What was the influence of global warming on Cyclone Chido, which devastated Mayotte?

Such a phenomenon had not been observed in the archipelago since 1934. Cyclone Chido hit Mayotte hard on Saturday December 14, destroying thousands of homes in its path and undermining the health system and the chain of food supply of the French department.

Four days after the disaster, and while the human toll promises to be particularly heavy, franceinfo takes stock of what we know about the link between this extreme meteorological phenomenon and global warming.

Invited to the Mayotte La 1ère plateau the day after the cyclone, the prefect François-Xavier Bieuville explained that he expected “hundreds” or even potentially “thousands” deaths in the territory. The intensity of the cyclone, although significant, is not exceptional for the region which sees “three systems of intensity equivalent to that of Chido on average each season”explains in the columns of Monde Céline Jauffret, head of Météo-France for the Indian Ocean zone.

To understand the extent of this toll, we must look at the trajectory of the cyclone, which is unusual in the region: Chido passed north of the island of Madagascar without hitting it. “A rare scenario, given the configuration of the area : most cyclones that come from the East land directly on Madagascar, which slows down their progress “explains to Figaro François Bonnardot, head of the forecast service at Météo-France Réunion.

The eye of the cyclone, the most devastating area of ​​the hurricane, therefore hit the Petite-Terre region directly and head-on as well as the northern and central regions of Grande-Terre, the main island of Mayotte. Gusts of up to 226 km/h were recorded in the commune of Pamandzi, reports Météo-France. However, the territory is made particularly vulnerable to weather conditions by its numerous tin houses.

In this catastrophe, global warming seems to have played an important role upstream. And for good reason, surface waters were around 30°C in this area of ​​the western Indian Ocean, almost 1.5°C higher than normal. This abnormally high temperature may have provided energy to Chido, and therefore increased his power. “High sea temperatures, which fueled the formation and rapid intensification of Chido, have increased 50-fold due to climate change”corroborates Imperial College London in its rapid study published on Tuesday.

According to this same first work by British researchers, global warming also intensified the cyclone’s winds by around 11 km/hour, taking it from category 3 to category 4 when it hit Mayotte. “If the atmosphere had not been overloaded with carbon emissions, [le cyclone] would have been a category 3 event”, according to Ralf Toumi, director of the Grantham Institute at Imperial College, cited in the rapid study. British scientists finally report finding that Category 4 storms hitting Mayotte have become more likely compared to pre-industrial times.

The network of European researchers ClimaMeter also tried to understand the impact of global warming in Saturday’s disaster. In a first rapid attribution study published Monday, scientists explain that the historical data available in the area are not complete enough to draw conclusions, due to the rarity of such a phenomenon on the archipelago.

The initial findings of Imperial College scientists will therefore need to be further consolidated in the weeks to come. “We will have to wait until we have modeling studies to determine the influence of climate change on Chido”agrees climatologist Christophe Cassou, research director at CNRS, on the Bluesky social network.

In any case, the future is not encouraging for the French department. Cyclone activity in this area could, in the coming years, be further modified under the influence of a warming climate, according to various scientific projections. “We must expect stronger surface winds, greater risks of submersion (…). We also expect more intense precipitation in cyclonic events,” takes place with our colleagues from Réunion The 1st Marie-Dominique Leroux, head of the studies and climatology division of Météo-France for the Indian Ocean.

Globally, the scenario is equally bleak. Even if the number of tropical cyclones does not increase, “climate change increases the occurrence of more intense and more destructive storms”, according to the World Weather Attribution network of scientists.

Since the 19th century, the average temperature of the Earth warmed by 1.1°C. Scientists have established with certainty that this increase is due to human activities, which consume fossil fuels (coal, oil and gas). This warming, unprecedented in its speed, threatens the future of our societies and biodiversity. But solutions – renewable energies, sobriety, reduced meat consumption – exist. Discover our answers to your questions on the climate crisis.