FAIRBANKS -- This winter was so unusually warm in Alaska -- and around the Arctic -- that it took even climate scientists by surprise.
And it's virtually certain that climate change is one of the factors driving that record-setting warmth.
At a Monday briefing during the Arctic Summit Science Week at the University of Alaska Fairbanks, one researcher called the record-high Arctic-wide temperatures posted in January and February "startling" and a major milepost in the long-term warming of the region.
"There's no doubt that the absolute record Arctic-wide temperatures being much greater than the previous record is probably the all-time surprise that we've seen in the Arctic," said Jim Overland, a research oceanographer at the National Oceanic and Atmospheric Administration.
Overland likened the record warmth to the then-shocking record-low sea ice posted in 2007.
"I keep getting surprised every couple years on how rapidly the Arctic is changing in ways we were not able to anticipate," he said.
Though other factors are at work, too, that change -- not mere happenstance -- is behind the new temperature extremes, other scientists said.
"As far as this winter goes, my hunch is that you'd come up with essentially a zero probability of that happening without climate change," John Walsh, chief scientist at the International Arctic Research Center at the University of Alaska Fairbanks, said at a separate briefing Wednesday. "If your question is, 'What are the odds of getting this warm a winter without climate change,' I would wager that it would be zero."
The convergence of persistent warm waters in the Pacific, followed by a powerful El Nino and in combination with other random factors, all added on top of long-term warming, "send us into a new temperature place that we've never seen before," Overland said. "We would have never expected such a jump in one year, and it has to do with the whole earth system shifting."
In addition to record-high Arctic-wide temperatures (including a spate of above-freezing readings near the North Pole) and an Arctic sea-ice extent on track to be the lowest or second-lowest on the satellite record, this winter also brought Alaska-specific milestones.
It was the second-warmest on record for Alaska, after the winter of 2000-01, but it was another measurement that grabbed scientists' attention -- what Rick Thoman called a "complete lack of deep-cold weather."
Thoman, the climate science and services manager for the National Weather Service in Alaska, said the lowest temperature recorded so far this winter is a "paltry 47 below," Thoman said. That was in Arctic Village around Christmas, he said. It might sound cold, but it is unusually high for a statewide minimum, he said.
"If this holds up, that would be -- by far -- the warmest Alaska minimum temperature for a whole winter," he said. Up to now, the record-high winter minimum temperature for Alaska is 53 below, recorded at Umiat on Feb. 18, 1988.
"There is very little chance that any community or person is going to observe a temperature at that level the rest of the season," Thoman said. "So this is really, really a mark of how unusual and how persistent that warmth has been."
Lack of extreme cold was "pretty remarkable" in Fairbanks, Walsh said. The city had no winter day in which temperatures fell below minus 30 degrees, he said. Usually, there are five to 10 days with temperatures under 40 below, he said.
And the winter warmth showed "really remarkable consistency" across the state, Thoman said.
All 13 of Alaska's weather regions recorded average December-to-February temperatures that ranked among the top five warmest in the nine-decade record. Most were in the top three, Thoman said, and three -- the western Gulf of Alaska coast, the Kodiak area and southwestern Alaska -- experienced their warmest December-to-January periods on record.
Statewide, 61 of the 91 days in that three-month period posted temperature averages that were significantly above normal, he said. Twenty-eight had near-normal temperatures, and only two fell into the below-normal category, he said. "If it was a perfectly average winter, you would expect about one-third in each category. Obviously, this was not that," he said.
Still, Walsh said, while this winter and the warm winters that preceded it provide "a preview of what's out there," cold could return to Alaska and elsewhere in the north.
"The thing about climate change is it's not a straight line from point A to B. It's an up-and-down path that gets higher and higher over time," he said. "So we could easily have a few winters that are in the more normal category. I think that the way I would interpret it is that this type of winter -- which, again, might have zero probability in a non-climate-change world -- would become more and more common as we go through the century."