Abrupt climate change

An abrupt climate change occurs when the climate system is forced to transition to a new climate state at a rate that is determined by the climate system energy-balance, and which is more rapid than the rate of change of the external forcing.[1] Past events include the end of the Carboniferous Rainforest Collapse,[2] Younger Dryas,[3] Dansgaard-Oeschger events, Heinrich events and possibly also the Paleocene-Eocene thermal maximum.[4] The term is also used within the context of global warming to describe sudden climate change that is detectable over the time-scale of a human lifetime. One proposed reason for the observed abrupt climate change is that feedback loops within the climate system both enhance small perturbations and cause a variety of stable states.[5]

Timescales of events described as 'abrupt' may vary dramatically. Changes recorded in the climate of Greenland at the end of the Younger Dryas, as measured by ice-cores, imply a sudden warming of +10°C within a timescale of a few years.[6] Other abrupt changes are the +4 °C on Greenland 11,270 years ago[7] or the abrupt +6 °C warming 22 000 years ago on Antarctica.[8] By contrast, the Paleocene-Eocene Thermal Maximum may have initiated anywhere between a few decades and several thousand years. Finally, Earth Systems models project that under ongoing greenhouse gas emissions as early as 2047, the Earth's near surface temperature could depart from the range of variability in the last 150 years, affecting over 3 billion people and most places of great species diversity on Earth.[9]

Definitions

According to the Committee on Abrupt Climate Change of the National Research Council:[1][10]

There are essentially two definitions of abrupt climate change:

  • In terms of physics, it is a transition of the climate system into a different mode on a time scale that is faster than the responsible forcing.
  • In terms of impacts, "an abrupt change is one that takes place so rapidly and unexpectedly that human or natural systems have difficulty adapting to it".
These definitions are complementary: the former gives some insight into how abrupt climate change comes about ; the latter explains why there is so much research devoted to it.

Current situation

The IPCC states that global warming "could lead to some effects that are abrupt or irreversible".[11]

In an article in Science, Richard Alley et al. said "it is conceivable that human forcing of climate change is increasing the probability of large, abrupt events. Were such an event to recur, the economic and ecological impacts could be large and potentially serious."[12]

A 2013 report from the U.S. National Research Council called for attention to the abrupt impacts of climate change, stating that even steady, gradual change in the physical climate system can have abrupt impacts elsewhere—in human infrastructure and ecosystems for example—if critical thresholds are crossed. The report emphasizes the need for an early warning system that could help society better anticipate sudden changes and emerging impacts.[13]

Regional changes

Lenton et al.[14] investigated tipping elements in the climate system. These were regional effects of global warming, some of which had abrupt onset and may therefore be regarded as abrupt climate change. They found that "Our synthesis of present knowledge suggests that a variety of tipping elements could reach their critical point within this century under anthropogenic climate change."

Ocean effects

A summary of the path of the thermohaline circulation. Blue paths represent deep-water currents, while red paths represent surface currents.

Global oceans have established patterns of currents. Several potential disruptions to this system of currents have been identified as a result of global warming:

Climate feedback effects

One source of abrupt climate change effects is a feedback process, in which a warming event causes a change which leads to further warming. This can also apply to cooling. Example of such feedback processes are:

Past events

The Younger Dryas period of abrupt climate change is named after the Alpine flower, Dryas.

Several periods of abrupt climate change have been identified in the paleoclimatic record. Notable examples include:

There are also abrupt climate changes associated with the catastrophic draining of glacial lakes. One example of this is the 8.2 kiloyear event, which associated with the draining of Glacial Lake Agassiz.[29] Another example is the Antarctic Cold Reversal, c. 14,500 years before present (BP), which is believed to have been caused by a meltwater pulse from the Antarctic ice sheet. These rapid meltwater release events have been hypothesized as a cause for Dansgaard-Oeschger cycles,[30]

Abrupt climate shifts since 1976

Had the 1997 El Niño lasted twice as long, the rain forests of the Amazon basin and Southeast Asia could have quickly added much additional carbon dioxide to the air from burning and rotting,[31] with heat waves and extreme weather quickly felt around the world (The "Burn Locally, Crash Globally" scenario.[32])

Most abrupt climate shifts, however, are likely due to sudden circulation shifts, analogous to a flood cutting a new river channel. The best-known examples are the several dozen shutdowns of the North Atlantic Ocean's Meridional Overturning Circulation during the last ice age, affecting climate worldwide.[12] But there have been a series of less dramatic abrupt climate shifts since 1976, along with some near misses.

This makes abrupt climate shifts more like a heart attack than like a chronic disease whose course can be extrapolated.[32] Like heart attacks, some abrupt climate shifts are minor, some are catastrophic—and one cannot predict which or when. The recent track record, however, is that there have been several sudden shifts and several near-misses in each decade since 1976.

