Origins and Evolution of the Local Climate Zone Classification

Systematic comparison of urban and rural air temperatures began over two centuries ago. This work demonstrated that cities are warmer, on average, than their rural surroundings. A century later, isothermal maps of cities were produced for the first time, and the term urban heat island was introduced to describe the common pattern of warmth associated with urban areas. However, as studies of the heat island proliferated worldwide, weaknesses were exposed in the communication of metadata about the field sites used in and around cities. The Local Climate Zone (LCZ) classification was introduced in 2012 to help overcome these weaknesses, and to consolidate earlier classifications of built form and urban heat. LCZs depict local landscapes that are defined by key urban canopy parameters, and that represent the diversity of field sites in urban temperature studies. Since 2012, global acceptance of the LCZ system has improved communication in the heat island literature, and enhanced interdisciplinary exchange of heat island properties, datasets, and methodologies. In recent years, use of LCZs has evolved well beyond the observational study of heat islands, to include mapping and modelling of urban environments for studies of human health, urban design, weather forecasting, climate mitigation/adaptation, and global environmental change. As use of the LCZ classification continues to grow, awareness of its origins and evolution becomes increasingly important for steering progress in the field.