This is how climate change multiplied the devastation of the DANA in Valencia

October 29, 2024 was marked as one of the most tragic days in the recent history of Spain due to the DANA that hit the region of Valencia and left 230 fatalities, billions in economic losses and rainfall that shattered records. And it is no wonder, because in stations like Turís, they accumulated 771.8 mm in just 16 hours and the national record for rainfall in one hour was broken with 184.6 mm. And now investigations are emerging about it.

Climate change. We know that this effect is altering the hydrological cycle at a global level, but now a new and exhaustive published study in Nature led by researcher Carlos Calvo-Sancho, has managed to measure exactly how and how much this storm was ‘doped’ by blame for anthropogenic global warming. And the most interesting thing is that it opens the door to the fact that these phenomena may be more common in the coming years.

Pure physics. Days after the disaster, rapid attribution initiatives such as Attribution and ClimaMeter They had already estimated, according to the most basic parameters, that this meteorological event had been twice as likely and 13% more intense due to climate change. Although at that time it was simply preliminary data that required confirmation and above all ‘sitting down’ to analyze it well.

That analysis has arrived many months later in a new work that goes far beyond these quick figures and focuses on the physical fundamentals. Here the researchers used very high resolution simulations under an approach called ‘Pseudo-Global Warming’.

A simulation. This approach is nothing more than recreating the October 2024 storm on a computer to see the devastation that occurred and then simulating it again by removing the effects of global warming from the formula. This is achieved by returning the atmosphere to the conditions of the pre-industrial era, which is like a reference point when talking about climate change.

The data. By comparing both simulated worlds, the supercomputer results showed the tremendous impact of the human hand on the storm. The most interesting results that were obtained can be summarized in four different points:

• Six-hour rainfall rates intensified by 21% under current weather conditions.
• The territory affected by rains exceeding 180 liters per square meter, which for the AEMET is the red notice limit, was expanded by 55%.
• The total volume of water falling directly on the Júcar River basin increased by 19%.
• The intensity of rain in one hour increased at a rate of 20% for each degree Celsius of temperature, something that is very relevant. And to understand it, we have to go to the Clausius-Clapeyron relationship, which dictates that the atmosphere should retain 7% more water vapor for each extra degree of temperature. Something that was duplicated here.

Because?. Here the question that many people can ask, both from the affected areas and from other parts of Spain, is clear: Why did it rain so much more than what the basic theory dictated? Here the science suggests that it all started with unusually high temperatures on the surface of the Mediterranean Sea, which reached record levels in the summer of 2024.

This injected a huge amount of water vapor into the system, and when comparing the current simulation with the pre-industrial one, the scientists detected, among other things, an 11.9% increase in the water that could precipitate or 11.9% more violent and faster updrafts.

The perfect cocktail. In short, the greater amount of water evaporated in the sea by high temperatures and air not only caused more rain, but also triggered an aerodynamic and thermal domino effect that made the storm much larger, longer lasting and more destructive than could be expected.

Towards the future. These findings are important to understand exactly what happened here, but they also raise a big warning: extreme hydrometeorological phenomena in the western Mediterranean are evolving aggressively.

In this way, the study highlights that the future scenarios projected by climatologists are already here, making it urgent and vital that we rethink our urban planning and our adaptation strategies to prepare for storms that are going to be increasingly more aggressive, as we keep seeing.

Images | EMU Chris LeBoutillier

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