Argentina's deadly rain more likely in a warming world, report says

Heavy rain that led to catastrophic flooding in central Argentina and killed 16 people earlier this month was partly fuelled by climate change and could become more frequent in a warmer world, a team of international scientists said on Thursday.

An analysis by the World Weather Attribution found extreme heat in the region leading up to the floods caused a warmer and more humid mass of air that clashed with a cold front from Argentina's Patagonian region, causing the torrential rains in Bahia Blanca, a port city about 550km south of Buenos Aires.

“The indicators of heat and humidity [leading to the floods] would have been virtually impossible without climate change,” Juan Rivera, one of the report's authors and scientists at Argentina's Institute for Snow Research, Glaciology and Environmental Sciences, said in a press conference on Wednesday.

Rivera said multiple days with temperatures surpassing 40ºC in northern and central Argentina, including a humid heatwave immediately preceding the rain, combined with increased humidity from the Amazon, led to an accumulation of moisture that dumped 300mm of rain over Bahia Blanca in just over six hours.

“These floods have no precedent in the national meteorological service stations,” Rivera added, noting that the cold front lingered over the area for several hours before moving on.

The study said extreme heat preceding rain are still rare events, occurring every 50 to 100 years, but climate change is making these temperatures more frequent and intense.

The year 2024 was the hottest on record as global temperatures exceeded 1.5ºC above pre-industrial levels for the first time and some scientists expect 2025 to also be among the hottest on record.

The report noted that while they were able to deduce a link to human-induced climate change and high temperatures, the link to heavy rainfall events was less conclusive due to discrepancies with global meteorological data sets.

“But don't be fooled by some of these uncertainties,” said Friederike Otto, co-lead of World Weather Attribution. “As the world continues to warm the chance of simultaneous or consecutive events hitting the same region will continue to increase and we need to be prepared for it.”

The report noted Bahia Blanca had undergone rapid urbanisation and did not have the necessary infrastructure to deal with the heavy rainfall. It added the region will face increased hazards in a warming world and the ageing population, combined with urban development and high population density, add to the risks.

Rivera noted the area had also experienced a devastating storm in 2023 that brought wind of more than 150km/h.

“Both extreme events had widespread impacts and common features linked to human-induced climate change: more frequent extreme heat and moister air, factors which fuelled the storms,” Rivera said, adding more studies are needed to understand the compounding risks of a warming world.

Reuters