Climate change will profoundly alter the dynamics of sea and land breezes in the Barcelona metropolitan area, trapping larger amounts of air pollutants over coastal areas and increasing health risks for millions of people. This is the conclusion of a study conducted by the Institute of Environmental Science and Technology of the Universitat Autònoma de Barcelona (ICTA-UAB), Spain, which produced high-resolution projections of future sea and land breeze behaviour and air quality under climate change scenarios for 2050 and 2100.

Sea and land breezes play a crucial role during the summer months. They act as a natural thermal regulator that mitigates extreme heat along the coast while also enhancing ventilation by dispersing and transporting urban pollutants from coastal areas inland. This process helps alleviate pollution levels in coastal zones, although it also shifts part of the impact to inland regions such as the Vic Plain, located approximately 70 km from Barcelona.

However, simulations from this new study reveal an unprecedented shift in this pattern by 2100. Rather than penetrating inland, the wind is projected to accelerate its along-shore component, reducing inland penetration and delaying the arrival of the sea breeze front by between one and two hours.

According to Gara Villalba, ICREA researcher at ICTA-UAB and the UAB Department of Chemical, Biological and Environmental Engineering, polluted air masses will therefore become trapped over coastal areas, which are also the most densely populated regions of Catalonia, prolonging population exposure to hazardous ozone levels. The most pronounced change will be in the pollutant tropospheric ozone (O₃), an invisible gaseous pollutant that is not emitted directly but is formed in the atmosphere from precursor pollutants—such as nitrogen oxides released by traffic and industrial activities—under conditions of intense solar radiation and elevated temperatures.

The study demonstrates that the widespread increase in temperatures will modify the structure of the lowest layer of the atmosphere, known as the planetary boundary layer, accelerating the chemical production of ozone. As a result of this combination of factors—enhanced ozone formation and a reduced capacity of winds to transport pollutants away—ozone concentrations along the coastline are projected to increase substantially by 2100.

“The study points to increases of 5 to 7 parts per billion in ozone concentrations across the central coastal and pre-coastal belts during the most severe heat events”, explains Sergi Ventura, the study’s lead author.

These findings raise new public health concerns for urban coastal areas, where prolonged exposure to ozone can trigger acute respiratory and cardiovascular problems, particularly among vulnerable populations during heat waves. The results also imply a significant shift in pollution risk patterns across the Barcelona metropolitan region.

The study highlights that future mobility plans and air quality policies cannot focus solely on reducing emissions from vehicles and industry. They must also urgently account for how global warming is modifying local wind systems and microclimatic processes that directly influence pollutant formation and transport.

Original article: Ventura, S., Badia, A., Segura-Barrero, R., Martilli, A., & Villalba, G. (2026). Projected changes in sea-land breeze dynamics and pollutant transport under future climate conditions. Science of the Total Environment, 1036, 181875. https://doi.org/10.1016/j.scitotenv.2026.181875