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[school-discuss] FOSS -- environmental friendly -- methane

On Tuesday 24 August 2004 4:47 am, Phil Driscoll wrote:

> Whilst not wanting to start a flame war - releasing still more CO2 into the
> atmosphere - remember that these cows are eating vegetation which only a
> few months earlier was fixing carbon from the atmosphere, and whilst there
> is undeniably a vast quantity of gaseous bovine output, there is no net
> increase in carbon in the atmosphere as a result of this (unless someone
> has worked out a way to feed cattle on coal or oil).

No flames -- just sticking to facts.  You can Google up studies on ruminant 
production of methane -- it is an infrared absorber in what is otherwise an 
atmospheric window.  Here is an excerpt from an unpublished proposal i wrote 
about 20 years ago:

     "Recently, from air samples averaged over a wide range of latitudes, it 
has been ascertained that the worldwide tropospheric mixing ratio of methane 
has increased by 11% from 1.52 ppmv in early 1978 to 1.684 ppmv in late 
1987(1). These observations are consistent with values derived from Antartic 
ice cores(2) and from near-infrared spectra of atmospheric methane overtone 
absorption bands (3).  In effect, this implies increasing methane 
concentrations at rate of 1% per year, with a corresponding doubling time of 
only 70 years.

     Several measurements on ice core samples from Antartica and Greenland 
indicate that the mean preindustrial atmospheric methane concentration was 
approximately double that during the last glaciation.  The current value is 
larger than the preindustrial level by more than a factor of two(4), 
suggesting that the increase of tropospheric CH4 is closely coupled to human 
activities (5,6).

     What is the significance of an increase in atmospheric methane?  As an 
infrared active gas, methane is one of the major "greenhouse gases".  An 
absorption band of CH4, corresponding to a vibration fundamental(7,8), lies 
at the high frequency edge of the 8-12 micrometer atmospheric window (9), the 
region of peak emission of the earth's thermal radiation (10).  This band 
absorbs a significant portion of upwelling terrestrial radiation, 
contributing to atmospheric heating (11) by an estimated 25% of that due to