CNN admits: In warming cities, urban heat island effect more important than greenhouse effect

Heat waves on the rise in big cities - CNN.com

There are two reasons for the increase in urban areas. First, temperatures in cities are rising because of the global greenhouse effect, which is intensifying as the vehicles we drive and the energy we consume emit more and more greenhouse gases.

Second, and more important, cities are warming because of the loss of trees and other natural land cover to make way for buildings, streets, and parking lots, which are composed of materials that absorb far more thermal radiation than the natural landscape.

Because of these two effects -- one global, the other local -- most large American cities are warming at more than twice the rate of their outlying rural areas and the planet as a whole, and this accelerated pace is at the root of the increasing frequency of heat waves.