High-resolution climate-driven potential evapotranspiration to assess climate change impacts on Mediterranean agriculture

Abstract

Potential evapotranspiration ( PET ) is a key driver of agricultural water demand, its estimation remains uncertain, particularly in topographically complex, water-limited regions such as the Iberian Peninsula (IP). This study develops and applies a high-resolution PET framework that first evaluates PET across multiple climate datasets, then uses the most suitable dataset to quantify future changes in atmospheric water demand and assess their implications for regional climatic stress and crop evapotranspiration across the Iberian Peninsula. PET is computed using the Hargreaves method for CHELSA, E-OBS, and ERA5-Land, and compared with PET from the Copernicus Climate Change Service CMIP6 Atlas for 1991–2010. Among the evaluated datasets, CHELSA offers the highest spatial resolution while maintaining consistency with the other evaluated datasets, allowing the representation of fine-scale physiographic gradients that are not resolved in the coarser CMIP6 fields. Although this added spatial detail improves the representation of regional climatic variability, it does not necessarily imply higher accuracy in the absence of independent observational validation. CHELSA was therefore selected to analyse future PET under SSP1-2.6, SSP3-7.0, and SSP5-8.5 (2041–2100). A ranking approach is applied to temperature, precipitation, PET , and climatic water balance at the NUTS-2 level to regionalise climatic stress across the IP. Further, PET is combined with FAO-56 crop coefficients to map ETc for vineyards, olive groves, and fruit trees throughout the IP. Results show an increase of high PET values across the IP. Under SSP5-8.5, central and southern Iberia exceeds 1,400–1,600 mm/year by the late century, and even Atlantic and mountain regions are projected to experience substantially higher evaporative demand than during the historical reference period. Ranking analysis indicates that climatic stress is higher in the interior (e.g., Castilla-La-Mancha, Extremadura, Madrid, Castilla y León, and Centro-Portugal). Crop-specific ETc increases across all regions, with olive groves and fruit-tree orchards in southern and eastern IP showing the greatest intensification, thereby indicating greater potential pressure on irrigation systems for perennial agriculture. Hence, the study demonstrates the added value of high-resolution, climate-driven PET for impact assessment, while highlighting the need for adaptation in water management, crop zoning, and agricultural practices under future climate change.