


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


July 20, 2016

MEMORANDUM

             SUBJECT:	Methods Utilized in Calculations for GHG Emissions Inventories for Final Aircraft GHG Contribution Finding

             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 methods utilized in the calculations for the Environmental Protection Agency's (EPA's) historical, current, and projected greenhouse gas (GHG) emissions inventories for the contribution finding in the agency's final aircraft GHG endangerment and contribution findings.  These methods pertain to both United States (U.S.) and global GHG emissions inventories (historical, current, and projected inventories).  This includes calculations for the following types of comparisons of U.S. covered aircraft GHG emissions and total U.S. aircraft GHG emissions:

        As a share of current total U.S. GHG emissions; 
        As a share of current U.S. transportation GHG emissions; 
        As a share of current total global GHG emissions; and
        As a share of the current global transportation GHG emissions.  

Refer to Attachments 1 and 2 of this memorandum for a description of the methods used in the calculations.



Attachments: 
 Explanation of Calculations for U.S. GHG Emissions in Cause or Contribute Finding (Attachment 1  -  Presentation format)
 Methods Utilized in Calculations for U.S. and Global GHG Emissions Inventories for Final Aircraft GHG Contribution Finding (Attachment 2  -  Excel file)



