Weaker and more frequent Mediterranean sea breezes in a warming climate.

The Mediterranean, a climate change hotspot, has experienced accelerated warming, which is expected to influence sea breezes (SB) speed and occurrence. The extent to which these local winds have changed remains unclear due to the scarcity of multidecadal observations. Here we present a regional-scale assessment of SB across the Western Mediterranean, based on an unprecedented 41-year homogenized observational database spanning multiple countries and stations. Since the 1980s, SB have become weaker while more frequent. We link these changes to the interplay of thermodynamic and dynamic mechanisms driven by regional warming. The warming-induced weakening of SB speeds is further amplified during heatwaves, with speed reductions of up to 10%. In contrast, their winter occurrence has risen by roughly 10% per decade, consistent with a higher frequency of anticyclonic conditions. These findings offer a new understanding of SB response to the warming of the Mediterranean, with key implications for climate-related risks such as heat extremes and air quality.