On a mud-flooded street in Utiel, Spain, October 30, 2024. MANU FERNANDEZ / AP
In an interview with Le Monde Antonio Aretxabala, doctor of Geology at the University of Zaragoza and an expert in natural disasters, explains how the rising temperatures of the Mediterranean Sea and the extensive urbanization of flood-prone areas in the Valencia region created the disaster that claimed almost 100 lives on the night of Tuesday, October 29, following a “cold drop” episode in southeastern Spain.
Torrential rains and flooding are nothing new to southeast Spain, but they seem to be increasingly destructive. Why is this so?
The temperature of the Mediterranean Sea continues to rise as a result of global warming. This summer, it broke records once again. As a result, the atmosphere is warmer and full of water vapor.
Now, when the warm, humid Mediterranean wind from the Levant meets a strip of cold air from the North Pole, as it did on Tuesday – a so-called isolated high-altitude low (“DANA” in Spanish) or “cold drop” – it causes torrential rain. It’s a meteorological phenomenon made all the more extreme by the fact that the air is charged with millions of tons of water due to the rise in temperatures. For example, around Valencia, for more than eight hours, nearly 500 liters per square meter fell; an exceptional intensity. This normally corresponds to a year’s rainfall.
France and Central Europe have also seen major flooding in recent weeks. Are we talking about the same phenomenon?
In all these cases, the Mediterranean’s warming is dynamite. The higher temperatures rise, the more water vapor enters the atmosphere. And the smaller the energy difference between the North Pole and the Equator, the more cold air currents tend to separate, wander, undulate and reach further and further south.
These extreme weather phenomena will continue to increase in frequency and intensity as we experience the real consequences of climate change.
At the same time, Spain’s Mediterranean region is experiencing a prolonged and severe drought. Is there a link between these two phenomena?
Just as strips of cold air move further and further south, masses of warm air move further and further north. With climate disruption, extreme events are on the increase: droughts are longer and rainfall is more violent. It’s a kind of climate chaos and it’s no surprise. Scientists have been sounding the alarm for 30 years.
The damage in Valencia was particularly severe. How do you explain this?
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