Why the ozone layer is recovering

The ozone layer protects all life on Earth from the sun’s harmful radiation. But by the 1980s, the widespread use of damaging chemicals caused a dramatic hole to open over Antarctica each year, driven by complex meteorological and chemical processes.

Thanks to the Montreal Protocol, the ozone layer has been steadily improving. The landmark international environmental agreement regulates the production and consumption of nearly 100 synthetic chemicals referred to as ozone-depleting substances, such as chlorofluorocarbons (CFCs), one of the main culprits. At the time, CFCs were widely used as solvents and in insulation, air conditioning, and spray cans, for example.

The Montreal Protocol has managed to eliminate 99% of the emissive uses of ozone-depleting chemicals – although there are still high levels of them in our atmosphere. Leftover traces of CFCs in building insulation all over the world, for instance, is a case in point. But encouragingly enough, scientists have noted a steady decline in its levels in the atmosphere.

One of the scientists studying the ozone layer closely is Dr Paul A. Newman, the Chief Scientist for Earth Sciences at NASA’s Goddard Space Flight Center in the Earth Sciences Division.

“Over time, steady progress is being made, and the ozone hole is getting smaller. At the end of 2022, we recorded a very large ozone hole over Antarctica, but we are still expecting a 1980-level recovery over Antarctica by around 2066 and by 2045 over the Arctic,” he says.

According to NASA, the size of the Ozone hole is determined from the area on earth that is enclosed by a line with a constant value of 220 Dobson Units (the unit of measure for total ozone).

1 Dobson unit (DU) is the number of molecules needed to create a layer of pure ozone that is 0.01 mm thick at a 0 °Celsius temperature and 1 atmosphere pressure (pressure on the earth’s surface).

It is valued at 0.001 atm-cm. When calculating the Ozone hole, 220 DUs are considered as a constant because values under this have not been found over the Antarctica before 1979. The ozone’s layer’s average thickness over the earth’s surface is 300 DU.

A climate agreement on track
Although some fluctuations in measurements are normal, Newman notes that the hole closing is all thanks to human-produced changes. “The Montreal Protocol has not only saved the ozone layer but is also one of the most effective climate agreements we have in place right now,” he says.

While the agreement saved the ozone layer in one sense, it created new climate issues. For example, as CFCs were phased out, environmentally dangerous alternatives – such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) – were introduced.

HFCs are human made greenhouse gases containing carbon, hydrogen, and fluorine and are mostly used as cooling agents and HCFCs are human-made compounds with hydrogen, chlorine, fluorine, and carbon used as production and extraction solvents by several industries (e.g. pharmaceuticals, chemicals).

While HCFCs were considered less harmful to the ozone layer as they contain less chlorine, do not accumulate for long in the atmosphere and are not as easily photolyzed, it was realised that they impact the ozone layer, nevertheless.

HFCs too were initially not included in the Montreal Protocol because they were considered to have no impact on the ozone layer. But in 2016, the Montreal Protocol was amended to include HFCs given their high impact on global warming. At that time it was agreed to phase down HFCs to avoid an increase in atmospheric temperature of 0.5°C by the end of the century and reduce the of CO2 emissions of by an estimated 70 billion tons by 2050.

Dr Vincent-Henri Peuch, Director of the Copernicus Atmosphere Monitoring Service (CAMS), also highlights the Montreal Protocol as an example of a successful course of action and collaboration between the scientific community and policymakers. “It has been a very well-organised process, with regular assessments to review the scientific data and amend the agreement accordingly,” he states.

“With Copernicus, the European Union wants to contribute to the required monitoring efforts. We shouldn’t take for granted that we have regulations and that virtually every country has agreed to abide by them. The international community needs to keep monitoring the atmosphere for rogue emissions,” Peuch notes.

Saving the ozone layer: lessons learned
In 2018, one of the most harmful Ozone Depleting Substance CFC-11 was measured in the atmosphere by The National Oceanic and Atmospheric Administration (NOAA) and The Advanced Global Atmospheric Gases Experiment (AGAGE). The scientific community triangulated where it was coming from. “Eventually, the emission was tracked to a province in eastern China and was quickly acted upon. The emissions stopped growing and fell to what we normally expect,” Newman explains.

Peuch and Newman agree that the scientific community is not there to police the actions of countries, governments, companies, or organisations. They monitor what is happening in the atmosphere, and then it’s up to the 198 signatories to act on that information. “With the protocol, decision-makers recognised and acted on a problem effectively. The encouraging news is that this can happen with our efforts to tackle climate change, too,” Newman says.

He believes the beauty of it all lies in that scientists can calculate and predict what will happen. “We could calculate that the continued use of these harmful chemicals would have added an additional 0.3 to 0.5°C increase to the Earth’s temperatures. This was on top of current global warming rates by 2100. We could prove it would have been an ecological disaster for the Earth if we had done nothing.”

Regarding the ozone layer, Newman and Peuch are both optimistic. They believe our efforts to reverse the damage can now be a blueprint of what countries can achieve when they trust science and are ready to make compromises and changes to preserve the environment.

Newman concludes, “The Montreal Protocol relied on science to create necessary actions, which was effective. It gave us good lessons and showed that we could change things together. It won’t be quick or easy, but extreme weather disasters and other phenomena are forcing people to see what will happen if we don’t act on climate change.”
Source: Wartsila

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