Self-sustained oscillations in the atmosphere (0 – 110 km): Structures and impacts D.Offermann, Ch.Kalicinsky, R.Koppmann, K.Matthes, H.Schmidt, W.Steinbrecht, J.Wintel Two Climate Circulation Models (HAMMONIA, WACCM) show self-sustained oscillations with periods between 2 and 150 years in the middle atmosphere. The periods in the two models are quite similar and very robust against disturbances. Intriguing vertical structures of amplitudes and phase are seen. Amplitudes are modulated with altitude, and phases frequently are constant in altitude layers, with 180° phase jumps in between. The nature of these oscillations is not easy to determine. A modal structure of phases and amplitudes or synchronization of adjacent atmospheric layers are briefly discussed. Synchronization (Arnold tongue) is difficult to prove because of the computational cost of the CCM. The self-sustained oscillations may have some impact on atmospheric analyses. Very long period oscillations can be mistaken for trends. Such a seeming trend depends on the time interval in which the data are taken. Temperature trends published in the literature show large, unexplained differences. These could find some clarification here. Measured methane results may also be affected. Self-suxstained temperature oscillations at the location of Wuppertal (51°N,7°E) show similar (but somewhat smaller) time structures as the long-term variations of global mean temperatures on the ground (GLOTI data). These results are from computer model runs where the greenhouse gases mixing ratios have been kept constant. The horizontal structure of the self-sustained oscillations needs to be analyzed to determine how representative a local value could be for the global average.