Effects of climate change on hydrogeological hazard: the case of the Niscemi landslides (Southern Sicily, Italy)

This study analyzes precipitation variability and the hydrometeorological conditions associated with extreme hydrogeological events in the Niscemi area (southern Sicily), combining historical series (1885–2020), ERA5 data, and future projections of rainfall intensity. The comparison between the hydrogeological events of October 12, 1997, and January 26, 2026 highlights how such events can develop through different hydrometeorological configurations, yet are both preceded by high soil moisture conditions, confirming the key role of antecedent precipitation and its temporal distribution. The climatic analysis shows that cumulative precipitation does not exhibit a significant linear trend but is strongly modulated by Euro-Mediterranean atmospheric circulation, with significant negative correlations with EA (ρ = -0.74) and MOI (ρ = -0.66), and more moderate correlations with NAO and WeMO. In contrast, mean rainfall intensity shows an increasing trend over time and is only weakly correlated with the indices, with a significant relationship observed only with WeMO (ρ = -0.34). The intensification is also associated with synoptic configurations characterized by positive NAO. Projections obtained using a SARIMAX model, forced with SSP scenarios, indicate a progressive increase in rainfall intensity throughout the 21st century, reaching up to approximately 40% under high-emission scenarios. Overall, the results highlight that extreme hydrogeological events arise from the interaction between atmospheric circulation variability, thermodynamic conditions, and antecedent rainfall conditions, emphasizing the need for integrated approaches to risk assessment in a climate change context.