Hailstorms in a warming climate: What future for France and insurance sector?

Hailstorms are a major source of insured losses in Europe, with unprecedented damage in France in 2022 exceeding €6 billion. Anticipating how hail frequency may evolve under climate change is therefore critical for insurance risk management. This study assesses future changes in atmospheric environments conducive to hail using EURO‑CORDEX regional projections based on CMIP5 simulations. Sixteen GCM–RCM pairs provide 6‑hourly atmospheric fields at 11 km resolution, enabling a temporal and spatial high‑resolution, multi‑model analysis. Following the approach of Rädler et al. (2018), we compute key convective indices - Lifted Index (LI), 0-6 km vertical wind shear, and accumulated precipitation - and flag hail‑conducive days as a proxy for hail occurrence. Over the historical baseline (1980–2005), France experienced approximately 75 hail-conducive days per season (April–October). By mid-century (2050), the multi-model mean projects ~95 days, corresponding to a ~26% increase, rising to ~40% by 2100 under RCP8.5. The upward trend is statistically significant; however, substantial spatial heterogeneity is observed across France and adjacent countries. These findings have direct implications for the insurance sector: increasing hail risk challenges current pricing models, portfolio management, reinsurance treaty, and underscores the necessity of integrating climate projections into catastrophe modeling frameworks.

Keywords: hailstorms; severe convective storms; EURO‑CORDEX; CMIP5; RCP8.5; Lifted Index; vertical wind shear (0–6 km); multi‑model ensemble; regional climate modeling; France; insurance risk.