Swedish Bogs Releasing Methane as Permafrost Melts and Rots
- The release of methane from a rotting permafrost region is one of
several identified "positive feedbacks" from global warming, since
the warming causes even more greenhouse gases, which cause even more
warming, and so on.
March 11, 2004, The Christian Science Monitor
Global warming has gone to the bogs
By Robert C. Cowen
Forget the melting glaciers. Global warming is revealing itself in
subtler ways. Think methane. Swedish bogs are releasing more methane
as climate warms and permafrost melts. Methane is a potent greenhouse
gas with 25 times the heat-trapping power of carbon dioxide (CO2).
With more methane in the air, climate warming could accelerate.
Meanwhile, just as global warming theory predicts, the atmosphere's
highest layers are getting colder and thinner. Contrary to
expectations, high atmospheric cooling is the way greenhouse gases,
such as CO2 and methane, interact with infrared (heat) radiation. At
low altitudes, they absorb heat coming up from below and radiate some
But where astronauts live, these gases release most of their heat out
into space, which cools the higher altitudes. The outer atmosphere
contracts as it cools, thinning out its density.
Satellites orbiting a few hundred miles out would feel less drag as
the air through which they travel becomes thinner.
That's how John Emmert and colleagues with the Naval Research
Laboratory in Washington found evidence that this long-expected
global warming effect is under way.
They report in the Journal of Geophysical Research that 30 years of
tracking data for 27 satellites and space junk show a steady decline
in outer atmospheric density.
That's good news for satellite owners who can use less rocket fuel to
keep their birds aloft. The news from Sweden is more troubling.
Bacteria in wetlands release methane as they break down organic
matter. It's the marsh gas that sometimes ignites to make spooky
lights in the night. This activity slows down when bogs freeze.
Northern peat bogs - especially in subarctic Eurasia - are major
sources of methane, which spreads throughout the world. Scientists
have wondered what will happen as permafrost continues to melt and
bogs become even more biologically active.
An international research team recently provided a window into that
future. The group, led by Torben Christensen and colleagues at Lund
University's GeoBiosphere Science Center in Sweden, studied 30 years
of changes in Sweden's Abisko region. Their results, published in
Geophysical Research Letters, show Sweden's sub-arctic bogs are
losing permafrost rapidly. It's completely gone in some areas. And
Dr. Christensen says that, at the Stordalen site, methane emission is
up "at least 20 percent, but maybe as much as 60 percent, from 1970
His team report warns that if its findings are typical of the
northern subarctic, global warming could accelerate as bogs thaw.
Laurence Smith at the University of California at Los Angeles and
colleagues with a joint Russian-American research team expressed a
similar concern last January in Nature.
Their studies of vast peat lands in Siberia show the bogs currently
absorb a lot of CO2 from the atmosphere while releasing methane. But
this could change. If global warming continues, the researchers warn
that chemical and biological activity in the bogs could break down
organic matter that now stores CO2, releasing a major new source of
the gas back into the atmosphere.
The bottom line is that we have to pay attention to subtle effects.
We're not going to be drowned by melting glaciers, but we might be
bitten by what's sneaking up on us.