A study published in Science has revealed that the amount of ozone present in the Antarctic ozone layer has increased. This is mainly due to the Montreal Protocol renowned international treaty, which regulated the use of substances responsible for ozone depletion.

A significant change in ozone columns, ozone concentration and the overall extent of the ozone hole confirms that the ozone layer is indeed ‘healing’, and that we can expect a full recovery in the mid-21st century.

In 2004, the maximum ozone hole occurred on September 22, 2004. Credit: NASA

According to MIT researchers, the ozone hole has been reduced by more than 4 million square kilometers, a very welcoming change since the year 2000 saw the worst state ever recorded of the ozone layer. The hole was first discovered in the 1950’s, and its widening was confirmed in the 1980’s. Scientists managed to establish which chemicals depleted the ozone layer. One of the most abrasive compounds is chlorine, alongside sunlight and high temperatures.

Fighting for earth’s natural sunscreen

The Montreal Protocol came into effect in early 1989, and it has seen eight revisions to keep the pace with the world’s stance on climate change and greenhouse gas emissions. Due to its results, it has been noted as one of the greatest efforts of international cooperation to date.

Since its first year into effect, emissions included in the Montreal Protocol have been registered to have significantly decreased. Many argue that it has a direct impact on human health, as the U.S. Environmental Protection Agency asserts that a complete recovery of the ozone layer will be able to percent over 280 million cases of skin cancer in the United States alone.

At first, ozone layer depletion was confused with global warming. Scientists often use the metaphor of depression on the layer, rather than a hole, as one might initially believe.

The main man-made components behind the ozone layer depletion are those known as chlorofluorocarbons (CFCs) which were present in most hairsprays and refrigerants in the 1980’s. Substitutes were created with CFCs, which allowed companies and governments to respond to the issue, but even if the depletion of ozone managed to convey most world leaders in the same decision, it is not possible to say the same about global warming. Perhaps, this is because the hole in the ozone layer is a direct and tangible result of human action, whereas global warming has not entirely convinced world powers to cut emissions.

Most Americans took immediate action and stopped using CFC aerosol sprays even before the binding legislation was imposed. There was a real concern of other holes in the ozone layer appearing in other parts of the earth since there were records of the ozone in the middle latitudes of the planet being slightly reduced over time. The hole in the ozone layer has achieved dimensions able to cover parts of Argentina, Australia, Chile, New Zealand and South Africa, which generates concern about the incidence of UV lights without the presence of ozone to stop them from causing cataracts and skin cancer in exposed individuals. Increased exposure to UV rays causes an increase in Vitamin D production, sunburn, cataracts and skin cancer.

In spite of all this, according to National Geographic, some scientists argue that a healing of the ozone layer could increase the effects of global warming in the Antarctic region. This is because ozone is a greenhouse gas. A lesser amount of ozone allows for cooler wind currents to flow the southern hemisphere of the earth.

The study by MIT researchers

The data regarding the study on the ozone layer hole showed that, although the recovery has been somewhat steady, large events where emissions reach the ozone layer, such as volcanic eruptions, slow the process in a significant manner. Although volcanic eruptions do not expel chlorine, they do increase the temperature of the nearby atmosphere.

It appears that the hole in the ozone layer changes its size throughout the year, depending on the amounts of atmospheric chlorine and temperature levels. August seems to be the month when the hole starts to widen, and by October it lies at its largest size over the year. The researchers noted that if they measured the amount of atmospheric chlorine and ozone-depleting factors in September, they were able to get a more accurate measure of the hole’s correct dimensions.

If these time-biased measurements did not take place, it wouldn’t be possible to confirm the ozone layer’s healing. It was the eruption of the Cabulco volcano in Chile that caused a major fluctuation in the data of 2015, which would have highlighted a record increase in the ozone hole for that year. On the other hand, Dr. Paul Newman from NASA said that, even if the data displays positive trends, the results could be interpreted differently if the MIT research team had included this past year, which shows a much larger ozone hole.

It is a very exciting finding, as Professor Ellen Swallow Richards from MIT stated: “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.”

Source: MIT