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Overview of GHG Emissions and Climate Change
<br /> Climate Change and Greenhouse Gases
<br /> Climate change is the observed increase in the average temperature of Earth's atmosphere and
<br /> oceans along with other substantial changes in climate(such as wind patterns, precipitation, and
<br /> storms) over an extended period.The term "climate change" is often used interchangeably with the
<br /> term "global warming," but"climate change" is preferred to "global warming" because it helps
<br /> convey other changes in addition to rising temperatures.The baseline against which these changes
<br /> are measured originates in historical records identifying temperature changes that have occurred in
<br /> the past,such as during previous ice ages.The global climate changes continuously, as evidenced by
<br /> repeated episodes of substantial warming and cooling documented in the geologic record.The rate
<br /> of change has typically been incremental,with warming or cooling trends occurring over the course
<br /> of thousands of years.The past 10,000 years have been marked by a period of incremental
<br /> warming, as glaciers have steadily retreated across the globe. However, scientists have observed
<br /> substantial acceleration in the rate of warming during the past 150 years.The United Nations
<br /> Intergovernmental Panel on Climate Change(IPCC) expressed that the rise and continued growth of
<br /> atmospheric CO2 concentrations is unequivocally due to human activities in the IPCC's Sixth
<br /> Assessment Report from 2021. Human influence has warmed the atmosphere, ocean, and land,
<br /> which has led the climate to warm at an unprecedented rate in the last 2,000 years. It is estimated
<br /> that between the period of 1850 through 2019,that a total of 2,390 gigatonnes of anthropogenic
<br /> CO2 was emitted. It is likely that anthropogenic activities have increased the global surface
<br /> temperature by approximately 1.07 degrees Celsius between the years 2010 through 2019.38
<br /> Furthermore,since the late 1700s, estimated concentrations of CO2, methane,and nitrous oxide in
<br /> the atmosphere have increased by over 43 percent, 156 percent, and 17 percent, respectively,
<br /> primarily due to human activity.39 Emissions resulting from human activities are thereby
<br /> contributing to an average increase in Earth's temperature.
<br /> Gases that absorb and re-emit infrared radiation in the atmosphere are called GHGs.The gases
<br /> widely seen as the principal contributors to human-induced climate change include carbon dioxide
<br /> (CO2), methane (CHa), nitrous oxides (N20),fluorinated gases such as hydrofluorocarbons(HFCs)and
<br /> perfluorocarbons(PFCs), and sulfur hexafluoride (SF6).Water vapor is excluded from the list of
<br /> GHGs because it is short-lived in the atmosphere, and natural processes, such as oceanic
<br /> evaporation, largely determine its atmospheric concentrations.
<br /> GHGs are emitted by natural processes and human activities. Of these gases,CO2 and CHa are
<br /> emitted in the greatest quantities from human activities. Emissions of CO2 are usually by-products of
<br /> fossil fuel combustion,and CHa results from off-gassing associated with agricultural practices and
<br /> 38 Intergovernmental Panel on Climate Change(I PCC).2021.Climate Change 2021:The Physical Science Basis.Contribution of Working
<br /> Group Ito the Sixth Assessment Report of the Intergovernmental Panel on Climate Change[Masson-DeImotte,V.,P.Zhai,A.Pirani,S.L.
<br /> Connors,C.Pean,S.Berger,N.Caud,Y.Chen,L.Goldfarb,M.I.Gomis,M.Huang,K.Leitzell,E.Lonnoy,J.B.R.Matthews,T.K.Maycock,T.
<br /> Waterfield,O.Yelekgi,R.Yu and B.Zhou(eds.)]Cambridge University Press.
<br /> https://www.ipcc.ch/report/a r6/wgI/downloads/report/IPCC_AR6_WG I_FuII_Report.pdf
<br /> 39 United States Environmental Protection Agency(U.S.EPA).2021.Climate Change Indicators:Atmospheric Concentrations of
<br /> Greenhouse Gases.Last updated April 2021.https://www.epa.gov/climate-indicators/climate-change-indicators-atmospheric-
<br /> concentrations-greenhouse-gases
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