WASHINGTON (AP) — A warmer world will likely make bigger and more damaging hail, a new study said.
Because climate change from the burning of fossil fuels should make more high-energy unstable air, which is conducive to hail forming, global storms pelting roofs, cars and the ground with hail bigger than a large marble will increase between 38% and 47% by the end of the century, depending on how much heat-trapping gas the world spews, a study in Wednesday's journal Nature said. And storms that produce smaller hail will shrink by 4% to 8%, researchers found.
Hail generally doesn't kill people, but it is expensive. It already costs the U.S. about $10 billion a year and around $80 billion globally, said study co-author John Allen, a meteorology professor at Central Michigan University.
Hail does more damage than tornadoes and generally costs “more than a couple hurricanes a year now,” Allen said in the morning from Guymon, Oklahoma, before he ventured out with scientists who drive into the heart of hail storms to figure out what makes them tick. “We’ve seen record hailstones in recent years. I find this extremely concerning because we’re not really building our environment to be resilient to hail. We don’t include this in our design standards, for example, for built homes in the U.S. or indeed internationally.”
Allen's computer simulations show the mix of larger stones will grow with climate change. Those are the ones that cause more damage, he and outside scientists said.
Bigger stones mean bigger problems
Bigger stones weigh more and fall through the air faster to hit with more power.
While small hail can damage crops, large hail of around 2 inches (5 centimeters) “can cause major damage to vehicles, roofs, solar panels, and other infrastructure,” said Andreas Prein, a climate scientist at ETH Zurich, who wasn’t part of the study.
One hole on a roof from a single hailstone can be patched, but many large stones hitting that roof usually means an expensive roof replacement, Allen said.
What happens is there's more water vapor in a warmer atmosphere — nearly 4% more per degree Fahrenheit (7% per degree Celsius) — and “that increases the available energy to the atmosphere and so we tend to get end up with stronger updrafts,” Allen said. “And that leads to more thunderstorms with updrafts capable of producing hail.”
But with warmer air, there's less cold as high up for smaller hailstones and they tend to melt more, where bigger ones don't, Allen said.
Previous studies have mostly focused on hail in the United States — which has the most hail — and didn't do the three-dimensional modeling of hail formation that the new study has done with lead authors out of China, Allen said. Other studies have looked at potential increase in frequency instead of size.
Hail is a global problem
Argentina, Europe, Canada and the U.S. Northern Plains will likely see the biggest increase in larger hail, while parts of the tropics should see a reduction because of smaller stones melting, Allen said.
“Hail is not just a U.S. problem,” Allen said. “Yes, we do see large losses here, but the global hail losses seem to be something that is really spiraling in recent years.”
Study authors looked at hail bigger and smaller than 1.2 inches (30 millimeters) in diameter, which is somewhere between a marble and golf ball, and about the size of a U.S. 50-cent coin. The team looked at three scenarios based on carbon emissions from the burning of coal, oil and gas. In a slightly optimistic scenario of not so much carbon pollution, larger hail increases by 38%. In a more pessimistic scenario, where temperatures rise nearly 2 degrees Fahrenheit (1 degree Celsius) even warmer than the other scenario, larger hail jumps by 47%.
“This is a meaningful climate signal,” said Walker Ashley, a Northern Illinois meteorology professor who wasn’t part of the study. “But disaster losses are not driven by the peril alone.”
As more people, more houses, more solar farms and more infrastructure move into areas prone to hail, the risk and damage increases, Ashley said. He added: “Climate change may be increasing the potential for larger, more damaging hail in some regions, but the future loss signal will also depend heavily on where people build, what they build, how resilient those structures are, and how land use changes.”
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