The majority of the population of the planet (6.6 billion) now live in urban areas, which have distinct impacts upon climate at scales from the local to the global. This urban effect is due to the physical form of the city (its three-dimensional geometry and material composition) and its functions (the day-to-day activity patterns that generate emissions of waste heat and materials into the overlying air). While a substantial body of knowledge on the science of urban climates has been developed over the past fifty years, there is little evidence that this knowledge is incorporated into urban planning and design practice. This paper focuses on this gap by examining the nature of urban climate expertise and the needs of those that make decisi...