The extreme rainfall and flash floods in Valencia, Spain in October 2024 were intensified by climate change.
New research highlights how increased atmospheric moisture and warming have amplified rainfall events.
Authors urge the need for enhanced climate adaptation strategies in the Western Mediterranean region.
The attribution of storms and associated rainfall to global warming and consequent climate change is challenging with many scientific gaps. But such analysis is also required to understand how smaller scale extreme weather events are getting modified by increased moisture in the atmosphere and other changes to atmospheric characteristics and the hydrological cycle.
A new attribution analysis of the extreme rainfall and flash floods in Valencia, Spain in October 2024 published in the journal Nature Communications on February 17, 2026 showed how sub-daily rainfall got intensified by warming and what gaps remain in such an analysis.
The region received a year’s worth of rainfall in a few hours, with official estimates of 771.8 mm in 16 hours over Turis. Around 185 mm of this rainfall came down in just one hour, which is an all-time record for Spain.
The resultant flash floods from the extreme rain on October 29 and October 30, 2024 killed over 200 people, which is the highest death toll from a flood-related disaster in Europe since 1967.
The torrent of rainfall that precipitated the floods was caused by a series of intense thunderstorms, in turn resulting from an isolated depression in the upper layers of the atmosphere also known as a cut-off low. The cold air in the upper layers was in contrast to the warm air coming through the lower layers from the North Atlantic Ocean.
This strong contrast created the necessary instability in the atmosphere for the development of the thunderstorms, according to the research paper. The cut-off low also attracted moisture from the Mediterranean Sea and northwest Africa in the form of atmospheric rivers, according to the paper.
The paper found that excess moisture in the atmosphere and other warming-related factors strengthened the one-hour rainfall during the storm event by 20 per cent per degree Celsius. This is around three times higher than what is expected from the Clausius-Clapeyron equation, according to which atmospheric moisture content increases by seven per cent with every degree Celsius of warming.
The scientists from various research institutions in Spain, Italy and Switzerland also attributed other rainfall characteristics of the storm event to warming. They found that the rate of six-hour rainfall during the storms was made 21 per cent more intense and the area with total rainfall above 180 mm was amplified by 55 per cent as compared to the pre-industrial times (1850-1900). The total volume of rainfall in River Jucar catchment also increased by 19 per cent due to warming and resultant moisture.
The current climate change attribution analysis is different from the rapid attribution analysis carried out by organisations like the World Weather Attribution (WWA) and ClimaMeter. Such rapid analysis is carried out using probabilistic, analogue or artificial intelligence-based models that focus on parameters such as total precipitation, wind speed and surface pressure. These analyses can be carried out quickly, which serves well for a rapid attribution.
While the rapid attribution analyses provide a first approach to how warming and consequent changes in climate are increasing the frequency and intensity of extreme weather events, the study authors said this is not the complete picture.
Their approach of physical-based approach explores the underlying characteristics of storm systems to reveal how warming could change the temperature, pressure and other atmospheric dynamics such as, in the case complicated micro-physics of cloud systems. “Although these detailed analyzes take longer, they offer a more comprehensive understanding of how extreme rainfall events are evolving under a warming climate”, wrote the authors of the study.
The physical-based approach also resolves the changes occurring at the sub-daily level such as three hour, six hour or even hourly during an extreme weather event. Such changes are poorly characterised in analysis based on daily parameters.
The researchers were able to find that the increased water vapour in the atmosphere due to evaporation from warming changes the characteristics of storms. For instance, the amount of heat energy released during a storm due to condensation of water vapour into liquid water is increased, winds speed up in the vertical direction and causes more intense cloud formation required for stronger storms with more rainfall.
“This study highlights that future projected scenarios for extreme rainfall events are already becoming evident. Such findings emphasize an immediate need to accelerate the development and implementation of climate change adaptation strategies, enhancing urban resilience in response to this growing threat, particularly within the Western Mediterranean region”, concluded the authors of the study.