Clathrate gun hypothesis

Methane clathrate is released as gas into the surrounding water column or soils when ambient temperature increases

The clathrate gun hypothesis is a proposed explanation for the periods of rapid warming during the Quaternary. The hypothesis is that changes in fluxes in upper intermediate waters in the ocean caused temperature fluctuations that alternately accumulated and occasionally released methane clathrate on upper continental slopes. This would have had an immediate impact on the global temperature, as methane is a much more powerful greenhouse gas than carbon dioxide. Despite its atmospheric lifetime of around 12 years, methane's global warming potential is 72 times greater than that of carbon dioxide over 20 years, and 25 times over 100 years (33 when accounting for aerosol interactions).[1] It is further proposed that these warming events caused the Bond Cycles and individual interstadial events, such as the Dansgaard–Oeschger interstadials.[2]

The hypothesis was supported for the Bølling–Allerød warming and Preboreal periods, but not for Dansgaard–Oeschger interstadials,[3] although there are still debates on the topic.[4] While it may be important on the millennial timescales,[5][6] it is no longer considered relevant for the near future climate change: the IPCC Sixth Assessment Report states "It is very unlikely that gas clathrates (mostly methane) in deeper terrestrial permafrost and subsea clathrates will lead to a detectable departure from the emissions trajectory during this century".[7]

  1. ^ Shindell, Drew T.; Faluvegi, Greg; Koch, Dorothy M.; Schmidt, Gavin A.; Unger, Nadine; Bauer, Susanne E. (2009). "Improved attribution of climate forcing to emissions". Science. 326 (5953): 716–718. Bibcode:2009Sci...326..716S. doi:10.1126/science.1174760. PMID 19900930. S2CID 30881469.
  2. ^ Kennett, James P.; Cannariato, Kevin G.; Hendy, Ingrid L.; Behl, Richard J. (2003). Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis. Washington DC: American Geophysical Union. doi:10.1029/054SP. ISBN 978-0-87590-296-8.
  3. ^ Maslin, M; Owen, M; Day, S; Long, D (2004). "Linking continental-slope failures and climate change: Testing the clathrate gun hypothesis". Geology. 32 (1): 53–56. Bibcode:2004Geo....32...53M. doi:10.1130/G20114.1. ISSN 0091-7613.
  4. ^ Maslin, M; Owen, M; Betts, R; Day, S; Dunkley Jones, T; Ridgwell, A (2010-05-28). "Gas hydrates: past and future geohazard?". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 368 (1919): 2369–2393. Bibcode:2010RSPTA.368.2369M. doi:10.1098/rsta.2010.0065. ISSN 1364-503X. PMID 20403833. S2CID 24574034.
  5. ^ Archer, David; Buffett, Bruce (2005). "Time-dependent response of the global ocean clathrate reservoir to climatic and anthropogenic forcing" (PDF). Geochemistry, Geophysics, Geosystems. 6 (3): 1–13. Bibcode:2005GGG.....6.3002A. doi:10.1029/2004GC000854. Archived (PDF) from the original on 2009-07-09. Retrieved 2009-05-15.
  6. ^ Cite error: The named reference Schellnhuber2018 was invoked but never defined (see the help page).
  7. ^ Fox-Kemper, B.; Hewitt, H.T.; Xiao, C.; Aðalgeirsdóttir, G.; Drijfhout, S.S.; Edwards, T.L.; Golledge, N.R.; Hemer, M.; Kopp, R.E.; Krinner, G.; Mix, A. (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S.L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L. (eds.). "Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks" (PDF). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, USA: 5. doi:10.1017/9781009157896.011.