Atmospheric ozone plays a critical role in limiting the penetration of biologically harmful, solar ultraviolet radiation to the Earth surface. Furthermore, the absorption of ultraviolet radiation from the Sun and infrared radiation emitted from the Earth's warm surface influence temperatures in the lower stratosphere, creating dynamically stable conditions with strongly reduced vertical exchange. Through industrial emissions, ozone-depicting catalysts have increasingly been produced in the stratosphere, leading to reductions in ozone. The situation is especially grave during springtime over Antarctica, where, since the 1980s, each year almost all ozone in the 14—22 km height region is chemically destroyed. This so-called "ozone hole" was not predicted by any model and came as a total surprise to all scientists. The ozone hole developed at a least likely location. Through the emissions of chlorofluorocarbons, humankind has created a chemical instability, leading to rapid loss of ozone. A question is whether there may be other instabilities that might be triggered in the environment by human activities.

1.1 Introduction

The study of the chemistry of the atmosphere is both of immediate scientific interest and of high social relevance. We first note that the gases that are most significant for atmospheric chemistry and for the Earth's climate are not its main components -nitrogen (N2), oxygen (O2), and argon (Ar), which together with variable amounts of water vapor make up greater than 99,9% of the molecules in the Earth's atmosphere -but rather are many gases that are found only in very low concentrations. The main gases cannot be influenced significantly by human activities. The minor gases can. Several of them play important roles in climate and atmospheric chemistry. Carbon dioxide (CO2), which currently has a concentration of approximately 360 among 1 million air molecules, is of crucial importance in that, together with water vapor and sunlight, it builds the organic molecules of living matter. Carbon dioxide is also of great significance for the Earth's climate, an important theme of this conference. However, despite these important aspects, CO2 plays no significant direct role in atmospheric chemistry.

The chemically reactive gases have even much lower abundances in the atmosphere than CO2. Several of them also act as greenhouse gases. One among these is ozone (O3),

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