Watkins and Simmonds (2000) analyzed trends in a number of sea ice parameters of the Southern Ocean that surrounds Antarctica, paying particular attention to data obtained from the Defense Meteorological Satellite Program Special Sensor Microwave/Imager over the period December 1987-December 1996. They conducted this work, they say, because "it has been suggested that the Antarctic sea ice may show high sensitivity to any anthropogenic increase in temperature." Specifically, they note that most climate models predict that "any rise in surface temperature would result in a decrease in sea ice coverage." So what did they find?
Contrary to what one would have expected if the climate alarmists were correct, the authors observed statistically significant increases in sea ice area and total sea ice extent between 1987 and 1996. Combining their results with earlier results for the period 1978-1987, both parameters showed increases over the entire 1978-1996 period. In addition, they determined that the 1990s experienced increases in the length of the sea ice season.
In a continuation of this work, Hanna (2001) published an updated analysis of Antarctic sea ice cover based on Special Sensor Microwave/Imager data for the period October 1987-September 1999, finding that the serial sea ice data depict "an ongoing slight but significant hemispheric increase of 3.7(±0.3)% in extent and 6.6(±1.5)% in area."
Yuan and Martinson (2000) also studied various aspects of the behavior of Antarctic sea ice extent, using data derived from brightness temperatures measured by the Nimbus-7 Scanning Multichannel Microwave Radiometer as well as the Special Sensor Microwave/Imagers. Among other things, they determined that the net trend in the mean Antarctic sea ice edge over the prior 18 years had been an equatorward expansion of 0.011 degree of latitude per year.
In a somewhat different context, Elderfield and Rickaby (2000) noted that sea ice cover in the Southern Ocean during glacial periods may have been as much as double the coverage of modern winter ice, suggesting that "by restricting communication between the ocean and atmosphere, sea ice expansion also provides a mechanism for reduced CO2 release by the Southern Ocean and lower glacial atmospheric CO2."
In considering the findings of those research papers that apply to the last few decades, if one were to infer anything about the planet in terms of what state-of-the-art climate models predict and what is known about sea ice behavior around Antarctica over the past few decades, one would be tempted to conclude that the globe has cooled over this period. Does that mean the generally accepted temperature history of the planet is in error? Or does it mean that the climate models are in error? Or does it mean that both are in error? The choice is yours.
References
Elderfield, H. and Rickaby, R.E.M. 2000. Oceanic Cd/P ratio and nutrient utilization in the glacial Southern Ocean. Nature 405: 305-310.
Hanna, E. 2001. Anomalous peak in Antarctic sea-ice area, winter 1998, coincident with ENSO. Geophysical Research Letters 28: 1595-1598.
Watkins, A.B. and Simmonds, I. 2000. Current trends in Antarctic sea ice: The 1990s impact on a short climatology. Journal of Climate 13: 4441-4451.
Yuan, X. and Martinson, D.G. 2000. Antarctic sea ice extent variability and its global connectivity. Journal of Climate 13: 1697-1717.