Climatic mesosphetic cooling: Employing the long time-series of ionospheric soundings from Norwegian stations (scientific note)

While so-called greenhouse gases are responsible for global warming in the lower atmosphere, they can also cause cooling in the middle atmosphere. Cooling of the middle atmosphere in turn causes shrinking. One consequence of this is that the ionosphere occurs at lower altitude. Observations at several global locations have indicated that the ionospheric F2 layer, at least, is sinking. Here, these phenomena and observations will be briefly reviewed. At Troms∅ (69°N), ionosonde observations exist since 1935 and a precis history will be given. Furthermore, similar datasets, albeit rather less extensive, exist for other Norwegian stations, notably Svalbard (≈80°N). In the light of work in other countries, we shall examine the potenial of the Norwegian data for studying climatic change in the arctic and sub-arctic. The importance of such archives and also future maintenance of ionospheric observations cannot be overstated