


                          UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
                            National Vehicle and Fuel Emissions Laboratory 2000 Traverwood Drive
                                 Ann Arbor, Michigan 48105-2498


July 1, 2016

MEMORANDUM

             SUBJECT:	Updated Databases for Emissions Inventories Used in Final Aircraft GHG Emissions Findings Compared to Proposed Findings

             FROM:	Bryan J. Manning, Mechanical Engineer Assessment and Standards Division
             Office of Transportation and Air Quality
             U.S. Environmental Protection Agency

TO:	The Air and Radiation Docket
             Docket No. EPA-HQ-OAR-2014-0828

This memorandum documents the updated databases utilized by the Environmental Protection Agency (EPA) for historical and projected emissions inventories in the contribution finding of the agency's final aircraft greenhouse gas (GHG) emissions findings  -  in comparison to the proposed findings, which were issued in July 2015.  These updated databases pertain to both United States (U.S.) and global GHG emissions inventories (historical and projected inventories).

U.S. Emissions Inventories 

For historical U.S. GHG emissions inventories in the final findings, which includes total U.S. GHG emissions, U.S. transportation GHG emissions, total U.S. aircraft GHG emissions, and U.S. covered aircraft GHG emissions, we utilized the 2016 EPA report entitled, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2014 (hereinafter "U.S. Inventory").  To determine U.S. covered aircraft GHG emissions, aircraft that both use jet fuel and are above the maximum takeoff mass (MTOM) thresholds of the international aircraft CO2 standards, we utilized data from the 2015 ERG report entitled, U.S. Jet Fuel Use and CO2 Emissions Inventory for Aircraft Below ICAO CO2 Standard Thresholds, in combination with the 2016 U.S. Inventory.  

For projections of U.S. GHG emissions inventories in the final findings, we forecast both total U.S. aircraft GHG emissions and U.S. covered aircraft GHG emissions according to the fuel consumption projections in the FAA Aerospace Forecast Fiscal Years 2016-2036.  For other transportation sources, we projected GHG emissions based on the U.S. Energy Information Administration's (EIA's) Annual Energy Outlook (AEO) 2015 with projections to 2040.

Global Emissions Inventories

For historical global GHG emissions inventories in the final findings, which includes total global GHG emissions, global transport GHG emissions, and global aircraft emissions we utilized the IPCC's 2013-2014 Fifth Assessment Report (AR5) for the year 2010.  We also provided updated 2012 estimates from other widely used and recognized global datasets, the World Resources Institute's (WRI) Climate Analysis Indicators Tool (CAIT) and the International Energy Agency (IEA).  For historical global emissions for aircraft that are covered by the International Civil Aviation Organization (ICAO) CO2 standard ("ICAO covered aircraft"), data are from ICAO's 2013 Environmental Report.  For the projections of ICAO covered aircraft GHG emissions in the final findings, we utilized the fuel burn forecasts from ICAO's 2013 Environmental Report.
