Earth:Climate inertia

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Short description: Slow response of complex feedback systems
Societal elements of inertia work to prevent abrupt shifts within pathways of greenhouse gas emissions, while physical inertia of the Earth system acts to delay the surface temperature response.

Climate inertia or climate change inertia is the phenomenon by which a planet's climate system shows a resistance or slowness to deviate away from a given dynamic state. It can accompany stability and other effects of feedback within complex systems, and includes the inertia exhibited by physical movements of matter and exchanges of energy. The term is a colloquialism used to encompass and loosely describe a set of interactions that extend the timescales around climate sensitivity. Inertia has been associated with the drivers of, and the responses to, climate change.


Earth's inertial responses are important because they provide the planet's diversity of life and its human civilization further time to adapt to an acceptable degree of planetary change. However, unadaptable change like that accompanying some tipping points may only be avoidable with early understanding and mitigation of the risk of such dangerous outcomes.[1][2] This is because inertia also delays much surface warming unless and until action is taken to rapidly reduce emissions.[3][4] An aim of Integrated assessment modelling, summarized for example as Shared Socioeconomic Pathways (SSP), is to explore Earth system risks that accompany large inertia and uncertainty in the trajectory of human drivers of change.[5]

Inertial timescales

Response times to climate forcing[6]
Earth System
Component		 Time
Constant
(years)		 Response
Modes
Atmosphere
Water Vapor
and Clouds		 10−2-10 HT, WC
Trace Gases 10−1-108 CC
Hydrosphere
Ocean Mixed
Layer		 10−1-10 HT, WC,
CC
Deep Ocean 10-103 HT, CC
Lithosphere
Land Surface
and Soils		 10−1-102 HT, WC,
CC
Subterranean
Sediments		 104-109 CC
Cryosphere
Glaciers 10−1-10 HT, WC
Sea Ice 10−1-10 HT, WC
Ice Sheets 103-106 HT, WC
Biosphere
Upper Marine 10−1-102 CC
Terrestrial 10−1-102 WC, CC
HT=Heat Transfer
WC=Water Cycle  CC=Carbon Cycle

The paleoclimate record shows that Earth's climate system has evolved along various pathways and with multiple timescales. Its relatively stable states which can persist for many millennia have been interrupted by short to long transitional periods of relative instability.[7]:19–72 Studies of climate sensitivity and inertia are concerned with quantifying the most basic manner in which a sustained forcing perturbation will cause the system to deviate within or initially away from its relatively stable state of the present Holocene epoch.[8][9]

"Time constants" are useful metrics for summarizing the first-order (linear) impacts of the various inertial phenomena within both simple and complex systems. They quantify the time after which 63% of a full output response occurs following the step change of an input. They are observed from data or can be estimated from numerical simulation or a lumped system analysis. In climate science these methods can be applied to a planet's energy balance, carbon cycle, water cycle and elsewhere.[6] For example, heat transport and storage in the ocean, cryosphere, land and atmosphere are elements within a lumped thermal analysis.[10][11]:627 Response times to radiative forcing via the atmosphere typically increase with depth below the surface.

Inertial time constants indicate a base rate for forced changes, but lengthy values provide no accompanying guarantee of long-term system evolution along a smooth pathway. Numerous higher-order tipping elements having various trigger thresholds and transition timescales have been identified within Earth's present state.[12][13] Such events might precipitate a rearrangement of internal energy flows along with abrupt shifts in climate and/or other systems at regional to global scale.[7]:10–15, 73–76

Climate response time

The response of global surface temperature (GST) to a step-like doubling of the atmospheric CO
2 concentration, and its resultant forcing, is defined as the Equilibrium Climate Sensitivity (ECS). The time constant associated with ECS provides a relevant measure of its response time for policy-making decisions. ECS is one of several idealized test cases which are commonly used by researchers to simulate the physics of forced climate changes. By definition, ECS presumes that ongoing emissions will offset the ocean and land carbon sinks following the step-wise perturbation in atmospheric CO
2.[4][14]

ECS response time is proportional to ECS and is principally regulated by the thermal inertia of the uppermost mixed layer and adjacent lower ocean layers.[10] Time constants fitted to the results from climate models have ranged from a few decades when ECS is low, to as long as a century when ECS is high. A portion of the variation between estimates arises from different treatments of heat transport into the deep ocean.[15][4]

Components

Thermal inertia

The observed accumulation of energy in the oceanic, land, ice, and atmospheric components of Earth's climate system since 1960.[16] The rate of rise has been partially slowed by the system's thermal inertia.

Thermal inertia is a term which refers to the observed delays in a body's temperature response during heat transfers. A body with large thermal inertia can store a big amount of energy because of its volumetric heat capacity, and can effectively transmit energy according to its heat transfer coefficient. The consequences of thermal inertia are inherently expressed via many climate change feedbacks because of their temperature dependencies; including through the strong stabilizing feedback of the Planck response.

