Don’think they really know….
Check it out:

Environmentalists and some climate scientists are now attributing much of Antarctica’s rapidly growing sea ice coverage to a processing error in the satellite data.

The massive growth of Antarctica’s ice sheets has confounded scientists for years now, as global warming was expected to shrink the polar ice caps. But while the Arctic has shrank some, Antarctic sea ice coverage has broken hundreds of records this year alone. On July 25, the South Pole sea ice reached 436,681 square miles above the 1981 to 2010 average — the 127th daily record for the year.