Claims of a new ‘tropical ozone hole’ spark controversy

A scientist recently claimed he had discovered a gargantuan hole in the ozone layer that first appeared over the tropics in the 1980s but has gone unrecognized until now. However, upon publishing his research, the scientist was quickly criticized by experts who called his study deeply flawed.

“I am surprised that this study has been published in its current form,” said Martyn Chipperfield, professor of atmospheric chemistry at the University of Leeds in England. Science Media Center (opens in a new tab)an independent UK-based press office that works with researchers, journalists and policy makers to disseminate accurate scientific information.

“The claim in this search for such a great ozone changes in the tropics have not been apparent in other studies, which makes me very suspicious,” Chipperfield said. before it can be accepted as fact.”

The author of the new study, Qing-Bin Lu, a professor in the Department of Physics and Astronomy at the University of Waterloo in Ontario, said he disagreed with the criticisms of Chipperfield and ‘others. “In my view, these criticisms are unfounded and cannot withstand scrutiny of the scientific literature,” he told Live Science in an email.

Related: Ozone-destroying CFCs could make a comeback at the end of the 21st century

The controversial report was published July 5 in the journal AIP Advances (opens in a new tab). The study went through the journal’s standard peer-review process, whereby an independent reviewer determined it was suitable for publication, said AT Charlie Johnson, Jr., AIP associate editor. Advances, to Live Science in an email. The journal’s editors then determined that the work was newsworthy enough to be highlighted as a featured article on their website.

“To our knowledge, we have not received any communication from the outside community questioning its validity,” Johnson said. “We encourage readers and researchers to contact authors whenever possible to discuss potential technical shortcomings, so that they can be addressed in corrections to the literature or in comments and responses.” Or, alternatively, readers can contact the newspaper directly, he said. At that time, the journal would work to validate any claims made about the work, seek an explanation or response from the author, and correct the literature, if necessary.

A new definition of the “ozone hole”?

Ozone – a gas consisting of O3 or oxygen atoms linked together in groups of three – forms in the Earth’s upper atmosphere. Most ozone is found in the stratosphere, the atmospheric layer between 6 and 31 miles (10 to 50 kilometers) above the planet’s surface. There, the gas acts as a kind of sunscreen, protecting Earth strong ultraviolet (UV) rays from the sun.

In the 1980s, scientists discovered that long-lived air pollutants called chlorofluorocarbons (CFCs) break down into chlorine and bromine when exposed to UV radiation beyond the ozone layer, according to NASA Earth Observatory (opens in a new tab). These reactive elements tear apart O3 molecules and thereby thin regions of the ozone layer, creating “holes”, primarily over Antarctica, where freezing atmospheric conditions allow ozone-shredding reactions to proceed very efficiently.

Conventionally, an ozone hole is defined as a region where the concentration of ozone drops below 220 “Dobson units” – a measure of the number of ozone molecules in a given column of air that extends from the planet surface to space. The discovery of holes in the ozone layer led to the 1987 Montreal Protocol, an international treaty to phase out the production of ozone-depleting chemicals such as CFCs, and now the ozone layer. ozone is on the way to recovery, according to the World Meteorological Organization (opens in a new tab) (WMO).

However, in Lu’s new study, he warned that a new hole in the ozone layer could threaten the lives of billions of people living in the tropics.

Specifically, Lu reported discovering a “large all-weather ozone hole” in the lower stratosphere over the tropics, 6.2 to 15.5 miles (10-25 km) above Earth’s surface. Earth. This hole is similar in “depth” to the seasonal ozone hole that opens over Antarctica in late winter and early spring, but covers an area seven times larger than that of the hole. spring Antarctic, he reported.

Related: “The blob” in the Pacific Ocean linked to an ozone peak

“The large, year-long tropical O3 hole could cause great global concern because it can lead to increased ultraviolet radiation at ground level and affect 50% of the Earth’s surface, which is home to around 50% of the world’s population. “, Lu wrote in the AIP report. “Exposure to increased levels of UV-B could increase the incidence of skin cancer and cataracts in man, weaken the man immune systemsdecrease agricultural productivity and negatively affect sensitive aquatic organisms and ecosystems.”

Rather than using the conventional definition of a hole in the ozone layer, Lu defined a hole as “an area of ​​O3 loss greater than 25% relative to the undisturbed atmosphere.” Ozone holes observed at the North Pole were marked by about a 25% drop in ozone, so this new definition is warranted, he told Live Science. It is critical to note that “no ozone hole over the tropics would be observed under the conventional definition of an ozone hole”, as total ozone levels over the tropics exceed the threshold of 220 Dobson units, Lu noted in his report.

Shortly after Lu’s study was published, Chipperfield and several other experts shared their critiques of the study with the Science Media Center.

“There is no ‘tropical ozone hole,'” said Paul Young, an atmospheric scientist at Lancaster University in England and co-lead author of the Scientific Assessment of Earth Depletion. the 2022 ozone layer, a report prepared by WMO and the United Nations.

“The author’s identification of a ‘tropical ozone hole’ comes down to him looking at percentage changes in ozone, rather than absolute changes, the latter being much more relevant to UV damage reaching the surface. “, said Young. “Interestingly, his paper also does not draw on the vast literature that explores and documents ozone trends in all regions of the atmosphere.”

According to Marta Ábalos Álvarez, researcher at the Department of Earth Physics and Astrophysics at the Complutense University of Madrid. This circulation has accelerated in recent years (opens in a new tab) due to climate changeand this acceleration explains the long-term patterns of ozone depletion seen in the tropics, she said.

“In my opinion, [Lu’s] The article lacks the scientific rigor necessary to be a reliable contribution,” said Ábalos Álvarez. “It contains a lot of reasoning with serious errors and unsubstantiated assertions, contradicting the previous results which are substantiated.

Originally posted on Live Science.

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