Climate change unleashed: physical-based attribution analysis proves human-induced amplification of Valencia's deadly flooding

Global warming intensifies the hydrological cycle, increasing heavy rainfall events worldwide. In October 2024, Valencia (Spain) experienced rainfall accumulations in a few hours surpassing annual averages (771.8 mm in Turís official weather station) and record-breaking in one hour in Spain (184.6 mm), which promoted devastating flash-floods. This event resulted in 228 fatalities and was the major weather event in losses for contemporary Spain. Here we present a physical-based attribution study using the WRF model sourced with CMIP6 models to assess the contribution of anthropogenic climate change (ACC) to rainfall intensity, moisture content, and storm dynamics (i.e., diabatic heating, vertical motions, microphysical processes). Observed climate change led to more intense precipitation and a greater extent of this extreme rainfall event by +20% C-1 in 1-h rainfall rate, consistent with Clausius-Clapeyron scaling. Enhanced availability of atmospheric water vapor due to higher Mediterranean and subtropical North Atlantic SST played a central role, while CAPE, diabatic heating, and stronger vertical velocities boosted the convective processes. A deeper warm cloud layer and elevated graupel concentration reveal microphysical mechanisms that enhanced precipitation volumes in a warmer climate. These results demonstrate that ACC intensifies flash-flood risks in the Mediterranean region, and in this particular case, intensified the 6-h rainfall rate by 21%, amplified the 180 mm total rainfall area by 55% and increased the volume of total rain within the river Jucar catchment by 19% compared to the pre-industrial era. This study highlights the urgent need for effective adaptation strategies and improved urban planning to reduce the growing risks of hydrometeorological extremes in a rapidly warming world.