Is there Greenhouse Cooling in the Thermosphere?
Thomas Ulich and Esa Turunen
Geophysical Observatory, FIN-99600 Sodankylä, Finland
Increased concentrations of greenhouse gases in the air are predicted to
cause cooling of the entire middle and upper atmosphere (Roble and
Dickinson, 1989); doubled mixing ratios of carbon dioxide and methane
would result in a 50 K decrease of the thermospheric temperatures.
Rishbeth (1990) predicted a consequent lowering of the peak height of the
ionospheric F2-layer by 20 km. Experimental evidence of a long term
trend, favouring interpretation as greenhouse cooling, was shown by Bremer
(1992). We compare high latitude data from Sodankylä Finland, (67.4 N,
26.7 E) with Bremer's results for mid-latitudes, and with other ionosonde
records. While Sodankylä shows a linear decrease of the peak height
during the last 40 years, the same trend is not observed at all locations
in this study.
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dioxide and methane modify the mean structure of the mesosphere
and thermosphere?, Geophys. Res. Lett. 16, 1441-1444.
- Rishbeth, H. (1990) A greenhouse effect in the ionosphere?, Planet.
Space Sci. 38, 945-948.
- Bremer, J. (1992) Ionospheric trends in mid-latitudes as a possible
indicator of the atmospheric greenhouse effect, J. Atmos. Terr.
Phys. 54, 1505-1511.