Editing Global warming potential (section)

== Definition ==
{{See also|Radiative forcing}}

The global warming potential (GWP) is defined as an "index measuring the [[radiative forcing]] following an emission of a unit mass of a given substance, accumulated over a chosen time horizon, relative to that of the reference substance, carbon dioxide (CO<sub>2</sub>). The GWP thus represents the combined effect of the differing times these substances remain in the atmosphere and their effectiveness in causing radiative forcing."<ref name=":2">IPCC, 2021: Annex VII: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_AnnexVII.pdf Glossary] [Matthews, J.B.R., V. Möller, R. van Diemen, J.S. Fuglestvedt, V. Masson-Delmotte, C.  Méndez, S. Semenov, A. Reisinger (eds.)]. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, 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. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.</ref>{{Rp|page=2232}}

In turn, ''radiative forcing'' is a scientific concept used to quantify and compare the external drivers of change to [[Earth's energy balance]].<ref name="nrcrf">{{cite book |author=National Research Council |title=Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties |publisher=The National Academic Press |year=2005 |isbn=978-0-309-09506-8 |doi=10.17226/11175}}</ref>{{rp|1–4}} Radiative forcing is the change in [[energy flux]] in the atmosphere caused by [[Climate variability and change|natural]] or [[Human impact on the environment#Impacts on climate|anthropogenic]] factors of [[climate change]] as measured in [[watt]]s per meter squared.<ref>{{cite web |last=Drew |first=Shindell |author-link= |year=2013 |title=Climate Change 2013: The Physical Science Basis – Working Group 1 contribution to the IPCC Fifth Assessment Report: Radiative Forcing in the AR5 |url=http://climate.envsci.rutgers.edu/climdyn2013/IPCC/IPCC_WGI12-RadiativeForcing.pdf |url-access= |url-status=live |archive-url=https://web.archive.org/web/20160304083735/http://climate.envsci.rutgers.edu/climdyn2013/IPCC/IPCC_WGI12-RadiativeForcing.pdf |archive-date=4 March 2016 |access-date=15 September 2016 |website=envsci.rutgers.edu |series= |publisher=[[Rutgers University]] |agency=[[IPCC Fifth Assessment Report|Fifth Assessment Report]] (AR5) |department=Department of Environmental Sciences, School of Environmental and Biological Sciences}}</ref>

=== GWP in policymaking ===
As governments develop policies to combat emissions from high-GWP sources, policymakers have chosen to use the 100-year GWP scale as the standard in international agreements. The [[Kigali Amendment]] to the [[Montreal Protocol]] sets the global phase-down of [[hydrofluorocarbon]]s (HFCs), a group of high-GWP compounds. It requires countries to use a set of GWP100 values equal to those published in the IPCC's Fourth Assessment Report (AR4).<ref name=":5">'''[https://treaties.un.org/doc/Treaties/2016/10/20161015%2003-23%20PM/Ch_XXVII-2.f-English%20and%20French.pdf Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer] (the "Montreal Protocol"), adopted at Kigali on October 15, 2016, by the Twenty-Eighth Meeting of the Parties to the Montreal Protocol (the "Kigali Amendment").'''</ref> This allows policymakers to have one standard for comparison instead of changing GWP values in new assessment reports.<ref>{{Cite web |date=August 8, 2024 |title=Understanding Global Warming Potentials |url=https://www.epa.gov/ghgemissions/understanding-global-warming-potentials |access-date=August 26, 2024 |website=US EPA, Greenhouse Gas Emissions}}</ref> One exception to the GWP100 standard exists: [[Government of New York (state)|New York state]]’s [[Climate Leadership and Community Protection Act]] requires the use of GWP20, despite being a different standard from all other countries participating in phase downs of HFCs.<ref name=":5" />