The annual ozone hole over Earth’s southern pole in 2024 was smaller than in many previous years, reflecting continued recovery of the ozone layer. On average, the ozone-depleted region during the peak depletion period from September 7 to October 13 was almost 20 million square kilometers, ranking as the seventh smallest since 1992, when the Montreal Protocol began to take effect. The hole reached 22.4 million square kilometers on its largest day, September 28-about three times the size of the contiguous United States.
Scientists attribute the gradual recovery to declining levels of chlorofluorocarbons (CFCs) and an unexpected infusion of ozone transported from northern air currents. But the layer remains far from fully healed. Satellite data collected since 1979 shows that this year’s ozone hole ranks as the 20th smallest area in size. Paul Newman, NASA’s chief scientist for Earth sciences, remarked that things are still going the right way from when international efforts began to curb CFCs in the early 2000s.
This layer of ozone forms an armor that protects life on Earth from destructive ultraviolet or UV radiation. This layer depletion causes further exposure to UV, which increases the risk of skin cancer, cataracts, and damage to all ecosystems, including aquatic life and crops. In the 1970s, researchers discovered that CFCs used as refrigerants, coolants in air conditioners, and propellants in aerosol sprays could greatly deplete atmospheric ozone. Within a decade and a half, extreme depletion had resulted in large holes over Antarctica.
The Montreal Protocol of 1987 mandated the phasing out of production of CFCs, and by 2010, most of the more harmful chemicals had been replaced by safer alternatives. The existing CFCs will still remain in the atmosphere and break down over a period of decades, though their contribution to new emissions has decreased dramatically. The result has been a gradual restoration of the ozone layer, with scientists predicting full recovery by 2066.
NOAA and NASA are tracking ozone with several tools, including satellite observations and weather balloons. The lowest concentration over the South Pole recorded in 2024 was 109 Dobson units on October 5, which is still much lower than the average 225 units that existed before CFC pollution became rampant in 1979. NOAA’s Bryan Johnson said, “There is a long way to go for it to fully recover.”.