Consequential effects

Extinction intensity.svg Cambrian Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Paleogene Neogene
Marine extinction intensity during the Phanerozoic
%
Millions of years ago
The Permian–Triassic extinction event, labelled "P-Tr" here, is the most significant extinction event in this plot for marine genera.

Abrupt climate change has likely been the cause of wide ranging and severe effects:

See also

References

  1. ↑ 1.0 1.1 Committee on Abrupt Climate Change, National Research Council. (2002). "Definition of Abrupt Climate Change". Abrupt climate change : inevitable surprises. Washington, D.C.: National Academy Press. ISBN 978-0-309-07434-6.
  2. ↑ 2.0 2.1 2.2 Sahney, S., Benton, M.J. & Falcon-Lang, H.J. (2010). "Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica" (PDF). Geology 38 (12): 1079–1082. doi:10.1130/G31182.1.
  3. ↑ Broecker, W. S. (May 2006). "Geology. Was the Younger Dryas triggered by a flood?". Science 312 (5777): 1146–1148. doi:10.1126/science.1123253. ISSN 0036-8075. PMID 16728622.
  4. ↑ Committee on Abrupt Climate Change, Ocean Studies Board, Polar Research Board, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, National Research Council. (2002). Abrupt climate change : inevitable surprises. Washington, D.C.: National Academy Press. p. 108. ISBN 0-309-07434-7.
  5. ↑ Rial, J. A.; Pielke Sr., R. A.; Beniston, M.; Claussen, M.; Canadell, J.; Cox, P.; Held, H.; De Noblet-Ducoudré, N.; Prinn, R.; Reynolds, J. F.; Salas, J. D. (2004). "Nonlinearities, Feedbacks and Critical Thresholds within the Earth's Climate System" (PDF). Climatic Change 65: 11–00. doi:10.1023/B:CLIM.0000037493.89489.3f.
  6. ↑ Grachev, A.M.; Severinghaus, J.P. (2005). "A revised +10±4 °C magnitude of the abrupt change in Greenland temperature at the Younger Dryas termination using published GISP2 gas isotope data and air thermal diffusion constants". Quaternary Science Reviews 24 (5–6): 513–9. Bibcode:2005QSRv...24..513G. doi:10.1016/j.quascirev.2004.10.016.
  7. ↑ Kobashi, T.; Severinghaus, J.P.; Barnola, J. (30 April 2008). "4 ± 1.5 °C abrupt warming 11,270 yr ago identified from trapped air in Greenland ice". Earth and Planetary Science Letters 268 (3–4): 397–407. Bibcode:2008E&PSL.268..397K. doi:10.1016/j.epsl.2008.01.032.
  8. ↑ Taylor, K.C.; White, J; Severinghaus, J; Brook, E; Mayewski, P; Alley, R; Steig, E; Spencer, M; Meyerson, E; Meese, D; Lamorey, G; Grachev, A; Gow, A; Barnett, B (January 2004). "Abrupt climate change around 22 ka on the Siple Coast of Antarctica". Quaternary Science Reviews 23 (1–2): 7–15. Bibcode:2004QSRv...23....7T. doi:10.1016/j.quascirev.2003.09.004.
  9. ↑ Mora, C (2013). "The projected timing of climate departure from recent variability". Nature 502: 183–187. doi:10.1038/nature12540.
  10. ↑ Harunur Rashid, Leonid Polyak, Ellen Mosley-Thompson (2011). "Abrupt climate change: mechanisms, patterns, and impacts". American Geophysical Union. ISBN 9780875904849. Retrieved 2013-09-17.
  11. ↑ "Summary for Policymakers". Climate Change 2007: Synthesis Report (PDF). IPCC. 17 November 2007.
  12. ↑ 12.0 12.1 12.2 Alley, R. B.; Marotzke, J.; Nordhaus, W. D.; Overpeck, J. T.; Peteet, D. M.; Pielke Jr, R. A.; Pierrehumbert, R. T.; Rhines, P. B.; Stocker, T. F.; Talley, L. D.; Wallace, J. M. (Mar 2003). "Abrupt Climate Change" (PDF). Science 299 (5615): 2005–2010. Bibcode:2003Sci...299.2005A. doi:10.1126/science.1081056. PMID 12663908.
  13. ↑ http://dels.nas.edu/Report/Report/18373
  14. ↑ Lenton, T. M.; Held, H.; Kriegler, E.; Hall, J. W.; Lucht, W.; Rahmstorf, S.; Schellnhuber, H. J. (2008). "Inaugural Article: Tipping elements in the Earth's climate system". Proceedings of the National Academy of Sciences 105 (6): 1786. doi:10.1073/pnas.0705414105.
