The hole in the ozone above Antarctica has persisted for decades - now, there are signs it's healing.
Chemical compounds known as chlorofluorocarbons were attributed to the damage. Aerosols such as hairspray, old fridges and old dry cleaning processes released the chemicals into the atmosphere.
In 1989, the Montreal Protocol was agreed to in order to phase them out. Now we're seeing the results of that action.
A new study, published on Friday in the Science journal, is proof we can heal the damage humans have caused, says lead author Susan Solomon.
"Aren't we amazing humans, that we did something that created a situation that we decided collectively, as a world, 'Let's get rid of these molecules'? We got rid of them, and now we're seeing the planet respond."
Antarctica suffered the worst damage from the chlorofluorocarbons. It's so cold that clouds form at lower altitudes, providing a platform for the chlorine to react on which then eats away at the ozone.
But with the healing trend, the ozone hole has shrunk by more than 4 million square kilometres since its peak in 2000.
"It will be many years before the hole closes completely, but we can now see signs that it is not only not getting worse, but actually starting to get better," Dr Solomon says.
"The world decided to take an action on these chemicals, and the planet is responding as we expected.
"People can take heart by seeing that our choices can help the environment."
While chlorofluorocarbons have been phased out, there are still chemicals that react to eat away at ozone.
What's now become the biggest threat is the nitrous oxide produced in agriculture, according to Waikato University's Joseph Lane.
"Nitrous oxide is not a particularly effective ozone-depleting substance, however it's produced in substantially larger amounts. In 2010 we became aware that nitrous oxide is now the dominant species responsible for breaking down ozone in the atmosphere."
He says bacteria in farm soil is feeding on fertilisers and animal urine, producing large quantities of the gas nitrous oxide.
"It is a significant compound that's considered in terms of climate change, so it has a significant global warming potential," Dr Lane says.
"But the lesser-known effect of nitrous oxide in the atmosphere is its ozone-depleting property."
Despite its links to global warming and ozone depletion, nitrous oxide is not regulated under any international treaties.