More than 400 people were killed in South Africa floods last month. Human-caused climate change is a big reason why, scientists say.

Catastrophic flooding wreaked havoc in South Africa last month, killing at least 448 people, displacing more than 40,000 more and destroying thousands of homes. According to a new analysis published on Friday, the toll of that devastation was made even worse by human-caused climate change.

The torrential rainfall bore down on South Africa in mid-April, causing landslides and massive floods in the Eastern Cape and KwaZulu-Natal provinces that the nation's president called "a catastrophe of enormous proportions." Many lost their loved ones in the middle of the night while they slept. One man said he lost 10 family members who were asleep in their home when flooding hit. Another woman recalled how her two daughters, age 11 and 17, were swept away as they slept in their shack. 

Nearly 14 inches of rain fell in the region from April 11 to 12, an amount that scientists from the World Weather Attribution global initiative described as "extremely high" for a two-day period. 

The scientists' analysis found that global warming made the event much more likely to occur. Their findings have not yet been peer-reviewed, but the group relies on peer-reviewed methods to conduct their research.

"We conclude that greenhouse gas and aerosol emissions are (at least in part) responsible for the observed increases," the scientists said. "...We conclude that the probability of an event such as the rainfall that resulted in this disaster has approximately doubled due to human-induced climate change." 

Climate analyst Izidine Pinto, the lead author of the analysis, said adaptation is essential for staving off the worst impacts of future disasters. 

"We need to drastically reduce greenhouse gas emissions and adapt to a new reality where floods and heatwaves are more intense and damaging," Pinto said. 

Scientists have been warning of these risks for years, with the latest analysis providing a stark reminder of the damage fossil fuels and greenhouse gas emissions are causing to humanity's ability to survive. Emissions create a dense layer in the atmosphere, trapping in heat that causes global average temperatures to increase. 

When Earth's oceans warm, the amount of water evaporated increases, creating heavier rainfall, more intense storms and flooding.

The risk of an event like the extreme rainfall in South Africa last month has doubled because of climate change, scientists concluded. If the world was 1.2 degrees Celsius cooler than it is now — roughly the average before industrialization — their analysis found an event like this would happen about once every 40 years. But in today's climate, it'll happen about every 20 years. Rainfall is now expected to be 4% to 8% heavier as a result, as well. 

And much like what happened in South Africa, extreme weather events will be particularly devastating in areas with economic disadvantages that are not adequately prepared. In this particular case, scientists pointed to governance challenges, older infrastructure and a poor warning system — challenges that are seen in many communities around the world. 

"If cities continue to develop in ways that concentrate the poorest and most marginalised people in flood prone, high risk areas, they will continue to be most affected when (sic) disaster's strike," the report states. "While rainfall during this event was extreme, this type of event is not unprecedented and is likely to happen again and with even greater intensity in the future."

The Associated Press contributed reporting.

In:
• Climate Change
• South Africa
• Flood