The shrinking of the Arctic ice cap has occurred before (8 October, p 12). In 1422 a Chinese squadron sailed in open water through Baffin Bay and then around the north coast of Greenland, and thereafter back to China charting the north coast of Siberia from the White Sea to the Bering Strait as it went (see 1421, The Year China Discovered the World by Gavin Menzies, Bantam Books).
This suggests that the Arctic ice cover varies in extent over the centuries and/or millennia. Presumably this effect will also be mirrored in the Antarctic. Assuming the Chinese voyage really happened, this indicates that there have been previous episodes of global warming which pre-dated the today's concerns about the production of "greenhouse gases".
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