LA sans smog, photo: Todd Jones via flickr.
Cities are greener places than people generally give them credit for, in terms of carbon emissions -- people generally live in tighter quarters and expend less energy in transportation than their suburban and rural cousins. However, if new research into methane emissions in Los Angeles is applicable to cities in general, the world's megacities may be bigger climate change culprits than previously thought. New research in the journal Geophysical Research Letters (via New Scientist) details this:Paul Wennberg of Caltech Pasadena studied the estimated methane emissions from greater Los Angeles and subtracted all known methane sources -- such as sewage, landfills, and livestock -- but only could account for about half of the total emissions. Somewhere between 0.14 and 0.34 megatons per year were found to come from unknown sources.
These unaccounted emissions may be coming from higher than expected leakages from landfills or sewage treatment plants, or from unknown natural geologic sources.
Cities Could Account For 15% of Human's Methane Emissions
If Los Angeles is indicative of other large urban areas -- something not yet determined, however -- then methane emissions from these unknown sources would amount to 7-15% of methane emissions linked to human activity.
via: New Scientist
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