Headline: Geo-Engineering. Untersuchung und Bewertung von Methoden zum Geo-Engineering, die die Zusammensetzung der Atmosphäre beeinflussen

This study investigates the influence of so-called stratospheric geoengineering on the global stratospheric ozone layer with global modeling tools. Stratospheric geoengineering is bound to produce a global cooling effect that is supposed to counterbalance to a certain extend the global warming trend due to anthropogenic greenhouse gas emissions. Current estimations assume that yearly injections of some 1-10 Mt sulphur equivalents are necessary to obtain the desired effect. In accordance to these estimations, we carry out sensitivity studies that that aim at quantifying the effects on the ozone layer as a function of the injection rate and certain key parameters and uncertainties.The results show a very complex linkage of the involved processes that determine the ozone layer. In particular, the interactions among the radiative properties of the sulphate aerosol, stratospheric circulation, the polar vortexes, and aerosol and ozone chemistry seem to be a key. Whereas chemical processes over the subtropical areas appear to induce an enhancement of the ozone layer of up to 5%, high latitudes and the polar areas seem to be up for a depletion of the ozone layer of up to 10%. However, these results are bound to a considerable amount of uncertainty of multiple origins, such that a reliable estimation of the implications of stratospheric geoengineering to the ozone layer may not at all be obtained with model experiments.