In 1974, two chemists from the University of California published an article discussing the threats of chlorofluorocarbon (CFC) gases to the ozone layer. CFCs were commonly used aerosol sprays and coolants in many refrigerators during that time. Mario Molina and Sherwood Rowland found out that the sun's UV rays break CFCs down into substances that include chlorine as they reach the stratosphere.
They concluded that the atmosphere had a “finite capacity for absorbing chlorine” atoms in the stratosphere. The US Environmental Protection Agency reported that one atom of chlorine can destroy more than 100,000 ozone molecules, eradicating ozone much more quickly than it can be replaced. According to National Geographic, an American pay television network and flagship channel that is owned by National Geographic Partners, this discovery earned them the 1995 Nobel Prize in chemistry.
In 1985, a team of scientists found a hole in the ozone layer over Antarctica which was later linked to CFCs, validating Molina and Rowland’s work. Studies after that revealed how the Earth’s layer had already depleted. Researchers revealed that stratospheric ozone decreased since 1979 between 4% and 6% per decade in mid-latitudes and between 10% and 12% per decade in higher southern latitudes.
The problem of ozone layer depletion also became prominent in the 1980s. According to Statistics Canada, an online site that provides statistical information including tables, microdata, and data visualizations, some results showed include annual ozone losses of 2% to 4% for mid-latitudes, Europe and North America; ozone losses during the 1980s in Australia ranged from 0.5% to 5%, and the ozone hole has become a regular feature of the southern hemisphere with total ozone losses of 60% to 70% reported each spring since 1985.
The Largest-Ever Ozone Hole in the Arctic
The ozone layer is considered an important part of the global atmosphere and climate system as it limits the amount of UV radiation from the sun to levels necessary for life on Earth. While we have made progress in stopping damage to the ozone layer, a lot of things still need to be done to protect and restore the atmospheric shield that sits in the stratosphere. Scientists said that a depleted ozone layer may likely cause serious consequences including higher rates of sunburn, skin cancer, eye damage, and other diseases.
Last March, scientists from the European Space Agency (ESA) detected what may be the largest hole in the ozone layer ever recorded over the Arctic. While both poles lose some ozone during their winters, the Arctic tends to lose much less than Antarctica. In a statement, the scientists reported that the ozone hole covers an area roughly three times the size of Greenland. This could expose people living at far northern latitudes to high levels of ultraviolet radiation if it grows much larger.
"From my point of view, this is the first time you can speak about a real ozone hole in the Arctic," Martin Dameris, an atmospheric scientist at the German Aerospace Center, said.
Scientists said that this ozone layer was the result of a combination of unusually low Arctic temperatures, sunlight, wind fields, and human emissions of ozone-depleting substances like chlorofluorocarbons (CFC). According to Nature.com, a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology, this year’s ozone layer depletion can surpass the ozone depletion in 1997 and 2011. “We have at least as much loss as in 2011, and there are some indications that it might be more than 2011,” Gloria Manney, an atmospheric scientist at NorthWest Research Associates in Socorro, New Mexico, said.
The researchers said that the Arctic doesn't usually see the same ozone-depleting conditions as the Antarctic because it has more variable temperatures and isn’t usually primed for ozone depletion. Every year, the Antarctic ozone hole opens due to the combination of frigid temperatures and man-made pollution. Jens-Uwe Grooß, an atmospheric scientist at the Juelich Research Centre in Germany, said that these conditions are much rarer in the Arctic. But this year, a "polar vortex" trapped so much cold air above the Arctic that there was more than at any time since 1979.
"The hole is principally a geophysical curiosity. We monitored unusual dynamic conditions, which drive the process of chemical depletion of ozone. [Those dynamics] allowed for lower temperatures and a more stable vortex than usual over the Arctic, which then triggered the formation of polar stratospheric clouds and the catalytic destruction of ozone,” Vincent-Henri Peuch, director of the Copernicus Atmosphere Monitoring Service, said.
Ozone Hole Over the Arctic Has Closed
Scientists have already assured that the conditions causing the ozone hole over the Arctic should soon change. Recently, scientists monitoring the "unprecedented" hole at the Copernicus Atmospheric Monitoring Service (CAMS) announced the closure. They have expected it to heal as temperatures increased, breaking down the Arctic polar vortex and allowing ozone-depleted air to mix with ozone-rich air from lower latitudes.
The good news is mainly attributed to the Montreal Protocol in 1987, a landmark agreement to phase out substances that affect the ozone layer. The accord was ratified by all 197 UN member countries. Without those regulations, the Arctic ozone hole this year could have posed a threat to human health.
"We don't know what caused the wave dynamics to be weak this year. But we do know that if we hadn't stopped putting chlorofluorocarbons into the atmosphere because of the Montreal Protocol, the Arctic depletion this year would have been much worse,” Paul Newman, chief scientist for Earth Sciences at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said.
According to EcoWatch, a leading environmental news site engaging millions of concerned individuals every month, scientists said that it is too early and too rare to say if the recent ozone depletion portends a new trend. Still, it’s safe to say that the world’s ozone layer is recovering. The 2018 Scientific Assessment of Ozone Depletion revealed that the ozone layer has been recovering at a rate of 1% to 3% per decade since 2000. "At these projected rates, the Northern Hemisphere and mid-latitude ozone is predicted to recover by around 2030, followed by the Southern Hemisphere around 2050, and polar regions by 2060," the ESA wrote.