Published: Wed, February 07, 2018
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The Ozone Layer Might Not Be Recovering Properly

The Ozone Layer Might Not Be Recovering Properly

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. More research now needs to be done in order to monitor and investigate the causes behind the continuing ozone decline in the lower stratosphere, they said.

Yet despite these increases, measurements showed 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 worrying news comes from a report that claims, while the ozone has been recovering over Antarctica, it has actually been thinning at lower latitudes.

Several recent studies, including one published last month in Geophysical Research Letters, point to a robust recovery of stratospheric ozone concentrations over Antarctica-the long-awaited payoff after the Montreal Protocol in 1987 mandated a global phaseout of chlorofluorocarbons and other ozone-eating compounds.

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

In the 20th century, when excessive quantities of ozone- depleting chlorinated and brominated hydrocarbons such as CFCs were released into the atmosphere, the ozone layer in the stratosphere - ie at altitudes of 15 to 50 kilometres - thinned out globally. It is produced in tropical latitudes and distributed throughout the rest of the world.

"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 global research team, per The Guardian.

Climate change may also be a factor, for example by sweeping ozone out of the tropics, the study suggests. This would be created by the use of certain chemicals in solvents, paint strippers and degreasing agents. "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. One is even used in the production of an ozone-friendly replacement for CFCs. But Dr. William Ball from ETH Zurich, who led the analysis, said: "The finding of declining low-latitude ozone is surprising, since our current best atmospheric circulation models do not predict this effect".

Another suspect is so-called "very short lived substances" (VSLS) - industrial chemicals that destroy ozone.

Although individual datasets had previously hinted at a decline, the application of advanced merging techniques and time series analysis has revealed a longer term trend of ozone decrease in the stratosphere at lower altitudes and latitudes.

" ... This new research is interesting and provides a novel perspective on changes in the ozone layer". 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.

Dr Justin Alsing from the Flatiron Institute in NY, who took on a major role in developing and implementing the statistical technique used to combine the data, said: "This research was only possible because of a great deal of cross-disciplinary collaboration". The study was conducted by 22 scientists at research centres in the U.S. and Europe.

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