Scientists
Find New Global Warming 'Time Bomb’
By Seth Borenstein
08 September, 2006
The Associated Press
WASHINGTON - Global warming gases trapped in the soil
are bubbling out of the thawing permafrost in amounts far higher than
previously thought and may trigger what researchers warn is a climate
time bomb.
Methane - a greenhouse gas
23 times more powerful than carbon dioxide - is being released from
the permafrost at a rate five times faster than thought, according to
a study being published today in the journal Nature. The findings are
based on new, more accurate measuring techniques.
‘‘The effects
can be huge,’’ said lead author Katey Walter of the University
of Alaska at Fairbanks said. ‘‘It’s coming out a lot
and there’s a lot more to come out.’’
Scientists worry about a
global warming vicious cycle that was not part of their already gloomy
climate forecast: Warming already under way thaws permafrost, soil that
has been continuously frozen for thousands of years. Thawed permafrost
releases methane and carbon dioxide. Those gases reach the atmosphere
and help trap heat on Earth in the greenhouse effect. The trapped heat
thaws more permafrost and so on.
‘‘The higher
the temperature gets, the more permafrost we melt, the more tendency
it is to become a more vicious cycle,’’ said Chris Field,
director of global ecology at the Carnegie Institution of Washington,
who was not part of the study. ‘‘That’s the thing
that is scary about this whole thing. There are lots of mechanisms that
tend to be self-perpetuating and relatively few that tend to shut it
off.’’
Some scientists say this
vicious cycle is already under way, but others disagree.
Most of the methane-releasing
permafrost is in Siberia. Another study earlier this summer in the journal
Science found that the amount of carbon trapped in this type of permafrost
- called yedoma - is much more prevalent than originally thought and
may be 100 times the amount of carbon released into the air each year
by the burning of fossil fuels.
It won’t all come out
at once or even over several decades, but if temperatures increase,
then the methane and carbon dioxide will escape the soil, scientists
say.
The permafrost issue has
caused a quiet buzz of concern among climate scientists and geologists.
Specialists in Arctic climate are coming up with research plans to study
the permafrost effect, which is not well understood or observed, said
Robert Corell, chairman of the Arctic Climate Impact Assessment, a study
group of 300 scientists.
‘‘It’s
kind of like a slow-motion time bomb,’’ said Ted Schuur,
a professor of ecosystem ecology at the University of Florida and co-author
of the study in Science.
Most of the yedoma is in
little-studied areas of northern and eastern Siberia. What makes that
permafrost special is that much of it lies under lakes; the carbon below
gets released as methane. Carbon beneath dry permafrost is released
as carbon dioxide.
Using special underwater
bubble traps, Walter and her colleagues found giant hot spots of bubbling
methane that were never measured before because they were hard to reach.
‘‘I don’t
think it can be easily stopped; we’d really have to have major
cooling for it to stop,’’ Walter said.
Scientists aren’t quite
sure whether methane or carbon dioxide is worse. Methane is far more
powerful in trapping heat, but only lasts about a decade before it dissipates
into carbon dioxide and other chemicals. Carbon dioxide traps heat for
about a century.
‘‘The bottom
line is it’s better if it stays frozen in the ground,’’
Schuur said. ‘‘But we’re getting to the point where
it’s going more and more into the atmosphere.’’
Vladimir Romanovsky, geophysics
professor at the University of Alaska at Fairbanks, said he thinks the
big methane or carbon dioxide release hasn’t started yet, but
it’s coming. In Alaska and Canada - which have far less permafrost
than Siberia - it’s closer to happening, he said. Already, the
Alaskan permafrost is reaching the thawing point in many areas.
Copyright © 2006 The
Associated Press