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  • What's Up with U.S. Greenhouse Gas Emissions?


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    What's Up with U.S. Greenhouse Gas Emissions?


    Back in August, the U.S. Energy Information Agency (EIA), part of the U.S. Department of Energy (DOE) that collects and reports certain energy-related data, posted an article centered on this graph:

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    That graph is labeled obscurely, but with partial accuracy, as showing U.S. "carbon dioxide emissions from energy demand."

    That's the same as "carbon dioxide emissions from energy use" or "carbon dioxide emissions from energy consumption," which is primary data collected by the EIA. It's relatively easy to track in real time, since it's essentially based on adding up the sales figures for coal, oil, and natural gas.

    Therein lies the first layer of confusion. The EIA does not include biomass combustion energy, hydroelectric power, or true renewables like wind and solar in its main energy consumption figures. Except for biomass, there is little CO2 associated with the use of these "alternative" energy sources.

    So the EIA graph in the article should be labeled as U.S. "carbon dioxide emissions from fossil fuel consumption." In fact, that's exactly how the graph is labeled in EIA's deeper technical reports. According to the most recent official EPA figures, carbon dioxide emissions from fossil fuel consumption represented about 79% of total U.S. greenhouse gas emissions in 2010.

    Starting a tally of the U.S. fossil fuel use "grade inflation," we can use these terms:

    (CO2 emissions from fossil fuel use) + (CO2 emissions from all other energy use) = (total CO2 emissions from energy use)

    The big headline on the EIA article adds another level of exaggeration. It says "U.S. energy-related CO2 emissions in early 2012 lowest since 1992." Note the shift from "energy-use" CO2 emissions to "energy-related" CO2 emissions.

    The headline is directly wrong because the underlying data does not include CO2 emissions from energy production and distribution — such as flaring of natural gas, an increasing element in the U.S. EIA seems to use the this sloppy label regularly.

    (CO2 emissions from energy use) + (CO2 emissions from energy production & distribution) = (energy-related CO2 emissions)

    The headline also sets people up for another natural error. While CO2 is the biggest greenhouse gas, it's not the only one. It's common practice in adding up climate numbers to convert all the differing units of other greenhouse gases into CO2-equivalent values.

    It's tedious to always say "CO2-equivalent greenhouse gas emissions." And pretty often, people just say "CO2 emissions" when "CO2-equivalent emissions" is what they really mean.

    That's just a little slippage in our language, but it has big implications for the numbers.

    (energy-related CO2 emissions) + (non-CO2 energy-related emissions) = (energy-related greenhouse gas emissions)

    Missing Methane

    The biggest energy-related non-CO2 emissions are methane — and that's huge.

    Estimates of energy-related methane emissions are in flux, as traditional industry numbers are being looked at more closely. Current research, in line with a recent NOAA report, suggests under-reporting by the fossil fuel industry may be on the order of 2% of natural gas used, suggesting total methane losses on the order of 4%.

    Since methane is about 21 times more potent as a greenhouse gas than CO2 in the time frame of a generation (according to the EPA, while some estimates go as much as five times higher), we can multiply (4% methane leakage) x (21 times GHG impact compared to CO2) = 84%. That shows that methane emissions from the natural gas system may have a CO2-equivalent greenhouse gas impact roughly comparable to the GHG impact in CO2 from burning the gas.

    While the methane emissions may prove to be somewhat smaller, there's little doubt they are significant.

    This is part of the picture described by guest bloggers Shakeb Afsah and Kendyl Salcito in the Climate Progress article "Shale Gas And The Overhyping Of Its CO2 Reductions."

    By leaving out methane, and other things, the EIA data really only describes one specialized slice of emissions. It's a big slice, but not one to freely generalize from.

    Because renewables are missing from the EIA data, which has been widely and inappropriately generalized, it's all too easy for pundits and reporters to simply compare the coal curve and the natural gas curve against the (baseless) overall conclusion of dropping emissions, and then call out lower natural gas prices as the cause of U.S. progress — leaving out the significant growth of renewables. But that's another story.

    Ultimate Confusion

    As noted above, it's apparently been easy for analysts and media alike have taken the EIA information to the final level of misinformation, trumpeting that:

    "In a surprising turnaround, the amount of carbon dioxide being released into the atmosphere in the U.S. has fallen dramatically to its lowest level in 20 years." (AP)

    and even:

    "Greenhouse gas emissions from the US have fallen sharply in recent years..." (Guardian)

    The claim is wrong, because to get to greenhouse gas emissions overall, all the non-energy-related emissions sources also need to also be included. To summarize and complete the equation:

    EIA data: (CO2 emissions from fossil fuel use)
    + (CO2 emissions from all other energy use)
    + (CO2 emissions from energy production & distribution)
    + (non-CO2 energy-related emissions)
    + (all non-energy-related greenhouse gas emissions)
    = total greenhouse gas emissions

    Methane, flaring, and biomass emissions not included in the primary EIA numbers mean those numbers don't fully reflect energy-related GHG emissions.

    According to the official U.S. GHG emissions inventory, the non-energy-related emissions (from agriculture, logging, other land use changes, etc.) represent another ~20% of the total, on top of the ~80% of GHG emissions that are directly energy-related.   >>>

    Discuss this article in the Architecture Forum...




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    A graph of first-quarter total carbon dioxide emissions from fossil fuel energy consumption in the United States from 1992 to 2012.
    Image: U.S. Energy Information Administration (EIA) Extra Large Image

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    The most recent official EPA inventory, reported in April 2012 and showing total U.S. emissions for 2010, shows our emissions going up that year.
    Image: U.S. Environmental Protection Agency (EPA) Extra Large Image

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    This NOAA chart graphs global carbon accumulation (in billions of metric tons) since 1960.
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