The polar bear problem | The Spectator

Much has been made of the 2007 summer ice retreat being the ‘greatest on record’, but records began only in 1979. In the 1920s and 1930s, there were probably still more open seasons; likewise in the medieval, Roman and other warm periods all the way back to the Holocene Optimum. Polar bears certainly survived such warmer spells, presumably by ranging somewhat further north. Indeed, fossils suggest that polar bears already existed in their current form during the last interglacial period, 120,000 years ago, when the Arctic was almost certainly wholly free of ice in late summer.

A total disappearance of sea ice at all seasons would undoubtedly doom the polar bear’s lifestyle. But no scientist in his wildest exaggerations is suggesting the disappearance of Arctic sea ice in winter. As long as there is pack ice for much of the year with an ice edge, plenty of seals and controls on hunting, the polar bear is going to thrive — and tent-based tourism to the Arctic is going to be dangerous.

Flashback: Complete barking madness from John Holdren, Obama's science advisor

At the 18:54 mark at the CBC "Climate Wars" podcast here [MP3], John Holdren says this:

...if you lose the summer sea ice, there are phenomena that could lead you not so very long thereafter to lose the winter sea ice as well. And if you lose that sea ice year round, it's going to mean drastic climatic change all over the hemisphere.