FEATURE - Scientist says ice meteors a sign of climate change
Date: 01-Oct-02
Country: SPAIN
Author: Emma Ross-Thomas
Jesus Martinez-Frias has spent the last two-and-a-half years investigating so-called megacryometeors - ice meteors - which tend to weigh more than 10 kg (22 lb) and have been known to leave 1.5 metre-wide (five feet) holes in houses.
He fears the formation of these hailstone-like blocks on clear days could be a worrying symptom of climate change.
"I'm not worried that a block of ice might fall on your head ... but that great blocks of ice are forming where they shouldn't exist," said Martinez-Frias, director of planetary geography at Spain's Astrobiology Centre in Madrid.
"Components of the atmosphere, like ozone and water, are changing in different levels of the atmosphere...We think these signs could be evidence of climate change," he said in a telephone interview with Reuters.
While Martinez-Frias said he was far from certain as to why the ice meteors formed, he said they were neither hoaxes nor blocks of ice falling from the bars or bathrooms of passing aircraft, as sceptics have suggested.
"We're not talking about hoaxes," Martinez-Frias said. "It's very easy to tell real and false ice blocks apart."
"It's not water from airplane toilets...Its isotopic composition bears the signature...of Iberian rain."
SMASHING WINDSCREENS
Ice clouds made from crystallised vapour trails of aircraft are well known to pilots, but Martinez-Frias suggests that because global warming involves one level of the atmosphere getting colder while another gets hotter, some ice clouds now remain longer.
Their centres then fall through the atmosphere, bouncing and gathering mass, to end up smashing through a car windscreen or, more usually, landing softly in a field, he suggested.
The first megacryometeor found this year in Spain - by a startled farmer riding his tractor in Soria - weighed 16 kg (35.27 lb).
Three others were found later, bringing the world total over the last decade to more than 50. But Martinez-Frias said only around a fifth of the ice meteors are ever found.
An ice meteor weighing around 200 kg (440 lb) has been found in Brazil, Martinez-Frias said. Other blocks have been found in Mexico and Australia.
The blocks form between four and nine-and-a-half km (two-and-a-half and six miles) above ground, he said.
Some scientists doubt whether hail can form on a clear day.
"Solid ice cannot form in the absence of thick, highly visible clouds," Charles Knight, a hail expert at the University Corporation for Atmospheric Research in Boulder, Colorado was quoted as saying in a supplement of Science journal.
But geologist Roger Buick of the University of Washington in Seattle told the same publication that a model created by Martinez-Frias and his team showing ice can form on a clear day was an "important advance in that it thoroughly documents and provides an explanation for a spectacular phenomenon."