An Assessment of the Magnitude of Urban Heat Islands

The differences in temperature between rural and urban stations have been used to quantify the magnitude of urban heat islands. However, there are a number of other influences that make it difficult to isolate the urban effect. The assessment presented in this paper attempts to remove as many non-rural/urban effects as possible prior to the analysis. These include differences in temperature caused by factors such as differences in the elevation of the stations, differences in the time of day that the observations were made, and differences in instrumentation. The magnitude of the determined rural/urban temperature difference may not represent the extremes of the urbanization effect because the urban stations may not be in the most heavily urbanized area. However, it does represent the magnitude of the urban contamination of historic temperature change signals.