August 9, 2022

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The discovery of an unexpected "huge" ozone hole over the tropics

The discovery of an unexpected “huge” ozone hole over the tropics

A “massive” ozone hole that was not expected to be located in the Earth’s atmosphere has been identified over almost the entire equatorial region.

The hole is a year-round hole in the planet’s ozone layer, seven times larger than the well-known Antarctic ozone hole that opens each year in the spring.

According to his research, the hole has actually been around for more than 30 years and covers an enormous area where half the world’s population could be, said Professor Cheng Bin Lu, a scientist from the University of Waterloo in Ontario, Canada. affected.

Tell independent: “Unlike the Antarctic ozone hole that appears only in the spring, the tropical ozone hole has appeared in all seasons since the 1980s, and its area is approximately seven times larger.

“[It] It can cause global concern because it can cause increases in ground-level UV radiation and associated risks for skin cancer, cataracts, and other negative effects on health and ecosystems in the tropics.”

He said there were “preliminary reports showing that levels of ozone depletion over the tropics were already threatening large numbers of their populations, and that the accompanying UV radiation reaching the regions was much greater than expected.”

Talking about finding a huge area of ​​depleted ozone, Professor Lu . said independent: “It seems inconceivable that the large tropical ozone hole has not been discovered before. But there are some fundamental challenges in making this discovery.

First, a tropical ozone hole was not expected from the prevailing photochemical theory. Second, in contrast to the seasonal Antarctic/Arctic ozone holes which appear mainly in the spring, the tropical ozone hole is essentially unchanged across seasons and is therefore not visible in the original observed data.”

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As with the Antarctic ozone hole, the research found that the natural ozone value has been depleted by about 80 percent at the center of the tropical ozone hole.

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

In the past, the presence of chlorofluorocarbons (CFCs) was considered the biggest cause of ozone layer depletion. The 1987 Montreal Protocol, which banned it, saw a significant decline in its use.

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

“This was unexpected from any of the climate photochemistry models,” said Professor Lu.

Professor Lu and colleagues two decades ago proposed a separate theory of ozone depletion, known as the cosmic ray-induced electron reaction (CRE), in which cosmic rays from space reduce the ozone layer in the atmosphere.

Tell independent: “The observed results strongly suggest that the Antarctic and tropical ozone holes must originate from an identical physical mechanism, and that the CRE mechanism showed excellent agreement with the observed data.

“CFCs are undoubtedly the main ozone-depleting gases, but cosmic rays play a major role in causing both polar and tropical ozone holes,” he added.

Publish the research in the journal Advance AIP.