Detailed investigations of the variability of the stratospheric ozone layer (in a height between about 15 to 40 km) and its long-term changes have shown that a full description of the observed fluctuations is only possible if dynamical as well as physical and chemical processes and their complex interactions (feedback) are considered. Moreover, it must be regarded that changes in the troposphere (surface to about 10 km height) in general also lead to modifications of the stratospheric composition and specifically of the ozone layer.
All these changes depend on the respective state of climate which itself is changing. Via radiative processes (e.g. absorption of UV radiation, emission of infrared radiation to space) and dynamical feedback mechanisms, changes in the chemical composition of the atmosphere itself contribute to climate change. Therefore, the development of the ozone layer and climate are connected in a complex manner. Hence, the assessment of the future evolution of climate and stratospheric ozone content is very complicated.
Together with analyses of long-term measurements, in particular those derived from satellite instruments, numerical models of the atmosphere are used to identify, investigate and evaluate single processes with regard to their meaning for the whole atmospheric system. So-called Chemistry Climate Models (CCMs) allow studying the feedbacks of dynamical and chemical processes. Comparison of results derived from model simulations and respective observations help to improve understanding atmospheric processes and their changes. Although the quality of atmospheric model systems have significantly improved in recent years and many processes can be reproduced in a realistic way, there are several uncertainties which indicate gaps in our understanding of atmospheric behaviour. The DLR-Institut für Physik der Atmosphäre cooperates with national and international partners to improve the knowledge about the Earth’s atmosphere and to better assess its future evolution.