Warming ecosystems in complex terrain – insights from four years of thermal infreared research in the Swiss bio-hydro-cryo spheres

Switzerland is among the regions experiencing the strongest warming trends in Europe, with air temperatures increasing well above the global mean. This amplified warming leads to heat stress across terrestrial, aquatic, and cryospheric ecosystems, affecting water availability, ecosystem functioning, and land–atmosphere energy exchange. Capturing these processes requires observations that directly resolve surface temperature dynamics at high spatial and temporal resolution.

Thermal Infrared (TIR) remote sensing has emerged as a key approach to address this need, particularly in light of upcoming satellite missions such as ESA LSTM, CNES/ISRO TRISHNA and NASA SBG-TIR. Over the past four years, different ecosystems in Switzerland have served as testbeds for advancing TIR-based ecosystem research within the ESA PRODEX-funded TRISHNA – Science and Electronics Contribution (T-SEC) project.  

This contribution synthesises scientific insights gained from T-SEC, highlighting recent methodological and instrumental advancements in thermal remote sensing. Key developments include modelling of thermal directionality, advances in calibration and validation strategies, and the use of field campaigns and laboratory measurements to better quantify uncertainties in TIR observations at different spatial, temporal, and spectral scales.  

The presented work spans a range of contrasting ecosystems, including Swiss forests, alpine glaciers and permafrost sites, and perialpine and alpine lakes.  Together, these case studies illustrate the potential and challenges of TIR remote sensing for monitoring ecosystem heat stress, water status, and energy fluxes – always with a particular focus on complex terrain. The results underline the importance of multi-scale, multi-sensor approaches to accurately retrieve surface temperature information. Such information is crucial for understanding ecosystem responses to a rapidly warming climate and for fully exploiting the capabilities of next-generation thermal satellite missions.