Ozone hole over Antarctica is smaller and started later than expected

by · Mail Online

The ozone layer above the Antarctic may be healing at last, according to a promising new study.

The Copernicus Atmospheric Monitoring Service (CAMS) found that the hole above the South Pole closed earlier than expected this year.

Following a four-year run of late closures, Earth's protective layer has finally returned to normal by closing in early December rather than later in the month.

In addition to closing early, the Antarctic ozone hole was also smaller and formed later than in the last few years.

After starting in late August, this year's ozone hole expanded to a peak of 8.49 million square miles (22 million square kilometres) by the end of September.

This is over 1.16 million square miles (3 million square kilometres) smaller than the unusually large ozone hole which formed in early September 2022.

Climate experts say Earth's protective gas layer is now back in line with the post-1997 average, raising hopes that it could be on its way to recovery.

Laurence Rouil, director of CAMS, says: 'Hopefully, we will see the first signs of recovery of the ozone hole in the coming decades.'

The 2024 Antarctic ozone hole was one of the smallest in recent years (pictured), formed later, and closed earlier 
Scientists have revealed some encouraging news for the planet as they find that the hole over the Antarctic is on its way to recovery following four years of worryingly large ozone holes (stock image)

The ozone layer is a thin layer of ozone gas – a molecule containing three oxygen atoms – that collects in Earth's upper atmosphere.

This layer plays an extremely important role in maintaining the balance of life on Earth as it absorbs harmful UVB radiation from the sun which causes sunburns, cancer, and blindness.

However, in 1985, scientists from the British Antarctic Survey discovered that chemicals called chlorofluorocarbons (CFCs) had burned a hole clean through the protective barrier.

In 1989, the Montreal Protocol outlawed the use of CFCs but the ozone layer is still yet to properly recover from the damage.

Each year during the Antarctic winter, as circling winds concentrate the remaining ozone-depleting chemicals over the South Pole, the hole re-opens for about four months.

While many scientists had hoped the ozone layer could recover as early as 2040, a series of extremely large ozone holes appeared to pour cold water on those notions.

For the past for years, the Antarctic ozone hole has lasted longer than normal and only closed during the second half of December

However, a promising set of new measurements suggest the Antarctic ozone layer is now back to 'business as usual'.

After starting in late August, this year's ozone hole expanded to a peak of 8.49 million square miles (22 million square kilometres) by the end of September. This is over 1.16 million square miles (3 million square kilometres) smaller than the unusually large ozone hole which formed in early September 2022
As of early December, measurements show that the ozone hole above the Antarctic (pictured) has fully closed 

What is the Polar Vortex?

The polar vortex is an atmospheric circulation pattern that sits high above the poles, in a layer of the atmosphere called the stratosphere.

This structure can weaken as a result of abnormal warming in the poles, causing it to split off into smaller ‘sister vortices’.

The split higher up in the atmosphere could eventually cause a similar phenomenon to ‘drip’ down to the troposphere – the layer of the atmosphere closest to the surface.

A split in the polar vortex can give rise to both sudden and delayed effects, much of which involves declining temperatures and extreme winter weather.

After reaching its peak area of 8.49 million square miles (22 million square kilometres), the 2024 ozone hole began to steadily reduce in size throughout October, in line with the historical average.

Then, as the circling winds known as the Polar Vortex collapsed in the first week of December, the hole quickly closed.

This makes this year's ozone hole far more short-lived those in previous years and shorter than even some years during the 1990s.

The last time the ozone hole above the Antarctic was so small was in 2019 when it reached its smallest size on record since its discovery. 

On September 8, 2019, the ozone layer hole reached a maximum size of 16.4 million square kilometres (6.3 million square miles).

However, this is not necessarily a sign that the ozone layer is making leaps and bounds towards recovery.

Rather, the duration and size of the hole in the ozone are largely determined by the strength of the Polar Vortex.

While the Montreal Agreement phased out 99 per cent of all ozone-depleting chemicals, the remaining one per cent still lingers in Earth's upper atmosphere.

As this graph shows, there is considerable variation in how late the ozone hole closes. The last four years have been extremely late closures following an exceptionally short-lived hole in 2019
The variability is due to the changing strength and stability of the Polar Vortex which concentrates ozone depleting substances (pictured) in the region above the South Pole where they produce the ozone hole 

During the southern winter, a large pillar of extremely cold, rotating air forms above the Antarctic.

This concentrates the remaining CFCs in an area where cold conditions and solar radiation enable them to deplete the layer of ozone gas.

