Four decades ago, scientists sounded the alarm after discovering a growing ‘hole’ in the ozone above Antarctica.
This protective layer of gas shields life on Earth from the sun’s harmful ultraviolet rays which can cause skin cancer, cataracts and damage to plants and marine life.
But now, in an ‘awesome’ turnaround, the ozone hole is actually healing, experts have found.
And, if the trend continues, it could eventually stay shut for good, they said.
While scientists have observed signs of ozone recovery in the past, this new study is the first to show – with high statistical confidence – that this healing is primary due to a reduction in the use of ozone-depleting substances.
Dr Susan Solomon, from the Massachusetts Institute of Technology, said: ‘There’s been a lot of qualitative evidence showing that the Antarctic ozone hole is getting better.
‘This is really the first study that has quantified confidence in the recovery of the ozone hole.
‘The conclusion is, with 95 percent confidence, it is recovering. Which is awesome. And it shows we can actually solve environmental problems.’
The ozone hole is actually healing, experts have found. And, if the trend continues, it could eventually stay shut for good, they said
While scientists have observed signs of ozone recovery in the past, this new study is the first to show – with high statistical confidence – that this healing is primary due to a reduction in the use of ozone-depleting substances
In 1985, scientists discovered a ‘hole’ in the ozone layer over Antarctica that opened up during the austral spring, between September and December.
Researchers found evidence that quickly confirmed the ozone hole’s cause – chlorofluorocarbons, or CFCs, which are chemicals that were then used in refrigeration, air conditioning, insulation, and aerosol propellants.
When CFCs drift up into the stratosphere, they can break down ozone under certain seasonal conditions.
The revelations soon led to the drafting of an international treaty that aimed to phase out the production of CFCs and other ozone-depleting substances, in the hopes of healing the ozone hole.
By 2016 there were key signs of ozone recovery, as the hole appeared to be shrinking with each year.
However it was unclear – until now – whether this was down to the reduction in CFCs or due to other influences such as El Niño, La Niña, and the polar vortex.
For the study, the team used simulations of the Earth’s atmosphere under different conditions and compared these to observations of how ozone in the Antarctic stratosphere was changing.
Over time, it became more clear that the ozone recovery was due mainly to reductions in ozone-depleting substances.
If the trend continues, and the ‘fingerprint’ of ozone recovery grows stronger, the researchers anticipate that soon there will be a year, here and there, when the ozone layer stays entirely intact.
And eventually, the ozone hole should stay shut for good.
Peidong Wang, who also worked on the study, said their findings ‘give us confidence that we can solve environmental problems’.
‘By something like 2035 we might see a year when there’s no ozone hole depletion at all in the Antarctic,’ he said. ‘And that will be very exciting for me.
‘And some of you will see the ozone hole go away completely in your lifetimes. And people did that.’
The findings were published in the journal Nature.
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.
