Climate FAQs: Urban Heat Island Effect

What about the urban heat island effect

Claims have been made that the surface temperature measurements are tainted by the proximity of data-generating thermometers to cities. While amplified warming does occur in urban areas and is an important local phenomenon, a number of independent and recent scientific studies have shown that urbanization is a negligible effect as far as continental- and hemispheric-space averages are concerned. Over land, temperature data come from fixed weather observing stations with thermometers housed in special instrument shelters. Records of temperature from many thousands of such stations exist. Some are in urban areas. Many are not.

One concern regarding the construction of global temperature records is the variety of changes that may affect temperature measurements at an individual station. For example, the thermometer or instrument shelter might change, the time of day when the thermometers are read might change, or the station might move. These problems are addressed through a variety of procedures (for example, checking for consistency with data from neighboring stations) that have proven to be very effective. Other, perhaps more subtle influences (e.g., urbanization) are addressed either actively in the data processing stage or through dataset evaluation to ensure as much as possible that the data are not biased. For instance, several studies have compared global surface temperature time series made up of only rural stations with the "standard" global temperature time series, only to find out that there is no significant bias.