It has now been almost four decades since scientists discovered the growing hole in Earth's ozone layer.

But climate researchers now say that the protective shield, around 20 miles above our planet's surface, could be well on its way to recovery.

New data gathered by NASA shows that the ozone hole over the Antarctic this year was the seventh smallest since 1992.

NASA and the National Oceanic and Atmospheric Administration (NOAA) predict that the layer could fully recover as soon as 2066.

Dr Paul Newman, leader of NASA’s ozone research team, says: 'The 2024 Antarctic hole is smaller than ozone holes seen in the early 2000s.

'The gradual improvement we’ve seen in the past two decades shows that international efforts that curbed ozone-destroying chemicals are working.'

However, the ozone hole still covered an average of almost 8 million square miles (20 million square kilometres) - three times the size of the contiguous United States.

Scientists caution that there is still a long way to go before the ozone layer returns to its natural thickness. 

As the ozone hole opens it allows increased levels of harmful UVB radiation to hit Earth which increases the risks of cancer and cataracts. 

Each year, a combination of ozone-depleting chemicals and cold temperatures combine to open the annual ozone layer hole above the Antarctic.

While this hole still allows harmful ultraviolet radiation to rain down on the Antarctic each year, it has recently begun to show promising signs of recovery.

Using a combination of satellite observations and ground-launched weather balloons, NASA and NOAA have measured the concentration of ozone gas in the atmosphere.

Their observations revealed that the annual ozone layer above the South Pole was relatively small compared to other years during its peak depletion between September 7 and October 13.

At its very largest extent on September 28 this year, the ozone hole covered an area of 8.5 million square miles (22.4 million square kilometres).

This comes as a stark contrast to 2023, during which the ozone hole reached a peak of 10 million square miles (26 million square kilometres) by September 10.

Although that is still significant, it is the 20th smallest hole since records began in 1979 and the seventh smallest since ozone-depleting CFCs were banned under the Montreal agreement.

CFCs (chlorofluorocarbons) are a type of human-made chemical which were widely used in aerosols and refrigeration. 

Since they were outlawed in 1992, CFCs' concentration in the atmosphere has gradually declined, allowing the ozone layer to begin its recovery.

A recent study from the Copernicus Atmosphere Monitoring Service (CAMS) found that the ozone hole had taken longer to form and was smaller than expected.

By September 13, the ozone hole was 18.48 million square kilometres (7.13 million square miles), smaller than the same time in recent years.

Meanwhile, the ozone layer above the North Pole has also shown indications of a potential recovery.

This year, particularly favourable weather allowed the Arctic ozone layer to become 14.5 per cent thicker than the post-1980 average.

According to NASA and NOAA's predictions, this means the ozone layer could be back to its pre-hole thickness in just over 40 years.

The scientists believe that the recent recovery is due to a combination of the natural decline in CFCs combined with an influx of ozone from areas north of the pole.

During the winter months, circling winds called the Polar Vortex typically concentrate ozone-depleting chemicals into a small area above the South Pole.

Then, as energy from the sun starts to hit the atmosphere in spring, the combination of cold temperatures and solar radiation starts to erode the ozone layer.

However, in June Antarctica experienced two rare 'sudden stratospheric warming events' which caused temperatures in the upper atmosphere to jump 15ºC (27ºF) and 17ºC (30.6ºF) respectively.

These spikes significantly weakened the Polar Vortex, reducing the rate of depletion and allowing more ozone to reach the area over the pole.

However, NASA also warns that the ozone layer still has a long road to recovery.

Stephen Montzka, senior scientist of the NOAA Global Monitoring Laboratory, says: 'For 2024, we can see that the ozone hole’s severity is below average compared to other years in the past three decades, but the ozone layer is still far from being fully healed.'

Scientists measure the thickness of the ozone layer using a measurement called Dobson units where anything less than 220 Dobson units (DU) is considered to be an ozone hole.

At its thinnest point this year on October 5, the atmosphere above the Antarctic measured just 109 DU.

That is somewhat thicker than the lowest level ever recorded when the ozone layer hit 92 DU in 2006, but still thin enough to create serious health risks.

A recent study even found that Antarctic wildlife such as seals and penguins are at greater risk of getting sunburnt due to ozone depletion.

According to Bryan Johnson, NOAA research chemist, 225 Dobson units was typical of the ozone cover above the Antarctic in 1979.

'So there’s still a long way to go before atmospheric ozone is back to the levels before the advent of widespread CFC pollution,' he said.