Trends in the upper atmosphere and ionosphere: Recent progress

The upper atmosphere and embedded ionosphere respond to increasing concentration of greenhouse gases and other drivers of long-term changes and trends. In this paper, the progress reached in investigations of long-term trends in the upper atmosphere and mesosphere in the last 2years is briefly summarized. First information appeared about trends in electron temperature (positive trend), thermospheric neutral wind (complex pattern), and total electron content (nonnegative trend). Some new information created partial apparent discrepancies, particularly in the case of ion temperature trends. The quantitative discrepancy between observation-based and model-based trends in mesospheric temperatures and in polar mesospheric clouds has largely been removed. The first observations of trends in CO2 concentration in the lower thermosphere suggest a way how to reduce the observation-model difference in the thermosphere and ionosphere. The scenario of trends in the upper atmosphere and ionosphere is now more complete than it was 2years ago, but still some gaps and discrepancies occur for further investigations.