Controlling greenhouse gas (GHG) emissions from aircraft poses perplexing challenges because aircraft can pass through numerous international regulatory regimes during a single day. Yet, aircraft GHG emissions account for 10 percent of U.S. transportation sector emissions and 2.7 percent of global transportation sector emissions. Thus, despite the significant difficulties they pose, aircraft emissions remain a focus of regulators. In 2016, important steps to regulate aircraft GHG emissions were taken at both the international and domestic level.
ICAO standards for GHG emissions from aircraft
The International Civil Aviation Organization (ICAO) is a United Nations agency that develops international aviation standards. ICAO’s mandate covers aviation safety, security, efficiency, capacity, and environmental protection. ICAO’s environmental standards are typically developed by the Committee on Aviation Environmental Protection (CAEP), comprising representatives from member states, the aviation industry, and nongovernmental organizations (NGOs). CAEP’s technical standards must be adopted by the ICAO Council and ICAO Assembly. Once ICAO adopts aviation standards, each member state is required to adopt standards that are at least as stringent and may ban the use within its airspace of any aircraft that does not meet ICAO standards.
In 2010 ICAO requested that CAEP develop a carbon dioxide emissions standard that would improve annual fuel efficiency and stabilize aviation GHG emissions at 2020 levels. Establishing such standards is particularly challenging given the paramount role that aircraft safety must play in aviation regulations and the need to develop a consensus approach among countries with interests that sometimes differ. Recognizing that aircraft GHG emissions are influenced by aerodynamics, weight, and engine technology, CAEP adopted an approach focusing on the entire aircraft instead of focusing solely on engines.
In February 2016, CAEP adopted recommendations for international GHG emission standards that would be applicable to both new aircraft types and in-production aircraft. The standards for new aircraft types would take effect in 2020. Less stringent standards for in-production aircraft would take effect in 2023 but could, nevertheless, result in the discontinuation of several currently-produced aircraft types.
At its October 2016 meeting, the ICAO Assembly “[w]elcomed the recommendation by CAEP on a new global CO2 emissions certification standard for aeroplanes,” but did not move to adopt the recommended standards. ICAO could take further action on CAEP’s recommended standards at its next meeting in March 2017.
At its October 2016 meeting, ICAO also approved a new agreement for GHG emissions from international flights, entitled the “Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).” See Resolution A39-3: Consolidated statement of continuing ICAO policies and practices related to environmental protection—Global Market-based Measure (MBM) scheme. CORSIA includes a market-based scheme that utilizes a global carbon offset program to cap net GHG emissions from international flights between participating nations. Sixty-five member states, including the United States, representing 85 percent of international aviation activity have signed CORSIA.
CORSIA caps GHG emissions from international aviation based on 2020 emissions and will reduce the overall GHG intensity of international aviation as the sector continues to grow. If GHG emissions from international aviation exceed 2020 levels, operators will be required to purchase carbon offsets to make up the difference in GHG emissions. CORSIA will take effect on a voluntary basis in 2021 and become effective on most signatory states in 2027. The requirement to purchase offsets will initially be applied to all aircraft operators on a pro rata basis. Beginning in 2030, offset requirements will be based in part on the performance of each individual aircraft operator, creating an incentive to reduce GHG emissions.
CORSIA directs CAEP to develop guidance regarding the generation of offsets as well as a central registry for offsets under the auspices of ICAO. Member states must develop the necessary regulatory framework to implement CORSIA by 2020.
U.S. regulation of GHG emissions from aircraft
In the United States, environmental aviation standards are issued by the Environmental Protection Agency (EPA). For issues with international impacts, EPA typically follows ICAO’s lead and adopts standards consistent with ICAO’s. (The United States is actively involved in the development of ICAO standards.) The timing of EPA’s regulation is intended to coincide with ICAO’s adoption of GHG emission standards.
In 2007, several NGOs petitioned EPA to regulate GHG emissions from aircraft. In 2012, EPA granted the petition and announced that it would begin the process of regulating aircraft GHG emissions. Prior to regulating air emissions from aircraft, the Clean Air Act requires EPA to make a determination that those emissions “cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare.” 42 U.S.C § 7571(a)(2)(A). On July 1, 2015, EPA issued a proposed endangerment determination along with an advanced notice of proposed rulemaking that solicited comment on several issues related to CAEP’s proposed GHG emissions standards. 80 Fed. Reg. 37,758 (July 1, 2015).
EPA’s final endangerment determination was issued on August 15, 2016, 81 Fed. Reg. 54,422 (Aug. 15, 2016), and relied heavily on the 2010 endangerment determination for GHG emissions from motor vehicles. EPA concluded that the scientific evidence supporting the 2010 endangerment determination remained valid and was further supported by additional studies published after 2010. EPA further concluded that GHG emissions from aircraft cause or contribute to the endangerment of public health and welfare based on a comparison of aircraft GHG emissions to domestic and global GHG emissions.
While EPA’s endangerment determination is a necessary prerequisite to the regulation of aircraft GHG emissions, the agency has not taken steps to issue such a regulation. Instead, the endangerment determination referenced CAEP’s recommendations and suggested that EPA intended to defer regulation until ICAO adopts international standards. In doing so, EPA noted that it had an obligation under the Clean Air Act to issue aircraft GHG regulations in response to the endangerment determination, but asserted that it had discretion with respect to the timing of those regulations.
EPA’s next steps will likely depend on the final adoption of GHG emission standards for aircraft by ICAO. There is no indication that EPA intends to depart from its past precedent of issuing regulations consistent with ICAO standards. Moreover, adoption of such regulations may be uncontroversial given the consensus-based approach followed by CAEP and ICAO. At the same time, given the change in administration, there may be some uncertainty regarding whether EPA will continue to implement or reconsider its endangerment determination and endorse the ICAO standards.