[asa] Methane: The Great Dying?

Dave,
My posts are not getting through to the ASA group, but
thought I'd at least share this with you, since it
explains more about the consequences of that 3 degree
rise in ocean temp. you mentioned, and how that will
raise the levels of methane in the atmosphere, a more
potent greenhouse gas than CO2:

"Bacteria produce methane as they decompose organic
matter in the ocean sediments, and in cold,
high-pressure environments, methane hydrates will
form. This is an ice-like solid that consists of
methane surrounded by water molecules in a lattice
structure. However, if the temperature warms, or the
pressure is reduced (for instance if local sea level
decreases), the hydrate will break up and release the
methane as gas which can bubble up through the ocean
and enter the atmosphere.

"What would be the consequences of such a large
emission of methane into the atmosphere? At present,
methane has a residence time of about 10 years before
it is oxidized to carbon dioxide. However, the
chemistry of this process is highly non-linear, and as
emissions increase, the capacity of the atmosphere to
deal with the excess methane decreases and the
residence time lengthens. This can lead to quite large
increases in the methane concentration. This matters
because molecule for molecule, methane is a more
powerful greenhouse gas than carbon dioxide. The
climate consequences depend very strongly on exactly
how long the extra methane hangs around...

"Methane plays a large role in present day climate
forcing (see "Trends of Measured Climate Forcing
Agents" for more details) and has more than doubled in
concentration since the pre-industrial period. This
study goes a long way in quantifying its role in
paleoclimate variability as well."

...Ocean Burps and Climate Change?
By Gavin Schmidt — January 2003

http://www.giss.nasa.gov/research/briefs/schmidt_02/

~~~~~~~

Colossal belches of methane--a greenhouse gas with
nearly 30 times the heat-trapping power of carbon
dioxide--may bubble up from the seafloor and
exacerbate global warming, some scientists now say.
Indeed, a slew of new research results presented at
the fall gathering of the American Geophysical Union
last week revealed clues as to how this might happen.

Scientific American, In Focus
December 20, 1999

Gas Blasts: Methane once frozen under the seafloor may
help heat up the climate
By Sarah Simpson
http://www.sciam.com/article.cfm?
articleID=0009ECCC-3F88-1C75-9B81809EC588EF21

~~~~~~~~~~~~~~~

Methane: the Great Dying?
Summary (Sep 04, 2003): Imagine a global catastrophe
that could wipe out ninety percent of life in the
oceans and seventy percent of land life. Just such a
cataclysmic event, known as the Great Dying, happened
on Earth 250 million years ago. A proposal that
methane explosions may have contributed to this
extinction draws on a local precedent in 1986, when a
soda lake in Cameroon, Africa, underwent just such an
event, the effects of which rippled out for more than
twenty-five kilometers.

http://www.astrobio.net/news/modules.php?
op=modload&name=News&file=article&sid=582&mode=thread&order=0&thold=0

--- David Campbell <pleuronaia@gmail.com> wrote:
>> It appears that every living thing emits gases
> that contribute to the
>> problem - so there is no Kyoto sink. We need to
> find a sink or else.
>>
>> Trees produce methane and as they rot, they
> release the carbon dioxide
>> that they stored.
>>
>> Can we produce a means of removing greenhouse
> gases without creating more
>> than we take out in the process? Or is this a
> perpetual machine problem?
>>
>
> Growing plants can take up more carbon dioxide than
> they release, though
> plants doing little growth do not; I would guess a
> similar situation would
> apply for methane-consuming bacteria, etc. In the
> natural balance of
> things, carbon is removed from easy availability
> through burial of organic
> material and by precipitation of carbonate minerals.
> Over geologic time,
> these will eventually return to the surface, but
> probably slowly enough for
> organisms to maintain a balance. I don't know how
> practical it is to try to
> bury more carbon. It might be feasible to bubble
> power plant exhaust
> through a calcium-rich, basic solution and thereby
> precipitate out some of
> the carbon dioxide.
>
> Gas hydrates can sequester greenhouse gases somewhat
> out of the way, but the
> long-term stability, the environmental impacts, and
> the practicality of
> trying to transform extra gases from the atmosphere
> into such are not
> known.
>
> It's probably a lot easier from a chemistry/physics
> perspective to produce
> less of the stuff, but rather harder from a human
> behavior perspective.
>
>
>
>
>
>> --
>> Dr. David Campbell
>> 425 Scientific Collections
>> University of Alabama
>> "I think of my happy condition, surrounded by
> acres of clams"
>>
>

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Received on Tue Jun 27 23:44:21 2006