Séminaire
Extreme climate events are those events that occur with extraordinary low frequency during a certain period of time (rarity), showing a very high magnitude (intensity) or duration, and causing sizeable impacts. Extreme weather and climate events include: heat waves, hot/cold spells, drought, extreme rainfall, hail storms, thunderstorms (supercells, squall lines), tornadoes, tropical cyclones, windstorms, winter storms (blizzard, ice storms, snowfalls), etc, while derived disasters include land slides, flash flood, wildfire, etc.
Changes in extreme weather and climate events have significant impacts on several sectors ranging from agriculture to energy, health, tourism, transport with consequent large impacts on the economies and on the population. It is widely recognized that extreme events today are among the most serious challenges to society in coping with a changing climate (CCSP, 2008), and confidence has increased that some extremes will become more frequent, more widespread and/or more intense during the 21st century (IPCC, 2007, 2013). Due to their impacts, the demand for information services on weather and climate extremes is growing, and the sustainability of economic development and living conditions certainly depends on our ability to manage the risks associated with extreme events.
Daily values of precipitation, minimum and maximum temperatures observed in Italy have been used in order to asses the changes in climate extremes occurred in the Country. The analysis has been performed using the RClimDex software specifically designed to evaluate the 27 indices suggested by the Climate Variability and Predictability Expert Team for Climate Change Detection Monitoring and Indices (
CLIVAR–ETCCDMI
). Results show, for temperatures, a significant increase of tropical nights and summer days, and a decrease of the number of cold days and days with frost. The extreme precipitation analysis does not show changes as evident as for the temperatures, however a small decreasing trend of total rainfall is captured in most of the stations, together with a decrease of the number of rainy days. Moreover the decrease in the cumulated rainfall as well in the total number of rainy days shows seasonal differences, while a change has been detected in the last few decades in the extremes and in the number of days exceeding fixed thresholds. Since the changes are not the same in all the Italian regions, some considerations will be presented relating the differences of extreme climate indices to the specific geographical features, and, for some of the extremes, their occurrence is analyzed also in relation to large scale configurations and weather types defined over Central Mediterranean. Finally, some considerations will be presented on the impacts of extreme events, which are the major reason for the increased request for the implementation of tailored climate services, on two sectors: human health (heat waves), and agriculture (hot spells, excess/deficit rainfall), which represents one of the most important sectors in the economy of the Country.