"The ozone depletion levels were worse than those detected in 2011, but it has already returned to normal, due to weather factors, and the hole has closed," the WMO spokeswoman Clare Nullis said.
She also explained that this anomaly happened due to both the occurrence of an especially cold winter in the stratosphere and substances harmful to the ozone layer, which were banned by the 1989 Montreal Protocol.
Nullis rejected any relationship between changes in the ozone layer and the reduction in polluting emissions that occurred in recent months because of the COVID-19 pandemic.
"It is very unusual for such a strong ozone depletion to occur in the northern hemisphere, but this year's polar vortex was exceptionally strong and persistent, and temperatures were low enough to allow stratospheric clouds to form for several months," the European Centre for Medium-Range Weather Forecasts (ECMWF) scientist Antje Inness explained.
The stratospheric ozone layer acts as a "protective shield" for terrestrial life from the potentially damaging effects of ultraviolet radiation. The reduction in ozone levels occurs every southern spring in Antarctica but is less common in the Arctic.