Aviation Emissions and Air Quality Handbook  conditions. 61  The FAA also funded the Partnership for Air Transportation Noise & Emissions  Reduction (PARTNER) and subsequently the Center of Excellence for alternative jet fuels and  environment (ASCENT) research initiatives to quantify the effects of aircraft exhaust contrails on global and U.S. climate and atmospheric composition. Similar research topics are  being examined at the international level by the ICAO. 62  In terms of U.S. contributions, the U.S. Government Accountability Office (GAO) reports that  " domestic aviation contributes about 3 percent of total carbon dioxide emissions, according to  EPA data ," compared with other industrial sources, including the remainder of the transportation  sector (20 percent) and power generation (41 percent). 63  The ICAO also estimates that GHG  emissions from aircraft account for roughly three percent of all anthropogenic GHG emissions  globally. 64  Importantly, actions are underway within the U.S. and by other nations to reduce  aviation's  contribution of GHGs through such measures as new aircraft technologies to reduce emissions  and improve fuel efficiency, renewable alternative fuels with lower carbon footprints, efficient air traffic management, market -based measures , and environmental regulations  including an aircraft CO$_{2 }$standard.  Presently, FAA’s principal guidance for assessing and reporting upon climate change and GHGs  for NEPA documents is described below; however, subsequent revisions should be consulted as  they become available.  Prepared by the CEQ, this Guidance presently serves as the FAA’s protocol for assessing  and reporting upon GHGs in NEPA documents.  From this, the FAA recommends the  following with respect to the documentation of GHGs in NEPA documents:  61 Nathan Brown, et. al.  The U.S. Strategy for Tackling Aviation Climate Impacts , 2010, 27$^{th }$International  Congress of the Aeronautical Sciences.  62 Lourdes Q. Maurice and David S. Lee. Chapter 5:  Aviation Impacts on Climate. Final Report of the  International Civil Aviation Organization (lCAO) Committee on Aviation and Environmental Protection  (CAEP) Workshop , October 29$^{th }$- November 2nd 2007, Montreal.  63 GAO,  Aviation and Climate Change. GAO Report to Congressional Committees , June 2009 [GAO-09-554];  http://www.gao.gov/new.items/d09554.pdf.  64 ICAO, Alan Melrose,  European ATM and Climate Adaptation: A Scoping Study , in ICAO Environmental  Report  2010,  http://www.icao.int/environmental-protection/Documents/EnvironmentReport- 2010/ICAO_EnvReport10-Ch6_en.pdf.  65 Council on Environmental Quality,  National Environmental Policy Act (NEPA) Draft Guidance,  “Consideration of the Effects of Climate Change and Greenhouse Gas Emissions.” , 75 Federal Register 8046,  2010, https://federalregister.gov/a/2010-3532  − If GHGs and climate are not relevant to the proposed action and alternative(s)  (i.e., because there would be no GHG emissions), this should be briefly noted and  no further analysis is required.  − Where the proposed action or alternative(s) would not result in a net increase in  GHG emissions (as indicated by quantitative data or proxy measures such • Federal Greenhouse Gas Accounting and Reporting Guidance. 65  6.3.2.  FAA NEPA Guidance  50$_{ }$