Mapping the evolution of outdoor summer thermal comfort in a Mediterranean country in the context of climate change

Climate change is modifying the outdoor thermo-hygrometric conditions to which people are subjected and the Mediterranean basin is particularly exposed to it, as it is scientifically classified by the IPCC as a climate change hotspot. The region experiences a rate of surface warming roughly 20% faster than global averages, coupled with severe summer rainfall decreases. This paper investigates the alterations of such conditions in Italy using a dataset of Mediterranean Outdoor Comfort Index (MOCI) hourly values produced through the Weather Research and Forecasting model for the past, current and future conditions under the Representative Concentration Pathways scenarios of the Intergovernmental Panel on Climate Change. The spatial-temporal variations of the MOCI index in the period from May to September are studied both at the national level through cartography and at the local level (at the level of single city point) through statistical approaches. Three cities with different climates are considered, namely Milan, Rome and Palermo. From the beginning of XXI, a reduction of 27.2% in cold sensations and an increase of 22.7% in heat sensations occurred. In the cities analyzed, the thermal stress will be more intense, frequent (MOCI close to 3) and long-lasting (50% of the period characterized by MOCI ' +1) in the future. This research provides indications that the deterioration of outdoor thermo-hygrometric conditions over the coming decades in several regions of a Mediterranean country (with prolonged periods of severe biometeorological stress) will significantly limit normal outdoor activities for extended periods and will consequently require a radical change in the behavior of local populations.