Over the past few decades, the climates of the Mediterranean basin have begun to show signs of tropicalization: a process of transition to a tropical climate.
Neither the Iberian Peninsula nor the Balearic Islands have a tropical climate; for this, the average temperature of the coldest month should be 18 °C or more. The contrast between Spanish winters and summers, as well as low winter temperatures, do not correspond to any tropical climate.
This manifests itself in several areas, including rising air and sea temperatures, changing atmospheric regimes and increasingly irregular rainfall.
Warmer air and seas
First of all, a sharp increase in temperatures – more pronounced than the world average – shortens Mediterranean winters and lengthens its summers, advancing spring and delaying the arrival of autumn. Some think that these transition seasons are almost gone. They still exist, but they have changed their date.
The temperature of the shallow and deep waters of the Mediterranean – to a depth of about 100 m – has also increased markedly.
These are clear and statistically significant trends. The water temperature south of Mallorca has exceeded 30 °C on some days in recent summers. These temperatures are similar, if not higher, than those observed in the Caribbean and the Gulf of Mexico.
Changing pressure systems
The main wind zones and pressure systems of the northern hemisphere, as well as the belt of tropical and subtropical high-pressure systems in the south of the Mediterranean basin – which are at the origin of the existence of the Sahara and other deserts at a similar latitude – all seem to be moving north.
This is due to the expansion of the Hadley cell, a global tropical atmospheric circulation that governs weather regimes at equatorial and tropical latitudes.
If this trend is confirmed, it will strengthen atmospheric stability in the Mediterranean region. Rainfall will become less regular, alternating long periods of drought and heavy showers.Also readThe government wants to end several programs to combat energy poverty… what if it was right?Damien Ernst
For several decades, atmospheric depressions have been developing in the Mediterranean, with characteristics reminiscent of those of tropical cyclones. They are called medical, « mediterranean mini-huricanes » or « tropical Mediterranean-type cyclones ».
These are low-pressure systems in the Mediterranean basin, with a warm core and a distinct eye, almost transparent, visible on satellite images, surrounded by a thick spiral cloud cover. They are accompanied by heavy rains and strong winds.
Data on air pollution episodes date back to a time before the 1960s, even before the beginning of global warming. It is true that the definition of these episodes has varied and has sometimes been quite wide; the list of cases identified – which has a hundred occurrences – therefore deserves to be reviewed. As a result, it is difficult to say that their frequency has increased with the increase in water and air temperatures.
For example, some suggested that the torrential rains that hit Catalonia in early October 2026 were due to a medical cyclone. However, this was not the reast. Neither the eye of the cyclone nor the spiral structure of the cloud were observed, the wind played no significant role and no low pressure zone formed. On the other hand, several convective cells and meso-scale convective systems have had a completely unusual, even unprecedented behavior
These storms need to be studied in detail to determine if they are involved in the tropicalization of the Mediterranean.
More and more irregular rains
Along the Spanish Mediterranean coasts and other countries of Southern Europe, torrential rains can be caused by various atmospheric phenomena. These include cold rains and persistent east winds, which transport moisture from the Mediterranean to coastal areas, as well as cyclogenesis processes at sea, convective mesoscale systems, and others. These factors can also act together.
Mediterranean geography and climate are complex, which makes weather forecasts particularly difficult. For a large part of the year, the forecasts are relatively simple thanks to several consecutive days of atmospheric stability and pleasant weather. On the other hand, at other times, it is very difficult to assess the scale and intensity of meteorological systems. Their complexity can generate unforeseen phenomena, making Mediterranean extreme weather phenomena among the most difficult to predict in the world.
These characteristics – the difficulty of predicting the intensity of precipitation, their surprising and erratic evolution – seem to have increased recently, especially since the sharp rise in global temperatures from 2022.
This represents a major challenge for forecasting services. They will have to update their procedures, pay particular attention to intermediate and local spatial scales, and refine their models to take into account the excess energy from the heat stored on the sea surface, especially in Mediterranean waters.
In addition, taking into account local observations of the public, as part of a real participatory science initiative, could complement the official data and improve the perception of the risk by the public itself.