Ocean inertia

The global ocean is Earth's largest thermal reservoir that functions to regulate the planet's climate; acting as both a sink and a source of energy.[17] The ocean's thermal inertia delays some global warming for decades or centuries. It is accounted for in global climate models, and has been confirmed via measurements of ocean heat content.[1][18] The observed transient climate sensitivity is proportional to the thermal inertia time scale of the shallower ocean.[19]

Ice sheet inertia

Even after CO
2 emissions are lowered, the melting of ice sheets will persist and further increase sea-level rise for centuries. The slower transportation of heat into the extreme deep ocean, subsurface land sediments, and thick ice sheets will continue until the new Earth system equilibrium has been reached.[20]

Permafrost also takes longer to respond to a warming planet because of thermal inertia, due to ice rich materials and permafrost thickness.[21]

Inertia from carbon cycle feedbacks

The impulse response following a 100 GtC injection of CO
2 into Earth's atmosphere.[22] The relative inertial effect of positive vs. negative feedback during early years is indicated by the pulse fraction which ultimately remains.

Earth's carbon cycle feedback includes a destabilizing positive feedback (identified as the climate-carbon feedback) which prolongs warming for centuries, and a stabilizing negative feedback (identified as the concentration-carbon feedback) which limits the ultimate warming response to fossil carbon emissions. The near-term effect following emissions is asymmetric with latter mechanism being about four times larger,[23][24] and results in a significant net slowing contribution to the inertia of the climate system during the first few decades following emissions.[3]

Ecological inertia

Depending on the ecosystem, effects of climate change could show quickly, while others take more time to respond. For instance, coral bleaching can occur in a single warm season, while trees may be able to persist for decades under a changing climate, but be unable to regenerate. Changes in the frequency of extreme weather events could disrupt ecosystems as a consequence, depending on individual response times of species.[20]

Policy implications of inertia

The IPCC concluded that the inertia and uncertainty of the climate system, ecosystems, and socioeconomic systems implies that margins for safety should be considered. Thus, setting strategies, targets, and time tables for avoiding dangerous interference through climate change. Further the IPCC concluded in their 2001 report that the stabilization of atmospheric CO
2 concentration, temperature, or sea level is affected by:[20]

  • The inertia of the climate system, which will cause climate change to continue for a period after mitigation actions are implemented.[2][25]
  • Uncertainty regarding the location of possible thresholds of irreversible change and the behavior of the system in their vicinity.
  • The time lags between adoption of mitigation goals and their achievement.

