Editing Permafrost (section)

==== Impact on global temperatures ====
[[File:Schuur 2022 century-scale permafrost projections.jpeg|thumb|Nine probable scenarios of [[greenhouse gas emission]]s from permafrost thaw during the 21st century, which show a limited, moderate and intense {{CO2}} and {{CH4}} emission response to low, medium and high-emission [[Representative Concentration Pathway]]s. The vertical bar uses emissions of selected large countries as a comparison: the right-hand side of the scale shows their cumulative emissions since the start of the [[Industrial Revolution]], while the left-hand side shows each country's cumulative emissions for the rest of the 21st century if they remained unchanged from their 2019 levels.<ref name="Schuur2022" />]]

Altogether, it is expected that cumulative greenhouse gas emissions from permafrost thaw will be smaller than the cumulative anthropogenic emissions, yet still substantial on a global scale, with some experts comparing them to emissions caused by [[deforestation]].<ref name="Schuur2022" /> The [[IPCC Sixth Assessment Report]] estimates that carbon dioxide and methane released from permafrost could amount to the equivalent of 14–175&nbsp;billion tonnes of carbon dioxide per {{convert|1|C-change|F-change}} of warming.<ref name="AR6_WG1_Chapter922" />{{rp|1237}}  For comparison, by 2019, annual anthropogenic emissions of carbon dioxide alone stood around 40&nbsp;billion tonnes.<ref name="AR6_WG1_Chapter922" />{{rp|1237}} A major review published in the year 2022 concluded that if the goal of preventing {{convert|2|C-change|F-change}} of warming was realized, then the average annual permafrost emissions throughout the 21st century would be equivalent to the year 2019 annual emissions of Russia. Under RCP4.5, a scenario considered close to the current trajectory and where the warming stays slightly below {{convert|3|C-change|F-change}}, annual permafrost emissions would be comparable to year 2019 emissions of Western Europe or the United States, while under the scenario of high global warming and worst-case permafrost feedback response, they would approach year 2019 emissions of China.<ref name="Schuur2022" />

Fewer studies have attempted to describe the impact directly in terms of warming. A 2018 paper estimated that if global warming was limited to {{convert|2|C-change|F-change}}, gradual permafrost thaw would add around {{convert|0.09|C-change|F-change}} to global temperatures by 2100,<ref>{{Cite journal |last1=Schellnhuber |first1=Hans Joachim |last2=Winkelmann |first2=Ricarda |last3=Scheffer |first3=Marten |last4=Lade |first4=Steven J. |last5=Fetzer |first5=Ingo |last6=Donges |first6=Jonathan F. |last7=Crucifix |first7=Michel |last8=Cornell |first8=Sarah E. |last9=Barnosky |first9=Anthony D. |author-link9=Anthony David Barnosky |date=2018 |title=Trajectories of the Earth System in the Anthropocene |journal=[[Proceedings of the National Academy of Sciences]] |volume=115 |issue=33 |pages=8252–8259 |bibcode=2018PNAS..115.8252S |doi=10.1073/pnas.1810141115 |issn=0027-8424 |pmc=6099852 |pmid=30082409 |doi-access=free}}</ref> while a 2022 review concluded that every {{convert|1|C-change|F-change}} of global warming would cause {{convert|0.04|C-change|F-change}} and {{convert|0.11|C-change|F-change}} from abrupt thaw by the year 2100 and 2300. Around {{convert|4|C-change|F-change}} of global warming, abrupt (around 50 years) and widespread collapse of permafrost areas could occur, resulting in an additional warming of {{convert|0.2-0.4|C-change|F-change}}.<ref name="ArmstrongMcKay2022" /><ref>{{Cite web |last=Armstrong McKay |first=David |date=9 September 2022 |title=Exceeding 1.5°C global warming could trigger multiple climate tipping points – paper explainer |url=https://climatetippingpoints.info/2022/09/09/climate-tipping-points-reassessment-explainer/ |access-date=2 October 2022 |website=climatetippingpoints.info |language=en}}</ref>