Are heavy rainfalls in central Italy influenced by climate changes?

In recent years there is a growing concern by the community, scientific and not, about global warming and climate changes. The fact that the global temperature is growing up after the increase of the greenhouse gases emissions is already known, but there is still wondering about its effect on the hydrological cycle and most of all on rainfalls. Many studies supported by the Intergovernmental Panel on Climate Change (IPPC) showed that there is a general increase of heavy rainfalls also in areas where total annual precipitation is not prominently changed. Changings about frequency, intensity, duration in rainfalls and in weather events in general are still object of wonderings and past studies referred to different regions don’t give an unanimous answer about their trends. Mediterranean Area, which includes Italy, is supposed to be one of the most reactive to the climate changes and strong effects of them are expected. This paper deals with the rainfall tendencies in Umbria Region, Central Italy, since almost all the regional territory is included in the Upper Tiber River Basin and many areas are prone to risk of flooding. The climate of Umbria region is variable from areas to areas, in fact the weather is cold and wet in the East areas, near the Apennine Mountains and hotter and drier in the West, close to Tuscany region. Because of this variability a lot of raingauges had been placed in the last 10-15 years and nowadays a very dense raingauge network is present (more than 90 raingauges for a regional area of 8464,33 Km2, about one station each 90 Km2). The aim of this paper is to analyse if the climate changes caused effects on the rainfalls’ intensity in Umbria. Three meteorological stations have been selected: Città di Castello, Todi and Orvieto. They provide the longest series of data and the best quality in their measurements because raingauges have never been relocated. Rainfall measurements began in the thirties and have gone on until nowadays even if there are some interruptions (most of all during the years of the Second World War). For each year there are maxima for 6 durations:1, 2, 3, 6, 12 and 24 hours. The analyses of the data of the three stations, and most of all the one referred to Todi, whose geographical position is barycentric in the regional territory, show that there are not considerable changes in rainfall maxima and intensities in the last seventy years.