The increase of temperatures and the decrease of precipitation are the two main settings of the actual hypothesis about climatic change in the Mediterranean area. The book analyses the development of the basic climatic elements in Valencia and Murcia during the last fifty years. The analysis is based on a strict selection of both, urban and rural observatories, the review of climatic fluctuations, the study of the atmospheric dynamism in the Mediterranean area - one of the most complex in the world - and a detailed exposition of the possible factors that cause climatic change. J. Quereda, E. Montón and J. Escrig belong to the Estació de Climatologia de la Universitat Jaume I, and A. Gil, J. Olcina and A. Rico are members of the Institut Interuniversitari de Geografia de la Universitat d'Alacant.