A “huge” ozone hole that was not suspected to exist was identified in the planet’s atmosphere in almost the entire tropical region.
It’s a year-round hole in the ozone layer, and it’s seven times bigger than the better-known Antarctic hole that opens every spring.
“The depth of this tropical all-season ozone hole is comparable to that of the well-known springtime ozone hole over Antarctica. At the center of the deepest tropical or Antarctic ozone hole, about 80 percent of the normal value of ozone is depleted, while the average annual reduction of the gas in the lower stratosphere over the tropics due to cooler temperatures is about 1.6 times greater than in Antarctica and 7.7 than in the Arctic”.
Qing-Bin Lu, a scientist at the University of Waterloo in Ontario, Canada, noted that according to his research, the hole has been around for about 40 years and covers an area so massive that half of the world’s population could be affected.
In an interview with the English newspaper The Independent, he stated: “Unlike the Antarctic ozone hole, which only appears in spring, the tropical one has been in all seasons since the 1980s. It could be a worrying issue for the world, since it can lead to increases in ultraviolet (UV) radiation at ground level and associated risks of skin cancer and cataracts, as well as other negative effects on health and ecosystems in tropical regions. These findings have a far-reaching role in understanding fundamental atmospheric processes and global climate change.”
He added that there are “preliminary reports showing that ozone depletion levels in equatorial regions are already endangering large populations, and the associated UV radiation reaching the regions was much higher than expected. The tropics constitute half of the planet’s surface and approximately half of the world’s population lives in them. The existence of the tropical ozone hole is of great global concern.
He maintained: “it sounds incredible that the great tropical hole was not discovered before. But there are some intrinsic challenges in achieving this finding. First, no tropical ozone hole was expected to exist from the prevailing photochemical theory. Second, unlike Antarctic/Arctic ozone holes that appear primarily in spring, the tropical one is essentially unchanged over the seasons and thus invisible in the original observed data.”
As with the Antarctic ozone hole, the normal value of that gas is found to be depleted by around 80 percent in the center of the tropical, according to the research. The new work has also highlighted differences in prevailing theories about how it is consumed.
In the past, the presence of chlorofluorocarbons (CFCs) was considered the main cause of depletion of the ozone layer. The 1987 Montreal Protocol, which banned them, has seen a major reduction in their use.
However, despite the global ban, the largest, deepest and most persistent ozone holes, over Antarctica, were still observed in the late 2000s and in 2020 and 2021. “This was unexpected from any of the photochemical-climate models,” explained Lu.
Another theory of ozone depletion, known as cosmic ray-driven electronic reaction (CRE), in which cosmic rays deplete ozone in the atmosphere, was first proposed by Lu and his colleagues two decades ago.
Lu said: “The observed results strongly indicate that both the Antarctic and tropical ozone holes must arise from an identical physical mechanism, and that the CRE mechanism has been consistent with the observed data. CFCs are undoubtedly the main ozone-depleting gases, but cosmic rays play a major triggering role in causing polar and tropical holes.”
The research is published in the journal AIP Advances.
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