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Ozone Levels Still Decreasing Away from Poles


While ozone levels in the upper atmosphere near the poles have been recovering, new research has found that the bottom part of the ozone layer at more populated latitudes is not recovering.

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The worst ozone-depleting substances are chlorofluorocarbons (CFCs) and other volatile chemicals containing chlorine or bromine. Emissions of these substances have been drastically reduced by international agreement, under the Montreal Protocol, to ban or restrict their production and consumption. As a result (we’d like to believe), the decline in the stratospheric ozone concentration has been arrested and there are some signs of recovery.

However, given the steep decline in emissions, we might have expected a better result for the ozone layer. This analysis of research results, published by an international group of scientists (Atmospheric Chemistry and Physics,, help us to understand why we haven’t.

Measurements of ozone concentration are made for a notional column of air stretching up from about 10 km above Earth’s surface to about 50 km. For the column as a whole, there has not been much change in ozone concentration during the period 1998–2016. When results for “slices” of the air in that column were examined, a more complex picture emerged. In the upper stratosphere (32–48 km) there has been a steady increase in ozone concentration, which is what was expected from the actions taken under the Montreal Protocol.

However, in a lower slice of the air column(13–24...

The full text of this article can be purchased from Informit.