The sudden, percussive crackle sounded as Barb Berlin stood in the garage of her farmhouse near Inman, Nebraska.
“I thought it was a gun,” she said.
Then came a white streak. She realized the sound wasn’t gunfire, but buckshot.
A fist-sized hailstone had hit the tin roof of Berlin’s garage. Soon others were leaving softball-sized craters in the hood of her Ford Mustang, parked outside.
“It was so loud and it was scary. I prayed a lot,” Berlin said, adding that she worried about her livestock. “I’ve never had hail like that before.”
Hail is a creeping danger. This year, amid a spring and summer of extreme weather, hail — not hurricanes, floods or tornadoes — has caused the most losses in the U.S., according to Gallagher Re, a global reinsurance firm that tracks such data.
And research suggests that large hailstones like the one Berlin saw on Monday will become more common as the Earth warms. That was the finding of a study published last month, which suggested that smaller, less damaging hailstones will become less likely.
The study, by researchers at Northern Illinois University, found that the frequency of hailstones about 4 cm or larger will increase by 15% to 75%, depending on the amount of greenhouse gases humans emit.
Hail forms when thunderstorms circulate raindrops in the upper atmosphere. It usually forms in places where the temperature is between -22 and -14 degrees Fahrenheit. The reason that climate change is affecting hail is that higher temperatures provide more energy to push air upward in thunderstorms.
“We see stronger rising air currents in the future because we have more atmospheric instability,” said Victor Gensini, one of the study’s lead authors and a professor of meteorology at Northern Illinois University.
These powerful updrafts cause hailstones to linger longer in parts of a storm that are favorable for hail formation, the study found. That, in turn, will cause them to accumulate more ice before they become too heavy and fall to the ground.
“Imagine taking a hair dryer, turning it on its side and pointing it up at the sky and trying to balance a ping-pong ball,” Gensini said, explaining how an updraft lifts a hailstone. “Now try to balance a baseball or a grapefruit. You need a much stronger updraft to balance the downward force of that.”
The prospect of larger hail, already one of the most expensive weather hazards in the U.S. and a major factor driving up insurance premiums, will only exacerbate these problems.
“Storm losses are a very, very big part of why premiums continue to rise and why there’s a huge reassessment of risk, not just by the insurance industry, but by banks and the federal government,” said Steve Bowen, Chief Science Officer for Gallagher Re.
He added that hail “represents approximately 50 to 80 percent of insured claims for losses from thunderstorms.”
According to Bowen, thunderstorms have been responsible for about $61 billion in economic losses in the U.S. this year. Hail was likely responsible for between $31 billion and $49 billion of that total. During the same period, tropical storms and floods combined have caused $14 billion in losses.
The atmospheric dynamics involved in hailstorms are complex and difficult to study. However, advances in climate and weather modeling allow scientists to create complex simulations of thunderstorms and their microphysics, including hail size.
For their research, Gensini and his fellow researchers incorporated future climate predictions into a weather model, similar to what weathermen use on television.
The study predicts that the Plains states will see fewer hail days, but that there will be more severe hail storms overall and in other regions.
While a warmer atmosphere causes hail to melt more quickly as it falls to the ground, that dynamic primarily affects smaller hailstones, which fall more slowly.
The terminal velocity of a baseball-sized hailstone is about 100 mph, according to Harold Brooks, a senior research scientist at the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory, who was not involved in the recent study. For comparison, a 1-inch hailstone falls at 20 to 30 mph.
He said the study’s findings were consistent with previous work. A 2017 study used a different modeling approach and predicted larger average hail sizes, but fewer days with hail. Researchers in Italy, meanwhile, evaluated more than a million hailstorms from 1988 to 2016 and suggested that storms produced fewer and larger hailstones.
“It makes sense. We’ve gotten some hints from observations,” Brooks said. “The basic physical mechanisms that they’re talking about, I don’t find that surprising at all.”
Although hail causes more financial damage each year than tornadoes, research on hail has generally been at a standstill until recent advances in radar and weather modeling.
“It just doesn’t seem as sexy as tornadoes,” Brooks said.
He added that important questions about hail still remain: “Can we learn enough about how hail forms and how hail size is distributed during a storm to make useful predictions a few hours in advance?”
Next year, Gensini and scientists from several other institutions are planning the first U.S. field study of hail since the 1970s. The researchers will chase hail storms like some tornadoes, trying to use mobile Doppler radars and other instruments to capture the internal physics of the storms.
After Monday’s storm in Nebraska, Berlin said she saw a lot of roofing company trucks driving through town. An insurance adjuster has already assessed her roof for damage. Her Mustang sustained about $3,500 in damage.
If she had warned earlier, she would have gotten her animals to safety and put her car in the garage. She didn’t get a hail warning in the forecast and didn’t get a warning from the weather app until after the storm had passed.
Fortunately, Berlin said, “no livestock was injured, but it was large enough to cause significant damage.”
This article was originally published on NBCNews.com