Watch Out For Falling Ice-Even in the Summer!
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Are falling ice balls a product of global warming?
Wednesday, December 10, 2003By Michael Woods, Pittsburgh Post-Gazette
BARCELONA, Spain -- A Spanish-American scientific team will be scanning the United States this winter for what might be one of the weirdest byproducts of global warming: great balls of ice that fall from the sky.
The baffling phenomenon was first detected in Spain three years ago and has since been reported in a number of other countries, including the United States. So scientists now plan to monitor in a systematic way what they call "megacryometeors" -- or great balls of ice that fall from the sky.
"I'm not worried that a block of ice may fall on your head," said Dr. Jesus Martinez-Frias of the Center for Astrobiology in Madrid. "I'm worried that great blocks of ice are forming where they shouldn't exist."
Ice balls, which generally weigh 25 to 35 pounds but can be much bigger, have punched holes in the roofs of houses, smashed through car windshields, and whizzed right past people's heads.
Incidents like those may be just the beginning, according to Dr. David Travis, who chairs the department of geography and geology at the University of Wisconsin-Whitewater.
"If megacryometeor formation is linked to global warming, as we suspect, then it is fair to assume that these events may increase in the future," Travis said.
Martinez-Frias pioneered research on megacryometeors in January 2000, after ice chunks weighing up to 6.6 pounds rained on Spain for 10 days.
At first, scientists thought the phenomenon was unique to Spain. During the past three years, however, they've accumulated strong evidence that megacryometeors are falling all around the globe.
More than 50 falls have been confirmed, and researchers believe that's a small fraction of the actual number, since others may hit unoccupied areas or melt before discovery.
Travis said most megacrymeteor falls occur in January, February and March.
Researchers were able to analyze ice samples from the 2000 incidents, thanks to witnesses who kept the material cold. Martinez's team quickly ruled out obvious explanations.
The ice balls, for instance, were not frozen water from toilets flushed on jetliners. The ice contained no human waste and none of the blue disinfectant used in airplane toilets. Air traffic control records showed that no planes flew over the areas near the ice falls, so the ice had not been shed from aircraft wings.
Chunks of debris from a comet? Again, lab tests showed that ice in megacryometeors had the distinctive chemical signature of ice in ordinary terrestrial hailstones.
Hail forms in the updrafts and downdrafts of thunderstorms. The updrafts carry droplets of super-cooled water, which freeze. More droplets hit the frozen particles as winds toss them around. The water freezes instantly and the hailstone grows, layer by layer.
Most hailstones weigh a fraction of an ounce, with 27 ounces the U. S. record.
Megacryometeors show the telltale onionskin layering seen in hailstones. They also contain dust particles and air pockets found in hail. But they are formed in cloudless skies, a notion that defies research on hail formation.
"Scientists are naturally reluctant to say something never can happen," said Charles Knight, a hail expert at the University Corporation for Atmospheric Research in Boulder, Colo. "But oh, dear. I would be tempted to say 'never' on this."
Knight has reviewed scientific papers on megacryometeors, and thinks the explanation that cites unusual atmospheric conditions possibly linked to global warming, is probably wrong, although he doesn't have a better one.
Global warming involves higher temperatures on Earth's surface, but creates colder conditions in the stratosphere, the uppermost layer of the atmosphere, according to Travis.
He has linked megacryometeor events to unusual conditions in the "tropopause," the boundary between the troposphere (the lower atmosphere) and the stratosphere. Located 5 to 9 miles above the surface, the tropopause marks the limit of clouds and is important in the development of storms.
Global warming may be making the tropopause colder, moister and more turbulent, Travis said, creating conditions in which ice crystals grow like ordinary hailstones in thunderclouds.
(Michael Woods can be reached at
mwoods@nationalpress.com or 1-202-662-7072.)
