Reply on RC1

Abstract

Atmospheric simulations by computer models exhibit oscillations with multi-annual, decadal, and even centennial periods. These oscillations are especially seen in the temperature. They extend from the ground up to the lower thermosphere. Recent analyses have shown that they exist even if the model boundaries are kept constant with respect to influences of the sun, ocean, and greenhouse gases. Therefore, these parameters appear not responsible for the excitation of these oscillations, However, influences of land surface/vegetation changes had not been enrirely excluded. This is studied in the present analysis. It turns out that such changes are also not candidates for such stimulation. Rather, it appears that the long- period oscillations are excited (internally) in the atmosphere itself. Long-term trends of atmospheric parameters as the temperature are important for the understanding of the climate change. Their study is mostly based on data sets that are one to a few decades long. The trend values are generally small, and so are the amplitudes of the long-period oscillations. It can therefore be difficult to disentangle these structures, especially if the interval of trend analysis is comparable to the period of the oscillations. If the oscillations are self-excited, there may be a non- anthropogenic contribution to the climate change which is difficult to determine. Long-term changes of the Cold-Point-Tropopause are analyzed here as an example.