Does the Enhanced Greenhouse Effect Affect the Upper Atmosphere?

Thomas Ulich

Sodankylä Geophysical Observatory, Sodankylä, Finland


The concentration of tropospheric carbon dioxide at Mauna Loa, Hawaii, has increased by about 13.5% between 1958 and 1994. Based on the assumption of doubled greenhouse gases, numerical models predict the stratopause to cool by up to 15 K. The mesosphere and thermosphere are expected to cool by 10 K and up to 90 K, respectively.

Evidence of this "greenhouse cooling" is limited. Temperature measurements from satellites and by lidar show cooling trends. However, these time series are still too short in order to draw definite conclusions. Decades of temperature measurements by sounding rockets suffer from their irregular distribution in time and location, but seem to agree that the atmosphere between 25 km and 75 km altitude has cooled slightly. The absorption of cosmic radio noise in the ionospheric D region is suggested to decrease due to mesospheric cooling. The altitude of maximum electron density is expected to lower due to shrinking of the underlying cooling atmosphere.

Here I will give a brief overview of the long-term behaviour seen in the data of various instruments. I will compare these observations with those of the Sodankylä Geophysical Observatory's long-term geophysical data from the European Arctic.