Cities are well known hot spots – literally. The urban heat island effect has long been observed to raise the temperature of big cities by 1 to 3°C (1.8 to 5.4°F), a rise that is due to the presence of asphalt, concrete, buildings, and other so-called impervious surfaces disrupting the natural cooling effect provided by vegetation. According to a new NASA study that makes the first assessment of urbanization impacts for the entire continental United States, the presence of vegetation is an essential factor in limiting urban heating.
Impervious surfaces’ biggest effect is causing a difference in surface temperature between an urban area and surrounding vegetation. The researchers, who used multiple satellites’ observations of urban areas and their surroundings combined into a model, found that averaged over the continental United States, areas covered in part by impervious surfaces, be they downtowns, suburbs, or interstate roads, had a summer temperature 1.9°C higher than surrounding rural areas. In winter, the temperature difference was 1.5 °C higher in urban areas.
“This has nothing to do with greenhouse gas emissions. It’s in addition to the greenhouse gas effect. This is the land use component only,” said Lahouari Bounoua, research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study.
So where have we seen a map like that before? Oh yes, the 2012 election map.
A few differences. The Upper Peninsula of Minnesota is liberal with out being warm (I blame the Canadians). The large liberal area in the Southwest that's not warm? It turns out there's actually a scientific explanation for that:
In cities like Phoenix built in the desert, the urban area actually has a cooling effect because of irrigated lawns and trees that wouldn’t be there without the city.