Originally published October 16 2005
Global warming in Alaska exacerbated by longer summers
by Mike Adams, the Health Ranger, NaturalNews Editor
Although warmer winters were the major focus of global warming research in Alaska, recent studies show that longer summers are contributing to the climate changes in the northernmost U.S. state, and The Casper Star-Tribune reports that the increase in shrubs and trees has started a cycle that will amplify atmospheric warming.
Global warming research in Alaska has centered largely on its warmer winters.
But a new paper concludes that summer warming in arctic Alaska also has had a strong effect on high latitude climate change.
Current trends resulting in less tundra and more shrubs and trees will further amplify atmospheric heating, by a factor of two to seven times, the authors conclude.
The study was published Thursday in an advance online publication, Science Express.
"Summer warming is more pronounced over land than over sea ice, and atmosphere and sea-ice observations can't explain this," said Terry Chapin, the study's lead author and a professor of ecology at the Institute of Arctic Biology at the University of Alaska Fairbanks.
The paper is a synthesis of multiple studies, said Matthew Sturm, a research physical scientist for the Army's Cold Regions Research and Engineering Laboratory Alaska, and another of the study's 21 authors.
Previous studies and paleoclimate evidence indicate that the Arctic summer is warmer than at any time in at least 400 years, according to the study.
The new study focused on summer and the increase in days of snow-free ground as a factor in high latitude warming.
Scientists used surface temperature records, satellite-based estimates of cloud cover and energy exchange, ground-based measurements of reflected light and field observations of changes in snow cover and vegetation to calculate the change.
The increase in snow-free ground permits changes in vegetation, such as more shrubs and advances of treelines.
Conversion of tundra to forest in the last 50 years accounted for only about 3 percent of the total warming caused by land-surface change.
In winter, shrubs and trees project above snow and absorb more heat than low-stature tundra that's likely to be completely covered by snow, Sturm said.
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