The topic of long-term changes and trends in the upper atmosphere, since Roble and Dickinson's seminal 1989 paper, remains relevant and current with ongoing controversies. Some of these issues have been resolved over time, while others have become even more controversial. This paper makes a significant contribution to this important topic. The authors have demonstrated that at least one of the widely used established empirical formulae for the ionospheric peak height, hmF2, introduces diurnal, seasonal, and long-term biases into hmF2 estimates. These biases are of similar, if not greater, magnitude than those expected from the long-term cooling resulting from increased greenhouse gases concentration.

This paper presents a new set of empirical models for describing variations in ionosphere-thermosphere electrodynamics in both hemispheres, as a function of season as well as prevailing solar wind and interplanetary magnetic field conditions. The models are based on combined measurements of magnetic field perturbations and ionospheric plasma drift made by the Swarm and CHAMP satellites. The chief advantage of these models is that they are the first empirical models of high-latitude ionospheric electrodynamics quantities in both hemispheres that are consistently derived. The model codes are open source and publicly available.

This paper gives an outlook on what will happen to the predictability of the ionosphere and upper atmosphere in the case we no longer should have relevant measurements in the mesosphere. It shows how important global measurements in the mesosphere are for the predictability of the variability of the ionosphere and thus for our communication and navigation systems. This is particularly important because the satellites that currently provide us with observations of the mesosphere have all already far exceeded their originally planned lifetimes (e.g. SABER, MLS, ...).

The paper explains why the solar activity index F30 is more suitable for ionospheric and thermospheric long-term trends.