Jet fuel climbs sharply as percentage of U.S. greenhouse gas emissions

In the United States, from 2013 to 2017, jet fuel use has jumped as a percentage of total greenhouse gas emissions, according to the most recent national inventory report (.pdf) released this April by the U.S. Environmental Protection Agency (EPA).

In 2013, jet fuel was responsible for 213 million metric tons of carbon dioxide equivalent emissions (CO2e), which represented 3.1% of the U.S. total (6,776 million metric tons). By 2017, jet fuel emissions climbed sharply to 250 million metric tons, which represented 3.8% of a slightly smaller total (6,534 million metric tons) [updated Aug 17 with small correction].

This means that, in just four short years, in the midst of a climate crisis, aviation emissions as a percentage of the U.S. total rose by more than 20% (one fifth) to reach unprecedented high levels in 2017.

“Using these radiative forcing factors, aviation was responsible for between 7.6% and 11.5% of U.S. carbon dioxide equivalent emissions in 2017.”

The impact of aviation is yet higher if one counts the “radiative forcing” due to the impact of high-altitude aviation emissions. This consideration may double (using an estimate from the CoolClimate calculator) or triple (using an estimate from Lee et al., 2009, in the journal Atmospheric Environment) the climate impact of aviation. Using these radiative forcing factors, aviation was responsible for between 7.6% and 11.5% of U.S. carbon dioxide equivalent emissions in 2017.

Moreover, all of these statistics count only the CO2e emissions from burning jet fuel. All other climate impacts of aviation, including materials and construction of the airplanes, and construction and operations of airports, are in addition to the numbers above.

It is sometimes stated that aviation is responsible for 2% of greenhouse gas emissions, without noting that contemporary U.S. aviation emissions are far higher. The most frequently given citations are to trade association web pages that lack details, or to a 20 year old IPCC estimate of global emissions that has not been updated. In the U.S. context, scientists and climate action advocates should no longer use this 2% figure unless they explain it more precisely.

[New paragraph Aug 21] An electric aviation technology company, AeroTEC, reports estimates that flying is 12% of emissions in the United States, and 4.9% globally, but it does not link to an authoritative information source. Overall, we simply need a scientifically authoritative current estimate of the direct and life-cycle climate impact of the aviation industry to replace the widely cited 2% number.

The high level of U.S. aviation emissions has been overlooked for several reasons, including the fact that jet fuel for international flights (called “international bunker fuels” in the EPA report) is excluded from official national accounts that are most commonly cited. For the statistics above, we included these international jet fuel amounts. This is a sensible approach, counting U.S. amounts for international bunker fuels in U.S. estimates (and, appropriately, excluding international amounts for fuels on incoming international flights). All data and computations for this post are shared in a public spreadsheet with citations.

No major U.S. environmental organization has a substantial campaign of any magnitude addressing aviation demand and rising aviation emissions. There are many initiatives related to offsets, but no large initiatives related to actual in-sector aviation emissions. Aviation is the most neglected of the large emissions sources for U.S. greenhouse gas emissions.

Aviation demand trends are dangerous, presenting a grave risk that the good we attempt to do in other sectors will be swamped by rising emissions in aviation.

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