The hole in the ozone layer is slowly closing up.
The ominous hole is the reason New Zealanders are told they can get sunburnt faster than in other places and why the country has the highest rates of melanoma skin cancer in the world.
While experts say the hole in the ozone is on track to be completely recovered by 2040 across most of the world and will fully bounce back by 2045 over the Arctic and by 2066 over the Antarctic - this doesn’t mean New Zealanders should forget their hats or ditch the sunblock.
NIWA Atmospheric Scientist Ben Liley says even if the ozone heals completely, New Zealand will always have a UV problem.
So what is the ozone layer and why is there a hole in it?
The ozone layer is like a layer of sunscreen over the earth that protects us from the sun’s ultraviolet (UV) rays.
It naturally breaks down and restores itself throughout the year, but over time it has become thinner, particularly over Antarctica where a big hole forms in the spring.
The ozone layer over New Zealand thins during summer, providing less protection from UV sunlight when we are closest to the sun and the sun is highest in the sky.
People are vulnerable to sunburn and melanoma in NZ
In New Zealand, the strength of UV radiation and its capacity to cause sunburn is approximately 40% higher than for similar latitudes in the northern hemisphere.
While lower ozone levels are one factor, research has found the angle of the sun relative to the horizon, lack of major atmospheric pollution or smog, outdoor lifestyles, and many New Zealanders having lighter-toned skin with less melanin have made the country vulnerable to sunburn and melanoma before the ozone hole came to be.
And because melanoma typically takes decades to develop after exposure to UV, research found melanoma rates were already high before the turn of the century when the ozone hole became an issue.
When did the hole in the ozone layer become a problem?
The hole in the ozone layer became an issue when humans started releasing substances that have chlorine and bromine into the stratosphere, like certain aerosol propellants and refrigerant gases, that destroy this protective layer.
In the 1980s, people started to realise the damage they were causing so in 1987 every country in the world signed the Montreal Protocol which was an international treaty to phase out these harmful substances to protect the ozone layer.
Liley says this is still seen as one of the most successful global efforts to protect the environment but seeing the effects of it has been painfully slow.
So how is the hole in the ozone layer doing these days?
Liley says the biggest problem is that even though these substances are banned, they are very slow to be removed from the stratosphere.
“When chlorine is not used up in destroying the ozone it recovers and destroys more and more,” he says.
“So one chlorine molecule can destroy 50,000 ozone molecules on average before it’s removed from the stratosphere.”
But even though change is slow, Liley says over the last couple of decades the ozone layer is improving and healing.
“It took us a long time but we have now started to see the reversal of that destruction and the gradual recovery of the ozone layer.”
Liley says one thing they know for sure is the ozone is looking much better than what it would have been without the Montreal Protocol.
“We would have had serious rates of burning and skin cancer of a large portion of the planet. But it is still a long way until things come right.
“It will be the same with climate change, when we decide to stop burning fossil fuels and releasing greenhouse gas, it will still take decades or centuries to see the damage reversed.”
There have been some setbacks
This summer in New Zealand experts are warning of higher rates of UV than in previous years.
NIWA meteorologist Dr Richard Turner says this could be due to a slight depletion of the ozone layer over the past few months because of the underwater volcanic explosion in 2022.
“Recent research suggests that the Tongan volcano injected so much water into the stratosphere that it may have created conditions that caused further loss of ozone.
“Luckily, any effect from the Tongan volcano on the ozone is reversible, as the water will be removed from the stratosphere in a few years.”
So the moral of the story is New Zealanders will always need to slip, slop, slap, and seek shade to protect themselves from our high UV rays, even on cloudy days because the healing ozone isn't going to stop you from getting sunburnt.