St. Louis has been hit by record flash flooding. Here's how it's related to climate change.

·Senior Editor
·4 min read

Record-breaking rainfall that caused flash flooding in the St. Louis area Tuesday morning, leaving cars trapped on streets, causing road closures and at least one death, is not just a freak occurrence: It’s a manifestation of human-caused climate change. By 7 a.m. Central time, rainfall since midnight averaged between 6 and 10 inches around the region.

That kind of saturation has been made more likely because warmer air holds more water and causes more water to evaporate, and it’s happening more frequently as a result.

John Ward, left, and a firefighter help Lynn Hartke wade through flash floodwater
A woman is helped through floodwater in St. Louis on Tuesday. (David Carson/St. Louis Post-Dispatch via AP)

“In recent years, a larger percentage of precipitation has come in the form of intense single-day events,” the Environmental Protection Agency said. “Nine of the top 10 years for extreme one-day precipitation events have occurred since 1996. The prevalence of extreme single-day precipitation events remained fairly steady between 1910 and the 1980s, but has risen substantially since then.”

So while the Southwest suffers through a 20-year megadrought — the driest two decades in the region in at least 1,200 years — it has also experienced a 10% increase in the heaviest precipitation events between 1956 and 2016, according to the U.S. Global Change Research Program.

Other regions are seeing more dramatic storms and experiencing more frequent and severe flooding. The Midwest has 42% more heavy precipitation events per year than it did 60 years ago, and the Northeast is seeing 55% more.

In St. Louis, more than 8 inches of rain fell in just seven hours in the city proper, easily beating its previous one-day record of 6.85 inches, according to the National Weather Service.

Abandoned cars
Abandoned cars on a shuttered Interstate 70 in St. Peters, Mo. (Robert Cohen/St. Louis Post-Dispatch via AP)

Part of Interstate 70 flooded, necessitating rescues of stranded residents and drivers. Although thunderstorms are ongoing, the rain was expected to taper off by late afternoon. At least one person and 10 puppies — a facility for rescued dogs flooded — have been reported dead.

Many stations in the St. Louis area's MetroLink commuter rail system flooded, causing delays of more than an hour. One driver, Jerome Smith, told CNN he was stuck on I-70 for three hours as the highway was covered by water. "You can see there’s cars up there floating around,” he said in a video he shared with the network. “It's just all boxed in — there’s nowhere for the water to go.”

Other cities in the Midwest and Northeast have recently seen similar overwhelming rainfall. Last year, the Detroit area got 6 inches of rain in June and 8 inches in August, flooding basements, garages and vehicles, and Hurricane Ida dumped more than 3 inches of rain on most of New York City in just one hour. The resulting flooding killed 11 people in basement apartments in the city and shut down every subway line. And last Monday, New York City got inundated again, as water cascaded down the stairs into subway stations like a waterfall. Central Park received the most rainfall it has ever recorded since measurements began in 1869.

A rescue underway in St. Peters
A rescue underway in St. Peters. (Robert Cohen/St. Louis Post-Dispatch via AP)

The flooding is likely going to get worse in the decades to come. A study published in January in the peer-reviewed British journal Nature Geoscience found hurricanes will expand farther north in the Northern Hemisphere.

“Some of the most populous seaside cities in the world — think New York, Tokyo, Shanghai ... always have had hurricanes, but very rarely,” study co-author Kerry Emanuel, a professor of atmospheric science at the Massachusetts Institute of Technology, told Yahoo News at the time. “If they start getting more hurricanes, and if they’re stronger, and if they’re pushing water on top of an already elevated sea level, that’s going to be trouble for them.”

And if the greenhouse gas emissions causing global warming are not swiftly reduced, the trouble will be even worse.

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