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landfills. Human-made GHGs, many of which have greater heat-absorption potential than CO2,
<br /> include fluorinated gases and SF6.40
<br /> Different types of GHGs have varying global warming potentials(GWP).The GWP of a GHG is the
<br /> potential of a gas or aerosol to trap heat in the atmosphere over a specified timescale (generally,
<br /> 100 years). Because GHGs absorb different amounts of heat, a common reference gas (CO2) is used
<br /> to relate the amount of heat absorbed to the amount of the gas emitted, referred to as "carbon
<br /> dioxide equivalent" (CO2e),which is the amount of GHG emitted multiplied by its GWP.Carbon
<br /> dioxide has a 100-year GWP of one. By contrast, methane has a GWP of 30, meaning its global
<br /> warming effect is 30 times greater than CO2 on a molecule per molecule basis.41,42
<br /> The accumulation of GHGs in the atmosphere regulates the earth's temperature.Without the
<br /> natural heat-trapping effect of GHGs,the earth's surface would be about 33 degrees Celsius (°C)
<br /> cooler.43 However,since 1750, estimated concentrations of CO2, CH4, and N20 in the atmosphere
<br /> have increased by 36 percent, 148 percent,and 18 percent, respectively, primarily due to human
<br /> activity.44 GHG emissions from human activities, particularly the consumption of fossil fuels for
<br /> electricity production and transportation, are believed to have elevated the concentration of these
<br /> gases in the atmosphere beyond the level of concentrations that occur naturally.
<br /> Greenhouse Gas Emissions Inventories
<br /> Global Emissions Inventory
<br /> Worldwide anthropogenic emissions of GHGs were approximately 49,000 million metric tons (MMT)
<br /> Of CO2e in 2010.45 Carbon dioxide emissions from fossil fuel combustion and industrial processes
<br /> contributed about 65 percent of total emissions in 2010. Of anthropogenic GHGs,CO2 was the most
<br /> abundant, accounting for over 75 percent of total 2010 emissions. Methane emissions accounted
<br /> for 16 percent of the 2010 total,while N20 and fluorinated gases accounted for 6 percent and 2
<br /> percent respectively.46
<br /> 40 U.S. EPA. 2021. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2019. April 2021.
<br /> https://www.a pa.gov/syste m/fi I es/docu m ents/2022-02/us-ghg-inventory-2022-main-text.pdf
<br /> 41 The IPCC's Sixth Assessment Report from 2021 determined that methane has a GWP of 30.However,the 2017 Climate Change Scoping
<br /> Plan published by the California Air Resources Board uses a GWP of 25 for methane,consistent with the Intergovernmental Panel on Climate
<br /> Change's Fourth Assessment Reportfrom 2007.Therefore,this analysis utilizes a GWP of 25.
<br /> 42 IPCC.2021.Climate Change 2021:The Physical Science Basis.Contribution of Working Group I to the Sixth Assessment Report of the
<br /> Intergovernmental Panel on Climate Change[Masson-Delmotte,V.,P.Zhai,A.Pirani,S.L.Connors,C.Pean,S.Berger,N.Caud,Y.Chen,L.
<br /> Goldfarb,M.I.Gomis,M.Huang,K.Leitzell,E.Lonnoy,J.B.R.Matthews,T.K.Maycock,T.Waterfield,0.YelekSi,R.Yu and B.Zhou(eds.)]
<br /> Cambridge University Press.https://www.ipcc.ch/report/ar6/wgl/downloads/report/IPCC_AR6_WGI_Full_Report.pdf
<br /> 43 World Meteorological Organization.2020."Greenhouse Gases."https://public.wmo.int/en/our-mandate/focus-
<br /> a reas/environment/greenhouse%20gases
<br /> 44 Forster,P.,V.Ramaswamy,P.Artaxo,T.Berntsen,R.Betts,D.W.Fahey,J.Haywood,J.Lean,D.C.Lowe,G.Myhre,J.Nganga,R.Prinn,G.
<br /> Raga,M.Schulz and R.Van Dorland.2007.Changes in Atmospheric Constituents and in Radiative Forcing.Climate Change 2007:The Physical
<br /> Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
<br /> [Solomon,S.,D.Qin,M.Manning,Z.Chen,M.Marquis,K.B.Averyt,M.Tignor and H.L.Miller(eds.)].Cambridge University Press,Cambridge,
<br /> United Kingdom and New York,NY,USA.https://www.ipcc.ch/site/assets/uploads/2018/02/aro-wgl-chapter2-l.pdf
<br /> 45 IPCC.2014.Climate Change 2014 Synthesis Report.Contribution of Working Groups I,II and III to the Fifth Assessment Report of the
<br /> Intergovernmental Panel on Climate Change[Core Writing Team,R.K.Pachauri and L.A.Meyer(eds.)].IPCC,Geneva,Switzerland.
<br /> 46 ibid.
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