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.