Already man-made climate changes are clearly evident around cities. Buildings and pavement tend to store more heat than vegetation in the surrounding countryside, hence temperatures can range some 4.0 degrees higher in the summer and 2.0 degrees higher in the winter.
Hansen says that UHI makes cities cooler
Such “heat islands” change wind patterns including creation of vertical plumes of hot air rising some 3,000 feet over some cities. As a result, a survey of nine American cities showed increased rainfall in the vicinity ranging from 9.0 to 27.0 percent. The severity of these storms is also affected. Near Houston, Tex., hailstorms were found to increase by 430 percent. The most detailed of these studies is under way in the St. Louis area, where an urban-related 25 percent increase of thunderstorms was found to affect some 1,000 to 2,000 square miles of the surrounding area. The cumulative effect of such changes from all cities is not known, but the possible interactions increase the likelihood of severe consequences as urbanization continues.
