Editing Positive feedback (section)

=== In climatology ===
{{See also|Climate change feedback|Runaway greenhouse effect}}
{{multiple image | total_width=500
| image1= Earth Energy Budget with GHE.svg |caption1= [[Earth's energy balance]] between space, the atmosphere, and Earth's surface. Human-caused increases in greenhouse gases [[greenhouse effect|stimulate]] positive feedback in [[global warming]].
| image2= 20220726 Feedbacks affecting global warming and climate change - block diagram.svg |caption2= Some effects of global warming can either enhance (positive feedbacks) or inhibit ([[negative feedback]]s) warming.<ref name=NASA_IntegratedSystem>{{cite web |title=The Study of Earth as an Integrated System |url=https://climate.nasa.gov/nasa_science/science/ |website=nasa.gov |publisher=NASA |date=2016 |archive-url=https://web.archive.org/web/20161102022200/https://climate.nasa.gov/nasa_science/science/ |archive-date=November 2, 2016 |url-status=live }}</ref><ref name=IPCC_AR6_SGI_FigTS.17>Fig. TS.17, ''[https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf Technical Summary],'' Sixth Assessment Report (AR6), Working Group I, IPCC, 2021, p. 96. [https://web.archive.org/web/20220721021347/https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_TS.pdf Archived] from the original on July 21, 2022.</ref>
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Climate ''forcings'' may push a climate system in the direction of warming or cooling,<ref>{{citation | author=US NRC | year=2012 | title=Climate Change: Evidence, Impacts, and Choices | url=https://www.scribd.com/doc/98458016/Climate-Change-Lines-of-Evidence | publisher=US National Research Council (US NRC) | url-status=live | archive-url=https://web.archive.org/web/20160503153121/https://www.scribd.com/doc/98458016/Climate-Change-Lines-of-Evidence | archive-date=2016-05-03 }}, p.9. Also available as [http://nas-sites.org/americasclimatechoices/files/2012/06/19014_cvtx_R1.pdf PDF] {{webarchive|url=https://web.archive.org/web/20130220184517/http://nas-sites.org/americasclimatechoices/files/2012/06/19014_cvtx_R1.pdf |date=2013-02-20 }}</ref> for example, increased atmospheric concentrations of [[greenhouse gas]]es cause warming at the surface. Forcings are external to the climate system and feedbacks are internal processes of the system. Some feedback mechanisms act in relative isolation to the rest of the climate system while others are tightly coupled.<ref>[http://www.nap.edu/openbook.php?record_id=10850&page=16 ''Understanding Climate Change Feedbacks,'' U.S. National Academy of Sciences] {{webarchive|url=https://web.archive.org/web/20120210122555/http://www.nap.edu/openbook.php?record_id=10850&page=16 |date=2012-02-10 }}</ref> Forcings, feedbacks and the dynamics of the climate system determine how much and how fast the climate changes. The main positive feedback in [[global warming]] is the tendency of warming to increase the amount of water vapour in the atmosphere, which in turn leads to further warming.<ref>{{cite web |url=http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch8s8-6-3-1.html |title=8.6.3.1 Water Vapour and Lapse Rate - AR4 WGI Chapter 8: Climate Models and their Evaluation |access-date=2010-04-23 |url-status=dead |archive-url=https://web.archive.org/web/20100409130123/http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch8s8-6-3-1.html |archive-date=2010-04-09 }}</ref> The main negative feedback comes from the [[Stefan–Boltzmann law]], the amount of heat radiated from the Earth into space is proportional to the fourth power of the temperature of Earth's surface and atmosphere.

Other examples of positive feedback subsystems in climatology include:
* A warmer atmosphere melts ice, changing the [[albedo]] (surface reflectivity), which further warms the atmosphere.
* Methane hydrates can be unstable so that a warming ocean could release more [[methane]], which is also a greenhouse gas. 
* [[Peat]], occurring naturally in [[peat bog]]s, contains carbon.  When peat dries it [[decomposes]], and may additionally burn. Peat also releases [[nitrous oxide]].
* Global warming affects the cloud distribution. Clouds at higher altitudes enhance the greenhouse effects, while low clouds mainly reflect back sunlight, having opposite effects on temperature.

The [[Intergovernmental Panel on Climate Change]] (IPCC) [[Fourth Assessment Report]] states that "Anthropogenic warming could lead to some effects that are abrupt or irreversible, depending upon the rate and magnitude of the climate change."<ref>{{cite journal |url=http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf |title=Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Pg 53 |author=IPCC |url-status=live |archive-url=https://web.archive.org/web/20100209153113/http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf |archive-date=2010-02-09 }}</ref>