Arctic is heating up, scientists say

An international panel of scientists reports that the Arctic is undergoing substantial and unprecedented warming despite sporadic signals of a cooling trend.

"For the last six years, Arctic temperatures were above average," said Jim Overland, an oceanographer at Pacific Marine Environmental Laboratory in Seattle and one of the authors of "State of the Arctic," the report issued Thursday by the National Oceanic and Atmospheric Administration.

The area in the Arctic covered by sea ice is declining, vegetation is now growing in tundra regions previously hostile to such growth, and the glaciers at the edge of the Greenland ice sheet are sliding away faster than ever, the panel said.

"This is a unique situation," Overland said.

Yet ocean and atmospheric patterns in the Arctic are still shifted around owing to natural cycles (or less-than-natural perturbations such as climate change), he said, which means short-term or localized measurements can give results that can -- taken alone -- indicate cooling.

"The Arctic has large region-to-region differences," Overland said. These transient, regional cycles that involve cooling could be masking the overall warming trend, he said.

Evidence of thickening of the ice sheet in some places, the slowing down of a wind-producing atmospheric cycle known as the Arctic oscillation and other pieces of the puzzle describing the Arctic environment have in the past been indicators of a cooling trend.

"There are these (cooling indicators) that the region is fighting back," said Jacqueline Richter-Menge, lead author of the NOAA report and a sea ice expert at the Army's Cold Regions Research and Engineering Laboratory in Hanover, N.H.

But although the ice sheet might be thickening in some places, Richter-Menge said, there's no question that the geographic area covered by ice in the Arctic continues to shrink.

"It was alarmingly thin in 2000, but it has thickened a bit lately," said James Morison, a University of Washington oceanographer who regularly measures Arctic conditions as director of the North Pole Environmental Observatory, sponsored by the National Science Foundation. Morison was not an author on this report.

But rather than take comfort in the polar ice sheet thickening, he said, we should consider the possibility that this might be evidence of the Arctic trying to enter a regular cooling phase and largely failing because of global warming.

"Me, I'm just holding my breath," Morison said. "The concern is that we've reached a tipping point."

When the Arctic's regional system actually reverts to a warming phase, he said, the impact of global climate change could be even worse than it is today.

The NOAA report, a consensus document reached by 20 experts from the U.S., Canada, Russia, Norway, Sweden, France, Germany and Poland, makes no such predictions. The intention was merely to review current data and arrive at agreement as to what is happening now to the Arctic.

Overall, the scientists agreed that the Arctic has been warmer by nearly 2 degrees Fahrenheit for the past five years; the extent of the sea ice in the polar regions has been shrinking; significant areas of permafrost are thawing; vegetation is spreading northward; and glaciers appear to be melting at a faster rate.

One major, if unstated, reason for the study is the scientific assumption that as the Arctic changes, so also can we expect changes across the entire planet.

The difference in temperature between the poles and the equator, Overland said, is a major influence governing Earth's climate and weather patterns. But it is a complex relationship that is difficult to predict.

P-I reporter Tom Paulson can be reached at 206-448-8318 or tompaulson@seattlepi.com.