Arctic Sea Ice Melt 20 Years Ahead of Schedule, Scientist Maintains Tipping Point Assertion

arctic summer ice melt 2008 image

image: Goddard Space Flight Center

You may find this hard to believe considering the wintry weather across much of the US, but the long term trend is still for warmer ice-free summers in Arctic. In fact we have probably already passed a tipping point and are 20 years ahead of schedule on the melting front, according to Mark Sezzere of the National Snow and Ice Data Center in Boulder, Colorado. Sezzere recently presented new evidence supporting his case:
Air Temps Above Melting Ice 5° Higher Than Averages
Presented at the American Geophysical Union meeting in San Francisco last week, Sezzere said that by measuring air temperatures in the Arctic after the annual summer melt over the past four years he found that in areas that were losing ice the air was up to 5°C warmer than the historical averages. (New Scientist)

These higher temperatures help slow ice growth during the winter; and even though current models predict this happening, according to Sezzere "it's all happening much faster than expected."

Other Researchers Disagree Over Tipping Point
Contrasting Sezzere's fast track to ice-free summers is the view of Cecelia Bitz of the University of Washington. At the AGU meeting Bitz suggests that though the long term trend is still towards ice free summers, the recent melting was more of a short term weather fluke than a tipping point. "A tipping point suggests falling off a cliff, which no way to climb back up. I can't see the evidence for this."

(TH note: I won't argue Bitz's science, but I don't think a tipping point implies a cliff, more of a see-saw or teeter-totter, if you will. Once you pass the center equilibrium everything accelerates to the opposite end point. It may be harder to come up from that opposite position but not impossible.)

via: New Scientist
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