Nearly 40 years after scientists discovered the hole in the ozone layer, Earth’s ‘sunscreen’ is now showing promising signs of recovery.
Ozone concentrations over the Arctic reached a record high in March of this year, according to a study by NASA’s Goddard Space Flight Center.
A warmer climate and slower jet stream caused the shielding gas layer to grow 14.5 percent larger than the post-1980 average.
Researchers say the ban on chlorofluorocarbons (CFCs) in the 1989 Montreal Protocol means the ozone layer is now on the path to full recovery by 2045.
Lead author Dr Paul Newman says: “The rise in ozone is a positive story as it is good for the environment and is encouraging news that the global Montreal Protocol agreement is producing 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 an unprecedented ozone hole opened over the pole.
The ozone layer is a mantle of ozone – a molecule made up of three oxygen atoms – that surrounds the entire planet.
This layer of gas in the upper atmosphere absorbs the sun’s harmful UVB radiation, protecting life on Earth from cancer, burns and blindness.
However, in 1985, scientists at the British Antarctic Survey realized that human activity had opened a hole in the ozone layer over the poles.
In 1989, the Montreal Protocol banned CFCs, the main chemical responsible for the deterioration of the ozone layer, but the ozone layer has not yet recovered.
Now, NASA scientists have made the encouraging discovery that ozone concentration over the North Pole reached a record level in March.
The discovery will be good news for wildlife that has been threatened by intense radiation during periods of ozone degradation, 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 by a metric called Dobson units, which refer to the amount of ozone in a column of air extending from the ground into space.
One Dobson unit (DU) is the number of ozone molecules required to form a layer 0.01 millimeters thick at 0°C (32°F) at sea level.
In March of this year, the ozone layer over the Arctic reached a monthly average of 477 DU.
This is six UD more than the previous monthly record and 60 UD more 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.
This is very positive for life on Earth, as the degradation of the ozone layer allows so much ultraviolet 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 that has 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 (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, these same weather patterns caused the Antarctic ozone hole (pictured) to form later and grow to a lesser extent 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 for rapid warming of the region.
In an article published in Geophysical research lettersResearchers argue that this is due to global climate systems that 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 surrounding the Arctic.
This caused air from higher latitudes to move toward the Arctic, bringing more ozone to the region above the North Pole.
Ultraviolet radiation from the sun (illustrated) can create serious threats to animal life in the polar regions. During March, when ozone was at its peak, researchers found that the UV index was up to 7 percent lower in the Arctic.
Additionally, these planet-sized waves slow down the polar vortex and warm the polar region, eliminating conditions that lead to ozone degradation.
Dr Newman says: ‘Arctic ozone is controlled by direct ozone depletion by chlorine and bromine compounds and ozone transport.
“In the first scenario, temperatures were too high for major depletion to occur.”
This has led to a period in which more ozone is brought to the Arctic than is being depleted, creating an exceptionally thick ozone layer.
However, Dr. Newman points out that the record could not have been broken if it were not for human actions.
Dr Newmans says: “Climate change is thought to be affecting the strength and stability of the stratospheric polar vortex.
This graph illustrates how total ozone at the North Pole has gradually increased since CFCs were banned in 1989.
As the ozone hole over Antarctica shrinks (illustrated) and the layer over the Arctic becomes thicker, scientists predict the ozone layer will fully recover by 2045 thanks to rapid global intervention.
‘In addition, global ozone is expected to increase slowly due to the Montreal Protocol. The combination of these two factors will create favorable conditions for higher polar ozone values.’
This more favorable period has also been 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 that this was due to a weaker polar vortex and warmer temperatures.
These results put ozone recovery in line with the upper end of most predictions.
Some models estimated there was a one in eight chance of record ozone being reached by 2025, with more record years expected in the future.
That means the ozone layer is expected to recover to its pre-1980s levels by 2045.
