“The heavy rains that caused catastrophic flooding in South Africa in mid-April were made twice as likely to occur by climate change, scientists said Friday.
An analysis of the flooding, which killed more than 400 people in Durban and surrounding areas in the eastern part of the country, found that the intense two-day storm that caused it had a 1-in-20 chance of occurring in any given year. If the world had not warmed as a result of human-caused emissions of greenhouse gases, the study found, the chances would have been half that, 1 in 40.
The study, by a loose-knit group of climate scientists, meteorologists and disaster experts called World Weather Attribution, is the latest in a string of analyses showing that the damaging effects of global warming, once considered a future problem, have already arrived. And extreme events like this one are expected to increase as warming continues.
“We need to drastically reduce greenhouse gas emissions and adapt to a new reality where floods and heat waves are more intense and damaging,” one of the study’s authors, Izidine Pinto, a climate scientist at the University of Cape Town, said in a statement issued by World Weather Attribution.
The flooding and related mudslides caused more than $1.5 billion in damage and were “the biggest tragedy that we have ever seen,” President Cyril Ramaphosa said at the time. Bridges and roads were destroyed and thousands of homes, many of them in makeshift settlements, were swept away or damaged.
World Weather Attribution conducts its analyses within days or weeks of an event, while it is still fresh in the public’s mind. This one looked at the two-day storm that hit eastern South Africa beginning on April 11 and produced rainfall totals of nearly 14 inches in some areas, half or more of the area’s annual total. The work has yet to be peer-reviewed or published, but it uses methods that have been reviewed previously.
This includes using observational data and two sets of computer simulations, one that models the world as it is, about 2 degrees Fahrenheit (1.1 degrees Celsius) warmer than it was before widespread emissions began in the late 19th century, and a hypothetical world in which global warming never happened.
The finding that the likelihood of such an extreme rain event has increased with global warming is consistent with many other studies of individual events and broader trends. A major reason for the increase is that as the atmosphere warms, it can hold more moisture.”