The Ozone Hole Will Close
The latest insights suggest that by the mid-21st century the ozone layer will have regained the thickness it had at in the early 1980s. This prediction is based on computer models which simulate physical, dynamic and chemical processes in the atmosphere. The results of computer simulations are validated for past time periods by comparing them with measurement data. Carefully evaluated models then form the foundation for providing reliable predictions of future developments.
Satellite measurements supply the data which enable comparisons. Ozone and trace-gas measurements are routinely acquired and processed at EOC. They come from the GOME-2 instrument on the MetOp-A and MetOp-B satellites of EUMETSAT, the European Organization for the Exploitation of Meteorological Satellites. GOME-2 continues the series initiated by the ESA instruments GOME on ERS-2 and SCIAMACHY on ENVISAT, which successfully monitored the ozone layer starting in 1995 and 2002, respectively. The GOME-2 spectrometers on MetOp-A and MetOp-B are operated in tandem and measure on a daily basis the horizontal and vertical global distribution of trace gases.
In addition to the reduction of chlorofluorocarbons, climate change will increasingly influence the ozone layer. In some parts of the world this can lead to so-called “over-recovery”, meaning that after the complete breakdown of CFCs ozone concentrations could increase to levels that are even higher than they were before the first noted occurrence of the ozone hole in the early 1980s. Changes in the amount of climate relevant trace gases, especially carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), will have a pronounced effect on the ozone layer from the middle of this century. It is predicted that increasing concentrations of CO2 and CH4 will strengthen the global ozone layer, whereas increasing N2O concentrations will lead to ozone reduction. In sum, these effects will lead to a thicker ozone layer outside tropical regions from mid-century. In the tropics, by contrast, the ozone layer will become thinner in the second half of the 21st century. This is because, in addition to chemical processes, scientists expect climate change to alter vertical airstreams, significantly influencing ozone distribution. "It appears that the complex interactions between climate change and ozone chemistry will lead to additional changes in the ozone layer, with regional variations. For that reason the evolution of the ozone layer needs to be continually monitored and analysed further" explains Professor Martin Dameris of EOC’s neighbouring Institute of Atmospheric Physics.
In the course of the next few decades, atmospheric composition will continued to be monitored with the help of the EU Copernicus satellites Sentinel-5P, -4 and -5. "Thanks to their high temporal and spatial resolution, with Sentinel spectrometers we will be able to monitor the formation and transport of pollutants even down to the level of large cities. In the end we will have high quality, validated data, suitable for scientific investigations" explains Dr.-Ing. Diego Loyola of the Remote Sensing Technology Institute.
These findings were compiled for the current report of the World Meteorological Organization (WMO) on the development of the ozone layer in the stratosphere. DLR scientists Prof. Martin Dameris, PD Dr. Veronika Eyring, Dr.-Ing. Diego Loyola, Dr. Hella Garny, Melanie Coldewey-Egbers and Prof. Robert Sausen participated in drawing up the WMO document as lead authors, contributors or reviewers. This report is published every four years, starting with the discovery of the ozone hole in 1985.