"It's a chance for policy-makers and industry to look for innovative ways to maximize the societal benefit of the fuels that we do use," he said. "I think there's lots that can be done to reduce fossil fuels that would have modest or even positive impacts on the economy."
The study found summer warming in Arctic Alaska and western Canada sped up over time. But explaining why was complicated.
Changes in ocean cycles influence winter temperatures and don't fully explain summer warmth. Shrinking sea ice also has the biggest impact on fall and winter conditions. More summer cloudiness tends to "dampen" the amount of sun beating down over the seasons, the scientists said.
Vegetation has spread, too, with tall shrubs advancing into the tundra and the tree line slipping north. Spring leaf-out has come 10 to 12 days earlier in Alaska over the past half century. But all these shifts, while moving faster and faster, account for only about 2 percent of the summer warming observed so far, the scientists said.
"The summer warming in Alaska is best explained by a lengthening of the snow-free season, causing sensible warming of the lower atmosphere to begin earlier," they concluded.
But as the shrubs expand in the tundra, their influence will grow -- catching more solar heat, trapping more insulating snow, enriching the soil with nutrients. Eventually vegetation will take over.
"Because of these feedbacks, there are lots of reasons to think that this warming will continue," Chapin said.
Understanding what factors are pushing the shrub expansion "would reduce the likelihood of unexpected surprises" in future summer warming, the scientists wrote.
Chapin, one of the most influential scientists in Alaska, said he hopes to begin looking into what factors might pushing climate changes in other areas of Alaska.
"I'm interested in asking similar questions for the boreal forest, where there's an increase in forest fires," he said.
RSS