Nearly four decades after scientists discovered the hole in the ozone layer, Earth’s “sunscreen” is now showing promising signs of recovery.
According to a study by NASA Goddard Space Flight Center, ozone concentrations over the Arctic reached record highs in March this year.
Warmer weather and a slower jet stream made the protective gas layer 14.5 percent thicker than the average after 1980.
Researchers say the banning of chlorofluorocarbons (CFCs) in the 1989 Montreal Protocol means the ozone layer is now on track for full recovery by 2045.
Lead author Dr Paul Newman says: ‘Increased ozone is a positive story because it is good for the environment and the encouraging news that the global Montreal Protocol Agreement is delivering positive results.’
Researchers have found that the ozone layer over the Arctic reached a record thickness in March 2020 (right). This is in stark contrast to March 2020 (left) when a record-breaking ozone hole formed over the Arctic
The ozone layer is a blanket of ozone – a molecule made up of three oxygen atoms – that wraps around the entire planet.
This gas layer in the upper atmosphere absorbs harmful UVB radiation from the sun and protects life on Earth from cancer, burns and blindness.
However, in 1985, scientists at the British Antarctic Survey realized that human activities had burned a hole in the ozone layer above the poles.
In 1989, the Montreal Protocol banned CFCs, the chemical primarily responsible for ozone depletion, but the ozone layer has still not recovered.
Now NASA scientists have made the encouraging discovery that ozone levels over the North Pole reached a record high in March.
The discovery will be good news for wildlife endangered by intense radiation during periods of ozone depletion, such as the opening of the ozone hole in 2020. Pictured: Polar bears on the Arctic island of Svalbard
The thickness of the ozone layer is measured using a metric called Dobson units, which refer to the amount of ozone in a column of air extending from the ground to space.
One Dobson Unit (DU) is the number of ozone molecules required to create a layer 0.01 millimeters thick at 0°C (32°F) at sea level.
In March this year, the ozone layer over the Arctic reached a monthly average of 477 DU.
That was six DU higher than the previous monthly record and 60 DU higher than the average for the period between 1979 and 2023.
On March 12, the ozone layer also reached a new record thickness of 499 DU.
After peaking in March, ozone levels remained well above average, breaking records for monthly averages in May, June, July and August.
That’s a big positive for life on Earth, because the destruction of the ozone layer allows so much UV radiation to bombard the planet that animals are now at risk of sunburn.
But in March, researchers estimated that the UV index was six to seven percent lower in the Arctic and two to six percent lower in the mid-latitudes of the Northern Hemisphere.
Ozone built up in the stratosphere normally absorbs almost all of the radiation coming from the sun. Holes in this layer allow more radiation to reach Earth
This year (shown in red), the thickness of the ozone layer over the Arctic was 14.5 percent greater than the post-1980 average. This was largely due to global weather patterns that weakened the jet stream
This year, the same weather patterns caused the Antarctic ozone hole (pictured) to form later and grow at a slower rate than in previous years
This is a significant change from March 2020, when scientists found that the ozone hole over the Arctic had opened to a record size, allowing the region to warm rapidly.
In an article published in Geophysical research lettersthe researchers claim that this is due to global weather systems that have changed the distribution of the atmosphere during winter.
Last winter, “planetary-scale waves” called Rossby waves moved through the upper atmosphere and slowed the jet stream that circles the Arctic.
This caused air from higher latitudes to move towards the Arctic, drawing more ozone to the area above the North Pole.
UV radiation from the sun (shown) can pose serious threats to wildlife in the polar regions. In March, when the ozone layer was at its peak, researchers found that the UV index in the Arctic was up to 7 percent lower
Additionally, these planet-sized waves slow the polar vortex and warm the Arctic, removing the conditions that lead to ozone depletion.
Dr. Newman says: ‘Ozone in the Arctic is controlled by direct depletion of ozone by chlorine and bromine compounds and ozone transport.
“In the first scenario, temperatures were too warm for much exhaustion.”
This has led to a period in which more ozone enters the Arctic than is depleted, creating an exceptionally thick ozone layer.
Dr. However, Newman points out that the record could not have been broken without human action.
Dr. Newmans says: ‘Climate change is thought to influence the strength and stability of the stratospheric polar vortex.
This graph illustrates how total ozone concentration in the Arctic has gradually increased since the ban on CFCs in 1989
As the ozone hole over Antarctic waters shrinks (illustrated) and the layer over the Arctic thickens, scientists predict the ozone layer will fully recover by 2045 thanks to rapid global interventions
‘In addition, global ozone concentrations are expected to increase slowly as a result of the Montreal Protocol. The combination of these two factors will create favorable conditions for higher polar ozone levels.”
This more favorable period was also reflected in the Southern Hemisphere, where scientists found that the ozone hole formed later and was smaller than average.
As in the north, scientists concluded this was due to a weaker polar vortex and warmer temperatures.
These results bring ozone recovery in line with the higher end of most forecasts.
Some models estimate that there is a one in eight chance of a record ozone layer by 2025, and more record years are expected in the future.
This means that the ozone layer is expected to recover to pre-1980s levels by 2045.