Europe faces rising risk of destructive hailstorms, study says

Global warming may lead to fewer hailstorms but larger and more damaging hailstones across Europe, according to new research.

The study, by scientists from Newcastle University, the Met Office and the University of Bristol, used European-scale simulations to model future hail under rising temperatures. Published in Nature Communications, the findings show that under a high-emissions scenario (RCP8.5), severe hail is likely to become less frequent overall, except in the case of very large hail.

Hailstones with a diameter of 2 cm are classed as severe, while 5 cm or more is considered very large. Larger hailstones cause far greater damage than smaller ones and even a small increase in size could outweigh any benefit from fewer storms.

The researchers say several factors explain the projected changes. As the atmosphere warms, hail forms higher up, where storm updrafts can be weaker, giving the ice more time to melt before reaching the ground. Weaker large-scale circulation could also disrupt the vertical profile of winds, creating conditions less favourable for organised thunderstorms.

However, the authors found that future warm seasons feature a warmer thunderstorm type similar to hail-producing storms in the tropics, where the largest hailstones can still reach the surface. They predict such storms will be most common over southern Europe, leading to regional increases in severe hail frequency.

Lead author Dr Abdullah Kahraman, senior researcher in severe weather and climate change at Newcastle University and visiting scientist at the Met Office Hadley Centre, said the effects of climate change on severe thunderstorms are more complex than previously thought. “High-resolution models can produce results that differ significantly from earlier research. Society may need to prepare for less frequent, yet more damaging hail events locally, in a five-degree warmer future,” he said.

Professor Lizzie Kendon, head of climate projections at the UK Met Office and professor of climate science at the University of Bristol, said the findings are “very concerning”. “They imply we need to be prepared for tropical-type hailstorms impacting Europe in the future, associated with very large hailstones that can cause severe impacts. This possibility also extends to the UK, although the risk of hail here remains low into the future,” she said.

Professor Hayley Fowler, professor of climate change impacts at Newcastle University, added that society must be better prepared for unprecedented extreme events. “This study shows that future storms in the Mediterranean could bring giant hail, with devastating impacts. Recent hailstorms have caused significant direct damage to properties and infrastructure, crops, and even aircraft,” she said.

The analysis shows the likelihood of very large hailstones decreases across central Europe and remains low over the British Isles and northern Europe, but increases in southern Europe in autumn and winter, offsetting declines in spring and summer.

The authors warn that warm-type thunderstorms in a future Mediterranean climate could amplify the impact of hailstorms in Italy and surrounding areas, with overall more frequent severe hail. They also acknowledge uncertainty about the effect of enhanced melting at higher freezing levels on the largest hailstones and recommend further studies to improve understanding of their potential to cause damage at the surface.