What About Antarctic Sea Ice Trends?

There is considerable media attention on Arctic sea ice trends, as we have discussed in our last few weblogs. The Independent highlights their latest news release as “Sea ice melts to record low because of global warming”. If this news article were accurate, and it is global warming (i.e., a global scale warming) that is causing the well below average summer ice cover in the Arctic, as documented at http://nsidc.org/data/smmr_ssmi_ancillary/regions/total_arctic.html#nsidc, we would also expect to see reductions of the Antarctic sea ice coverage (a large portion of which melts in the summer and then refreezes in the winter). For the period 1973-2002 we examined this issue and found no trend over time in Antarctic sea ice coverage (see Figures 8 and 9a in Pielke et al. 2004). A NASA press release from August 2002 reported on “Satellites show overall increases in Antarctic sea ice cover.”

Trend analyses to near the current time of Antarctic sea ice area and extent anomalies are available from The National Snow and Ice Data Center’s website . In their data, a continued increase in the areal coverage of Antarctic sea ice is evident!

Why is this not also reported by the media? In terms of a global warming effect, is the area reduction in the Arctic sea ice compensated by an area increase of sea ice in Antarctica?

The positive trend in the Antarctic, in contrast to the Arctic, raises questions about the causes of the sea ice trend. If it were a “global warming” signal (i.e., “global in extent”), we should expect similar behavior in both hemispheres. However, if warming is the reason for the reduction the area coverage of Arctic sea ice, it is a regional warming effect. As we have emphasized in our weblog, it is on the regional scale that we need to focus our attention with respect to human-caused and natural variations and long-term change of climate. The differences in trends between the Arctic and Antarctic emphasizes that we need a regional focus.

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