“I never thought I would write this.” Juan Jesús González Alemán is a meteorologist and researcher at the State Meteorological Agency (Aemet). He has been studying cyclones with tropical characteristics for 15 years, events that, by requiring very warm seas, are typical of other regions of the planet. The expert published an article this week about the extreme episode of rain that affected Catalonia in the first days of October. Still stunned and bewildered, he pointed out that what happened was a “real attempt to form a tropical cyclone from a group of very intense storms.” Their hypothesis is that this unprecedented event with no precedent on the peninsula is explained by an “extremely warm” Mediterranean, with temperatures well above 26 °C on a sustained basis.
It is known - the scientific evidence is overwhelming - that an increasingly warmer Mediterranean acts as fuel for the torrential rains that hit Spain in autumn. As the temperature increases, evaporation and the amount of water vapor available in the atmosphere intensifies, which can be discharged abruptly when it coincides with a DANA or a storm and the right conditions are present for the development of storms. The tragic floods in Valencia two years ago, with a death toll of 232, are an example.
When talking about this relationship - hot Mediterranean and torrential rains - meteorologists agree that the warm sea acts as a factor that fuels the episode, but it is not enough on its own: a favorable atmospheric configuration, air rising mechanisms and conditions that allow storms to persist or repeat over the same territory are also needed. That is, a warmer sea does not by itself cause extreme rainfall.
For González Alemán, this sentence has now been called into question. In this latest storm, the main source of energy has been “the latent heat that was released in condensation.” "This refutes, to a certain extent, an idea that is often repeated: that 'a warm Mediterranean Sea does not generate high-impact storms on its own.' Yes, it can generate them, and what happened these days is quite clear proof," the researcher states in his article.
In 2026, the Mediterranean Sea has recorded a historic and unprecedented marine heat wave, breaking numerous surface temperature records since spring. In the Balearic Sea, the marine heat wave began early in April (surface temperature of 16.3 °C, 1.1 °C above normal) and continued with May at 19.7 °C (+1.8 °C) and June at 24.2 °C (+2.4 °C), reaching the all-time highs in the ECMWF series since 1941.
According to Aemet, at the end of June the water reached 26.63 °C, which was 2.6 °C above normal and equal values for the second half of August. At the start of that month, the Dragonera buoy (Mallorca) set an absolute record of 33.02 °C, the highest temperature ever recorded in its entire measurement network. On average, the western Mediterranean region has spent more than 186 days above the annual climate average, with warming attributed to climate change of around an additional 2°C.
Monitoring the average temperature of the western Mediterranean makes it possible to verify to what extent the sea retains the heat accumulated during the previous months. Water has a great capacity to store energy and loses that heat gradually, so the end of summer does not necessarily mean the end of thermal anomalies.
Explained in this way, an increase of 3 ºC may seem small and insignificant, but in a sea it is “absolutely outrageous.” "It may not be enough for a glass of water or coffee, but for a sea it entails many impacts. A brutal accumulation of energy is required to heat millions of square kilometers of surface," explains Paco Pastor, an expert who has been measuring and monitoring the temperature of the Mediterranean for years as a researcher in the meteorology and climatology area of the CEAM Foundation.
The seas and oceans are the main store of excess heat in the Earth system, since they retain around 90% of this surplus. They act as natural regulators that automatically manage the balance of the planet. However, as a result of the accumulation of greenhouse gases in the atmosphere, which humans continue to release at very high levels by burning fossil fuels, this protective shield is weakening. The energy imbalance – the balance between the energy that reaches Earth and that which is expelled into space – is raising the temperature of the water.
A scientific analysis signed by an international team of researchers from World Weather Attribution (WWA) shows that extraordinary heat is being incorporated into the usual climate. Anthropogenic warming has added about 1.4°C to maximums off the peninsula and about 1.9°C in the western Mediterranean. Now, the conditions are in place for a peak of 30 ºC to occur every five years. Without human warming, around 2,000 times would have been expected in the western Mediterranean.
In closing his informative article, González Alemán stated that the formation of this tropical cyclone in Catalonia is a case “worthy of study” that opens new lines of research in the scientific field. The almost chronic heat of the sea is not only generating the fuel for extreme storms. It is creating the conditions for phenomena that until now seemed foreign to the Mediterranean.
The El Niño effect: The Earth is already suffering changes in climate patterns due to the El Niño effect, as the more intense anomalous warming of the surface waters of the Pacific is known, which alters the atmosphere and triggers changes in rainfall and temperatures. It is already a fact that we are facing a “Superniño”, with records that touch the 4ºC anomaly on the coasts of Peru and Ecuador. Pastor clarifies that this phenomenon does not have a direct impact on the Mediterranean. "What we call teleconnections are established by being far from the source, from the Pacific. We are talking about very complex mechanisms and nothing immediate. There is no analysis or study that relates what is happening in the Mediterranean with El Niño. The general warming trend exceeds this phenomenon," he explains.
