Long‐Term Trends in the Ionospheric Equivalent Slab Thickness as a Proxy of Climate Change in the Ionosphere

Abstract Global warming warms the lower atmosphere, but cools and contracts the upper atmosphere. These changes also affect the ionosphere, altering the vertical distribution of plasma through changes in the plasma scale height. Here, we use ionospheric equivalent slab thickness ( τ ) multidecadal time series, derived through observations from co‐located ionosonde and GNSS receiver at three stations spanning low to high latitudes, to investigate long‐term trends (LTT) derived via the empirical mode decomposition. Results indicate a general decreasing LTT in τ in a range between −0.10 and −0.62 km/year. Then, we empirically derive a relation between τ and the plasma scale height at the F2‐layer peak through an empirical ionospheric model, allowing us to estimate the effect that such changes have on the vertical distribution of ionospheric plasma.