Climate change, compounded by a weak La Niña phase, significantly intensified the extreme rainfall that triggered deadly flooding across Southern Africa in recent weeks, according to new scientific research.

The floods, which affected Mozambique, South Africa, Zimbabwe, and Eswatini, have reportedly killed up to 200 people and displaced hundreds of thousands, highlighting how climate-driven extreme weather is colliding with deep-rooted social and infrastructure vulnerabilities across the region.

Scientists found that the intensity of extreme rainfall events has increased by about 40 percent since pre-industrial times, with some areas receiving more than a year’s worth of rain in just a few days. The prolonged downpours overwhelmed river systems, destroying homes and farmland, which also disrupted essential services long after the rain subsided.

In South Africa, the impacts extended to the Kruger National Park, where severe flooding damaged roads, bridges, and tourist facilities, forcing temporary closures and causing tens of millions of dollars in losses, according to the country’s environment ministry.

Rainfall intensity rising in a warming climate

The study analysed 10-day extreme rainfall events across the region and found clear evidence that human-induced climate change has significantly increased their severity. Observational data show that rainfall associated with such events is now around 40 percent more intense than it would have been in a pre-industrial climate.

While rainfall events of this magnitude remain relatively rare, estimated to occur roughly once every 50 years, researchers noted that they would have been even less likely without global warming.

According to Izidine Pinto, Senior Climate Researcher at the KNMI Royal Netherlands Meteorological Institute, the science is clear: human-caused climate change is supercharging rainfall events like this with devastating impacts for those in its path.

“Our analysis shows that the continued burning of fossil fuels is not only increasing the intensity of extreme rainfall, but turning events that would have happened anyway into something much more severe,” Pinto said.

Although climate models struggled to precisely quantify how much worse the floods were made by climate change, scientists stressed that the observational evidence leaves little doubt about the trend.

“A 40 percent increase in severity in the observational data is impossible to explain without climate change,” Pinto added, noting that warmer air holds more moisture, creating conditions for heavier downpours.

La Niña as a force multiplier

In addition to long-term warming, the current weak La Niña phase played a significant role in increasing the likelihood and intensity of the rainfall.

La Niña is known to bring wetter-than-average conditions to parts of Southern Africa, but researchers say its effects are now unfolding in a much warmer and more moisture-rich atmosphere.

Bernardino Nhantumbo, a climate researcher at Mozambique’s National Institute of Meteorology (INAM), said the region is accustomed to La Niña, but climate change is increasingly acting as a force multiplier.

“This study shows that the natural wet signal of La Niña was amplified by about 1.3 degrees Celsius of global warming, creating a perfect storm that overwhelmed the lower Limpopo River basin,” Nhantumbo said.

The result, he added, was rainfall far beyond what communities and infrastructure were designed to withstand, hence the incurred losses and casualties.

High vulnerability, low resilience

Researchers emphasised that the scale of destruction cannot be understood through climate hazards alone. Across the affected countries, a large share of the population lives in informal settlements and flood-prone areas, often without adequate drainage, durable housing, or access to basic services.

Prolonged rainfall caused widespread structural failures, collapsing homes, and washing away roads, leaving many people displaced weeks after the floods.

“When 90 percent of homes are made of sun-dried earth, they simply cannot withstand this much rain,” Nhantumbo said. “The structural collapse of entire villages is a stark reminder that our communities are now being tested by weather they were never designed to endure.”

The floods also devastated agricultural areas, compounding food insecurity in communities already grappling with economic pressures and climate stress.

Beyond immediate destruction, the floods triggered serious public health risks. Damage to infrastructure disrupted access to clinics, interrupted treatment for chronic illnesses, and compromised medical cold-chain systems. Floodwaters also affected drinking water quality, increasing the risk of waterborne diseases.

“This event demonstrates how climate change can turn an extreme weather event into a long-term health and humanitarian crisis,” said Renate Meyer, Technical Advisor on Climate and Conflict at the Red Cross Red Crescent Climate Centre.

“When floodwaters destroy medical infrastructure and block access to clinics, the consequences for communities last long after the water recedes,” Meyer said, adding that national Red Cross societies are already witnessing these prolonged impacts.

She stressed the need for greater investment in community-led preparedness, flood-resilient infrastructure, and strengthened transboundary early warning systems as climate extremes intensify.

A case of climate injustice

Scientists and humanitarian experts described the floods as a stark example of climate injustice, with communities that have contributed little to global emissions bearing the brunt of climate impacts.

“This is a textbook case of climate injustice,” said Friederike Otto, Professor of Climate Science at Imperial College London.

“The people of South Africa, Mozambique, Zimbabwe, and Eswatini have not contributed meaningfully to climate change, nor are they profiting from fossil fuels. Yet they are the ones losing their lives, homes, and livelihoods,” Otto said.

She cautioned against framing such disasters as unavoidable natural events, noting that rising emissions are directly shaping their severity.

“A 40 percent increase in rainfall intensity is not a small statistical anomaly,” Otto said. “For families living in informal settlements, it can be the difference between minor flooding and total structural collapse.”

As Southern Africa continues to experience more intense and unpredictable rainfall, researchers warn that without rapid emissions reductions and sustained investment in adaptation, similar disasters are likely to become more frequent and more destructive.

“We have the knowledge and the tools to stop this from getting worse,” Otto said. “What is missing is the political will to prioritise people and resilience over short-term economic interests.”