Thermal infrared radiation trends in Switzerland

Downward Thermal Infrared Radiation (DTIR) is the Earth’s radiative energy budget component anticipated to undergo the strongest changes due to climate warming (increasing DTIR should be the most direct consequence of an increasing greenhouse effect). Long-term DTIR time series (25-30 years) are becoming available and allow testing whether the DTIR trends are as expected, particularly if they are significantly positive. Long-term monitoring of DTIR is performed at four stations in Switzerland since the mid-1990’s and corresponding trend analysis showed that these are generally significantly positive. However, trends computed on periods of various length show a significant variability and point to inhomogeneity in the time series most likely due to instrument calibration. It is shown that such inhomogeneity can be resolved by calibration adjustment if DTIR redundant measurements are performed and raw data are available.