Climate change scenarios for temperature and precipitation in Aragón (Spain).

By applying a two-step statistical downscaling technique to four climate models under different future emission scenarios, we produced future projections of the daily precipitation and the maximum and minimum temperatures over the Spanish region of Aragón. The reliability of the downscaling technique was assessed by a verification process involving the comparison of the downscaled reanalysis data with the observed data--the results were very good for the temperature and acceptable for the precipitation. To determine the ability of the climate models to simulate the real climate, their simulations of the past (the 20C3M output) were downscaled and then compared with the observed climate. The results are quite robust for temperature and less conclusive for the precipitation. The downscaled future projections exhibit a significant increase during the entire 21st century of the maximum and minimum temperatures for all the considered IPCC future emission scenarios (A2, A1B, B1), both for mid-century (increases relative to the 1971-2000 averages between 1.5°C and 2.5°C, depending on the scenario) and for the end of the century (for the maximum temperature of approximately 3.75°C, 3.3°C, and 2.1°C for A2, A1B, and B1 scenarios respectively, and for the minimum temperature of 3.1°C, 2.75°C, and 1.75°C). The precipitation does not follow such a clear tendency (and exhibits greater uncertainties), but all the scenarios suggest a moderate decrease in rainfall for the mid-century (2-4%) and for the end of the century (4.5-5.5%). Due to the clear spatial differences in climate characteristics, we divided the studied area into five sub-regions to analyse the different changes on these areas; we determined that the high mountains (Pyrenees, Mediterranean-Oceanic transitional climate) and the lands of the Ebro River Basin (Continental sub-Mediterranean climate) will probably be the most affected.