The hole in the ozone layer in the Southern Hemisphere has grown larger than usual this year, surpassing the entire ice-covered continent in area. This year’s Antarctic ozone hole is already among the 25% largest since records began and continues to grow. Scientists believe that climate change may be the cause.
The European Union’s Copernicus Atmosphere Monitoring Service reported on September 16, 2021, that the ozone hole, which occurs every year in the southern spring, increased significantly last week after an average start.
Ozone exists about 11 to 40 km above the Earth’s surface in the stratosphere and acts as a sunscreen for the planet by absorbing the harmful portion of ultraviolet radiation.
“Forecasts show that this year’s hole has developed slightly larger than usual,” said Vincent-Henri Peuch, who heads the EU’s satellite monitoring service.
“We’re looking at a pretty big and potentially deep hole in the ozone layer,” he said. In recent years, the hole in the ozone layer has grown to a maximum of 20 million square kilometres (8 million square miles) under normal weather conditions. In 2020, the ozone hole peaked in early October at about 24 million square kilometers, larger than in previous years.
Peuch noted that last year’s ozone hole also began unremarkably, but then turned into one of the longest lasting on record.
Atmospheric ozone absorbs ultraviolet light that comes from the sun. The ozone hole is responsible for more of this high-energy radiation reaching the earth, where it can damage living cells. The polar vortex, a band of ice-cold air high above Antarctica, plays an important role here. This band, which is formed during the Antarctic winter, traps ozone-depleting substances above the Antarctic, damaging the layer and causing the ozone hole to be at its widest around September. When the air masses warm up in spring, the system usually recovers and the layer can become thicker again. This year, however, temperatures in the stratosphere were in the lower range than usual for an unusually long time. Researchers believe this is due to climate change.
Ozone killer banned since 1987
The Montreal Protocol, signed in 1987, bans harmful chlorofluorocarbons (CFCs) and other substances known to destroy the protective ozone layer that absorbs harmful ultraviolet (UV) radiation. CFCs were first developed in the 1930s for use in refrigeration systems and later used as propellants in aerosol spray cans. CFCs are now banned in 197 countries.
Concentrations of harmful substances in the atmosphere have levelled off since the Protocol entered into force and are slowly declining, providing the basis for the gradual restoration of the ozone layer.
Experts say that while the ozone layer is beginning to recover, it will likely take until the 2060s for ozone-depleting substances to completely disappear from the atmosphere. However, the latest measurements indicate that this regeneration process is slowing down and that a full recovery cannot be expected until 2070 at the earliest.
Some countries still use the banned substances (CFCs) illegally. By chance, researchers at NOAA’s Boulder office came across far greater amounts of the ozone killer trichlorofluoromethane in the atmosphere during a routine measurement in 2017 than they had expected.
At least 40 to 60 percent of the trichlorofluoromethane emissions are expected to come from a region in northeast China. Trichlorofluoromethane is one of the chlorofluorocarbons, better known as CFCs.
Heiner Kubny, PolarJournal