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
Abstract
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.
References:
- Roble, R. G., Dickinson, R. E. How will changes in carbon dioxide
and methane modify the mean structure of the mesosphere and
thermosphere? Geophysical Research Letters, pt. 12. Suppl.
to vol. 16, p. C1441, 1989.
- Rishbeth H., A greenhouse effect in the ionosphere? Planetary and
Space Science, pt. 7. Suppl. to vol. 38, p. C945, 1990.
- Hauchecorne, A., Chanin M.-L., Keckhut, P. Climatology and trends of
the middle atmospheric temperature (33-87 km) as seen by Rayleigh
Lidar over the south of France, Journal of Geophysical Research,
pt. D8. Suppl. to vol. 96, p. C15297, 1991.
- Bremer, J., Ionospheric trends in mid-latitudes as possible indicator
of the atmospheric greenhouse effect, Journal of Atmospheric and
Terrestrial Physics, pt. 11/12. Suppl. to vol. 54,
p. C1505, 1992.