LAUSR

Abstract Anthropogenic polluting substances, mainly CO2, affect the lower atmosphere where they excite the well-known greenhouse warming. However, they also affect the upper atmosphere (mesosphere, thermosphere and embedded ionosphere), where they cause long-term trends stronger than those in the troposphere. Calculations of long-term trends in the upper atmosphere suffer from various problems, which may be divided into three groups: (1) natural variability, (2) data problems, and (3) methodology. These problems have often been underestimated in trend calculations, which lead to controversial trend results. Here we briefly treat various problems of long-term trend calculations in the upper atmosphere and some ways how to deal with these problems are suggested.