Anyone spending a hot summer day along Spain’s Mediterranean coast will be familiar with the phenomenon: in the afternoon, the cooling sea breeze arrives, providing welcome relief in many areas. However, this natural “air-conditioning effect” appears to be losing strength. This is the conclusion of a new international study, the findings of which have now been published.
Spain Expat Press Editorial Team
by Marlon Gallego Bosbach
Researchers analysed weather data spanning more than four decades and reached a surprising conclusion: sea breezes across the western Mediterranean have weakened significantly since the early 1980s. The areas most affected are Spain’s Mediterranean coastline and the Balearic Islands.
More than 40 years of weather data analysed
For the study, measurement data from 39 weather stations along the coasts of Spain, France, Italy and North Africa were analysed. The research covers the period from 1981 to 2021.
The results were clear: around 90 per cent of all measuring stations recorded a long-term decline in the wind speed of the typical sea breeze.
On average, the strength of the sea breeze decreased by around 11 per cent. During the summer months, the decline is even more pronounced, reaching approximately 12.7 per cent. Scientists describe this as a trend that can be observed across almost the entire western Mediterranean region.
Spain particularly hard hit
Spain is among the regions where the changes are particularly pronounced. The largest decline was recorded in the Balearic Islands, where the sea breeze has lost around 17.6 per cent of its strength on average since measurements began. Along Spain’s Mediterranean coastline, its speed has also fallen significantly, decreasing by around 17 per cent – well above the overall average.
Among the areas particularly affected are cities and regions such as Barcelona, Castellón, Tortosa, Almería, Málaga, Ibiza, Palma de Mallorca and Menorca. Depending on the location, the wind speed of the cooling sea breeze has decreased by as much as 25 per cent.
The opposite should have happened
The surprising aspect of the study is that, according to previous scientific understanding, the sea breeze should actually have become stronger.
The formation of a sea breeze is relatively easy to explain. During the day, the land heats up much faster than the sea. The warm air above the land rises, causing cooler air from the sea to flow inland.
As the Mediterranean region is warming particularly rapidly due to climate change, many experts had previously assumed that this temperature difference would become greater in the future, resulting in stronger sea breezes.
However, the measurements show exactly the opposite.
Why is the sea breeze becoming weaker despite this?
According to the researchers, several factors are working together at the same time.
Firstly, stable high-pressure systems are occurring more frequently over the Mediterranean. At the same time, hot air masses from the Sahara are reaching southern Europe more often. Added to this are increasingly longer and more intense heatwaves.
This warm air stabilises the atmosphere. Put simply, it creates a kind of “lid” that restricts vertical air exchange. As a result, the typical circulation between land and sea can no longer develop as effectively, causing the sea breeze to lose strength.
Especially noticeable during heatwaves
The effect is particularly pronounced during periods of extreme heat.
Ironically, at the very time when millions of people along the Mediterranean coast rely on the cooling effect of the sea breeze, it becomes even weaker.
Depending on the region, researchers recorded a further reduction in wind speed of between around five and ten per cent during heatwaves.
Temperatures have been rising for decades
Alongside the changes observed in the sea breeze, the study also documents the significant rise in temperatures.
Since 1981, the average air temperature in the studied region has increased by around 1.3 degrees Celsius. At the same time, the surface temperature of the Mediterranean Sea has risen by approximately one degree.
For years, the Mediterranean region has been considered one of the global hotspots of climate change. Due to its geographical location, the sea and the atmosphere in this area are particularly sensitive to rising temperatures.
What are the consequences?
The scientists identify several possible consequences.
A weaker sea breeze initially means less natural cooling for millions of people in Spain’s coastal regions. Densely built-up cities in particular could experience even higher temperatures in the future.
In addition, air quality may also deteriorate. Normally, the sea breeze helps to disperse pollutants and fine particulate matter inland or out over the sea. If this air exchange becomes weaker, pollutants can remain concentrated over urban areas for longer periods.
Rainfall patterns could also change. As the sea breeze transports moisture inland, its weakening could have a long-term impact on local thunderstorms, dry periods and the regional water balance.
Research aims to improve predictions of future impacts
The authors of the study emphasise that their findings provide important insights for future climate and urban planning.
Coastal regions such as Valencia, Alicante, Murcia, Barcelona and Palma de Mallorca are particularly dependent on the natural cooling provided by the sea breeze during the summer months. If the observed trend continues, heatwaves could become even more severe in the future than previously expected.
The study once again shows that the effects of climate change involve more than just rising temperatures or increasingly frequent extreme weather events. Even seemingly everyday weather phenomena, such as the familiar Mediterranean sea breeze, are changing – with direct consequences for the lives of millions of people along Spain’s coastline.
