Air Date: Week of September 9, 2005

Living on Earth's Jennifer Chu reports on new shrub growth in the Arctic that may be part of a warming feedback loop.

Transcript

CURWOOD: Just ahead: saving all creatures great and small in the aftermath of Hurricane Katrina. First, this Note on Emerging Science from Jennifer Chu.

[SCIENCE NOTE THEME]

CHU: In the barren core of Arctic tundra, winter seems infinite, endless, as if it could – and would – last forever. And it almost does. Eight to ten months out of the year, it is winter in the treeless land at the top of the world. But cropping up amid the starkness and the snow are increasing numbers of shrubs – shrubs that could shift the tundra’s delicate energy balance and cause warming of several degrees over the next few decades.

A new study by the American Geophysical Union found that increasing vegetation reduces the earth’s albedo, or the reflection of the sun’s rays from the surface. While snow reflects solar energy, dark-colored shrubs absorb it. The study monitored terrain ranging from forested canopy to tundra, and found that melting began several weeks earlier in places where shrubs were exposed than in snow-covered areas.

Climate warming seems to stimulate shrub advancement. Scientists call it a feedback loop- increased shrub growth produces higher temperatures, and higher temperatures induce further growth. Scientists predict that if shrubs continue to grow on the tundra, winter heating could increase by up to 70 percent over a period of decades. And the continued transition from tundra to shrub land could substantially alter the character of the Arctic.

That’s this week’s Note on Emerging Science. I’m Jennifer Chu.

CURWOOD: And you're listening to Living on Earth.