  15. ↑ Trenberth, K. E.; Hoar, T. J. (1997). "El Niño and climate change" (PDF). Geophysical Research Letters 24 (23): 3057–3060. Bibcode:1997GeoRL..24.3057T. doi:10.1029/97GL03092.
  16. ↑ Meehl, G. A.; Washington, W. M. (1996). "El Niño-like climate change in a model with increased atmospheric CO2 concentrations". Nature 382 (6586): 56–60. Bibcode:1996Natur.382...56M. doi:10.1038/382056a0.
  17. ↑ Broecker, W. S. (1997). "Thermohaline Circulation, the Achilles Heel of Our Climate System: Will Man-Made CO2 Upset the Current Balance?" ([DEAD LINK]). Science 278 (5343): 1582–1588. Bibcode:1997Sci...278.1582B. doi:10.1126/science.278.5343.1582.
  18. ↑ 18.0 18.1 Manabe, S.; Stouffer, R. J. (1995). "Simulation of abrupt climate change induced by freshwater input to the North Atlantic Ocean" (PDF). Nature 378 (6553): 165. Bibcode:1995Natur.378..165M. doi:10.1038/378165a0.
  19. ↑ Beniston, M.; Jungo, P. (2002). "Shifts in the distributions of pressure, temperature and moisture and changes in the typical weather patterns in the Alpine region in response to the behavior of the North Atlantic Oscillation" (PDF). Theoretical and Applied Climatology 71 (1–2): 29–42. Bibcode:2002ThApC..71...29B. doi:10.1007/s704-002-8206-7.
  20. ↑ Comiso, J. C. (2002). "A rapidly declining perennial sea ice cover in the Arctic" (PDF). Geophysical Research Letters 29 (20): 17–11–11–4. Bibcode:2002GeoRL..29t..17C. doi:10.1029/2002GL015650.
  21. ↑ Malhi, Y.; Aragao, L. E. O. C.; Galbraith, D.; Huntingford, C.; Fisher, R.; Zelazowski, P.; Sitch, S.; McSweeney, C.; Meir, P. (Feb 2009). "Special Feature: Exploring the likelihood and mechanism of a climate-change-induced dieback of the Amazon rainforest" (PDF). PNAS 106 (49): 20610–20615. Bibcode:2009PNAS..10620610M. doi:10.1073/pnas.0804619106. ISSN 0027-8424. PMC 2791614. PMID 19218454.
  22. ↑ Alley, R. B.; Meese, D. A.; Shuman, C. A.; Gow, A. J.; Taylor, K. C.; Grootes, P. M.; White, J. W. C.; Ram, M.; Waddington, E. D.; Mayewski, P. A.; Zielinski, G. A. (1993). "Abrupt increase in Greenland snow accumulation at the end of the Younger Dryas event" (PDF). Nature 362 (6420): 527–529. Bibcode:1993Natur.362..527A. doi:10.1038/362527a0.
  23. ↑ Farley, K. A.; Eltgroth, S. F. (2003). "An alternative age model for the Paleocene–Eocene thermal maximum using extraterrestrial 3He". Earth and Planetary Science Letters 208 (3–4): 135–148. Bibcode:2003E&PSL.208..135F. doi:10.1016/S0012-821X(03)00017-7.
  24. ↑ Pagani, M.; Caldeira, K.; Archer, D.; Zachos, C. (Dec 2006). "Atmosphere. An ancient carbon mystery". Science 314 (5805): 1556–1557. doi:10.1126/science.1136110. ISSN 0036-8075. PMID 17158314.
  25. ↑ 25.0 25.1 Zachos, J. C.; Röhl, U.; Schellenberg, S. A.; Sluijs, A.; Hodell, D. A.; Kelly, D. C.; Thomas, E.; Nicolo, M.; Raffi, I.; Lourens, L. J.; McCarren, H.; Kroon, D. (Jun 2005). "Rapid acidification of the ocean during the Paleocene-Eocene thermal maximum". Science 308 (5728): 1611–1615. Bibcode:2005Sci...308.1611Z. doi:10.1126/science.1109004. PMID 15947184.
  26. ↑ Benton, M. J.; Twitchet, R. J. (2003). "How to kill (almost) all life: the end-Permian extinction event" (PDF). Trends in Ecology & Evolution 18 (7): 358–365. doi:10.1016/S0169-5347(03)00093-4.
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  30. ↑ Bond, G.C., Showers, W., Elliot, M., Evans, M., Lotti, R., Hajdas, I., Bonani, G., Johnson, S., (1999). "The North Atlantic's 1–2 kyr climate rhythm: relation to Heinrich events, Dansgaard/Oeschger cycles and the little ice age" (PDF). In Clark, P.U., Webb, R.S., Keigwin, L.D. Mechanisms of Global Change at Millennial Time Scales. Geophysical Monograph (112). American Geophysical Union, Washington DC. pp. 59–76. ISBN 0-87590-033-X.
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Further reading

External links