Ozone Layer Thinning Over Non-Polar Regions, Scientists Warn

Doug Carpenter
February 7, 2018

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.

It is clear from Antarctic data that the ozone layer is beginning to recover where it was worst affected, though it will take many more decades before it is back to its condition of the 1970s.

For the study, the team made a record on ozone layer for 30 years by combining measurements of atmospheric ozone from 11 different datasets.

However, despite this success, scientists have today revealed that stratospheric ozone is likely not recovering at lower latitudes, between 60N and 60S (London is at 51N), due to unexpected decreases in ozone in the lower part of the stratosphere. However, a team led by researchers from ETH Zurich and the Physikalisch- Meteorologisches Observatorium Davos in Switzerland have found that despite the ban on CFCs, the concentration of ozone in the lower part of the stratosphere has continued to decline at latitudes between 60 degree South and 60 degree North.

The cause of the decline is unknown but might be the result of global warming. These substances were banned in 1989 in accordance with the Montreal Protocol external linkand since then the ozone layer in the upper stratosphere has recovered significantly, particularly in the polar regions.

But in the lower stratosphere, when there is the most ozone, levels are falling.

Study co-author Professor Joanna Haigh, Co-Director of the Grantham Institute for Climate Change and the Environment at Imperial College London, said: "Ozone has been seriously declining globally since the 1980s".

Although they're not certain what's causing this decline, the authors suggest two possibilities.

"The potential for harm in lower latitudes may actually be worse than at the poles".

Scientists are not yet sure what accounts for this continuing decline but one explanation could be that climate change modifies the pattern of atmospheric circulation. On the other hand, very short-lived substances containing chlorine and bromine are on the rise, and could increasingly enter the lower stratosphere, for example as a result of more intense thunderstorms. "The impact of the Protocol is undisputed, as evidenced by the trend reversal in the upper stratosphere and at the poles", said Thomas Peter, from ETH Zurich.

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. "These short-lived substances could be an insufficiently considered factor in the models", said Ball.

To conduct the analysis, the team developed new algorithms to combine the efforts of multiple worldwide teams that have worked to connect data from different satellite missions since 1985 and create a robust, long time series.

During the 1980's scientists discovered that a large hole had formed in the ozone layer, and exposed the Antarctic to much higher levels of the radiation compared to the other locations on Earth. The researchers will now focus on determining what the most likely cause for the decline of ozone could be, and whether it is connected to the presence of VSLSs in the earth's stratosphere.

The study was conducted by researchers from institutions in Switzerland, the United Kingdom, the USA, Sweden, Canada and Finland, and included data gathered by satellite missions including those by NASA.

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