Climate Change Projections of Aridity Conditions in the Iberian Peninsula

The assessment of aridity conditions is a key factor for water management and the implementation of mitigation and adaptation policies in agroforestry systems. Towards this aim, three aridity indices were computed for the Iberian Peninsula (IP): the De Martonne Index (DMI), the Pinna Combinative Index (PCI), and the Erinc Aridity Index (EAI). These three indices were first computed for the baseline period 1961-1990, using gridded observational data (E-OBS), and subsequently, for the periods 2011-2040 (short range) and 2041-2070 (medium range), using an ensemble of six regional climate model (RCM) experiments generated by the EURO-CORDEX project. Two representative concentration pathways (RCPs) were analyzed, an intermediate anthropogenic radiative forcing scenario (RCP4.5) and a fossil-intensive emission scenario (RCP8.5). Overall, the three indices disclose a strengthening of aridity and dry conditions in central and southern Iberia until 2070, mainly under RCP8.5. Strong (weak) statistically significant correlations were found between these indices and the total mean precipitation (mean temperature) along with projected significant decreasing (increasing) trends for precipitation (temperature). The prevalence of years with arid conditions (above 70% for 2041-2070 under both RCPs) are projected to have major impacts in some regions, such as southern Portugal, Extremadura, Castilla-La Mancha, Comunidad de Madrid, Andalucia, Region de Murcia, Comunidad Valenciana, and certain regions within the Aragon province. The projected increase in both the intensity and persistence of aridity conditions in a broader southern half of Iberia will exacerbate the exposure and vulnerability of this region to climate change, while the risk of multi-level desertification should be thoroughly integrated into regional and national water management and planning.