the 1987 Montreal Protocol has helped reduce the emissions of ozone‑depleting substances. Scientists estimate that, if current trends continue, the ozone layer could recover to pre‑1980 values by about 2040 for the global mid‑latitudes, by about 2045 over the Arctic and by roughly 2066 over Antarctica.
Ozone in the stratosphere, located roughly seven to 25 miles above Earth’s surface, absorbs the sun’s harmful ultraviolet‑B radiation and protects human health and ecosystems. Depletion of that layer, first detected above Antarctica in the 1980s, was linked to chlorofluorocarbons and other ozone‑depleting chemicals used in refrigeration, air‑conditioning, firefighting foam and aerosol products. The Montreal Protocol led to the phasing out of more than 99 percent of those substances.
Despite signs of recovery in the upper stratosphere at lower latitudes, scientists cautioned that the picture is mixed. A study published in Atmospheric Chemistry and Physics and assessments by the WMO indicated that ozone is likely not recovering between about 60°N and 60°S. Researchers cited a number of plausible drivers, including changes in atmospheric circulation driven by climate change that may shift ozone away from tropical production regions, and the influence of very short‑lived substances (VSLSs) containing chlorine and bromine used in solvents, paint strippers and degreasing agents.
In addition, the British Antarctic Survey highlighted an interaction with global warming: a slight cooling of the stratosphere is a side effect of greenhouse‑gas driven warming in the lower atmosphere, and cooler stratospheric temperatures favour formation of polar stratospheric clouds that promote ozone destruction. "A side effect of global warming is that the temperature of the ozone layer is falling slightly," the survey said, noting that such conditions can delay Antarctic ozone recovery.
WMO scientists stressed that levels of chlorine and bromine from historical production remain sufficient to produce significant ozone loss under conducive conditions. "There remains an essential need for the world to continue careful systematic monitoring of both stratospheric ozone and of ozone‑depleting substances and their replacements," said Matt Tully, chair of WMO’s Scientific Advisory Group on Ozone and Solar UV Radiation.
The agency’s 2024 assessment and the recent peer‑reviewed study both underscored the Montreal Protocol’s effectiveness in reducing many long‑lived ozone‑depleting gases and enabling measurable recovery in parts of the stratosphere. At the same time, researchers urged continued observation and regulation of replacement chemicals, including VSLSs, and careful tracking of climate‑driven changes in atmospheric circulation that could alter ozone distribution.
Health and environmental impacts of stratospheric ozone depletion include increased risks of skin cancer and cataracts in humans and damage to terrestrial and marine ecosystems from elevated ultraviolet radiation. While continued reductions in the most harmful long‑lived substances have reduced the overall risk, episodic and regional ozone loss can still occur when meteorological conditions and remaining chemical loads align.
Scientists and policymakers said the latest data provide a milestone in a multi‑decade effort to repair the ozone layer, but they emphasized that the recovery is not complete and that vigilance remains necessary. Monitoring networks, international cooperation on both legacy substances and emerging compounds, and integration of ozone protection with broader climate policy were cited as priorities to ensure the long‑term restoration of the atmospheric shield.
The WMO and contributing researchers plan to continue annual assessments of stratospheric ozone and ozone‑depleting substances and to refine projections as more observations and model results become available.