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Shared Socioeconomic Pathways in the IPCC Sixth Assessment Report [1]: 14 
SSP Scenario
Estimated warming
(2041–2060)
Estimated warming
(2081–2100)
Very likely range in °C
(2081–2100)
SSP1-1.9 very low GHG emissions:
CO2 emissions cut to net zero around 2050
1.6 °C 1.4 °C 1.0 – 1.8
SSP1-2.6 low GHG emissions:
CO2 emissions cut to net zero around 2075
1.7 °C 1.8 °C 1.3 – 2.4
SSP2-4.5 intermediate GHG emissions:
CO2 emissions around current levels until 2050, then falling but not reaching net zero by 2100
2.0 °C 2.7 °C 2.1 – 3.5
SSP3-7.0 high GHG emissions:
CO2 emissions double by 2100
2.1 °C 3.6 °C 2.8 – 4.6
SSP5-8.5 very high GHG emissions:
CO2 emissions triple by 2075
2.4 °C 4.4 °C 3.3 – 5.7

The IPCC Sixth report did not estimate the likelihoods of the scenarios [1]: 12  but a 2020 commentary described SSP5–8.5 as highly unlikely, SSP3–7.0 as unlikely, and SSP2–4.5 as likely. [2]

However, a report citing the above commentary shows that RCP8.5 is the best match to the cumulative emissions from 2005 to 2020. [3]

  1. ^ a b 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, NY, USA, pp. 3−32, doi:10.1017/9781009157896.001.
  2. ^ Hausfather, Zeke; Peters, Glen P. (2020-01-29). "Emissions – the 'business as usual' story is misleading". Nature. 577 (618–620): 618–620. Bibcode: 2020Natur.577..618H. doi: 10.1038/d41586-020-00177-3. PMID  31996825. S2CID  256819346. Retrieved 2021-09-03.
  3. ^ Schwalm, Christopher R.; Glendon, Spencer; Duffy, Philip B. (2020-08-03). "RCP8.5 tracks cumulative CO2 emissions". PNAS. 117 (33): 19656–19657. Bibcode: 2020PNAS..11719656S. doi: 10.1073/pnas.2007117117. PMC  7443890. PMID  32747549.