"Without accounting for GHG emissions from land use change, the carbon footprint of food produced and not eaten is estimated to 3.3 Gtonnes of CO2 equivalent: as such, food wastage ranks as the third top emitter after USA and China." (FAO)
"Anthropogenic greenhouse gas emissions in 2010 have reached 49 ± 4.5 GtCO2 eq/yr." (IPCC)
[Calculation: If total global GHG emissions = 49 Gtonnes, then food waste would account for 6.7% of total GHG emissions.]
Food and Agriculture Organization, “Food Wastage Footprint: Impacts on Natural Resources,” Summary Report, 2013, 6, accessed May 28, 2014, http://www.fao.org/docrep/018/i3347e/i3347e.pdf
Intergovernmental Panel on Climate Change (IPCC), "IPCC Fifth Assessment Synthesis Report: Climate Change 2014 Synthesis Report, Approved Summary for Policymakers," November 1, 2014, SPM-5, accessed November 11, 2014, http://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_SPM.pdf.