In Texas, Florida and across the globe, warmer climate makes flooding ‘more unprecedented'

Miami Herald

2 days ago

As the Texas flooding death toll reached 95 on Monday — at least 27 of them children — and Tropical Storm Chantal prompted dozens of water rescues in North Carolina, some Floridians were reminded of the disastrous 'rain bomb' in 2023 that hit faster and harder than any hurricane in living memory.
Though no one died from the 2 feet of rain that deluged Fort Lauderdale in a single day in April two years ago, the relentless rain forced hundreds to flee to Red Cross shelters, covered airport runways, filled the tunnel that runs under the New River and turned downtown streets into raging rivers.
And, despite the sheer speed with which these floods took people by surprise, they have another thing in common: Climate change made them even more catastrophic.
While the tropical system stuck over Texas' Hill Country — also known as 'Flash Flood Alley' — was expected to cause flooding, 'we also know that climate change is adding just a little bit of extra rain,' Shel Winkley, who worked as a broadcast meteorologist for a CBS-affiliate in Texas, told the Miami Herald.
Overall, the climate is now 1.3 degrees Celsius warmer than before humans started burning fossil fuels, which releases greenhouse gases that trap heat within the atmosphere. The warmer the atmosphere, the more moisture it can hold, and, consequently, release.
Heavier rainfalls likely made the Texas flooding 'even more unprecedented,' said Winkley, who taught at Texas A&M University. 'The question is, would it have come down as fast, and would the river have risen as quickly as it did, without that climate change influence?'
Using a rapid analysis to show how the floods are linked to climate change, scientists in Europe determined that warmer weather fueled the Texas disaster as overall weather conditions in that specific region had gotten wetter compared to the past. The severity of the event, they said, can't be explained by naturally occurring changes to the climate and weather.
Research by Climate Central, a nonprofit science and communications group, also found that, over the past 50 years, rainfall has become heavier in cities like San Antonio, some 60 miles south of the worst flooding, with rainfalls now increased by 6 percent.
In Miami, Climate Central's analysis, which is based on NOAA data, found that the hourly rainfall intensity increased by 12 percent.
Both Florida and Texas are adversely affected because they lie on the Gulf of Mexico, which is currently between 2 to 3 degrees Fahrenheit warmer than the average for the beginning of July, conditions that are 10 to 30 times more likely because of climate change.
This extra heat has given more water molecules the energy they need to 'escape' from the surface and evaporate into the atmosphere, where they're supplying additional moisture, which makes rainfall more intense.
'Climate change loads the dice toward more frequent and more intense floods,' Davide Farranda, an expert on extreme weather events at the French National Center for Scientific Research, said in a statement, adding that the Texas flood 'shows the deadly cost of underestimating this shift.'
'We need to rethink early warning systems, land-use planning, and emergency preparedness. And above all, we must reduce greenhouse gas emissions to limit future risks,' he said.
While cutting greenhouse gas emissions is the only proven solution that can stop things from getting even worse, our atmosphere and oceans react slowly to the CO2 we're emitting. The impact of the fossil fuels burnt today will be felt in decades to come.
That makes adaptation a necessity, especially in places like South Florida, where a lot of infrastructure dates back to the 1950s.
'These extreme events are likely to become more frequent,' said Ben Kirtman, an atmospheric scientist at the University of Miami, referring to the 2023 rain bomb, which overwhelmed Fort Lauderdale with such a sudden deluge that schools had to shut down for two days.
A 1-in-500-year flood, he said, referring to a flood that, statistically speaking, is so devastating it occurs once every 500 years, 'that will maybe be a 1-in-a-100-year flood, or a 1-in-20-year flood,' Kirtman said.
Cities, he said, need to know what to plan for, so infrastructure can be hardened, and at least some catastrophes can be avoided.
Figuring out not just how much rainfall we can expect, but also the frequency and duration of rainfall is exactly what Kirtman and colleagues from across Florida, including the US Geological Service, are trying to figure out.
Six inches of rainfall might not be a lot for a city like Miami, but it wouldn't be able to handle six inches of rain over three, four or five days. Within a year, he and his colleagues hope to have some preliminary data.
Even with that data, keeping people and properties safe from ever heavier flooding can simply prove too costly. Miami, for example, would have had to pay $5.1 billion to upgrade its infrastructure for a 1-in-10-year storm, an extra $1.3 billion compared to adapting for a 1-in-5-year storm. The city tried to find a middle ground, upgrading some projects to higher and others to lower levels.
Though Floridians are used to storms, heavy rain and flooding, being surrounded by a warmer Gulf on all sides and the fact that hurricanes have already become more intense doesn't bode well, Winkley said. And while Florida was less susceptible to river flooding due to its lack of hills, the Texas flood, he said, was 'a warning for everybody.'
This climate report is funded by Florida International University, the John S. and James L. Knight Foundation and the David and Christina Martin Family Foundation in partnership with Journalism Funding Partners. The Miami Herald retains editorial control of all content.