How significant a source of emissions is air travel?
The transportation sector is one of the largest contributors to U.S. carbon dioxide emissions, second only to the power sector, and aircraft comprise a significant and rapidly growing emission source within that sector. In 2013, aircraft accounted for nearly 11 percent of carbon dioxide emissions from the U.S. transportation sector, making them responsible for about 3 percent of total U.S. carbon dioxide emissions. Commercial air travel accounted for most of the aircraft carbon dioxide emissions, with military and general aviation making up the rest.
From 1990 to 2013, U.S. carbon dioxide emissions from domestic commercial flights grew 4 percent. Recent studies estimate that U.S. aircraft emissions will increase substantially in the next 20 years. Moreover, airplanes remain the single largest source of carbon dioxide emissions within the U.S. transportation sector that is not yet subject to greenhouse gas regulations.
U.S. aviation is part of the increasingly interconnected global aviation sector, which makes up about 2 percent of global carbon dioxide emissions but is one of the fastest growing sources. From 1990 to 2010, global aircraft carbon dioxide emissions grew about 40 percent. If global aviation were a country, it would rank as the seventh largest carbon dioxide emitter, and U.S. aircraft emissions are 29 percent of all global aircraft emissions. Absent new policies, global aircraft emissions are projected to triple by 2050.
Figure 1: 2013 U.S. carbon dioxide emission, by sector and transportation source
The transportation sector is responsible for more than one-third of U.S. carbon dioxide emissions. Aircraft are responsible for nearly 9 percent of U.S. transportation sector carbon dioxide emissions.
Source: U.S. Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2013 (Washington, DC: U.S. Environmental Protection Agency, 2015), http://www.epa.gov/climatechange/Downloads/ghgemissions/US-GHG-Inventory-2015-Main-Text.pdf.
What is the status of regulation?
In 2012, the DC District Court ruled that the U.S. Environmental Protection Agency (EPA) is required under the Clean Air Act to determine whether greenhouse gas emissions from aircraft cause or contribute to air pollution, which may reasonably be anticipated to endanger public health or welfare. An endangerment finding would trigger regulation under the Clean Air Act.
On June 10, 2015, EPA issued its proposed endangerment finding for greenhouse gas emissions from aircraft under section 231 of the Clean Air Act. The proposed finding builds on the previous 2009 endangerment finding for light-duty vehicles and found greenhouse gas emissions from aircraft engines used in certain types of aircraft are responsible for contributing to climate change, which threatens public health and welfare. Covered aircraft are those subject to international carbon dioxide emission standards, subsonic jet aircraft — ranging from smaller jet aircraft such as the Cessna Citation II to larger jet aircraft such as the Boeing 747 — and subsonic turboprop aircraft — e.g., Bombardier Q400. The proposed endangerment finding will receive public comment before a final endangerment finding may be issued. The final endangerment finding itself would not impose any restrictions on aircraft. It is however a necessary step in determining whether EPA must regulate greenhouse gas emissions from aircraft.
How does EPA action fit with global action?
Unlike stationary sources, such as power plants, and many mobile sources, such as cars, aircraft frequently travel between jurisdictions with different environmental laws and standards. As such, the United Nation’s International Civil Aviation Organization (ICAO) serves as a global forum to develop policies and standards for the global industry, including a comprehensive set of measures to address greenhouse gas emissions. ICAO is developing a market-based system for aircraft to reduce total emissions from the sector, including through the use of offsets. It is also developing technology-based emission standards for covered aircraft, which are expected to be proposed in February 2016 and adopted later in that year.
Traditionally, both the EPA and the Federal Aviation Administration (FAA) have worked within the ICAO process to establish international emission standards and related requirements for other pollutants. Under this approach, international emission standards are first adopted by ICAO, and EPA subsequently initiates rulemaking under section 231 of the Clean Air Act to establish domestic standards equivalent to international standards where appropriate. Both EPA and FAA expect to take a similar approach in promulgating future domestic aircraft greenhouse gas standards for covered aircraft.
What are the next steps?
EPA issued an advanced noticed of proposed rulemaking at the same time as the proposed endangerment finding. The notice solicits comments on a variety of issues related to setting an international carbon dioxide standard for aircraft, including whether such standards should apply to in-production aircraft or new aircraft type designs, the appropriate effective date for a potential international carbon dioxide standard, as well as the appropriate stringency level. However, it does not impose any standards or regulatory requirements at this time.
EPA’s endangerment finding and advanced notice of proposed rulemaking lay the groundwork for U.S. adoption of international emission standards. Once ICAO adopts emission standards for covered aircraft in 2016, EPA is expected to begin rulemaking under section 231 of the Clean Air Act to establish domestic aircraft engine emission standards for covered aircraft that are of at least equivalent stringency as the international emission standards.
President Obama’s signature on a law authorizing the Secretary of Transportation to bar U.S. airlines from participating in the European Union’s emissions trading system underscores the urgent need for a global approach to reducing greenhouse gas emissions from the fast-growing aviation sector.
The new law is the latest salvo in an international brouhaha triggered by the EU’s attempt to regulate greenhouse gas emissions from flights to or from Europe. Dozens of countries, including the United States, protested the move as an affront to national sovereignty and a violation of international aviation agreements. The EU acted after years of talks within the International Civil Aviation Organization (ICAO) failed to result in a global agreement to reduce aviation emissions.