Assessment of Future Precipitation Patterns in Greece Using ETCCDI Climate Indices

Extreme hydroclimatic events are expected to increase in intensity, frequency, and duration, with droughts posing a major threat to Mediterranean countries. In regions such as Greece, the anticipated reduction in water availability may have significant impacts on critical economic sectors. This study investigates the effects of climate change on the hydrological regime of Greece over the period 1971–2100. To this end, high-resolution regional climate simulations were employed under two Representative Concentration Pathways (RCPs): the moderate-emissions scenario RCP4.5 and the high-emissions scenario RCP8.5. Twelve precipitation-related indices from the Expert Team on Climate Change Detection and Indices (ETCCDI) were calculated annually for 58 meteorological stations across the country. Long-term trends were assessed using Sen’s Slope estimator, and projected percentage changes were computed for the end of the 21st century. Our results indicate a clear trend toward drier conditions across most of Greece. The most substantial reductions in total precipitation were observed in mountainous western areas, while lowland regions showed notable increases in consecutive dry days. By 2100, mean annual precipitation (PrcpTOT) is projected to decline by approximately 12% under RCP4.5 and 29% under RCP8.5. Consecutive dry days (CDD) are expected to increase by 12% and 40%, respectively. Furthermore, indices representing the percentage of total precipitation from very wet (R95pTOT) and extremely wet days (R99pTOT) reveal a growing contribution of extreme rainfall events, particularly in the northern and western mainland, as well as the North Aegean islands. This study combines high-resolution projections with multiple precipitation indices, providing a comprehensive assessment of long-term hydroclimatic conditions in Greece. However, uncertainties remain due to limitations in climate models, especially in precipitation modelling, which may affect the precision of local-scale projections. Overall, these findings highlight the increasing variability and severity of future hydroclimatic extremes in Greece, emphasizing the urgent need for effective mitigation and adaptation strategies to address climate change.