We are beginning to know the toll of Cyclone Ian: at least 107 dead, and 50 billion dollars in damage. It is the biggest hurricane to hit Florida in 60 years. Details from Mathilde Fontez, editor-in-chief of the scientific magazine Espiloon.
franceinfo: These extreme cyclones lead climatologists to consider modifying the scale of dangerousness of these phenomena, Ian was classified in category 4. And there could be a category 6?
Mathilde Fontez: Yes, there is the example of Ian. But especially from Hurricane Patricia which hit Central America in 2015, with winds of 350 km/h – it is the most intense ever observed. And Dorian, in 2019, who was also particularly violent. It’s a bit like temperature records: cyclone power records have been piling up in recent years. And the cause is the same: global warming.
The climatologists, in the IPCC reports in particular, predicted that these extreme events were going to become more frequent, and intense?
Yes. For cyclones, this is easily explained: the rise in ocean temperature increases the energy available to trigger and power them. A study published last spring shows that the frequency of category 3 and above cyclones should double by 2050. Wind speeds could increase by more than 20% in places. Hence the question: that of creating a new category of cyclones.
Today, there are 5 categories, depending on the wind speed in cyclones…
That’s it: it’s a scale that was developed in 1969, to assess the effects of cyclones on human populations, in particular to trigger evacuation strategies. But in fact, it does not take into account this increase in the frequency and intensity of cyclones. In fact, climatologists did not think it would go so fast. This summer alone, all the extreme events surprised by their magnitude: the heat wave in England, the monsoon in Pakistan…
The models hadn’t foreseen that?
Not to this extent, for most of them. We realize that climate models are not necessarily well adapted to extreme events. It is a question of resolution, these phenomena are small. And also physical complexity: they are controlled by effects that are difficult to model, such as the coupling between the ground and the atmosphere, for example.
Work is underway to improve them. And for cyclones, to take into account parameters other than wind speed. Because we know that it is above all water that kills: rains, floods. A new risk scale could take that into account.