What’s the plan, Sam? Why the United States still needs to lead on aviation emissions.

Four years ago, I explained why the United States needs to lead in developing policies to control greenhouse gases from aircraft, owing both to the country’s large share of current emissions and also its history as a heavy polluter. I estimated that the average U.S. citizen consumed about three times as much jet fuel as a typical European, six times that of the global average, and as much as 70 times that of a typical Indian citizen. Since carbon dioxide (CO₂) emissions are proportional to fuel use, that translates to a large climate burden from American travel. I concluded that the U.S. needed to up its game on aviation and climate, in particular by proposing a CO₂ standard for aircraft under the U.S. Clean Air Act and by proactively engaging in international climate negotiations. So, how well do those arguments hold up today?

To dig into this, I’ve revisited the U.S. Energy Information Agency’s (EIA) jet fuel use statistics to estimate per capita fuel use in 2016, the latest year for which data is available for five key regions. Data from the World Bank’s World Development Indicators provided each country’s population and identified countries with more outbound than inbound tourists. That’s needed to distinguish between citizens of those countries traveling abroad from residents of other countries sharing the same flights. I also used ICAO’s 2016 Air Transport Statistical Results to isolate international aviation activity from domestic on the assumption that domestic flights in a given country were taken wholly by residents, not international tourists.

The figure below illustrates the results. Two values are shown for each country: the per capita fuel use adjusted for countries with more or less outbound travelers than inbound visitors (within the colored character), and fuel use estimated directly from flights without correction for nationality (bottom of graphic).  Overall, I estimate that global per capita jet fuel use increased by about 12% from 2010 to 2016. Adjusted per capita fuel use in the U.S. (285 liters per person) and Europe (120 liters per person in the EU-28) remains markedly higher than the rest of the world. The average U.S. citizen continues to consume about six times the jet fuel of the global average, but countries like China and India are closing the gap somewhat from our previous assessment. In particular, per capita Chinese fuel use has risen from less than half of the world average to about three-quarters of the average in this estimate, driven by a 65% increase in absolute fuel use from 2010 levels. This compares to an 18% increase in the U.S. and a smaller (7%) increase in the EU.

Adjusting for asymmetric international tourism reduces per capita fuel use by several percent in Europe and the U.S. but increases Chinese per capita fuel use by about one-third, owing to large outbound tourist flows. While not shown in the graphic, adjustments for individual European countries can be even larger. An estimate of UK per capita fuel use in 2016 almost doubles, from 218 to 424 liters, after adjusting for outbound tourism. In sun-kissed Portugal, per capita consumption falls three-quarters, from 153 liters down to 38 liters, after accounting for inbound tourism from countries like the UK.

The data still suggest that, in a fair world, the responsibility for addressing aviation emissions should start in the developed world.  How do current policies compare to this basic observation?

At the international level, it’s somewhat of a mixed bag. Both the UN’s fuel efficiency standard for new aircraft and its Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) have either implicit or explicit means of dealing with differences in levels of development between countries. The CO₂ standard, which will regulate the fuel efficiency of aircraft manufactured largely in developed states, could impose costs on manufacturers but could also provide fuel savings for airlines, many of which operate in the developing world. Separately, CORSIA redistributes some of the offsetting burden from faster growing airlines, which might otherwise need to offset growth above the 2020 emissions baseline, to their slower-growing peers. This approach is important to avoid penalizing “late mover” airlines in developing countries but somewhat dilutes the incentive for airlines to directly reduce rather than offset emissions.

At the regional level, the U.S. and European states could adopt aviation climate measures above and beyond ICAO’s minimum requirements. Here, the EU has taken a clear lead. The EU emissions trading system, which imposes a price on carbon for domestic and intra-EU flights, could also be applied to international routes to and from Europe if participation rates and offset quality under CORSIA disappoint. In addition, a number of northern European states are using their domestic markets as a testing ground for new technologies to decarbonize aviation. Norway has announced a target to electrify all short-haul flights by 2040 and will implement an advanced biofuels mandate starting next year. Sweden is considering renewable fuels mandates requiring up to 30% use by 2030, with one airline committing to promoting carbon capture technologies to offset domestic aviation emissions. In Germany, Lufthansa has announced plans to introduce power to liquid (PtL) fuel for domestic German flights from Hamburg.

On this side of the pond, however, there is much less to brag about. Almost a decade after first being sued, and more than four years after admitting that it is legally obligated to do so, U.S. EPA has yet to propose a single measure to control aircraft CO₂. The lack of a U.S. domestic CO₂ standard leaves U.S. manufacturers in the unenviable position of needing to certify future planes abroad, no doubt an uncomfortable development given recent revelations about certifying the 737 MAX. On the CORSIA front, FAA recently released voluntary guidance, rather than binding regulations, for monitoring and reporting emissions. That raises questions about the enforceability of future offsetting requirements, particularly if countries like China don’t commit to participating in the initial phase of CORSIA starting in 2021. Under that scenario, it’s unlikely that U.S. carriers will voluntarily offset emissions on routes where their competitors won’t have to.

So, what exactly should the U.S. be doing, then? First and foremost, it’s high time for the U.S. to propose a CO₂ standard for new aircraft. Since ICAO’s recommended standard is too weak to require additional action from manufacturers, that standard could include provisions to apply it to in-service fleets rather than just new aircraft. Second, since CORSIA only covers international aviation, some consideration should be given to supplemental policies (e.g. incentives, taxation, etc.) to address CO₂ emitted during domestic flights, which account for about two-thirds of emissions from U.S. airlines. Finally, the U.S. should ensure that supersonic airliners, which could be five to seven times as carbon intensive as equivalent subsonic designs, aren’t given special treatment under environmental standards. For that issue, even benign neglect could double as a form of climate leadership.

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