Ozone layer is recovering, but slowly
Earth's protective ozone layer is showing signs of recovery thanks to action under the Montreal Protocol. However, changes in the atmosphere due to climate change mean that the goal of returning to the pre-1980 state is unlikely to be achieved by the end of the century, explain Elizabeth Weatherhead of the University of Colorado at Boulder and Signe Bech Andersen of the Danish Meteorological Institute.
The two researchers evaluated the results of 14 computer models whose data were based on measurements from satellites and ground stations. It was shown that the ban on ozone-depleting substances caused the ozone concentrations in the stratosphere to rise again. The effect is more pronounced than expected, particularly in the mid-latitudes of the northern hemisphere. However, this could be the result of natural fluctuations, the scientists point out.
It is far too early for a general all-clear, Weatherhead and Andersen continue, since it is not foreseeable how climate change will affect further ozone development. In the high latitudes, for example, higher temperatures in turn promoted cooling in the stratosphere and thus the formation of polar stratospheric clouds, which in turn contribute to ozone depletion. While substances such as chlorofluorocarbons (CFCs) have had an impact on ozone values in the past, in the future this will primarily be due to air temperatures, atmospheric dynamics and the occurrence of trace gases. Among other things, the researchers name various nitrogen compounds, which in turn can destroy ozone.
The Montreal Protocol to ban CFCs was adopted in 1987 after researchers first observed the depletion of the ozone layer over Antarctica in the early 1980s and were able to link this to the impact of the chemicals. Now ratified by more than 180 countries, it formulates legal requirements for the production and use of substances containing halogens.
