The ozone layer hole has reached in 2026 an unusually large extent over Antarctica. According to the data published on November 4 by NASA and the National Oceanic and Atmospheric Administration of the United States (NOAA), it has been the seventh largest of the last 48 years of observations, if the average surface during the period of maximum ozone loss is taken into account.
Between September 7 and October 13, the hole covered on average about 25 million square kilometers, an area more than double that of the United States. Its maximum extent in a single day was recorded on September 18, when it reached 27.1 million square kilometers.
Despite this growth, scientists insist that the figure does not represent a setback in the recovery of the ozone layer. The evolution of a specific year may be conditioned by the meteorological conditions in the stratosphere, while the long-term trend depends, to a large extent, on the reduction of the chemical compounds that destroy ozone.
A more intense polar vortex has favored its expansion
The explanation for the size reached this year is related to the behavior of the Antarctic polar vortex, a wind current that surrounds the continent and helps to maintain low temperatures in the stratosphere.
In 2026, this system has been especially intense and persistent. According to researchers at NASA and NOAA, the weather systems that typically rise from the lower layers of the atmosphere and contribute to weakening the vortex were weaker during August and September.
As a result, stronger winds remained farther from the South Pole and cold conditions that favor ozone destruction lasted longer. In the Antarctic stratosphere, low temperatures allow the formation of polar stratospheric clouds, whose particles facilitate the chemical reactions that release chlorine and bromine capable of breaking down ozone molecules.
This phenomenon helps explain why the hole can grow or shrink notably from one year to the next without necessarily changing the underlying trend.
Why growth does not mean that the ozone layer is getting worse
To interpret the data, it is necessary to distinguish between the extent of the hole and the amount of ozone that is lost. In 2026, the surface area has been one of the largest of the last decades, but the loss has not reached the levels of the most severe episodes recorded in the past.
Measurements carried out by the NOAA at the South Pole station placed the minimum ozone concentration directly over the observatory at 105 Dobson units on October 17. The figure is above the historical minimum recorded at that point, 92 Dobson units in October 2006.
Therefore, a hole with a larger extent does not necessarily imply a more intense destruction of ozone across the entire region. The affected surface area, the ozone concentration, and the duration of the phenomenon are different indicators that scientists analyze together.
In addition, the hole is not a physical opening in the atmosphere. It is an area in which the ozone concentration drops below a given threshold, usually 220 Dobson units.
The Montreal Protocol continues to drive recovery
The evolution of 2026 also does not invalidate the progress achieved since the Montreal Protocol entered into force in 1987. This international agreement established the gradual reduction of substances that damage the ozone layer, such as chlorofluorocarbons (CFCs), used for decades in refrigerants, aerosols, and other products.
According to the NOAA, chlorine levels in the Antarctic stratosphere originating from ozone-destroying substances have decreased by approximately one third compared with the peaks reached in the 1980s.
The reduction of these compounds explains why the 2026 hole could have been between 3.5 and 5.2 million square kilometers larger if the substances that destroy ozone were still present in the atmosphere at the maximum concentrations recorded around the year 2000.
Recovery, however, is slow. These compounds can remain in the atmosphere for decades, so their effects do not disappear immediately after emissions are reduced. Scientists’ estimates place the recovery of the Antarctic ozone layer around the decade of 2070.
Thus, this year’s evolution shows that recovery is not linear: weather conditions can lead to seasons with more extensive holes, but the sustained reduction of harmful substances remains the decisive factor for the ozone layer to progressively return to its previous levels.