INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. 36: 987 – 1004 (2016) Published online 30 June 2015 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/joc.4401 Extreme temperature and precipitation events over Italy: assessment of high-resolution simulations with COSMO-CLM and future scenarios Alessandra Lucia Zollo, a,b * Valeria Rillo, a Edoardo Bucchignani, a,b Myriam Montesarchio a,b and Paola Mercogliano a,b a Regional Models and Geo-Hydrogeological Impacts Division, Centro Euro-Mediterraneo sui Cambiamenti Climatici (CMCC), Capua, Italy b Meteorology Laboratory, Centro Italiano Ricerche Aerospaziali (CIRA), Capua, Italy ABSTRACT: This study presents a detailed analysis of the present and expected future extreme climate conditions over Italy through the use of some extreme indicators. Climate data for this analysis were provided by the regional climate model COSMO-CLM, using different grid spacing to ascertain the real importance of using higher resolution climate data, especially over such a complex topography as Italy. Four simulations were carried out at spatial resolutions of 0.125 ∘ and 0.0715 ∘ , driven by ERA-Interim Reanalysis and the CMCC-CM global model. We investigated the ability of the model to represent realistically the climatology of a subset of climate indicators defned by the Expert Team on Climate Change Detection and Indices (ETCCDI) for precipitation and temperature. Several high-resolution observational data sets available over some Italian regions were therefore used in order to offset the limited number of observations available over Italy in the E-OBS data set and its coarse grid. We found that the increase in resolution could have interesting benefts in representing such extreme indices, especially in the more orographically complex areas. Finally, we investigated future climate changes regarding extreme weather events expected under anthropogenic climate change scenarios, employing the IPCC RCP4.5 and RCP8.5 greenhouse gas concentrations, showing that such events are expected to increase over Italy. KEY WORDS extremes; regional scenarios; high-resolution simulation; climate change Received 10 November 2014; Revised 11 May 2015; Accepted 11 May 2015 1. Introduction The warming of the climate system in recent decades is evident from observations and is mainly related to the increase in anthropogenic greenhouse gas concentrations (IPCC, 2012). The effects of climate change do not only affect mean regimes but also extreme events. Indeed, a changing climate may lead to changes in the frequency, intensity, spatial extent, duration and timing of weather and climate extremes. It is of great importance for regional and local institutions to be aware of risks related to present and future climate extremes in order to develop suitable adaptation strategies. The world’s largest reinsurance com- pany, Munich Re, has calculated that more than 90% of all disasters and 65% of associated economic damage are weather- and climate-related (Munich Re, 2011). More specifcally, in recent years, Italy has been struck by sev- eral high-intensity weather events, which caused serious damage and loss of human life due to demographic vulner- ability (high-density population) and orographic features. From the analysis of historical series for Italy (Brunetti et al., 2006), a change in temperature and precipitation * Correspondence to: A. L. Zollo, Meteorology Laboratory, Centro Ital- iano Ricerche Aerospaziali (CIRA), via Maiorise s.n.c., Capua, CE 81043, Italy. E-mail: a.zollo@cira.it patterns in the last two centuries has been detected: in terms of mean annual values, a fairly uniform temperature increase of 1 ∘ C per century has been observed, with a gen- erally higher trend for minimum than maximum tempera- tures. Moreover, Brunetti et al. (2001) found a reduction in low-intensity and an increase in high-intensity precipi- tation events over the 20th century. Assessment and projection of extreme weather trends are very important issues for society as they represent a fundamental step to provide risk assessment. However, evaluation of weather extremes and their changes is more complicated to study and harder to predict than average cli- mate properties because extremes are, by defnition, rare events (García-Cueto and Santillán-Soto, 2012). Regional climate models (RCMs) can be considered useful tools for assessing climate extremes as they are able to cap- ture extreme events sometimes entirely absent in general circulation model (GCM) simulations (IPCC, 2001). In particular, in regions where local features affecting the atmospheric fow, such as topography and coastal pro- cesses, are prevalent, fner-resolution simulations with state-of-the-art mesoscale models are required to repro- duce observed weather and climate (Soares et al., 2012). Changes in the occurrence of extreme events in Europe have been investigated by Beniston et al. (2007), using © 2015 Royal Meteorological Society