Each year, as the northern hemisphere enters autumn, the opposite happens above the South Pole, where the austral spring begins. In this region, a vast area of the stratosphere—known as the ozone layer—becomes significantly depleted, creating what is commonly called the ozone layer hole. This phenomenon has been observed since the 1980s and continues to raise questions about why such a large breach still exists despite global efforts to address it. According to NASA, in 2025, the ozone hole reached 21.08 million square kilometers, one of the smallest areas recorded since 1992. The Montreal Protocol (1987), along with the Kigali Amendment (2016), has helped eliminate more than 99 percent of the harmful substances responsible for ozone destruction. According to the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), the Antarctic ozone layer should return to its 1980 levels by 2066, compared to 2045 for the Arctic and 2040 for the rest of the globe. The mechanism behind the ozone hole is now well understood by climatologists. Between August and October, during the austral spring, a chemical reaction is triggered in the stratosphere above Antarctica. The extreme cold of the polar winter, combined with the presence of specific stratospheric clouds, activates chemicals that destroy ozone at an impressive rate. This results in an area that can cover several million square kilometers becoming nearly devoid of this protective layer, which is crucial for filtering the sun's ultraviolet rays. The size of the hole varies from year to year. In 2023, the hole reached a surface area of 26.1 million square kilometers, but by 2025, it peaked at 21.08 million square kilometers before closing completely by early December. NASA has classified this as one of the smallest observed since the start of satellite measurements in 1992. The Montreal Protocol, signed in 1987, aimed to gradually eliminate the chemicals responsible for ozone layer destruction, particularly chlorofluorocarbons (CFCs), once widely used in aerosols, refrigerators, and air conditioners. The result has been the elimination of more than 99 percent of these harmful substances worldwide. In 2016, the Kigali Amendment was added to the protocol, incorporating hydrofluorocarbons (HFCs), gases used as replacements for CFCs but with a high global warming potential. This amendment is considered a key milestone, as it has helped prevent an additional increase in global temperatures between 0.5 and 1 degree Celsius by 2050. According to the latest joint assessment report from the WMO and UNEP, the ozone layer above Antarctica should return to its 1980 levels by 2066. This deadline is due to the particular severity of the phenomenon at the South Pole. For comparison, the Arctic is expected to return to its original state by 2045, while the rest of the world will achieve this by 2040. Since the year 2000, the size and depth of the Antarctic hole have been decreasing slowly but steadily, an encouraging sign that confirms the effectiveness of the measures taken. However, a recent study has tempered this optimism: some substances authorized as raw materials for the production of plastics appear to have leaks significantly higher than expected, approaching 3.6 percent compared to the initial estimate of 0.5 percent. In this less favorable scenario, the full return to the 1980 state could be delayed by about seven additional years. Beyond the numbers and projections, the history of the ozone hole tells a rare story of collective success in the environmental field. While current climate crises sometimes struggle to generate coordinated global responses, the Montreal Protocol demonstrates that an international consensus, applied rigorously over several decades, can reverse a trend initially considered alarming. The WMO Secretary-General recently recalled this with accuracy: since 2000, the ozone layer has been recovering, and it is now permissible to hope for a complete recovery within a few decades. However, this success is never entirely assured. The recently highlighted industrial leaks remind us that no environmental victory is definitive as long as scientific and political vigilance remains constant. As the ozone hole opens once again this season above the South Pole, it embodies both the proof that a coordinated global action can work and the reminder that the road to a fully restored atmosphere remains long.