I do not think that jawbone means what you think it means

On Wednesday, Andrew Revkin, a reporter with the New York Times for whom I have great respect, noted in his blog that scientists in Norway's Svelbard archipelago have unearthed a polar bear jawbone they believe to be 110,000 to 130,000 years old, which would mean that polar bears were around during the last interglacial period, known as the Eemian.  Andrew says that:

This is significant because it could confirm genetic hints that the species has lived through at least a couple of protracted warm spells in which Arctic temperatures were likely several degrees warmer than at present.

Andrew is largely echoing the comments of Dr. Ólafur Ingólfsson, who found the jawbone, and speculated in a BBC story about the find:

"And what's interesting about that is that the Eemian - the last interglacial - was much warmer than the Holocene (the present).

"This is telling us that despite the ongoing warming in the Arctic today, maybe we don't have to be quite so worried about the polar bear. That would be very encouraging."

It would be encouraging, if only it were true. The problem with Dr. Ingólfsson's analysis is that--even granting for the sake or argument that polar bears can survive a climate as warm as the Eemian interglacial--most global warming models predict that we're headed for a climate far warmer than that.

According to ice cores studies from Northern Greenland, the climate during the Eemian was about 5 degrees warmer (Celsius) than it is today.  The Arctic Climate Impact Assessment, by contrast, estimates that Arctic temperatures will increase by 5 - 7 degrees in the coming century, which may well be an underestimate given the actual warming trends we're seeing.  Indeed, based on the most reliable models of sea ice decline, the United States Geological Survey, has estimated that two thirds of the worlds polar bears will be extinct by 2050 and that the remaining populations have 40% - 70% chance of going extinct by the end of the century.  Now add to that the fact that the rate that sea ice is actually disappearing in the Arctic far outstrips what even the models predict.  There was, in fact, less ice in the Arctic in 2007 than over half of the climate models predicted for 2050.  And the truly scary part is that we simply don't know what the upper limit on Arctic warming is.  Scientists believe that during a period know as the "Palaeocene/Eocene thermal maximum," approximately 55 million years ago, the Arctic had a climate the resembled contemporary Florida.

"My hope," "Andrew ends his post by saying "is that it’s possible to convey the significance of Arctic and global climate change without overstating what’s at stake."

That's a hope we can all share, but jawbone or not, polar bears are one of the things that are at stake--and if we don't act soon, they may be gone before we know it.