Poster for NSSR Meeting 1996, Oslo, Norway

Is there Greenhouse Cooling in the Thermosphere?

Thomas Ulich and Esa Turunen

Geophysical Observatory, FIN-99600 Sodankylä, Finland

Abstract

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.

References:

Roble, R. G., and Dickinson, R. E., (1989) How will changes in carbon 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.