Climate change drives deadlier Mediterranean winter storms
Human driven climate change has sharply increased the lethality and intensity of winter storms across the western Mediterranean, with recent tempests now about one third more deadly than they would have been in a pre industrial climate, according to an international team of scientists. Their assessment links a devastating sequence of storms that swept Spain, Portugal and Morocco between mid January and mid February to warmer air and sea conditions that are loading each system with more moisture and producing heavier downpours. Researchers found that days with the heaviest rainfall in these events now see roughly one third more precipitation than would have occurred before global temperatures rose by about 1.3 degrees Celsius, dramatically raising the risk of flash floods, landslides and infrastructure failures.
The storms, each powerful enough to receive a name, drove hurricane force gusts and record breaking rain into communities already saturated by weeks of unsettled weather. In Grazalema, a mountain village in Spain’s Cadiz province known as one of the country’s wettest locations, gauges registered 512.5 millimetres of rain in just 24 hours during Storm Leonardo, more than Madrid typically records in an entire year. Over a 10 day span, nearly 1,300 millimetres fell there, smashing a local record that had stood since 1948 and forcing groundwater up through floors and walls as aquifers overflowed beneath homes. Across Spain, Portugal and Morocco, the barrage of low pressure systems tore up roads, collapsed sections of highway, closed rail links and triggered mass evacuations. Tens of thousands of emergency personnel were deployed and Morocco shouldered the largest displacement toll, with around 150,000 people forced from their homes, while Spain’s government pledged more than €7 billion in reconstruction aid.
To quantify the role of climate change, scientists combined observed rainfall trends with climate model simulations for two study regions spanning southern Iberia, northern Morocco, northern Portugal and northwestern Spain. In the northern area, where models reproduced the patterns seen in observations, the analysis showed that human caused greenhouse gas emissions have made intense daily rainfall about 11 percent stronger than it would have been in a cooler world. In the southern zone, model performance was less consistent, so researchers could not assign a precise percentage to the human influence, even though real world data there showed even steeper increases in the most extreme downpours. The study also highlighted the role of a persistent “blocked” high pressure system over Scandinavia and Greenland, which acted like an atmospheric barrier and steered one storm after another into western Europe. Exceptionally warm Atlantic waters west of the Iberian Peninsula and moisture laden atmospheric rivers added further fuel, effectively supercharging the storms with additional water vapour.
For climate scientists, the western Mediterranean’s ordeal underscores how incremental warming is transforming familiar weather patterns into dangerous disasters. They argue that what were once manageable winter storms are increasingly capable of overwhelming river defences, drainage systems and transport networks, especially in densely populated and highly urbanised coastal zones. The combination of more intense rainfall, ageing infrastructure and construction in floodplains is amplifying vulnerabilities across the region, turning sequences of storms into cascading crises that affect housing, agriculture and critical services. Experts say the latest findings add to a growing body of evidence that climate change is intensifying the global hydrological cycle and demand urgent investment in warning systems, land use planning and resilient infrastructure to match a future in which the definition of “extreme” shifts year after year.
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