This year’s hole in the Earth’s protective ozone layer — which grew to be larger than Antarctica — is finally set to close this week, atmospheric scientists have said.
Ozon absorbs the UV light of the sun and acts like a shield. The absence of ozone means that more high-energy radiation from the sun reaches Earth. This can cause damage to living cells.
By chemical reactions that are driven by solar power and involve by-products human-made chemicals, the ozone layer becomes depleted.
The size of the annual hole — which forms during the southern hemisphere’s summer — is strongly dependant on weather conditions, and boosted by cold.
These natural fluctuations aside, experts believe that the hole will be permanently closed by 2050 due to restrictions on ozone-depleting chemical introduced in 1987.
This hole is unusually big and will last only few days longer than the one last year. It was also the longest lasting since 1979.
According to the European Centre for Medium-Range Weather Forecasts (ECMWF), this year’s hole was the 9th largest on record, reaching 8.8 million square miles.
In contrast, 2020’s hole was the 11th largest — at 8.7 million square miles — with the largest on record having formed during 1998, at 9.4 million square miles.
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This year’s hole in the Earth’s ozone layer — which grew to be larger than Antarctica, as pictured here on Oct. 15 — is finally set to close this week, atmospheric scientists have said
The hole currently in progress is only expected to be a few more days than the last one, which was uncharacteristically large. This is the December 20th, 2021 total column-ozone field forecast. It shows the closeness of the hole.
‘Both the 2020 and 2021 Antarctic ozone holes have been rather large and exceptionally long-lived,’ said the ECMWF’s Copernicus Atmosphere Monitoring Service (CAMS) director Vincent-Henri Peuch.
“These episodes, which are longer than usual, do not indicate that the Montreal Protocol does not work. They would be even more if it did not.
Interannual variability caused by meteorological and dynamical factors can impact the severity of the ozone hole. They also have an effect on the recovery process.
‘CAMS also keeps an eye on the amount of UV radiation reaching the Earth’s surface and we’ve seen in recent weeks very high UV indexes — in excess of 8 — over parts of Antarctica situated below the ozone hole.’
(The UV Index goes up to 11 For humans, a level of eight means a very high risk of harm from unprotected sun exposure.)
In the 1970s scientists first discovered that the loss of the ozone layers was greater than what could be explained by temperature fluctuations, weather conditions, or volcanic eruptions.
Instead, it was determined that human-made chemicals — in particular halocarbons refrigerants and chlorofluorocarbons (CFCs) — were exacerbating the depletion.
In 1987, these manufacture and consumption of these products began to be phased out under an international treaty known as the Montreal Protocol.
Yet, because many of these ozone-depleting chemicals can be up there for decades, it is slow for the ozone to get back to normal.
In fact, experts have predicted that it will take until the 2060s before the harmful substances used in refrigerants and spray cans have completely disappeared from the atmosphere.
‘CAMS monitors and observes the ozone layer by providing reliable and free-to-access-data based on different types of satellite observations and numerical modelling,’ said Dr Peuch.
According to him, this makes it feasible for detailed monitoring of inception, development, and closure of the year’s ozone hole.
“We can track the development of the ozone seasons and compare them with the 40-year history using the combined data.
The Ozone layer is 25 miles high in the stratosphere and serves as natural sunscreen.
The molecule Ozone, which is composed of three oxygen atoms, occurs in very small quantities.
At approximately 7 to 25 miles in the stratosphere above Earth, the ozone layers acts as sunscreen. They protect the planet against potentially dangerous ultraviolet radiation. This can cause sunburns, skin cancers, or even damage the plants.
It’s grown in tropical regions and is distributed all over the world.
Photochemical reactions that combine the sun with pollution (emissions from vehicles) can create ozone closer to the ground. This is what forms harmful smog.
While warmer than-average temperatures in the stratosphere have helped to reduce ozone depletion over the past 2 years, the area of the current ozonehole is still larger than it was during the 1980s, which marked the beginning of Antarctica’s depletion.
The stratosphere is located approximately 7 to 25 miles up above Earth’s surface. It acts like a sunscreen and protects the planet from harmful UV radiation
Because levels of bromine and chlorine, which are ozone depleting chemicals, remain high enough that they can cause significant ozone losses.
CFCs were first identified in 1970s as chemicals that destroyed the stratosphere.
En 1987, the Montreal Protocol was signed. It led to CFCs’ elimination and recently the first sign of the Antarctic ozone recovery.
Lower latitudes’ upper stratosphere is showing signs of recovery as well, which proves that the Montreal Protocol is effective.
But the new study, published in Atmospheric Chemistry and Physics, found it is likely not recovering at latitudes between 60°N and 60°S (London is at 51°N).
Although the cause of the problem isn’t clear, researchers think it could be that climate change has altered the patterns of atmospheric circulation. This is causing more ozone from the tropics.
Another possibility, they say is the destruction of ozone by very short-lived chemicals (VSLSs), that contain bromine and chlorine.
Chemicals that are referred to as VSLSs can be used as paint strippers and solvents as well as as as degreasing agents.
One of them is even used for the manufacture an ozone-friendly substitute for CFCs.