warming to ice melt: on abrupt climate change

dramatic increase in ice loss this year

If "the Arctic is the canary in the coal mine for climate warming,” says NASA climate scientist Jay Zwally, "the canary has died. It is time to start getting out of the coal mines.”

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 (via CNN).

Yesterday, Lonnie Thompson addressed this topic at the Fall meeting of the American Geophysical Union in SF, and the hall was packed...with good reason. The world's preeminent ice man was presenting up-to-the-minute findings on the recent acceleration in ice loss.

Thompson showed who glaciers all over, and ice sheets in both Greenland and Antartica, are disappearing at an increasing rate that is blowing scientists' minds. On this basis, there is a much greater likelihood of abrupt climate change, especially including greater sea level rise sooner.

Says Thompson, "nature is the time-keeper and none of us can see the clock!"

Right up there with Thompson's blockbuster was Mark Serreze's Nye Lecture on Arctic climate change.

Serreze notes that the state of ice thickness observed in 2007 is quite similar to the modelled state in 2020, suggesting that 2007 is the new 2020.

As noted by Real Climate's Ray Pierrehumbert, "Since 2005 there has been a 25% decline in Arctic sea ice at the time of minimum, equal to the combined area of Texas and California. What's more, the drop in 2007 was way below the already steep trend line for 1978-2002."

And, speaking of "tipping points", Pierrehumbert notes that "factors contributing to the unusual 2007 drop include an unusual pattern of atmospheric circulation, with high pressure over the Central Arctic and low pressure over Siberia. This brings a lot of warm air into the Arctic. How does this fit into the longer term pattern? It comes back to the thinning again: the sea ice was so vulnerable to this situation (which has happened before) because it is so thin."

Says Pierrehumbert, "to put the contribution of Greenland melt in perspective, IPCC 2006 put sea level rise at 1.28 mm/yr, but based on the latest GRACE data on ice sheet melt, the estimated number is now 2.2mm/yr, of which 30% is due to Greenland and 20% due to Antarctica."

Pierrehumbert concludes, "every new revision seems to be upward, and it's far from clear what the ceiling will be once things shake out."

Ya gotta hope the Bali boys are watching this canary, too...

Published by Ken on December 13th, 2007 tagged Climate Change, Island Vulnerabilities

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