The Snowball Effect of Global WarmingBy
- The Snowball Effect of Global Warming
By Robert Roy Britt
LiveScience Managing Editor
posted: 06 September 2005
09:46 am ET
In a twist to the proverbial snowball effect, warmer Arctic
temperatures are stimulating plant growth, which darkens the
landscape and causes more sunlight to be absorbed rather than
The result: Winter heating could increase by 70 percent, according to
a new study.
The study examined western Alaska during the winters of 2000 through
2002. Shrubs and other vegetation became more abundant, the
researchers found. Because the plants are darker than the tundra that
typically covers the region, the surface gets darker. The
study "presents the first evidence that shrub growth could alter the
winter energy balance of the Arctic and subarctic tundra in a
substantial way," the scientists announced today.
The study will be detailed Sept. 7 in the first issue of the Journal
of Geophysical Research-Biogeosciences, published by the American
In areas where shrubs were exposed in mid-winter, melting began
several weeks earlier in the spring compared to snow-covered terrain.
Yet the shrubs' branches produced shade that slowed the rate of
melting, so that the snow melt finished at approximately the same
time for all the sites examined.
Matthew Sturm, leader of the study, said warming in the region seems
to have stimulated shrub growth, which further
warms the area and creates a feedback effect that can promote higher
temperatures and even more growth. This feedback could, in turn,
accelerate increases in the shrubs' range and size, he said.
The Alaskan tundra covers some 1.5 million square miles (4 million
square kilometers). "Basically, if tundra is converted to shrubland,
more solar energy will be absorbed in the winter than before," Sturm
said. And while previous research has shown that warmer temperatures
during the Arctic summer enhance shrub growth, "our study is
important because it suggests that the winter processes could also
contribute to and amplify the rate of the [growth]."