Climate-change related evolution of future building cooling energy demand in a Mediterranean Country

The Mediterranean area is especially vulnerable to climate change and is already experiencing a notable increase in the demand for cooling residential buildings. This study investigates the evolution of the Cooling Degree Hours (CDHs) across Italy for the cooling seasons in the last two decades (2001–2020) as well as projecting the future evolution for the years 2050 and 2080 following two scenarios designed by the Intergovernmental Panel on Climate Change. Building cooling energy demand of buildings is proportional to CDHs, which reflect both the duration and the magnitude of cooling needs. CDHs are calculated using hourly outdoor temperature, extrapolated here from the gridded outputs of the Weather Research and Forecasting (WRF) model. Italy was chosen as a case study due to its geographical position and its climatic variety. For analytic purposes, the dataset of past and future CDH was clustered into four 5-years groups. Results for 2001–2005 and 2006–2010 are similar, whilst marked differences show an almost exponential growth appearing in the two more recent 5-year periods. For example, in 2011–2015 the median CDH is about two times that of previous years; in 2016–2022 this becomes four times. The maximum levels of mapped CDHs in the last 5-years period are almost twice those of the first period. As for the four future cases, the 2080-RCP8.5 case differs significantly from the others, especially in the highest values. This behavior mainly affects specific areas, such as big cities, the Po valley and coastal urban areas of South Italy that were already the warmest at the beginning of the 21st century. These changes demonstrate future high building cooling demands in densely populated areas. A combination of CDHs and demographic data allows to prioritize the Italian regions in terms of interventions to upgrade the existing building stock.