In Texas, a massive storm dumped as much as 15 inches of rain, fueling floods that claimed at least 104 lives this past week. In New Mexico, another storm unloaded 3 1/2 inches of monsoonal rains in 90 minutes, spurring flooding that killed three people. In North Carolina, Tropical Storm Chantal deposited up to 10 inches of rain, triggering flooding that resulted in five deaths.
The “extreme precipitation” that occurred in all three places is becoming increasingly common and more intense due to climate change, according to experts.
“These are roughly one-in-1,000-year events, [and] would be extremely rare in the absence of human-caused warming,” said Michael Mann, a University of Pennsylvania climate scientist, to HuffPost.
One key factor behind heavier rains is a warmer atmosphere, which is a direct result of climate change. Warm air can hold more moisture, so more precipitation is unleashed when storms occur. For every degree-Celsius that the atmosphere’s temperature increases, the amount of water vapor in it can go up by 7%, per NASA.
“The scientific literature shows that a warming atmosphere increases water vapor availability to storms. That’s just basic physics,” said James Marshall Shepherd, director of the atmospheric sciences program at the University of Georgia.
Additionally, Mann’s research has found that extreme weather conditions are now being locked in place for longer periods, meaning that phenomena like the heat dome that fueled an East Coast heatwave in June and the storms that led to Texas rains are effectively lingering over one area.
More extreme precipitation could have serious implications for flooding. However, it’s far from the only element that contributes to such natural disasters, which are the product of “rainfall intensity, land surface conditions, and other factors,” said Shepherd.
“This region is known as ‘Flash Flood Alley’ for a reason. However, the natural process has a steroid on top of it,” Shepherd said of the Texas Hill Country area that was hit with floods this week.
Other natural disasters, such as drought and wildfires, are also making places vulnerable to flooding in new ways.
“In the case of these latest flooding events in Texas and New Mexico, these regions have been heavily impacted by drought and wildfire over the past year,” said Mann. “This can lead to parched, hardened ground, which is unable to absorb rainfall, forcing it to run off in rivers and streams.”