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Temperature trends

The increase of anthropogenic greenhouse gases and their effects on global climate change has been widely investigated for atmospheric layers close to the ground in the current climate debate.

The global change of the temperature in the middle atmosphere maximizes in the altitude range from 50 to 75 km. In the atmosphere above ~8 km, there is a reversal in the temperature trend: an increase in the level of greenhouse gases leads to an additional cooling of the middle atmosphere induced by enhanced infrared emission to space. Any investigation about the physical causes of this rapid change in the upper atmosphere might only be answered by numerical climate models (e.g. LIMA). We conclude that the balance of infrared radiation is mainly determined by carbon dioxide and ozone.

Only a few long-term time series of observations exist, e.g., lidar temperature measurements in France since 1979, which document prominent temperature trends of about 3-4 Kelvin per decade at heights near 65-70 km at midlatitudes in summer (see Fig 1). These measurements demonstrate beyond doubt that the cooling of the upper atmosphere is about a factor 10 larger than the greenhouse warming near the surface. Hence, the height region of 50-75 km appears to be a powerful indicator for efficiently detecting a climate signal.

The figure shows temperature trends from different observations (July, 45°N) and calculated trends from LIMA, adapting different reanalyses in the lower altitude range (0-45 km, "20th century": 0-28 km).

Selected publications

  • F.-J. Lübken, G. Baumgarten and U. Berger, Long term trends of mesopheric ice layers: A model study, J. Atmos. Solar-Terr. Phys., doi:10.1016/j.jastp.2020.105378, 2021.
  • F.-J. Lübken, U. Berger, and G. Baumgarten, Temperature trends in the midlatitude summer mesosphere, J. Geophys. Res., 118, 13347-13360, doi:10.1002/2013JD020576, 2013.
  • U. Berger and F.-J. Lübken, Mesospheric temperature trends at mid-latitudes in summer, Geophys. Res. Lett., L22804, doi:10.1029/2011GL049528, 2011.