A large, year-round ozone hole, seven times larger than the Antarctic ozone hole, has been discovered

Scientists have revealed a large, all-season ozone hole in the lower stratosphere over the tropics. It is comparable in depth to the well-known springtime Antarctic hole but is roughly seven times greater in area.

Despite it being a recent discovery, it turns out that the ozone hole is not new, and has been around since the 1980s. It has been sitting above tropical regions for at least 40 years, it seems.

The observed data agree with the cosmic-ray-driven electron reaction (CRE) model and strongly indicate the identical physical mechanism working for both Antarctic and tropical ozone holes.

Qing-Bin Lu, a scientist from the University of Waterloo in Ontario, Canada has published the discovery in AIP Advances.

What is an all-season ozone hole?

A year-round, or all-season ozone hole is an area of ozone loss larger than 25% compared with the undisturbed atmosphere.

This particular ozone hole is in the lower stratosphere over the tropics and is seven times greater than the springtime Antarctic hole.

Ozone holes can cause cancer and disrupt entire ecosystems

“The tropics constitute half the planet’s surface area and are home to about half the world’s population,” said Lu. “The existence of the tropical ozone hole may cause a great global concern.

“The depletion of the ozone layer can lead to increased ground-level UV radiation, which can increase risk of skin cancer and cataracts in humans, as well as weaken human immune systems, decrease agricultural productivity, and negatively affect sensitive aquatic organisms and ecosystems.”

Underwater image of schools of fish, underwater plants,
© Andrew Stowe

Unconventional models: a huge surprise for the scientific community

Lu’s observation of the ozone hole comes as a great surprise to his peers in the scientific community.

This is because Lu’s discovery was not predicted by conventional photochemical models – his observed data agree well with the cosmic-ray-driven electron reaction (CRE) model and strongly indicate the identical physical mechanism working for both Antarctic and tropical ozone holes.

As with the polar ozone hole, approximately 80% of the normal ozone value is found to be depleted at the centre of the tropical ozone hole. Preliminary reports show that ozone depletion is already endangering large populations and the associated UV radiation reaching these regions is much worse than feared.

It was in the mid-1970s that atmospheric research suggested that the ozone layer – which absorbs most of the sun’s ultraviolet radiation – might be depleted because of industrial chemicals, primarily chlorofluorocarbons (CFCs).

In 1985 the Antarctic ozone hole was discovered. This confirmed CFC-caused ozone depletion. Although bans on such chemicals have helped slow ozone depletion, ozone depletion persisted.

Lu calls for further studies of ozone depletion

Lu explains that tropical and polar ozone holes play a major role in cooling and regulating stratospheric temperatures, mirroring the formation of three “temperature holes” in the global stratosphere. The most recent discovery may prove crucial to better understanding global climate change, the scientist hopes.

The new, all-season ozone hole is building upon previous studies of the CRE-initiated ozone-depleting mechanism that he and his colleagues originally proposed about two decades ago.

“The present discovery calls for further careful studies of ozone depletion, UV radiation change, increased cancer risks, and other negative effects on health and ecosystems in the tropical regions,” Lu concludes.


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