Reports are filtering through various media outlets that the amount of global sea-ice present at the end of 2008 was the same (or only slightly lower than) that recorded in 1979, when the first satellite measurements of sea-ice were taken. The conclusion is drawn that reports and expectations of both warming and polar ice-loss are therefore overstated.

This seems firstly to confuse area with volume, and secondly simply a case of cherry-picking of data that ignores trend-lines. It is clear that a proper regression analysis of the data, (credit to Tamino.wordpress.com), although not yet statistically significant, shows a downward trend in the three decades of satellite monitoring.

Moreover, as ‘The Cryosphere Today’ reports, global climate models have always predicted greatest loss during the summer months in the northern hemisphere, predictions which have been borne out by recent observations. In addition, models have always been uncertain as to the effects of warming on sea-ice extent in the southern hemisphere, while more confidently predicting the summer loss in the Arctic. The respective sea-ice areas are almost one million sq. km below 1979 values in the northern hemisphere, and 0.5 million sq. km above in the southern hemisphere.  

Indeed, there have been suggestions during the past three years that the initial response in the Antarctic may be for sea-ice to increase as increased evaporation through atmospheric warming translates into greater snowfall onto sea-ice (http://www.sciencedaily.com/releases/2005/06/050630064726.htm).

Stephen Davenport

11th January 2009