Ozone depletion has been one of the most urgent concerns regarding climate change. The issue has been the subject of long discussion and controversy in the scientific realm.
Recently, a significant ozone hole that can harm 50% of the world’s population has been discovered in the lower stratosphere over the tropics.
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What is the ‘New Ozone Hole’?
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In a recent study that was published in AIP Advances, it was revealed that the new ozone hole is seven times larger than the Antarctic ozone hole, which only appears in the spring.
Professor Qing-Bin Lu of the University of Waterloo in Ontario, Canada, claims in his research that this all-new ozone hole has been since the 1980s and, unlike the Antarctic one, is perpetually present.
Lu claims in his study, “the depth of this tropical ozone hole is equivalent to that of the well-known springtime Antarctic ozone hole.”
The study, entitled “Observation of substantial and all-season ozone losses across the tropics.” Additionally, it claims that with the rise in the amount of ultraviolet radiation, the whole-year large tropical ozone hole may harm 50% of the Earth’s surface.
Scientist Lu has also hypothesized that whereas the Antarctic one often arises in the spring, the tropical one should do so year-round.
A new definition for ‘ozone hole’?
In technical terms, “ozone hole” does not literally refer to a place where there is no ozone; rather, it refers to an area where the ozone layer is particularly low.
The term “ozone hole” refers to an area where the amount of ozone drops below 220 “Dobson Units,” which is a measurement of the number of ozone molecules in a certain column of air that extends from the surface of the earth to space.
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According to the World Meteorological Organization (WMO), the ozone layer is currently on the road to recovery after the 1987 Montreal Protocol, an international convention intended to phase out the manufacture of ozone-depleting chemicals like CFCs was passed in response to the finding of ozone holes.
However, Lu warned in his recent study that the lives of billions of people living in the tropics may be at serious risk to a recently discovered ozone hole.
In place of the standard definition, Lu stated that an ozone hole is “an area of O3 loss larger than 25% compared with the undisturbed atmosphere.” Lu told Live science that the North Pole ozone hole was identified by an approximately 25% decrease in ozone, hence the new definition is accurate.
Since the overall ozone levels over the tropics exceed the 220 Dobson Unit cutoff, Lu stated in his report that “no ozone hole over the tropics would be observed using the usual definition of an ozone hole.”
Different Ozone classification
Good Ozone: Ozone is a substance that naturally exists in the stratosphere, the highest atmosphere of the Earth, where it creates a barrier that protects humankind from the sun’s harmful ultraviolet rays.
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This “good” ozone is being steadily destroyed by man-made substances known as Ozone-Depleting Substances (ODS), such as methyl bromide, carbon tetrachloride, halons, chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and methyl chloroform.
Then there is Bad Ozone. Near the surface of the Earth, in the lower atmosphere (troposphere), pollutants emitted by vehicles, power plants, industrial boilers, refineries, chemical industries, and other sources react chemically with sunlight to produce ozone.
Ozone layer depletion
The term “ozone layer depletion” describes chemically induced stratospheric ozone layer destruction that goes beyond natural processes. Ozone in the stratosphere is continuously produced and destroyed by natural cycles.
However, a number of ODS accelerate the process of ozone breakdown, leaving ozone levels lower than usual.
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These compounds were formerly utilized and sometimes still are used in coolants, foaming agents, fire extinguishers, solvents, insecticides, and aerosol propellants. These ozone-depleting chemicals degrade very slowly after being discharged into the atmosphere.
In fact, they can survive for years as they travel through the troposphere and into the stratosphere. There, the UV radiation from the sun breaks them down, releasing chlorine and bromine molecules that deplete the stratospheric ozone.
Increased ground-level UV radiation from the protective layer may raise the risk of skin cancer and cataracts in people. Furthermore, it can also weaken human immunity and reduce agricultural productivity.
Scientists concerned over the new study
Other scientists who were not involved in the study have expressed concern about its conclusions.
Martyn Chipperfield, Professor at the School of Earth and Environment, University of Leeds, told Down to Earth, “One of the concerns is that the theory of ozone loss proposed by Lu has been discredited.”
The other problem, in Chipperfield’s opinion, is that this study used the ozone change dataset from the 1960s.
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He noted that the issue is that there weren’t many observations made in the 1960s and those that were made were based on poor model reconstructions.
He also pointed out, “Ozone trends from the 1960s can be evaluated using other, better datasets that are extensively used in the community. They don’t exhibit this large drop in ozone.”
Susan Solomon, a Climate Science, and Atmospheric Chemistry professor at the Massachusetts Institute of Technology told DTE, that a significant proportion of the decline in tropical ozone is likely a result of changes in the stratospheric winds that carry up ozone-deficient tropical air.
A significant proportion of the decline in tropical ozone is likely a result of changes in the stratospheric winds that carry up ozone-deficient tropical air.
She told DTE that she remain unconvinced that cosmic rays were the primary cause of the ozone layer’s deterioration in the poles. She continued by saying that the putative cosmic ray claim was not supported by any specific chemical calculations.