In AR4 (the 4th assessment report of the Intergovernmental Panel on Climate Change) the trend in Antarctic (southern hemisphere) sea ice was reported as small (5.6 +/- 9.2 thousand km^2/yr) and not statistically significant, but in AR5 (the 5th assessment report) it is reported as both statistically significant and much larger (16.5 +/- 3.5 thousand km^2/yr). Even at this rate the Arctic is still losing sea ice 3 times as fast as the Antarctic is gaining it, but the larger trend is still surprising; such a large rate of increase is, more and more, turning out to be incompatible with computer model simulations.
A new paper submitted to the Cryosphere Discussion (Eisenman, I., Meier, W. N., and Norris, J. R.: A spurious jump in the satellite record: is Antarctic sea ice really expanding?, The Cryosphere Discuss., 8, 273-288, doi:10.5194/tcd-8-273-2014, 2014) suggests that much, if not most, of the upward trend in southern hemisphere sea ice may be due to a spurious jump caused by an undocumented change to how the data are processed. It also explains the dramatic difference in the state of affairs between what was reported in AR4 and what was in AR5 just a few years later.
Open Mind 