Interview
Meteorologist Isabel Moreno: A hot sea and a humid sky caused the extreme Spain floods
‘I think at the end of the day, we have to start from the assumption that we have to adapt to extreme weather events, no matter what.’
All indications point to climate change being responsible for the flooding that claimed more than 155 lives in Spain last week. At the same time, scientists are being cautious: one cannot directly attribute an event, however catastrophic, to climate change, at least without having done extensive research on it first.
However, according to an initial quick analysis by the World Weather Attribution (WWA), a global group of experts, torrential rains are 12 percent more intense and twice as likely to occur compared to the pre-industrial climate, that is, without the 1.3 °C of warming the planet has already undergone. The analysis is only preliminary, because climate models have not yet been used to simulate such an event in a world without human-induced warming. Nevertheless, the WWA concluded that climate change was the most likely causal factor, because a warmer atmosphere can contain more moisture, leading to stronger downpours.
Using the Clausius-Clapeyron equation, one can determine that at 1.3 °C of global warming, the atmosphere can hold about 9 percent more water vapor. In addition, according to a separate analysis by Climate Central, another group of climate specialists, climate change also made warm Atlantic Ocean temperatures 50 to 300 times more likely, which added moisture to the storm.
We interviewed Isabel Moreno, a Spanish physicist, meteorologist and climate change specialist. “The issue is that we are in a situation in which the atmosphere is able to hold more water vapor, and this is an incontrovertible fact,” she told il manifesto.
The temperature of the Mediterranean Sea has never been higher.
On the Spanish coast, the Mediterranean is 22 °C today [on Oct. 31]! In September it was 30 °C, and in Italy it was even higher. Imagine what could have happened if there was such an event a month ago. The Mediterranean basin is where climate change is being felt the most.
Why?
These events are more typical for the Mediterranean basin because they interact with the winds and energy that come from the sea. And then, on the southeast coast of Spain, the high terrain is very close to the sea. The latter brings moist winds, which further load the atmosphere with “fuel.” And then the sea, being so warm, releases its energy: the “match” to start the fire. Then, there is the issue of mountains: we have a series of mountains near the Spanish coast that help precipitation form.
And then there is the problem of prediction.
Making a prediction about a DANA [isolated high-level depression] is very complicated because, first of all, these are quite erratic systems, in which a small change from the initial position can give you a completely different result from what you had predicted. And then, we have to take into account the fact that these systems can generate smaller systems within them, such as particular storms. That's where forecasting becomes even more complicated, because knowing where a front will circulate, which is relatively easy to study, is not the same thing as determining exactly where a storm or a thunderstorm will form. One can estimate how much water a DANA might release, but it is possible that because of the chaotic situation in the atmosphere, a particular thunderstorm will remain anchored for a long time in a particular place and end up dropping an enormous amount of precipitation.
But in this case, the forecasts have been quite reliable.
Yes, and from many days before. We knew that a significant amount of precipitation would fall and we knew the areas where this might occur. Even though the quantity of water that finally fell was significantly higher than the high number that had been predicted. This is all the more reason to take action. 200 l/m² was predicted, and in some places it was as high as 600! To get an idea, since the Mediterranean coast is one of the driest regions in the Mediterranean basin, in many areas this volume of water is more than the average rainfall in a year, all falling in a few hours. And then, if it falls on urban areas instead of depopulated ones, catastrophe is guaranteed.
What should the authorities do?
I think at the end of the day, we have to start from the assumption that we have to adapt to extreme weather events, no matter what. I mean, we know that they are increasing as a result of climate change. And that with time, it's all going to get worse and worse. But even if climate change didn’t exist, we would still have to adapt to the extreme weather events anyway. We don't know when, but they are sure to happen again. They have happened before. We have to have plans so that an extreme weather event doesn’t turn into a catastrophe. If there is a red warning in effect, the authorities should give you a permission slip not to go to work. Administrative protocols and economic measures need to be in place. And for that to happen, one needs political authorities that will do their job.
Originally published at https://ilmanifesto.it/la-meteorologa-isabel-moreno-la-miccia-di-questi-eventi-e-il-riscaldamento-del-mare on 2024-11-01