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Update on Antarctic Sea Ice Extent
Parkinson, C.L.  2004.  Southern Ocean sea ice and its wider linkages: insights revealed from models and observations.  Antarctic Science 16: 387-400.

What was done
Among a number of other things, the author reviews the history of satellite observations of sea ice extent in the Southern Ocean about Antarctica, concentrating on data obtained from the Scanning Multichannel Microwave Radiometer aboard the Nimbus 7 satellite and subsequent satellite-based Special Sensor Microwave Imagers, because these platforms provide, in her words, "the best long-term record of changes in the full Southern Ocean ice cover."  From the data obtained from these sensors, she thus plots 12-month running means of Southern Ocean sea ice extent from November 1978 through December 2002.

What was learned
There is significant multi-year variability in the data, which begin at the top of a peak and end at the bottom of a trough; but in spite of the high beginning point and low end point, which tend to mitigate against a long-term upward trend, the data exhibit just such a feature, the slope of which least-squares-fit line is 12,380 1,730 km2 sea ice extent per year.

What it means
Interestingly, over the period of time that climate alarmists claim has exhibited the most extreme global warming of the past two millennia, and in spite of the fact that they have historically claimed such warming should be most evident in earth's polar regions, and that it should lead to a decrease in polar sea ice extent, just the opposite has occurred in the Southern Ocean about Antarctica.  What is doubling damaging to their dogma is the fact that Southern Ocean sea ice extent is extremely sensitive to warming, decreasing from a 24-year-average maximum monthly value of 18.23 x 106 km2 in September to a similarly-calculated minimum monthly value of 2.98 x 106 km2 in February, which represents the disappearance of nearly 84% of each year's maximum sea ice cover.  Given a little more seasonal warmth, it would disappear altogether each February.  But it doesn't.  It continues to slowly but surely grow in the mean.

Reviewed 11 May 2005