气候临界点

气候临界点（英語：climate tipping point）是一个关键阈值，越过该阈值会导致系统状态发生巨大且通常不可逆的变化。气候科学家使用术语“临界点”来表明气候系统的脆弱性。系统一旦“倾覆”，很可能对人类社会产生严重影响。 政府間氣候變化專門委員會（IPCC）早在2000年代就开始考虑临界点的可能性。当时IPCC得出结论，只有在全球相对前工业时代变暖大于或等于4 °C时才会触发临界点。但现在认为，在今天的升温水平（略高于1 °C）下，就有显著概率已经达到了临界点，而升温 2°C的情景下大概率越过了临界点。 地球系统中可能触发临界点的大尺度要素称为临界要素（tipping element）。气候系统中至少15个不同要素，例如格陵蘭冰原和南極冰蓋，被认为是可能的临界要素。一个危险是，如果某个系统的临界点被越过，可能会导致一连串的其他临界点被相继越过。如果发生这种连锁反应，全球平均温度可能将会上升至高于过去120万年任何时期，地球将变成“温室地球”。 临界点未必是突变的。例如，平均温升在1.5-2 °C之间时，格陵蘭冰原将在数千年内不可逆转地融化。然而，美國地球物理聯盟2021年的一项研究表明，南极洲的思韦茨冰架有可能在2025年之前破碎。 温室和冰室地球（英语：Greenhouse and icehouse Earth） 气候敏感性（英语：Climate sensitivity） 地球限度理論 地理工程学 Otto, I.M. Social tipping elements for stabilizing climate by 2050. PNAS. February 4, 2020, 117 (5): 2354–2365. PMC 7007533 . PMID 31964839. doi:10.1073/pnas.1900577117.  IPCC steps up warning on climate tipping points in leaked draft report. The Guardian. 2021-06-23 [2021-07-22]. （原始内容存档于22 July 2021） （英语）.  Lenton, TimothyM.; Rockström, Johan; Gaffney, Owen; Rahmstorf, Stefan; Richardson, Katherine; Steffen, Will; Schellnhuber, Hans Joachim. Climate tipping points — too risky to bet against. Nature. 2019-11-27, 575 (7784): 592–595. Bibcode:2019Natur.575..592L. PMID 31776487. doi:10.1038/d41586-019-03595-0 （英语）.  Climate tipping points could topple like dominoes, warn scientists （页面存档备份，存于互联网档案馆）, The Guardian, 3 June 2021 Climate change driving entire planet to dangerous 'tipping point‘ （页面存档备份，存于互联网档案馆）, National Geographic, 28 November 2019 Lenton, Timothy M. Tipping points in the climate system. Weather. 2021, 76 (10): 325–326. ISSN 0043-1656. doi:10.1002/wea.4058 （英语）.  Lenton, T.M.; Held, H.; Kriegler, E.; Hall, J.W.; Lucht, W.; Rahmstorf, S.; Schellnhuber, H.J. Tipping elements in the Earth's climate system. Proceedings of the National Academy of Sciences. 2008, 105 (6): 1786–1793. Bibcode:2008PNAS..105.1786L. PMC 2538841 . PMID 18258748. doi:10.1073/pnas.0705414105.  Climate scientists fear tipping points (maybe you should too) 互联网档案馆的存檔，存档日期14 November 2021., PhysOrg, 25 October 2021. Explainer: Nine ‘tipping points’ that could be triggered by climate change 互联网档案馆的存檔，存档日期11 February 2020., Carbon Brief, 10 February 2020 Wunderling, Nico; Donges, Jonathan F.; Kurths, Jürgen; Winkelmann, Ricarda. Interacting tipping elements increase risk of climate domino effects under global warming. Earth System Dynamics. 2021-06-03, 12 (2): 601–619 [4 June 2021]. Bibcode:2021ESD....12..601W. ISSN 2190-4979. doi:10.5194/esd-12-601-2021. （原始内容存档于4 June 2021） （英语）.  Sheridan, Kerry. Earth risks tipping into 'hothouse' state: study. Phys.org. 2018-08-06 [2018-08-08]. （原始内容存档于3 October 2019）. Hothouse Earth is likely to be uncontrollable and dangerous to many ... global average temperatures would exceed those of any interglacial period—meaning warmer eras that come in between Ice Ages—of the past 1.2 million years.  Frank Pattyn; Catherine Ritz; Edward Hanna; Xylar Asay-Davis; Rob DeConto; Gaël Durand; Lionel Favier; Xavier Fettweis; Heiko Goelzer. The Greenland and Antarctic ice sheets under 1.5 °C global warming. Nature Climate Change (Journal Nature). 2018, 8 (12): 1053–1061 [2022-05-09]. Bibcode:2018NatCC...8.1053P. doi:10.1038/s41558-018-0305-8. （原始内容存档于2022-06-15）.  Tipping points in Antarctic and Greenland ice sheets. NESSC. 12 November 2018 [2019-02-25]. （原始内容存档于26 February 2019）.  Douglas, Benn I.; Luck, Adrian; Åström, Jan A.; Crawford, Anna; Cornford, Stephen L.; Bevan, Suzanne L.; Gladstone, Rupert; Zwinger, Thomas; Alley, Karen. Rapid fragmentation of Thwaites Eastern Ice Shelf, West Antarctica. The Cryosphere Discussions. 20 September 2021: 1–25 [2022-01-25]. doi:10.5194/tc-2021-288. （原始内容存档于2022-02-01） （英国英语）.  Pettit, Erin C.; Wild, Christian; Alley, Karen; Muto, Atsuhiro; Truffer, Martin; Bevan, Suzanne Louise; Bassis, Jeremy N.; Crawford, Anna; Scambos, Ted A.; Benn, Doug. Collapse of Thwaites Eastern Ice Shelf by intersecting fractures.. AGU Fall Meeting. New Orleans: American Geophysical Union. 2021-12-15 [2022-05-09]. C34A-07. （原始内容存档于2022-04-20）.