Effect of climate change on reference evapotranspiration at the subnational scale: case study of Egypt

Purpose - This study’s fundamental objective is to assess climate change impact on reference evapotranspiration (ETo) patterns in Egypt under the latest shared socioeconomic pathways (SSPs) of climate change scenarios. Additionally, the study considered the change in the future solar radiation and actual vapor pressure and predicted them from historical data, as these factors significantly impact changes in the ETo. Design/methodology/approach - The study utilizes data from the Coupled Model Intercomparison Project Phase 6 (CMIP6) models to analyze reference ETo. Six models are used, and an ArcGIS tool is created to calculate the monthly average ETofor historical and future periods. The tool considers changes in actual vapor pressure and solar radiation, which are the primary factors influencing ETo. Findings - The research reveals that monthly reference EToin Egypt follows a distinct pattern, with the highest values concentrated in the southern region during summer and the lowest values in the northern part during winter. This disparity is primarily driven by mean air temperature, which is significantly higher in the southern areas. Looking ahead to the near future (2020–2040), the data shows that Aswan, in the south, continues to have the highest annual ETo, while Kafr ash Shaykh, in the north, maintains the lowest. This pattern remains consistent in the subsequent period (2040–2060). Additionally, the study identifies variations in ETo, with the most significant variability occurring in Shamal Sina under the SSP585 scenario and the least variability in Aswan under the SSP370 scenario for the 2020–2040 time frame. Originality/value - This study’s originality lies in its focused analysis of climate change effects on ETo, incorporating crucial factors like actual vapor pressure and solar radiation. Its significance becomes evident as it projects ETopatterns into the near and distant future, providing indispensable insights for long-term planning and tailored adaptation strategies. As a result, this research serves as a valuable resource for policymakers and researchers in need of in-depth, region-specific climate change impact assessments.