Infrared Backradiation under low humidity conditions: An Evaluation of Greenhouse Gas Impact

Ernst Hammel, Martin Steiner, Robert Glaubauf

This study examines the impact of greenhouse gases (GHG) on infrared back radiation (IRBR) in extreme desert and midlatitude winter conditions. Employing MODTRAN simulations, pyrgeometer measurements and energy balance fit models, we assess the impacts of CO₂, Argon (Ar), N2O and R-134a. Results indicate that increasing CO₂ concentrations yield a very limited additional IRBR effect, whereas R-134a exhibits significant radiative forcing even at trace levels. These findings highlight the critical role of synthetic GHGs in climate dynamics and provide insights into radiative forcing in arid regions, enhancing climate model accuracy for desert environments and contribute to the general assessment of the impact of increasing CO₂ concentrations in our atmosphere. Likewise, these measurements have shown again that the contribution of CO2 to the total back radiation is largely saturated within the historical concentration boundaries far beyond current levels and back radiation by water vapor is the dominant effect.