Published: Wed, February 07, 2018
Sci-tech | By Spencer Schmidt

Ozone layer keeps thinning out despite decades of protection

Ozone layer keeps thinning out despite decades of protection

Since the 1970s, global ozone has been deteriorating, due to man-made chemicals. The worrying news comes from a report that claims, while the ozone has been recovering over Antarctica, it has actually been thinning at lower latitudes.

The ozone layer is recovering over Antarctica but thinning over highly populated areas, potentially exposing more than a billion people to harmful radiation, researchers have warned. Much of it is in the lower part of the stratosphere, where it absorbs UV radiation from the Sun which can damage DNA in plants, animals and humans if it reaches the Earth's surface. That led to governments phasing out the CFCs, which led to the first results of healing of the ozone shield above the Antarctic. "What it says to me is that we're now looking at effects that are more subtle than that original problem we were taking on" when the Montreal Protocol was adopted. They found that from 1998 to 2016, ozone in the lower stratosphere ebbed by 2.2 Dobson units-a measure of ozone thickness-even as concentrations in the upper stratosphere rose by about 0.8 Dobson units.

The ozone layer, which protects life on earth from harmful ultra-violet radiation, continues to deplete on a global scale contrary to recent scientific assumptions, say an worldwide team of scientists led by researchers in Zurich.

Dr Ball said: "The study is an example of the concerted worldwide effort to monitor and understand what is happening with the ozone layer; many people and organisations prepared the underlying data, without which the analysis would not have been possible". That is the case this year and at the moment there is significant ozone depletion over northern Ireland and Scotland.

It is not yet possible to assess the consequences that this continuing lower stratospheric ozone depletion will have for humans and the ecosystem. "To enable predictions of future ozone amounts, and to identify whether (and what) action might be needed to prevent further decreases, it is extremely important to understand what is causing the observed downward trend".

"The study is in lower to mid latitudes, where the sunshine is more intense, so that is not a good signal for skin cancer", said Joanna Haigh at Imperial College London, a member of the worldwide research team, per The Guardian. Yet despite these increases, measurements show that the total ozone column in the atmosphere has remained constant, which experts took as a sign that ozone levels in the lower stratosphere must have declined.

"The potential for harm in lower latitudes may actually be worse than at the poles". "The decreases in ozone are less than we saw at the poles before the Montreal Protocol was enacted, but UV radiation is more intense in these regions and more people live there", informed Haigh.

Although they're not certain what's causing this decline, the authors suggest two possibilities. One is that climate change is altering the pattern of atmospheric circulation, causing more ozone to be carried away from the tropics.

Ball and his colleagues suspect that the culprit is "very short-lived substances" (VSLSs): ozone-eating chemicals such as dichloromethane that break down within 6 months after escaping into the atmosphere.

The reason is not known, but it could be to do with chemicals used in paint stripper which were previously believed to be too volatile to affect the stratosphere.

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