Global warming quadruples the intensity of torrential rains in Spain

As temperatures rise in Spain due to global warming, destructive rains have become stronger. In half a century, the intensity of torrential rains has increased 4.5 times, according to a data collection carried out by the Polytechnic University of Catalonia.

The power and consequences of torrential storms in Spain continue to illustrate the toll imposed by this phenomenon resulting from the climate crisis. This week, one person died and another remains missing, swept away by the waters of a violent rain in the torrent paris from Mallorca. Last March, Storm Nelson killed four people. That’s just the toll from 2024. Deaths from destructive storms can be traced from year to year. Just 12 months ago, in September 2023, another episode of torrential rain killed six people. Storm Gloria in 2020 left 13 dead in its wake. A very violent and very localized storm caused the loss of 13 lives in Mallorca in 2018.

“The analyses show an increase in these extreme weather events over the period we are studying,” say the UPC researchers. The increase is “significant” both for episodes of very heavy rains – with more than 30 mm of rain – and for those of torrential rains – 60 mm or more – which, according to these calculations, show “an increase in intensity of 360%” since 1971.

This work has clarified the trends already described, for example, in the AEMET documents, which explain how the data “indicate an increase in the frequency and intensification of situations that cause very heavy or torrential rains of significant magnitude throughout the Spanish Mediterranean territory”.

Influences of heat

Precisely, the rainfall records of the half-century studied by the UPC show that “the episodes of very heavy rains are relatively widespread throughout the peninsula and the Balearic Islands”. As for the even more intense (torrential) rains, they have multiplied “in Andalusia, Castile-La Mancha, the region of Murcia, the Valencian Community, the south of Catalonia, the Balearic archipelago, Aragon, Navarre and the Basque Country”. The most intense areas are concentrated in particular on the Mediterranean coast.

In the context of global warming, the researchers looked for the interaction between the escalation of temperatures in Spain and the precipitation pattern. “The maximum temperature measured is the indicator that shows the greatest correlation between total precipitation and droughts,” they conclude.

And they add in particular: “In the case of extreme precipitation, the strongest correlation occurs with the minimum temperature measured.” This means, they continue, that “the years that are warmer at night are those that show a stronger tendency towards extreme precipitation.”

The most significant thing is that we are experiencing a climate paradox because there will be more and more drought, but with specific moments when it rains, giving the impression that the sky is going to fall on our heads.

Joseph Roca
— Researcher at the Polytechnic University of Catalonia

It is precisely the intense heat that triggers nights with unprecedented temperatures due to their height. Tropical nights (with 20°C) have become normal and so-called torrid nights (+25°C) have increased sixfold since 1980, according to AEMET.

“The most significant thing is that we are experiencing a climate paradox because there will be more and more drought, but with specific moments when it rains, giving the impression that the sky is going to fall on our heads,” explains one of the authors of the study, Josep Roca.

Because the downside is that rainfall in general is scarcer in the peninsula and the Balearic Islands. During the same study period, a decrease in total rainfall of 8.9% was observed. This change towards a drier Spain with higher temperatures is what led this research team to calculate that at this rate, in just a few decades, the majority climate will become steppe rather than Mediterranean.

Without a change in the transformation trend, the typically Mediterranean climate would go from 24.43% of the peninsular and insular territory in the reference period 1971-2000 to 10.13% in the period 2040-2060. A whole expansion of what they call “brown” Spain.