Sea level rise

The global average sea level has risen about 250 millimetres (9.8 in) since 1880.[1]

Between 1901 and 2018, average global sea level rose by 15–25 cm (6–10 in), an average of 1–2 mm (0.039–0.079 in) per year.[2] This rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022.[3] Climate change due to human activities is the main cause.[4]: 5, 8  Between 1993 and 2018, thermal expansion of water accounted for 42% of sea level rise. Melting temperate glaciers accounted for 21%, while polar glaciers in Greenland accounted for 15% and those in Antarctica for 8%.[5]: 1576  Sea level rise lags changes in the Earth's temperature, and sea level rise will therefore continue to accelerate between now and 2050 in response to warming that has already happened.[6] What happens after that depends on human greenhouse gas emissions. Sea level rise may slow down between 2050 and 2100 if there are deep cuts in emissions. It could then reach slightly over 30 cm (1 ft) from now by 2100. With high emissions it may accelerate. It could rise by 1 m (3+12 ft) or even 2 m (6+12 ft) by then.[4][7] In the long run, sea level rise would amount to 2–3 m (7–10 ft) over the next 2000 years if warming amounts to 1.5 °C (2.7 °F). It would be 19–22 metres (62–72 ft) if warming peaks at 5 °C (9.0 °F).[4]: 21 

Rising seas affect every coastal and island population on Earth.[8][9] This can be through flooding, higher storm surges, king tides, and tsunamis. There are many knock-on effects. They lead to loss of coastal ecosystems like mangroves. Crop production falls because of salinization of irrigation water. Damage to ports disrupts sea trade.[10][11][12] The sea level rise projected by 2050 will expose places currently inhabited by tens of millions of people to annual flooding. Without a sharp reduction in greenhouse gas emissions, this may increase to hundreds of millions in the latter decades of the century.[13] Areas not directly exposed to rising sea levels could be vulnerable to large-scale migration and economic disruption.

Local factors like tidal range or land subsidence will greatly affect the severity of impacts. The varying resilience and adaptive capacity of individual ecosystems, sectors, and countries are also factors.[14] For instance, sea level rise in the United States (particularly along the US East Coast) is already higher than the global average. It is likely to be 2 to 3 times greater than the global average by the end of the century.[15][16] Yet, of the 20 countries with the greatest exposure to sea level rise, 12 are in Asia. Eight of them collectively account for 70% of the global population exposed to sea level rise and land subsidence. These are Bangladesh, China, India, Indonesia, Japan, the Philippines, Thailand and Vietnam.[17] The greatest impact on human populations in the near term will occur in the low-lying Caribbean and Pacific islands. Sea level rise will make many of them uninhabitable later this century.[18]

Societies can adapt to sea level rise in three ways. Managed retreat, accommodating coastal change, or protecting against sea level rise through hard-construction practices like seawalls[19] are hard approaches. There are also soft approaches such as dune rehabilitation and beach nourishment. Sometimes these adaptation strategies go hand in hand. At other times choices must be made among different strategies.[20] A managed retreat strategy is difficult if an area's population is increasing rapidly. This is a particularly acute problem for Africa. There, the population of low-lying coastal areas is likely to increase by around 100 million people within the next 40 years.[21] Poorer nations may also struggle to implement the same approaches to adapt to sea level rise as richer states. Sea level rise at some locations may be compounded by other environmental issues. One example is subsidence in sinking cities.[22] Coastal ecosystems typically adapt to rising sea levels by moving inland. Natural or artificial barriers may make that impossible.[23]

