Spatiotemporal variability and trends of urban light pollution in global cities

The continuing urbanization process is expected to exacerbate various impacts on the natural environment, such as thermal changes at the local scale in densely populated urban neighborhoods. One of the side consequences of urbanization is the need for nighttime artificial lighting primarily to provide visibility, for safety reasons, and for ornamental illumination of monuments, buildings, parks, etc. To understand the rather complex issue of the spatial distribution of artificial light at night and its links to population density, urban form, and function, the patterns of nighttime radiance (NTR) at the local level should be studied on the grounds of a globally defined and well-recognized classification of urban neighborhoods. The Local Climate Zone (LCZ) scheme was initially designed to analyze local temperature variations and urban heat island effects at the local scale. Despite that, its applications, such as climate-sensitive design, building energy consumption, carbon emissions, quality of life, air quality, urban vegetation phenology, and ecosystem patterns, grow exponentially. This contribution addresses the following research questions: (1) Are LCZ classes a suitable urban typology to provide detailed information on light pollution derived from satellite measurements? (2) What are the recent trends in urban light pollution in individual types of LCZ? (3) Do regional differences or significant trends exist in urban light pollution? (4) Can a spatiotemporal analysis of nighttime radiance across LCZ assess the effects of technological innovations and implementation of light pollution-reducing policies in urban lighting? Overall, we aim to start a cross-disciplinary discussion on the methods of assessing urban light pollution on the urban neighborhood (local) level.