International Conference: Problems of Geocosmos
Is there a Greenhouse Cooling
in the Upper Atmosphere?
Thomas Ulich and Esa Turunen
Geophysical Observatory, FIN-99600 Sodankylä, Finland
Increased concentrations of greenhouse gases in the air cause a cooling of
the strato-, meso-, and thermosphere (Roble and Dickinson, 1989); the
atmosphere is expected to shrink. Rishbeth (1990) predicted a lowering of
the peak height of the ionospheric F2 layer by 15-20 km for doubling of the
mixing ratios of carbon dioxide and methane.
Lidar measurements in southern France show a cooling of about 4 K between 60
and 70 km altitude for a period of 10 years between 1980 and 1990 (Hauchecorne
et al., 1991). These records, however, span less than a solar cycle and
are therefore too short to reveal long-term changes.
Bremer (1992) observed lowering of the F2 layer peak height at
Juliusruh/Rügen, Germany, which he intepreted in agreement with
Rishbeth's prediction to be due to greenhouse cooling.
We compare long-term data from Sodankylä, Finland, with other ionosonde
records. The evolution of the F2 peak height varies considerably
among the stations studied in this work; while Sodankylä data shows
generally lowering of the F2 peak height, this is not observed in all
four seasons and not at all locations analyzed in this study.
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