Are European Cities Getting Warmer? Investigating the Urban Heat Island Phenomenon in Europe from 1981-2018 through the Use of NOAA-AVHRR Data

The Urban Heat Island (UHI) effect is one of the most prominent signs of human impact on the Earth system. This phenomenon has significantly altered the energy exchange between land surfaces and the atmosphere which has led to several negative impacts on the quality of city life in terms of air and water quality, energy consumption, vegetation growth and human health. European cities are particularly vulnerable to UHI because of their high degree of urbanization, as illustrated by the 2003 heatwave which claimed thousands of lives. However, the existing body of research mostly concentrates on local-scale and/or short-term analyses, which leaves long-term effects at continental scale poorly understood. Within the TIMELINE project of the Earth Observation Center (EOC) of the German Aerospace Center (DLR), a consistent AVHRR Land Surface Temperature (LST) product has been generated, which is employed in this study to determine the intensity of the surface UHI (SUHI) over Europe for the period 19812018. Specifically, the objective is to analyze the long-term SUHI trends and corresponding changes over European cities, as well as to gain insights on their relationships with different variables, like climate, land use and land cover (change), vegetation indices and day-night temperature differences. First results point towards a remarkable increase in both SUHI spatial extent and intensity across the entire continent.