Wednesday, December 12, 2007

Ominous Arctic Melt Worries Experts


By SETH BORENSTEIN, AP Science Writer (excerpted, click title for full article)

An already relentless melting of the Arctic greatly accelerated this
summer, a warning sign that some scientists worry could mean global
warming has passed an ominous tipping point. One even speculated that
summer sea ice would be gone in five years.

Greenland's ice sheet melted nearly 19 billion tons more than the
previous high mark, and the volume of Arctic sea ice at summer's end was
half what it was just four years earlier, according to new NASA
satellite data obtained by The Associated Press.

"The Arctic is screaming," said Mark Serreze, senior scientist at the
government's snow and ice data center in Boulder, Colo.

Just last year, two top scientists surprised their colleagues by
projecting that the Arctic sea ice was melting so rapidly that it could
disappear entirely by the summer of 2040.

This week, after reviewing his own new data, NASA climate scientist Jay
Zwally said: "At this rate, the Arctic Ocean could be nearly ice-free at
the end of summer by 2012, much faster than previous predictions."

So scientists in recent days have been asking themselves these
questions: Was the record melt seen all over the Arctic in 2007 a blip
amid relentless and steady warming? Or has everything sped up to a new
climate cycle that goes beyond the worst case scenarios presented by
computer models?

"The Arctic is often cited as the canary in the coal mine for climate
warming," said Zwally, who as a teenager hauled coal. "Now as a sign of
climate warming, the canary has died. It is time to start getting out of
the coal mines."

It is the burning of coal, oil and other fossil fuels that produces
carbon dioxide and other greenhouse gases, responsible for man-made
global warming. For the past several days, government diplomats have
been debating in Bali, Indonesia, the outlines of a new climate treaty
calling for tougher limits on these gases.

What happens in the Arctic has implications for the rest of the world.


NASA's "Tipping Points" panel and slide show materials:

http://www.nasa.gov/topics/earth/tipping_points.html

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