A Positive Greenhouse Effect

The huge number of greenhouses in Almeria, Spain reflect so much sunlight back into the atmosphere that they are actually cooling the province, Spanish researchers have found. Scientists from the University of Almeria reported in the Journal of Geophysical Research that while the rest of Spain has warmed by .5° C (.9° F) since 1983, Almeria has cooled by .3° C (.5° F). Using satellite images and data, the scientists then determined that the white roofs of the greenhouses reflect far more radiation back into the atmosphere than the semi-arid pastureland surrounding the greenhouses. Almeria now has the largest concentration of greenhouses in the world, covering 26,000 hectares (64,000 acres). The researchers say their greenhouse work shows the value of covering buildings and other surfaces, such as roads, with light-colored surfaces in order to counteract rising temperatures from the other greenhouse effect.