HOW IS THE HOLE IN THE OZONE FORMED? 

Chlorine and bromine-containing substances accumulate within the Polar Vortex where they stay chemically inactive in the darkness. 

Temperatures in the vortex can fall to below -108 degrees Fahrenheit and ice crystals in Polar stratospheric clouds can form, which play an important part in the chemical reactions. 

As the sun rises over the pole, the sun’s energy releases chemically active chlorine and bromine atoms in the vortex which rapidly destroy ozone molecules, causing the hole to form. 

SOURCE: CAMS

Mr Rouil says: 'The Montreal Protocol and its subsequent amendments have been highly effective in curbing emissions of ozone-depleting substances, but there is still some variability in this process due to the natural variation of the other atmospheric variables at play.'

This year, however, two sudden atmospheric warming events in July disrupted the Polar Vortex and prevented the concentration of CFCs above the South Pole – leading to a smaller ozone hole. 

On the other hand, scientists also believe that a similar disturbance to the Polar Vortex could have been the reason the ozone hole was so severe through the last four years.

Scientists believe that the Hunga Tonga Hunga Ha’Apai volcano eruption in 2021-2022 created an unusually strong long-lasting Polar Vortex.

The eruption injected several million tonnes of water vapour into the stratosphere which helped the rotating climate pattern remain stable for longer.

This led to four years of unusually large and persistent ozone holes following the exceptionally short and small 2019 ozone hole.

Scientists now say the ozone layer hole is back to 'business as usual' following four years of very large holes. This has raised hopes of a full recovery by the year 2066
Despite some variation, the data shows that the ozone layer hole has improved in terms of depth and area since 2000

Yet, despite this yearly variability, the overall trend of the ozone layer is moving towards a healthy recovery.

Every four years, the UN World Meteorological Organisation (WMO) produces a flagship report on the state of the ozone layer.

The report published in 2023 found that the ozone layer was on track to reach pre-1980 values by 2066 over the Antarctic, by 2045 over the Arctic, and by 2040 over the rest of the world.

Read More

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In fact, observations show that the Antarctic ozone hole has been improving in depth and area since 2000.

This is not only great news for Antarctic wildlife that were previously being put at risk of sunburn and cancer, but also for the rest of us.

By blocking UV radiation, the ozone layer prevents one form of solar energy from reaching Earth and further warming our atmosphere.

According to the WMO's most recent report, the ozone's recovery to date has already prevented warming of 0.3-0.5°C (0.54-0.9°F) by 2100.

The Ozone layer sits in the stratosphere 25 miles above the Earth's surface and acts like a natural sunscreen

Ozone is a molecule comprised of three oxygen atoms that occurs naturally in small amounts. 

In the stratosphere, roughly seven to 25 miles above Earth's surface, the ozone layer acts like sunscreen, shielding the planet from potentially harmful ultraviolet radiation that can cause skin cancer and cataracts, suppress immune systems and also damage plants. 

It is produced in tropical latitudes and distributed around the globe. 

Closer to the ground, ozone can also be created by photochemical reactions between the sun and pollution from vehicle emissions and other sources, forming harmful smog.

Although warmer-than-average stratospheric weather conditions have reduced ozone depletion during the past two years, the current ozone hole area is still large compared to the 1980s, when the depletion of the ozone layer above Antarctica was first detected. 

In the stratosphere, roughly seven to 25 miles above Earth's surface, the ozone layer acts like sunscreen, shielding the planet from potentially harmful ultraviolet radiation

This is because levels of ozone-depleting substances like chlorine and bromine remain high enough to produce significant ozone loss. 

In the 1970s, it was recognised that chemicals called CFCs, used for example in refrigeration and aerosols, were destroying ozone in the stratosphere.  

In 1987, the Montreal Protocol was agreed, which led to the phase-out of CFCs and, recently, the first signs of recovery of the Antarctic ozone layer. 

The upper stratosphere at lower latitudes is also showing clear signs of recovery, proving the Montreal Protocol is working well.

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).

The cause is not certain but the researchers believe it is possible climate change is altering the pattern of atmospheric circulation - causing more ozone to be carried away from the tropics.

They say another possibility is that very short-lived substances (VSLSs), which contain chlorine and bromine, could be destroying ozone in the lower stratosphere.

VSLSs include chemicals used as solvents, paint strippers, and as degreasing agents.

One is even used in the production of an ozone-friendly replacement for CFCs.