Editing Causes of climate change (section)

==== Methane and nitrous oxide ====
[[File:The Global Methane Budget 2008–2017.png|thumb|Main sources of global methane emissions (2008–2017) according to the [[Global Carbon Project]]<ref name="Saunois_2020">{{cite journal |last1=Saunois |first1=M. |last2=Stavert |first2=A.R. |last3=Poulter |first3=B. |display-authors=etal |date=July 15, 2020 |title=The Global Methane Budget 2000–2017 |url=https://essd.copernicus.org/articles/12/1561/2020/ |journal=Earth System Science Data  |language=en |volume=12 |issue=3 |pages=1561–1623 |bibcode=2020ESSD...12.1561S |doi=10.5194/essd-12-1561-2020 |issn=1866-3508 |access-date=28 August 2020 |doi-access=free|hdl=1721.1/124698 |hdl-access=free }}</ref>|right]]
Methane emissions [[enteric fermentation|come from livestock]], manure, [[Environmental impact of rice cultivation|rice cultivation]], landfills, wastewater, and [[coal seam gas|coal mining]], as well as [[fugitive gas emissions|oil and gas extraction]].<ref>{{harvnb|EPA|2020}}; {{harvnb|Global Methane Initiative|2020|ps=: Estimated Global Anthropogenic Methane Emissions by Source, 2020: [[Enteric fermentation]] (27%), Manure Management (3%), Coal Mining (9%), [[Municipal Solid Waste]] (11%), Oil & Gas (24%), [[Wastewater]] (7%), [[Rice|Rice Cultivation]] (7%)}}</ref> Nitrous oxide emissions largely come from the microbial decomposition of [[fertilizer|fertiliser]].<ref>{{harvnb|EPA|2019|ps=: Agricultural activities, such as fertilizer use, are the primary source of N<sub>2</sub>O emissions}}; {{harvnb|Davidson|2009|ps=: 2.0% of manure nitrogen and 2.5% of fertilizer nitrogen was converted to nitrous oxide between 1860 and 2005; these percentage contributions explain the entire pattern of increasing nitrous oxide concentrations over this period}}</ref>

[[Methane]] and to a lesser extent [[nitrous oxide]] are also major forcing contributors to the [[greenhouse effect]]. The [[Kyoto Protocol]] lists these together with [[hydrofluorocarbon]] (HFCs), [[Fluorocarbon|perfluorocarbons]] (PFCs), and [[sulfur hexafluoride]] (SF<sub>6</sub>),<ref name="kyoto">{{Cite web |title=The Kyoto Protocol |publisher=[[UNFCCC]] |url=http://unfccc.int/resource/docs/convkp/kpeng.html |access-date=9 September 2007 |archive-date=25 August 2009 |archive-url=https://web.archive.org/web/20090825212122/http://unfccc.int/resource/docs/convkp/kpeng.html |url-status=live }}</ref> which are entirely artificial gases, as contributors to radiative forcing. The chart at right attributes anthropogenic greenhouse gas [[Air pollution|emissions]] to eight main economic sectors, of which the largest contributors are [[power station]]s (many of which burn coal or other [[fossil fuel]]s), industrial processes, transportation [[fuel]]s (generally [[fossil fuel]]s), and agricultural by-products (mainly methane from [[enteric fermentation]] and nitrous oxide from [[fertilizer]] use).<ref>{{citation |title=7. Projecting the Growth of Greenhouse-Gas Emissions |url=http://www.hm-treasury.gov.uk/d/Chapter_7_Projecting_the_Growth_of_Greenhouse-Gas_Emissions.pdf |pages=171–4 |url-status=dead |archive-url=https://web.archive.org/web/20121104032244/http://www.hm-treasury.gov.uk/d/Chapter_7_Projecting_the_Growth_of_Greenhouse-Gas_Emissions.pdf |archive-date=4 November 2012 |df=dmy-all}}, in [http://webarchive.nationalarchives.gov.uk/20100407172811/http://www.hm-treasury.gov.uk/stern_review_report.htm Stern Review Report on the Economics of Climate Change] (pre-publication edition) (2006)</ref>
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