Super-typhoons in Asia, storm Boris in Europe and hurricanes in North America: extreme precipitation, exacerbated by the very abnormally high temperatures on the planet for more than a year, marked the month of September around the world.
September 2024 was the second warmest September on record, continuing a series of records or near-records that make it “virtually certain that 2024 will be the hottest year ever measured”, the European Copernicus Observatory announced on Tuesday . 2024 would thus beat the established record… in 2023.
“The extreme rainfall of the last month, which we are seeing more and more often, has been made worse by a warmer atmosphere”, with in places “months of rain in a few days”, says Samantha Burgess, deputy director of the climate change department (C3S) of Copernicus.
The observatory’s monthly bulletin highlights the examples of storm Boris, synonymous with exceptional flooding in Central Europe, the monsoon which “severely hit” Pakistan, and the typhoon Krathon which hit Taiwan and the Philippines in early October.
September was also marked by the devastation of super typhoons Yagi And Bebinca in Asia, deadly floods in Nepal and Japan or even the hurricane Helene in the United States.
In West and Central Africa, an intense rainy season has caused more than 1,500 victims, four million victims and 1.2 million displaced people, according to the International Organization for Migration (IOM).
With an average temperature of 16.17°C on the surface of the globe, September 2024 does not beat the record of September 2023, which surprised the scientific community with its magnitude.
But if residents of France, the American east coast or central Asia may be surprised, after experiencing cooler temperatures than usual, September globally remains significantly warmer than in the past.
Annual record in sight
September 2024 is thus, globally, 1.54°C warmer than a normal September in the pre-industrial climate (1850-1900), reports Copernicus.
In the observatory database, September 2024 is the 14e over the last 15 months to be 1.5°C warmer than during this period, therefore exceeding the most ambitious limit that States set for themselves by approving the 2015 Paris Agreement.
The probability is very high that 2024 will be the first calendar year to cross this now symbolic limit.
Such an anomaly of 1.5°C should however be observed on average over several decades to consider that the climate, currently warmed by around 1.3°C, has reached this bar. For the Intergovernmental Panel on Climate Change (IPCC), this threshold could be observed by 2030-2035, given the current trajectory of humanity’s greenhouse gas emissions, not yet in decline.
Strengthened storms
These incessant temperature records are fueled by the unprecedented overheating of the oceans, which cover more than two thirds of the planet and have absorbed more than 90% of the excess heat caused by human activity.
In September, the average sea surface temperature remained at an extraordinary degree of heat, continuing an uninterrupted series since May 2023. And the sea ice surface is well below average at both poles, notes Copernicus.
In addition to the immediate impacts of marine heatwaves on corals, seagrass beds, crustaceans and fish, this lasting overheating of the oceans, the main regulator of the earth’s climate, affects marine and atmospheric currents.
Warmer seas release more water vapor, providing additional energy for typhoons, hurricanes or storms. Especially since the warming of the air makes it possible to retain more water (up to 7% more per degree Celsius of warming), favoring extreme precipitation.
“On average, the destructive potential of hurricanes has increased by around 40% due to the 1°C warming that has already occurred,” Michael Mann, a climatologist at the University of Pennsylvania, told AFP.
These climate observations will be the background to the UN negotiations at COP29 in Baku in November. Nations must agree on how to provide developing countries with the trillions of dollars needed for their energy transition and to protect themselves from more frequent disasters.