The intensity of storm Harry was amplified by climate change. The role of global warming in the extreme weather event that struck Sicily, Sardinia and Calabria has been confirmed by a study conducted by ClimaMeter, an international scientific consortium led by Davide Faranda, a researcher at the French Cnrs who specialises in attributing extreme weather events to climate change.

Storm Harry brought torrential rain, extreme winds, floods and landslides

"The storm – the study's authors explain – was characterised by intense and persistent rainfall, very strong winds and extreme waves along the Ionian and Tyrrhenian coasts. In eastern Sicily, cumulative precipitation triggered flash floods and river overflows, inundating urban areas, damaging homes and businesses, and forcing the precautionary evacuation of several municipalities. Coastal areas were particularly exposed, with waves reaching 9–10 metres in height that caused significant coastal erosion, damage to roads, railways and port infrastructure, as well as flooding of low-lying coastal neighbourhoods."

Across the three southern Italian regions, economic losses have been estimated at at least 2 billion euros. The municipality of Niscemi, in the province of Caltanissetta, partially collapsed following a massive landslide. Sardinia, meanwhile, declared a state of emergency.

Wind speeds up 15 per cent due to global warming

According to the ClimaMeter report, the rise in average global temperature increased the severity of the storm. Conditions comparable to those of cyclone Harry would, in past decades, have produced less intense events. For instance, near-surface wind speeds increased by 4–8 kilometres per hour, representing a rise of 15 per cent.

To reach this conclusion, the researchers compared the meteorological configuration that developed over southern Italy in recent days with similar atmospheric systems recorded during the periods spanning 1950 to 1987 and 1988 to 2023. The results indicate that a storm of this kind remains a very rare event, which in practice limits the available points of comparison. Nevertheless, it is possible to assert that the intensity of the extreme event was exacerbated by global warming.

"We interpret this event – the study states in its conclusions – as driven by exceptional meteorological conditions, whose intensity was amplified by human-induced climate change, through an increase in average temperature and a strengthening of atmospheric circulation."