updated 3/10/2009 11:34:21 AM ET 2009-03-10T15:34:21

Levels of methane in the Norwegian Arctic increased in 2007 possibly because the thawing northern tundra released more of the greenhouse gas into the atmosphere, officials said Monday.

The concentrations of methane gas measured at the remote islands of Svalbard rose by 0.6 percent in 2007 compared to the previous year, according to a statement by the Norwegian Pollution Control Authority.

The latest figure was also 1 percent higher than in 2004. A sharp rise in methane levels could dramatically increase global warming, the authority said.

Similar increases were noted at other monitoring stations in Ireland and northern Canada. The cause has yet to be determined but preliminary figures suggest the trend continued in 2008, the statement said.

"One theory is that large quantities of methane that are naturally stored in the permafrost of North America and Russia, and under the sea floor in Arctic waters, might be being released into the atmosphere due to warmer temperatures and less snow and ice cover," said Cathrine Lund Myhre, of the Norwegian Institute for Air Research.

"That is a relatively large increase, especially since methane levels were virtually stable from 1999 until 2005," said Myhre. "The increases being bigger at Svalbard than other areas can be an indication that the source is in the far north."

The two bodies jointly monitor 23 climate and ozone damaging gas levels in the atmosphere at Zeppelin Mountain on Svalbard, some 300 miles north of the Norwegian mainland.

Authority director Ellen Hambro said the 2007 results were important details for global climate treaty talks due to open in Copenhagen, Denmark in December.

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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