<div>Nick wrote:</div>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid"><br>Regarding livestock and global warming, they contribute, by expelling methane, 18 percent of all greenhouse gases, more than all world transport combined. In developing countries raising cattle also requires burning forests, which overall contributes another 18 percent of greenhouse gases.
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<div>Can you provide scientific references for the data you offer above? I am finding documentation of this data difficult.</div>
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<div>Methane releases from livestock do not add up to 18 percent of greenhouse gases from human activity or 18 percent of the human sourced greenhouse effect, given the sources I've read.</div>
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<div>A source listed below gives methane releases in the USA, many from non agricultural sources (landfills, coal mines, oil and gas operations) as 9 percent of total human sourced greenhouse gases. The amount from livestock would be a fraction of this amount.
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<div>The GWP (global warming potential) would need to be considered, given that methane is a more powerful greenhouse gas than CO2, though it dissipates in the atmosphere much faster. I wonder if this 9 percent figure is corrected for GWP. Of course this is only data for the USA, so global percentages of methane release could be very different:
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<div><a href="http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html">http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html</a></div>
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<div>According to this source below, significant methane releases are associated with the huge increase in rice cultivation (anaerobic decomposition in paddies):</div>
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<div><a href="http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/co2_change.html">http://www-das.uwyo.edu/~geerts/cwx/notes/chap01/co2_change.html</a></div>
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<div>NASA article claiming rice cultivation adds 8 percent of total global methane releases, or it did till recent changes, much of this coming from China:</div>
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<div><a href="http://www.gsfc.nasa.gov/topstory/2002/1204paddies.html">http://www.gsfc.nasa.gov/topstory/2002/1204paddies.html</a></div>
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<div>This source below (asserting CO2 is 80 percent of the human sourced greenhouse effect) combined with other data I've read on the percentages of atmospheric concentration of other greenhouse gases, suggests methane from all human impacts contributes about 10 percent of the current human sourced greenhouse effect, allowing for GWP. Even if this figure is in error, I doubt that just the methane from livestock will equal 18 percent of the human sourced greenhouse effect, given the percentage influence of CO2, nitrous oxide, carbon monoxide, CFCs, etc. and methane from other sources:
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<div><a href="http://www.nature.com/nature/journal/v344/n6266/abs/344529a0.html">http://www.nature.com/nature/journal/v344/n6266/abs/344529a0.html</a></div>
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<div>Another source below gives a figure for methane's GWP over the next hundred years as 18 percent of the total human impact, but the amount of methane from fossil fuel related and waste treatment and disposal sources is a large percentage of this total. Consider that even if methane contributes 18 percent to the GWP, in absolute amount of percentage of release it is at a much smaller level, because it is a more powerful greenhouse gas than the dominant greenhouse gas from human sources, CO2. This source is data from 2000, and fossil fuel use has increased dramatically in the past 6 years, thus the 14 percent figure for the transportation sector is now in error:
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<div><a href="http://en.wikipedia.org/wiki/Image:Greenhouse_Gas_by_Sector.png">http://en.wikipedia.org/wiki/Image:Greenhouse_Gas_by_Sector.png</a></div>
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<div>As far as burning of forests contributing 18 percent of atmospheric CO2 from human impacts, I cannot verify this figure either. The source above gives a figure of 10 percent of greenhouse gas emissions for land use and biomass burning, which should include forest burning impacts. This source below gives a figure from burning of forests and deforestation of 7-10 percent of the CO2 emissions from fossil fuels:
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<div><a href="http://www.stanford.edu/dept/news/pr/2004/biomass-812.html">http://www.stanford.edu/dept/news/pr/2004/biomass-812.html</a></div>
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<div>Quote from article above:</div>
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<div>Of forest burning, about 80 percent results in permanent deforestation - meaning the land is now used for some other use, such as grazing, agriculture or buildings. The remaining 20 percent of trees are regrown. When forests are permanently replaced by other plant types - shrubs, grasses, crops, all of which contain less carbon than do trees - the carbon difference accumulates in the atmosphere. "The total carbon dioxide emission from permanent deforestation is on the order of 7 to 10 percent of global fossil-fuel-carbon-dioxide emission," Jacobson says.
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<p>Jacobson's calculations used a model honed over 14 years and emission data from a variety of sources. He is an author of two textbooks - Fundamentals of Atmospheric Modeling (Cambridge University Press, 1999) and Atmospheric Pollution: History, Science, and Regulation (Cambridge University Press, 2002).
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<p>Given these estimates of methane releases from livestock in absolute amounts, and in terms of the GWP of these methane releases, methane from livestock does not equal the amount of CO2 from the transport sector, which according to the source below contributes over 18 percent of global human sourced CO2 emissions, nor does it equal this CO2s GWP.
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<p><a href="http://earthtrends.wri.org/updates/node/135">http://earthtrends.wri.org/updates/node/135</a></p>
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<p>Vision2020 Post: Ted Moffett</p></div>
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