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‘Huge’ unexpected ozone hole spotted over tropics

A “huge” hole in the ozone layer, which was not expected to exist, has been identified in the Earth’s atmosphere over almost the entire tropical region.

The hole is a year-round gap in the planet’s ozone layer and is seven times larger than the better-known Antarctic ozone hole, which opens every spring.

Professor Qing-Bin Lu, a scientist from the University of Waterloo in Ontario, Canada, said that according to his research, the hole has been there for more than 30 years and covers an area so vast that half the world’s population could be affected .

He said The Independent: “Unlike the Antarctic ozone hole, which occurs only in spring, the tropical ozone hole has appeared at all times of the year since the 1980s, and its area is about seven times larger.

“[It] could cause global concern as it may lead to increases in ground-level UV radiation and associated risks of skin cancer and cataracts, as well as other negative impacts on health and ecosystems in tropical regions.”

He said there were “preliminary reports showing that ozone depletion over the equatorial regions is already endangering large populations there and the associated UV radiation reaching the regions was far greater than expected.”

Talking about finding the vast area of ​​depleted ozone, Professor Lu shared The Independent: “It sounds incredible that the great tropical ozone hole wasn’t discovered before. But there are some intrinsic challenges to this discovery.

“First, the current photochemical theory expected that no tropical ozone hole existed. Second, unlike the seasonal Antarctic/Arctic ozone holes, which occur primarily in spring, the tropical ozone hole remains essentially unchanged across the seasons and is therefore not visible in the originally observed data.”

Like the Antarctic ozone hole, normal ozone levels are found to be reduced by about 80 percent at the center of the tropical ozone hole, the study said.

The new research has also revealed differences in prevailing theories about how ozone is depleted.

In the past, the presence of chlorofluorocarbons (CFCs) was thought to be the largest cause of ozone depletion. The 1987 Montreal Protocol that banned them has led to a significant reduction in their use.

But despite the global ban, the largest, deepest and most persistent ozone holes – over Antarctica – were still observed in the late 2000s and into 2020-2021.

“This was not unexpected from any of the photochemistry-climate models,” Professor Lu said.

A separate theory of ozone depletion known as the cosmic-ray-driven electron reaction (CRE), in which cosmic rays from outer space reduce ozone in the atmosphere, was first proposed two decades ago by Professor Lu and his colleagues.

He said The Independent: “The observed results strongly suggest that both Antarctic and tropical ozone holes must arise from an identical physical mechanism and that the CRE mechanism has shown excellent agreement with the observed data.”

He added: “CFCs are undoubtedly the most important ozone-depleting gases, but cosmic rays play an important initiating role in the creation of both polar and tropical ozone holes.”

The research is published in the journal AIP progress.