Friday, July 27, 2007

Global warming can be a homewrecker

In recent years there have been numerous stories of large chunks of ice falling from a clear sky. AP reports today that it happened again July 26 in Dubuque, Iowa, where a chunk that may have weighed 50 pounds crashed through the roof of a woman's house.

In the past, media coverage has focused on the likelihood that such ice chunks originate from an airplane (either accumulated on the outside of the craft, or ejected from the lavatories), but now a more sinister suspect is starting to ooze into the reporting. We get an early warning in the second paragraph (emphasis added):
Authorities are unsure of the ice's origin but have theorized the chunks either fell from an airplane or naturally accumulated high in the atmosphere — both rare occurrences.
How can a 50-pound chunk of ice accumulate naturally in the atmosphere? What malevolent force can suspend ice long enough to grow that large on a clear day, when even the most violent of thunderstorms could never sustain the necessary updrafts?

You guessed it -- climate change!

Enter Dr. David Travis, expert on earthbound phenomena, but not necessarily atmospheric science:
David Travis, a professor of geography and geology and an associate dean at the University of Wisconsin-Whitewater, has studied the phenomenon of large chunks of ice falling from a clear sky. He said it's possible the ice could have been a megacryometeor — "similar to a hailstone, but without the thunderstorm."

[...] Most megacryometeor sightings have occurred in coastal areas, where atmospheric turbulence helps keep ice suspended long enough to grow into large chunks.

Travis' research team speculates the phenomenon could be linked with global warming, suggesting that climate change might make the tropopause portion of the atmosphere colder, moister and more turbulent.

A total guess, based on zero evidence, in other words.

Maybe I'm the one who's weak on the atmospheric science, so I'm open to being educated here. What kind of updraft is necessary to suspend an ice chunk of that weight, and how long must that updraft be sustained to allow the chunk to grow to that weight? Do such updrafts actually occur in nature?