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Catastrophic floods around the world

Scientists have emphasised the impacts of climate change on the water cycle for decades. The latest IPCC report, published on 9 August, is even more precise about the extreme events that will result from them, in the dedicated chapter 11.

Climate change takes the form of stronger summer heatwaves and more frequent tropical nights at medium latitudes such as Canada and Europe. Warm air can contain more water, leading to more rainfall. The report also underlines the global nature of climate change and its associated disasters: all the regions of the world are already affected by these transformations of the climatic system.

Unfortunately, summer 2021 has provided a wealth of illustrations. In July, around the world, nearly 1,000 deaths occurred due to flooding caused by extreme rainfall within very short times. These events occurring in China, Germany, Belgium and the United States, show that Europe, relatively spared up to now, is at present affected by extreme meteorological events due to the effects of climate change, in the same way as Asia and Africa.



In China, the official figure for the floods that struck in mid-July was 300 deaths. Most of these victims came from the city of Zhengzhou in the province of Henan, where the equivalent of one year’s rain fell in three days. Many people lost their lives in underground infrastructures: a subway train was engulfed and some people were killed in underground carparks and in a road tunnel. In all, 20,000 people were evacuated. The city of Zhengzhou is located in the basin of the yellow River, which has often been the source of lethal floods (read the minutes of the IFGR session in China).




A collapsed sign is seen next to a river at a flood-affected area, following heavy rainfalls, in Schuld, Germany, July 15, 2021. REUTERS/Wolfgang Rattay

In Germany, more than 200 were killed and damage worth billions of euros occurred. A four-year drought had hardened the ground to a depth of two metres, leading to landslides. It is possible that these dramatic meteorological events sound the end of a period in which Western Europe felt itself safe. For Toralf Staud, scientific journalist with Süddeutsches Zeitung,

« the country is not prepared »,

and risk prevention had been greatly neglected. This disaster may finally place the climate emergency at the heart of the country’s political agenda. In addition to the IPCC report, a study by the World Weather Attribution (WWA) published on 24 August states that “climate change increased the probability and intensity” of this disaster. Yet again, the water cycle comes into question, as it is intensifying and leading to increased humidity in the atmosphere and thus precipitations.


New York


At the beginning of September, severe floods struck New York following the passage of hurricane Ida. To date, more than 40 people have lost their lives; roads were transformed into torrents in only a few minutes. As at Zhengzhou, it seems clear that underground infrastructures are especially vulnerable: the New York subway was hit and many people drowned in basement apartments. The Mayor of New York, Bill de Blasio, described it as a “historic meteorological event” and declared a state of emergency, the first in the city’s history despite the recurrent disasters of the last ten years. The governor of the State of New York, Kathy Hochul, declared that “due to climate change, it’s something that will happen regularly”.


An absolute necessity to adapt


In addition to the combat against climate change by reducing greenhouse gas emissions, these floods show the absolute necessity to prepare for adapting to future disasters, some of which are inevitable.

A report by the World Meteorological Organisation published this summer showed that catastrophes caused by extreme meteorological events (floods, heatwaves) have increased five-fold over the last 50 years. Between 1970 and 2019, floods around the world have led to 58,700 deaths and losses worth $115 billion. Conversely, the report revealed that the death rate of each extreme meteorological event had decreased, thanks to the development of early warning systems around the world. These systems must therefore be implemented more widely in vulnerable regions.


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