The ozone layer is on track to substantially heal by 2030, and fully heal by mid-century, according to a new assessment by the United Nations.

The critical atmospheric buffer zone was nearly annihilated in the 1980s when scientists noticed that it was rapidly fading and discovered the cause of the depletion as aerosol chemicals such as chlorofluorocarbons (CFCs).

These scientists then rallied world leaders to phase the chemicals out and succeeded, setting a historic precedent for scientific advocacy, and saving humanity from the devastating consequences of losing the ozone layer

And now the Montreal Protocol, the global treaty signed in 1987 that protects the ozone, is paying off.

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“The Montreal protocol is one of the most successful multilateral agreements in history for a reason,” Erik Solheim, head of UN Environment, said in a statement. “The careful mix of authoritative science and collaborative action that has defined the protocol for more than 30 years and was set to heal our ozone layer is precisely why the Kigali amendment holds such promise for climate action in future.”

Since 2000, the ozone has been healing at a rate of 1% to 3% per year, according to the UN. The ozone layer is in the upper portion of the atmosphere and blocks the most harmful ultraviolet rays. Without it, rates of skin cancer, eye damage, and more would increase, according to the Guardian.

Back in the early 20th century, CFCs were introduced as an alternative to toxic substances like ammonia, and they started to be used in common household amenities like refrigerators and air conditioners.

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When CFCs rise up into the atmosphere, ultraviolet light begins to separate the compound and the freed chlorine molecules react negatively with other substances in the ozone.

When it was learned that the ozone was rapidly deteriorating — mostly following the rise of air conditioners — the culprit was soon identified as CFCs.

Over the years, the Montreal Protocol has been updated to target new ozone-depleting chemicals that have been identified.

In 2016, the Montreal Protocol was expanded to include the Kigali amendment, which covers hydrofluorocarbons, another substance toxic to the ozone. The Kigali amendment is expected to be ratified next year.

Later that year, it was discovered the the ozone was once again declining because of an unexpected surge in CFCs. The source of these emissions was traced to China, but they’ve yet to be stopped. The UN and other global regulators are currently pressing the Chinese government to halt these emissions.

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Even with this setback, however, the ozone is recovering, the UN reports, and the benefits of its recovery go beyond stopping ultraviolet radiation.

Ozone-depleting substances are also greenhouse gas emissions and their elimination could prevent 0.4 degrees Celsius in warming. The Paris climate agreement aims to keep global temperatures from rising more than 1.5 or 2 degrees Celsius above pre-industrial levels, so 0.4 degrees could make or break the global agreement.

The Montreal Protocol also shows that countries can come together to protect the environment in emergency situations. While the challenge of climate change is more complex than banning aerosols, and requires “unprecedented changes in all aspects of society,” the commensurate consequences are more extreme than losing the ozone and could therefore inspire bolder action.