Global projections of hail hazard frequency under climate change

Hail can injure people and damage infrastructure, with hailstorms a driving cause of insured losses. Hailstorms are expected to be affected by global warming, primarily via changes to atmospheric instability, wind shear, and the height of the melting level. However, the nuances of expected changes remain uncertain and are generally only studied regionally, partly because global climate models typically lack the fine grid spacing required to explicitly resolve hailstorms. Here, we show global projections using an ensemble of four hail proxies to estimate hail-prone conditions occurrence frequency in eight global climate models. We use a temperature-based framework and show projected changes in global hail hazard frequency in scenarios with two and three degrees of warming over a recent historical period. By analysing changes in the "ingredients" for the proxies we can determine which factors are most pertinent to the changes in hail-prone conditions. Under global warming, the multi-model multi-proxy results show general poleward shifts in hail-prone condition frequency, and shifts from the warm season to the cool season in many regions. The results reinforce the benefit of using proxies designed specifically for hail for such studies, since some more general thunderstorm proxies neglect the effects of temperature and can show significantly different results. Finally, we use our results to analyse changes in hail exposure to various crops worldwide. This work encompasses the first global projections for severe storms using proxies specifically designed for hailstorms.