Andrew Revkin, blogger for the New York Times, posts (emphasis mine):

For more than a decade, I’ve been probing changes in Arctic climate and sea ice and their implications for the species that make up northern ecosystems and for human communities there.

There are big changes afoot, with more to come should greenhouse gases continue to build unabated in the atmosphere. There will be impacts on human affairs in the Arctic, for worse and better, as we explored extensively in 2005 and I’ve followed here since.

But even as I push for an energy quest that limits climate risk, I’m not worried about the resilience of Arctic ecosystems and not worried about the system tipping into an irreversibly slushy state on time scales relevant to today’s policy debates. This is one reason I don’t go for descriptions of the system being in a “death spiral.”

The main source of my Arctic comfort level — besides what I learned while camped with scientists on the North Pole sea ice — is the growing body of work on past variability of conditions in the Arctic. The latest evidence of substantial past ice variability comes in a study in the current issue of Science. The paper, combining evidence of driftwood accumulation and beach formation in northern Greenland with evidence of past sea-ice extent in parts of Canada, concludes that Arctic sea ice appears to have retreated far more in some spans since the end of the last ice age than it has in recent years.