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In May 2023, Italy’s Emilia-Romagna region experienced devastating, if not unprecedented, floods that caused widespread damage to infrastructure, homes, businesses, and farmland. Seventeen people lost their lives, and the disaster caused an estimated €8.5 billion in damages. The persistent rainfall and resulting landslides and flooding displaced tens of thousands of residents, leaving a deep mark on the region’s economy and communities.
New research from the Euro-Mediterranean Center on Climate Change (CMCC) sheds light on why this extreme event occurred, the role that climate change may have played , and what it could mean for the future of the Mediterranean region and beyond.
The study “ A cul-de-sac effect makes Emilia-Romagna more prone to floods in a changing climate ,” published in Scientific Reports , finds that the extreme flooding was not the result of a single extreme precipitation event, but was fueled by prolonged accumulation of rain over several days.
CMCC scientists describe a “cul-de-sac” effect, where mountains block moisture from the Adriatic Sea, trapping rain over the region and causing extremely rare floods which, statistically, would be expected to happen only once every 500 years.
Researchers identified a stationary cyclone over central Italy as a key driver, channeling humid air from the Adriatic Sea toward the region of Emilia-Romagna. A similar configuration is also believed to have led to flooding in the same area in 2024.
“Our analysis shows that the kind of persistent cyclone that caused the 2023 and 2024 Emilia-Romagna floods is not unique to this region. Other Mediterranean areas with similar geography could face the same risks – and these events may become more frequent as the climate continues to change ,” says CMCC senior scientist Enrico Scoccimarro , first author of the study. “This has important implications for how we design and operate early warning systems.”
The study introduces a new metric, cyclone density persistence , which could help develop more effective early warning systems. By tracking the presence and persistence of such cyclones, forecasters may improve predictions of extreme precipitation events, not only for short-term forecasts but potentially for seasonal outlooks as well.
“This work represents the first step in a long-term plan to develop Early Warning Systems for flood events on a seasonal timescale at CMCC,” says Scoccimarro. “We aim to assess the capability of our numerical models and AI-based tools to forecast the large-scale conditions that lead to extreme precipitation events . Our goal is to go beyond current limitations of state-of-the-art numerical models, and aim at higher skills in directly forecasting extreme precipitation, and help communities better prepare for floods.”
Analysis of historical data suggests that conditions favoring these prolonged, extreme rainfall events have been increasing over the past 40 years. With climate change, these “cul-de-sac” floods may become more frequent – highlighting the urgent need for improved monitoring, forecasting, and planning across vulnerable Mediterranean regions.