Wednesday, September 23, 2009

Stirring the Ice Cap Controversy

A MSNBC report cites new observations of the Greenland and Antarctic ice caps shows significant degradation and loss of thickness that increased over the past decade:
"Dynamic thinning of Greenland and Antarctic ice-sheet ocean margins is more sensitive, pervasive, enduring and important than previously realized," researchers wrote in the paper published online Wednesday in the peer-reviewed journal Nature.

Using 50 million laser readings from a NASA satellite, scientists for the first time calculated changes in the height of the vulnerable but massive ice sheets and found them especially worse at their edges. That's where warmer water eats away from below. In some parts of Antarctica, ice sheets have been losing 30 feet a year in thickness since 2003, according to the study.

Some of those areas are about a mile thick, so they've still got plenty of ice to burn through. But the drop in thickness is speeding up. In parts of Antarctica, the yearly rate of thinning from 2003 to 2007 is 50 percent higher than it was from 1995 to 2003.
That may be trouble, or not. If you only have a few years worth of data, is it truly possible to extrapolate trends to the future? The new laser data is great at providing a snapshot of information for the past few years, but can we know what kinds of variations in the ice caps were 100 years ago? 200 years ago, particularly when we've only been exploring the polar regions for just over 100 years?

It seems that the models may have issues with another ice cap - the Arctic. As National Geographic reports this month:
This year's cooler-than-expected summer means the Arctic probably won't experience ice-free summers until 2030 or 2040, scientists say.

Some models had previously predicted that the Arctic could be ice free in summer by as soon as 2013, due to rising temperatures from global warming.

However, that scenario required Arctic sea ice to shrink at the record-setting pace of summer 2007, when sea ice coverage dropped to 1.6 million square miles (4.13 million square kilometers), said Walter Meier, a scientist at the U.S. National Snow and Ice Data Center in Boulder, Colorado.

This summer Arctic sea ice shrank to only 1.97 [ed: NatGeo left out million] square miles (5.1 million square kilometers). The 2009 drop is still the third largest on record, but it's not as big as some scientists had feared. (Explore a vanishing sea-ice interactive.)
The National Geographic report omits some key information. How large were the Arctic cap before they shrank. There is a seasonal variation, and if you provide only the summer data (when it's at its smallest), you can't exactly tell what the winter data is - when the caps are at their largest. That compares with last year's National Geographic report, which predicted that the ice caps might disappear altogether as soon as next year. This year's report shows that scientists are pushing back the complete melting of the cap to as far as 2040, compared with 2030 in the range provided last year. The scientists provide ranges for their models, and while global warming proponents push the earliest dates and the anti-global warming proponents holding to the latter dates, I see a continued lack of data on which to mount a massive overhaul of global enterprises to restrain emissions, particularly when the effects aren't exactly known and that the costs to reduce global temperatures a fraction of a degree are in the trillions of dollars.

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