See also

References

  1. ↑ 1.0 1.1 Hansen, James; Kharecha, Pushker; Sato, Makiko; Masson-Delmotte, Valerie et al. (3 December 2013). "Assessing "Dangerous Climate Change": Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature". PLOS ONE 8 (12): e81648. doi:10.1371/journal.pone.0081648. PMID 24312568. Bibcode: 2013PLoSO...881648H. 
  2. ↑ 2.0 2.1 Tebaldi, Claudia; Friedlingstein, Pierre (13 October 2017). "Delayed detection of climate mitigation benefits due to climate inertia and variability". Proceedings of the National Academy of Sciences 110 (43): 17229–17234. doi:10.1073/pnas.1300005110. PMID 24101485. 
  3. ↑ 3.0 3.1 Mathews, H. Damon; Solomon, Susan (26 April 2013). "Irreversible Does Not Mean Unavoidable". Science (American Association for the Advancement of Science) 340 (6131): 438–439. doi:10.1126/science.1236372. PMID 23539182. Bibcode: 2013Sci...340..438M. https://www.science.org/cms/asset/7446d1ba-b4b9-4c2d-945b-ea04ca0547d6/pap.pdf. 
  4. ↑ 4.0 4.1 4.2 Hansen, James E.; Sato, Makiko; Simons, Leon; Nazarenko, Larissa S.; Sangha, Isabelle; von Schuckmann, Karina; Loeb, Norman G.; Osman, Matthew B.; Jin, Qinjian; Karecha, Pushker; et al. (8 December 2022). "Global Warming in the Pipeline". arXiv:2212.04474 [physics.ao-ph].
  5. ↑ Weyant, John (2017). "Some Contributions of Integrated Assessment Models of Global Climate Change". Review of Environmental Economics and Policy 11 (1): 115–137. doi:10.1093/reep/rew018. ISSN 1750-6816. 
  6. ↑ 6.0 6.1 Joussaume, Sylvie (1999). Climat d'heir á demain. Paris: CNRS Editions - CEA. ISBN 978-2271057327. 
  7. ↑ 7.0 7.1 National Research Council (2002). Abrupt Climate Change: Inevitable Surprises. The National Academic Press. doi:10.17226/10136. ISBN 978-0-309-13304-3. 
  8. ↑ Marcott, Shaun A.; Shakun, Jeremy D.; Clark, Peter U.; Mix, Alan C. (8 March 2013). "A Reconstruction of Regional and Global Temperature for the Past 11,300 Years". Science 339 (6124): 1198–1201. doi:10.1126/science.1228026. PMID 23471405. Bibcode: 2013Sci...339.1198M. https://www.science.org/doi/10.1126/science.1228026. 
  9. ↑ Steffen, Will; Rockström, Johan; Richardson, Katherine; Lenton, Timothy M.; Folke, Carle; Liverman, Diana; Summerhayes, Collin P.; Barnosky, Anthony D. et al. (6 August 2018). "Trajectories of the Earth System in the Anthropocene". PNAS 116 (33): 8252–8259. doi:10.1073/pnas.1810141115. PMID 30082409. Bibcode: 2018PNAS..115.8252S. 
  10. ↑ 10.0 10.1 Hansen, J.; Russell, G.; Lacis, A.; Fung, I.; Rind, D.; Stone, P. (1985). "Climate response times: Dependence on climate sensitivity and ocean mixing". Science 229 (4716): 857–850. doi:10.1126/science.229.4716.857. PMID 17777925. Bibcode: 1985Sci...229..857H. https://pubs.giss.nasa.gov/docs/1985/1985_Hansen_ha09600g.pdf. 
  11. ↑ Gerald R. North (1988). "Lessons from energy balance models". in Michael E. Schlesinger. Physically-based Modelling and Simulation of Climate and Climatic Change (NATO Advanced Study Institute on Physical-Based Modelling ed.). Springer. ISBN 978-90-277-2789-3. 
  12. ↑ Lenton, Timothy M.; Held, Hermann; Kriegler, Elmar; Hall, Jim W; Lucht, Wolfgang; Rahmstorf, Stefan; Schellnhuber, Hans Joachim (2008-02-12). "Tipping elements in the Earth's climate system". PNAS 105 (6): 1786–1793. doi:10.1073/pnas.0705414105. PMID 18258748. Bibcode: 2008PNAS..105.1786L. 
  13. ↑ Armstrong McKay, David; Abrams, Jesse; Winkelmann, Ricarda; Sakschewski, Boris; Loriani, Sina; Fetzer, Ingo; Cornell, Sarah; Rockström, Johan et al. (9 September 2022). "Exceeding 1.5°C global warming could trigger multiple climate tipping points" (in en). Science 377 (6611): eabn7950. doi:10.1126/science.abn7950. ISSN 0036-8075. PMID 36074831. https://www.science.org/doi/10.1126/science.abn7950. 
  14. ↑ Sherwood, S.C.; Webb, M.J.; Annan, J.D.; Armour, K.C.; Forster, P.M.; Hargreaves, J.C.; Hegerl, G.; Klein, S.A. et al. (22 July 2020). "An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence". Reviews of Geophysics 58 (4): e2019RG000678. doi:10.1029/2019RG000678. PMID 33015673. Bibcode: 2020RvGeo..5800678S. 
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Gregory2000
  16. ↑ von Schuckman, K.; Cheng, L.; Palmer, M. D.; Hansen, J.; Tassone, C. et al. (7 September 2020). "Heat stored in the Earth system: where does the energy go?". Earth System Science Data 12 (3): 2013-2041 50px Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License. doi:10.5194/essd-12-2013-2020. Bibcode: 2020ESSD...12.2013V. https://essd.copernicus.org/articles/12/2013/2020/. 
  17. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Scott2006
  18. ↑ Cheng, Lijing; Foster, Grant; Hausfather, Zeke; Trenberth, Kevin E.; Abraham, John (2022). "Improved Quantification of the Rate of Ocean Warming". Journal of Climate 35 (14): 4827–4840. doi:10.1175/JCLI-D-21-0895.1. Bibcode: 2022JCli...35.4827C. 
  19. ↑ Royce, B. S. H.; Lam, S. H. (25 July 2013). "The Earth's Equilibrium Climate Sensitivity and Thermal Inertia". arXiv:1307.6821 [physics.ao-ph].
  20. ↑ 20.0 20.1 20.2 "Climate Change 2001: Synthesis Report". IPCC. 2001. http://www.ipcc.ch/ipccreports/tar/vol4/011.htm. 
  21. ↑ M. W., Smith (1988). "The significance of climatic change for the permafrost environment". p. 19. 
  22. ↑ Joos, F. et al. (8 March 2013). "Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: A multi-model analysis". Atmospheric Chemistry and Physics 13 (5): 2793–2825 50px Material was copied from this source, which is available under a Creative Commons Attribution 3.0 Unported License. doi:10.5194/acpd-12-19799-2012. https://www.atmos-chem-phys.net/13/2793/2013/. 
  23. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Gregory2009
  24. ↑ Archer, David (2009). "Atmospheric lifetime of fossil fuel carbon dioxide". Annual Review of Earth and Planetary Sciences 37 (1): 117–34. doi:10.1146/annurev.earth.031208.100206. Bibcode: 2009AREPS..37..117A. https://orbi.uliege.be/handle/2268/12933. 
  25. ↑ Samset, B.H.; Fuglestvedt, J.S.; Lund, M.T. (7 July 2020). "Delayed emergence of a global temperature response after emission mitigation". Nature Communications 11 (3261): 3261. doi:10.1038/s41467-020-17001-1. PMID 32636367. Bibcode: 2020NatCo..11.3261S. 



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