Climate and Bioclimate Change in Different Climatic Areas in Italy

In the current study trends in precipitation and temperatures recorded during the last century in three different climatic areas in Italy were investigated and compared. The three areas are the River Reno mountain watershed (Re) located in the continental area, the Calabria region (Ca) located in the South of the peninsula and Sicily (Si), an island also located in the South. Bioclimatic parameters, such as evapotranspiration and aridity index were also analysed to check the climate change effects on vegetation. Seasonal and annual total rainfall and mean temperature, measured in 187 precipitation stations and in 50 thermometric stations during the 1921-2007 period, were checked with the Mann-Kendall non-parametric test, at a 0.05 probability level, to look for a trend. Moreover, the linear trend analysis was also performed in order to display the linear regression in the examined period. Trend-line slopes (b) were calculated by the least-square linear fitting method. Ten-year-running average was analysed to show long-term tendencies. The overall results showed the importance of climate change analyses on a regional scale. In fact, the Linear Regression Coefficients (b), and sometimes even their sign (positive or negative), were very different in the areas studied. Yearly precipitation (Py) decreased in all the areas (b equals to -209, -320 and -285mm/100 years in Re, Ca and Si, respectively) whereas, on a seasonal scale, the linear trends were negative or positive in the different quarters of the year and areas. Minimum temperature (Tymin) generally increased in all the areas, whereas maximum temperature (Tymax) showed both an increasing and a decreasing trend. As a consequence, mean temperature showed a positive trend for Re (b = 1.2-1.9°C/100 years) and Si (2°C/100 years) whereas a slight decreasing trend (-0.8 °C/100 years) was observed in Ca. Considering the opposite trends in Tymin and Tymax, evapotranspiration (ET0) decreased in both Re (-43-342 mm/100 years) and Ca stations (-112mm/100 years), whereas no significant trend was detected in Si. Due to the fine scale effects of precipitation and temperature variations, the trend of the aridity index confirmed that only the island (Si) is particularly vulnerable to water stress and desertification processes under climate change conditions, although the aridity conditions were increased in all the regions.