October 31, 2024
Dozens dead and missing. The damage caused by the violent flood that hit Spain, particularly the Valencia region, is incalculable. In eight hours, a year’s worth of rain fell. A phenomenon that is unprecedented in the last century in terms of intensity, as explained by the Cnr climate physicist, Antonello Pasini, “because climate change has something to do with it”.
What is Dana, the phenomenon that hit Spain?
«It is what we also call “cold drop“: the currents at medium-high latitudes go from West to East with undulations. Sometimes it happens that these undulations become so deep and come towards the South that drops of cold air detach themselves. These cold air masses descend to lower latitudes and become stationary: they go neither forward nor backward. This is why they are dangerous, because they remain in the same area for a long time and can bring rainfall for many days. Then the stronger the thermal contrast, the stronger they are. It is not an unusual phenomenon, it has happened other times, even in Valencia itself. But my Spanish colleagues explain to us how the intensity of this precipitation is unprecedented in the last century.”
Why is it unprecedented?
«Because climate change has something to do with it. The fact that the Mediterranean is now invaded by African anticyclones, rather than by the Azores anticyclones, is precisely due to climate change, because anthropogenic global warming has caused this equatorial and tropical circulation to expand northwards. All the anticyclones, therefore, which previously remained permanently over the Sahara desert, now enter the Mediterranean, bringing great heat and great drought. But when they retreat and cooler air arrives, as in this case, a very strong thermal contrast is formed: the sea gives heat and humidity and makes the precipitations more violent.”
Is what is happening in Spain the same phenomenon that has occurred in Italy in recent weeks?
«There are similar phenomena because when African anticyclones retreat, cold currents enter. Then there are various ways in which atmospheric flows collide, it doesn’t always have to be a “cold drop”. But when cold currents arrive on a pre-existing warm and humid air, on a warm soil and a warm sea these things are created, it is the thermal contrast”.
Now there are those who say that “fortunately” high pressure is returning in Italy and there is this mild climate. But to what extent is it “lucky” to have these temperatures and this sky at the end of October?
«On the one hand we say that we had rain and now we shouldn’t suffer from drought. However, long periods of unseasonal heat lead to poor rainfall and less filling of the aquifers. And, above all, if the sea and the air remain warm, when the disturbances arrive – and they necessarily arrive in autumn and then at the beginning of winter – the damage is greater. There is an extremization of the phenomena.”
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**Interview with Dr. Antonello Pasini, Climate Physicist**
**Editor:** Good evening, Dr. Pasini. Thank you for joining us today to discuss the severe floods that recently hit Spain, particularly the Valencia region.
**Dr. Pasini:** Thank you for having me.
**Editor:** Could you explain what DANA is and how it contributed to the recent flooding?
**Dr. Pasini:** Certainly. DANA, or “cold drop,” is a meteorological phenomenon that occurs when cold air descends over warmer waters, such as those of the Mediterranean Sea. This creates significant atmospheric instability, which can lead to extreme weather events, including heavy rainfall. In this case, cold air masses detached from the usual atmospheric currents and lingered over Valencia, resulting in unprecedented rainfall.
**Editor:** You mentioned that this rainfall was extreme. What made it so unprecedented compared to historical data?
**Dr. Pasini:** The intensity of the rainfall was remarkable. In just eight hours, a year’s worth of rain fell in some areas. This level of precipitation in such a short time frame has not been recorded in the last century, primarily because of the ongoing impacts of climate change. Warmer temperatures and shifting weather patterns have increased the likelihood and severity of these events.
**Editor:** How does climate change specifically influence the behavior of these weather patterns?
**Dr. Pasini:** Climate change has modified the positioning of atmospheric systems. For example, the Mediterranean is increasingly dominated by African anticyclones rather than the traditional Azores anticyclones. This shift is a consequence of anthropogenic global warming, which has expanded tropical and equatorial weather patterns further north. As a result, the conditions favoring such extreme weather events are becoming more prevalent.
**Editor:** What are the potential implications of this phenomenon for Spain and other Mediterranean countries moving forward?
**Dr. Pasini:** If trends continue, we can expect to see more frequent and intense weather events, including heavy rainfall and subsequent flooding. This not only threatens infrastructure and ecosystems but also poses risks to public safety and can strain emergency response systems. It is critical that both governments and communities prepare for such eventualities by improving infrastructure and emergency protocols.
**Editor:** Thank you, Dr. Pasini, for your insights into this tragic event and the broader implications of climate change. We appreciate your time.
**Dr. Pasini:** Thank you. It’s important to keep these discussions ongoing so we can better prepare for the future.