  1. ^ "Climate Change Indicators: Sea Level / Figure 1. Absolute Sea Level Change". EPA.gov. U.S. Environmental Protection Agency (EPA). July 2022. Archived from the original on 4 September 2023. Data sources: CSIRO, 2017. NOAA, 2022.
  2. ^ IPCC, 2019: Summary for Policymakers. In: IPCC Special Report on the Ocean and Cryosphere in a Changing Climate [H.-O. Pörtner, D. C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, A. Alegría, M. Nicolai, A. Okem, J. Petzold, B. Rama, N. M. Weyer (eds.)]. Cambridge University Press, Cambridge, UK and New York, New York, US. https://doi.org/10.1017/9781009157964.001.
  3. ^ Cite error: The named reference WMO_20230421 was invoked but never defined (see the help page).
  4. ^ a b c IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, New York, US, pp. 3−32, doi:10.1017/9781009157896.001.
  5. ^ WCRP Global Sea Level Budget Group (2018). "Global sea-level budget 1993–present". Earth System Science Data. 10 (3): 1551–1590. Bibcode:2018ESSD...10.1551W. doi:10.5194/essd-10-1551-2018. This corresponds to a mean sea-level rise of about 7.5 cm over the whole altimetry period. More importantly, the GMSL curve shows a net acceleration, estimated to be at 0.08mm/yr2.
  6. ^ National Academies of Sciences, Engineering, and Medicine (2011). "Synopsis". Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia. Washington, DC: The National Academies Press. p. 5. doi:10.17226/12877. ISBN 978-0-309-15176-4. Box SYN-1: Sustained warming could lead to severe impacts
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  8. ^ McMichael, Celia; Dasgupta, Shouro; Ayeb-Karlsson, Sonja; Kelman, Ilan (2020-11-27). "A review of estimating population exposure to sea-level rise and the relevance for migration". Environmental Research Letters. 15 (12): 123005. Bibcode:2020ERL....15l3005M. doi:10.1088/1748-9326/abb398. ISSN 1748-9326. PMC 8208600. PMID 34149864.
  9. ^ Bindoff, N. L.; Willebrand, J.; Artale, V.; Cazenave, A.; Gregory, J.; Gulev, S.; Hanawa, K.; Le Quéré, C.; Levitus, S.; Nojiri, Y.; Shum, C. K.; Talley, L. D.; Unnikrishnan, A. (2007). "Observations: Ocean Climate Change and Sea Level: §5.5.1: Introductory Remarks". In Solomon, S.; Qin, D.; Manning, M.; Chen, Z.; Marquis, M.; Averyt, K. B.; Tignor, M.; Miller, H. L. (eds.). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. ISBN 978-0-521-88009-1. Archived from the original on 20 June 2017. Retrieved 25 January 2017.
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  11. ^ "Sea level to increase risk of deadly tsunamis". United Press International. 2018.
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  13. ^ Cite error: The named reference Kulp2019 was invoked but never defined (see the help page).
  14. ^ Mimura, Nobuo (2013). "Sea-level rise caused by climate change and its implications for society". Proceedings of the Japan Academy. Series B, Physical and Biological Sciences. 89 (7): 281–301. Bibcode:2013PJAB...89..281M. doi:10.2183/pjab.89.281. ISSN 0386-2208. PMC 3758961. PMID 23883609.
  15. ^ Choi, Charles Q. (27 June 2012). "Sea Levels Rising Fast on U.S. East Coast". National Oceanic and Atmospheric Administration. Archived from the original on May 4, 2021. Retrieved October 22, 2022.
  16. ^ "2022 Sea Level Rise Technical Report". oceanservice.noaa.gov. Retrieved 2022-07-04.
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  18. ^ Mycoo, M., M. Wairiu, D. Campbell, V. Duvat, Y. Golbuu, S. Maharaj, J. Nalau, P. Nunn, J. Pinnegar, and O. Warrick, 2022: Chapter 15: Small islands. In Climate Change 2022: Impacts, Adaptation and Vulnerability [H.-O. Pörtner, D. C. Roberts, M. Tignor, E. S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, New York, US, pp. 2043–2121 |doi=10.1017/9781009325844.017.
  19. ^ "IPCC's New Estimates for Increased Sea-Level Rise". Yale University Press. 2013.
  20. ^ Thomsen, Dana C.; Smith, Timothy F.; Keys, Noni (2012). "Adaptation or Manipulation? Unpacking Climate Change Response Strategies". Ecology and Society. 17 (3). doi:10.5751/es-04953-170320. JSTOR 26269087.
  21. ^ Trisos, C. H., I. O. Adelekan, E. Totin, A. Ayanlade, J. Efitre, A. Gemeda, K. Kalaba, C. Lennard, C. Masao, Y. Mgaya, G. Ngaruiya, D. Olago, N. P. Simpson, and S. Zakieldeen 2022: Chapter 9: Africa. In Climate Change 2022: Impacts, Adaptation and Vulnerability [H.-O. Pörtner, D.C. Roberts, M. Tignor, E. S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, New York, US, pp. 2043–2121 |doi=10.1017/9781009325844.011.
  22. ^ Nicholls, Robert J.; Marinova, Natasha; Lowe, Jason A.; Brown, Sally; Vellinga, Pier; Gusmão, Diogo de; Hinkel, Jochen; Tol, Richard S. J. (2011). "Sea-level rise and its possible impacts given a 'beyond 4°C (39.2°F)world' in the twenty-first century". Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences. 369 (1934): 161–181. Bibcode:2011RSPTA.369..161N. doi:10.1098/rsta.2010.0291. ISSN 1364-503X. PMID 21115518. S2CID 8238425.
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