Governor Brown of California caused a stir with his announcement the week before last that the state will intensify its greenhouse gas (GHG) reduction efforts, with an aggressive new target of reducing GHG emissions to 40% below 1990 levels by 2030, accelerating progress toward the goal of cutting GHG emissions 80% below 1990 levels by 2050. (The Brown administration's press statement is here; representative sampling of the news coverage here and here and here.) California, now in its fourth year of a historic drought, is already well on its way to reaching the goal set under the Schwarzenegger administration of reducing GHG emissions to 1990 levels by 2020. Can it step up its efforts enough to meet Brown's target? We think so. But ignoring major sources of GHG emissions will make the task harder than it already is — and right now California is ignoring a big one: aviation.
Typically we think about aviation in terms of international or national policy, and unquestionably we need to tackle the problem of aviation carbon emissions at those levels. But aviation has important local implications too, and it can—and in California's case should—be a subject of state policy as well.
California, a relatively wealthy state with extensive national and international linkages, is responsible for a disproportionate share of U.S. aviation traffic, fuel use, and CO2 emissions. California Air Resources Board (ARB) GHG inventory suggests that aviation, including all departing commercial flights and general aviation, accounted for 7% of statewide GHG emissions (or 36 MMT CO2e) in 2012. We wondered how that compares with other states on a per capita basis. Estimating California emissions using jet fuel consumption data from the Energy Information Administration, it turns out, closely tracks ARB’s inventory and yields the same 7%. So we estimated each state’s aviation emissions on a residential per capita basis using EIA's fuel data and U.S. Census Bureau population estimates. Based on this metric, California’s emissions also appear large compared to other states' (figure). (Note: We excluded military jet fuel from these statewide averages by using U.S. Air Force annual fuel consumption data and reported purchase amount and capacities of U.S. refineries operated by top suppliers for a [rough] adjustment.)
This per capita approach has the effect of allocating emissions to a state based on the airport of departure, which over a round trip assigns half of emissions to the state of origin and half to the destination. It's a reasonable approach for aviation because no one envisions emissions being regulated by states or nations overflown. It is admittedly not perfect. Some states have more out-of-state travelers (including tourists and those from neighboring states) and thus have higher state fuel consumption without adjustment to the population count. Certain states appear to rank high in per capita emissions not because their residents fly more, but because they have a large number of petroleum refineries. New Jersey has the largest per capita aviation emissions in the Lower 48 in part because fuel is carried from the Gulf Coast to Linden, New Jersey, and then delivered to the three major New York airports (EWR, JFK, LGA). Several other states have refineries either numerous or large enough to influence their estimated per capita emissions, including Louisiana (19), California (18), Texas (27), and Mississippi (3 large refineries).
Nonetheless, within those limitations, it enables us to make some useful comparisons. Among the 48 contiguous states, annual aviation per capita emissions varied from only 100 lbs CO2/person (West Virginia) to 3,600 lbs CO2/person (New Jersey). California was ranked fourth, right after refinery- or pipeline-heavy New Jersey, Louisiana, and Mississippi, with about 2,100 lbs CO2/person. In contrast, the average American emitted just under 1,400 lbs CO2 per year from air travel. (Alaska's and Hawaii's high per capita emissions are attributable to factors including lower population densities, higher incidence of overseas travel, tourism, and greater need for air cargo operations.)
Drilling down even further, to the local level, can also be thought-provoking. The Bay Area Air Quality Management District’s local greenhouse gas inventory (2007, so a bit dated) can be married with California’s fuel consumption data to estimate CO2 emissions from aviation for the San Francisco Bay Area. As before, this number includes estimated jet fuel consumption from all departing commercial flights and general aviation. Airline ticketing data suggests that approximately half of domestic passengers transiting Bay Area airports are in fact Bay Area residents (U.S. DOT DB1B Coupon data, 2013), which is also consistent with our accounting convention of splitting emissions 50/50 between origin and destination airport. Combined, this data suggests that, on a residential per capita basis, CO2 emissions from domestic and international flights departing from Bay Area airports (SFO, OAK, and SJC) add up to about 3,700 lbs CO2 per year—75% more than the California average, and more than two and a half times that of the average American. Aircraft accounted for about 11% of total Bay Area CO2 emissions in 2013, or about as much as agriculture, off-road equipment, and residual fuel combined, and about three-quarters as much as from all electricity generation for the Bay Area (figure).
Note: 2011 and 2014 emission inventory projections from BAAQMD (2010) were used to interpolate values for 2013. Sources: Bay Area Air Quality Management District, “Source Inventory of Bay Area Greenhouse Gas Emissions” (2010 update); EIA California jet fuel consumption for 2013. Icons.
To be sure, these are sketchbook estimates for now. Still, they pass an initial laugh test. The aviation carbon footprint of the average Bay Area resident really is much greater than that of the average American, especially those in “flyover country.” California represents about 12% of the U.S. population, but planes leaving there are responsible for roughly 19% of national jet fuel use. Back in 2009, the California Air Resources Board acknowledged that aviation was an important part of the state’s “missing inventory”. However, aviation is still off the radar in Governor Brown’s climate policy. That’s unfortunate, as California has proven time and again that it has the resources and ability to act boldly on climate change.
If national and international policymakers continue to pass the buck on aviation emissions, it may be time for California to step forward again. It could begin by expanding its aviation emissions inventory to include more than just intrastate flights (accounts for only about 10% of emissions)—at a minimum, other domestic departures out of California should be included as well. In addition, California could consider integrating aviation under a cap-and-trade program. Finally, it could work more closely with its airports to identify reduction plans similar to the one just announced by Boston's Logan International Airport, which recently drafted a climate change plan aiming to reduce carbon emissions by 40% and energy consumption by 26% below 2012 levels by 2020.