Around 30 years ago, the world came together to attempt to mend a widening hole in the Earth's ozone layer, which plays a very important role in shielding us from the Sun's ultraviolet rays. A new report compiled by leading environmental agencies has revealed that this long-term healing strategy is continuing to pay dividends, though evidence is emerging that harmful compounds are still slipping through the cracks.

It was in 1989 that the Montreal protocol on Substances that Deplete the Ozone layer was enacted, aiming to put a stop to the release of chemical compounds found in fridges, aerosols and dry cleaning products called CFCs. Some modeling suggests that if these compounds were simply left to eat away at the ozone layer, there could now be as many as two million extra skin cancer cases around the world each year.

With most of the world coming together to ban these harmful compounds, the ozone layer was put on a path to recovery. This was always going to be a long and drawn out process, but scientists watching on are gathering more and more evidence that it is now on the mend.

In 2016, MIT researchers reported the "first fingerprints of healing" of the ozone layer over the Antarctic. The latest study, titled "Scientific Assessment of Ozone Depletion: 2018," is backed by the UN, NASA and the World Meteorological Organization, and is the bearer of more good news. It states that upper stratospheric ozone is building at a rate of one to three percent per decade since 2000.

The scientists say these current trends indicate the ozone layer will be completely healed over the polar regions by 2060, while the damage done over the Southern Hemisphere should be completely erased by sometime in the 2050s. The ozone layer over the Northern Hemisphere and mid-latitude regions, meanwhile, is expected to be entirely patched up sometime in the 2030s.

These projections stem from analysis of ozone-depleting substances in the atmosphere, which the scientists say continue to decrease. This is in spite of rogue CFC emissions arising from mysterious sources. In 2010, the chemical CFC-11, was added to the banned substances of the Montreal Protocol for its ozone-eating tendencies. But scientists tracking its concentration have found that levels of CFC-11 are not declining as they would be if these bans were properly adhered to.

Back in May, scientists published a study in Nature reporting that CFC-11 levels between 2014 and 2016 were 25 percent higher than the average between 2002 and 2012, indicating a new source of emissions had emerged. Consequent enquiries by UK-based NGO the Environmental Investigation Agency (EIA) has led to a new report, published this month, which claims to home in on theses sources.

The EIA claims to have interviewed 22 companies from 10 provinces in China, with 18 of those confirming the use of CFC-11 as the main blowing agent in their production of foam insulation. According to the report, the Chinese government has since made moves to quash these sources of CFC-11 by carrying out a nationwide inspection, but further work is needed to really pin down the sources and the extent of the damage.

In any case, scientists are hailing the progress we've made in healing the ozone layer as a success, and a possible template for solving other environmental dilemmas. The Kigali Amendment to the Montreal Protocol is expected to come into force in 2019 and is hoped to see the phasing out of hydrofluorocarbons, which don't contain ozone-depleting chlorine or bromine, but are potent greenhouse gases that have been adopted as alternatives for traditional ozone-depleting substances in a range of sectors.

"The Montreal Protocol is one of the most successful multilateral agreements in history for a reason," said Erik Solheim, head of UN Environment. "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."