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Journal Articles Earth System Dynamics Year : 2021

Climate model projections from the Scenario Model Intercomparison Project (ScenarioMIP) of CMIP6

Claudia Tebaldi
Kevin Debeire
Veronika Eyring
Erich Fischer
John Fyfe
  • Function : Author
Reto Knutti
Jason Lowe
  • Function : Author
Brian O'Neill
  • Function : Author
Benjamin Sanderson
Detlef van Vuuren
Keywan Riahi
Malte Meinshausen
Zebedee Nicholls
Katarzyna B Tokarska
George Hurtt
Elmar Kriegler
  • Function : Author
Jean-Francois Lamarque
Gerald Meehl
Richard Moss
  • Function : Author
Susanne E Bauer
Olivier Boucher
Victor Brovkin
Young-Hwa Byun
Martin Dix
Silvio Gualdi
Huan Guo
Jasmin G John
Slava Kharin
Youngho Kim
  • Function : Author
Tsuyoshi Koshiro
Libin Ma
  • Function : Author
Dirk Olivié
Swapna Panickal
Fangli Qiao
  • Function : Author
Xinyao Rong
  • Function : Author
Nan Rosenbloom
Martin Schupfner
  • Function : Author
Alistair Sellar
Tido Semmler
Xiaoying Shi
Zhenya Song
Christian Steger
Ronald Stouffer
  • Function : Author
Neil Swart
Kaoru Tachiiri
  • Function : Author
Qi Tang
Hiroaki Tatebe
Evgeny Volodin
  • Function : Author
Klaus Wyser
Xiaoge Xin
  • Function : Author
Shuting Yang
Yongqiang Yu
Tilo Ziehn

Abstract

Abstract. The Scenario Model Intercomparison Project (ScenarioMIP) defines and coordinates the main set of future climate projections, based on concentration-driven simulations, within the Coupled Model Intercomparison Project phase 6 (CMIP6). This paper presents a range of its outcomes by synthesizing results from the participating global coupled Earth system models. We limit our scope to the analysis of strictly geophysical outcomes: mainly global averages and spatial patterns of change for surface air temperature and precipitation. We also compare CMIP6 projections to CMIP5 results, especially for those scenarios that were designed to provide continuity across the CMIP phases, at the same time highlighting important differences in forcing composition, as well as in results. The range of future temperature and precipitation changes by the end of the century (2081–2100) encompassing the Tier 1 experiments based on the Shared Socioeconomic Pathway (SSP) scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) and SSP1-1.9 spans a larger range of outcomes compared to CMIP5, due to higher warming (by close to 1.5 ∘C) reached at the upper end of the 5 %–95 % envelope of the highest scenario (SSP5-8.5). This is due to both the wider range of radiative forcing that the new scenarios cover and the higher climate sensitivities in some of the new models compared to their CMIP5 predecessors. Spatial patterns of change for temperature and precipitation averaged over models and scenarios have familiar features, and an analysis of their variations confirms model structural differences to be the dominant source of uncertainty. Models also differ with respect to the size and evolution of internal variability as measured by individual models' initial condition ensemble spreads, according to a set of initial condition ensemble simulations available under SSP3-7.0. These experiments suggest a tendency for internal variability to decrease along the course of the century in this scenario, a result that will benefit from further analysis over a larger set of models. Benefits of mitigation, all else being equal in terms of societal drivers, appear clearly when comparing scenarios developed under the same SSP but to which different degrees of mitigation have been applied. It is also found that a mild overshoot in temperature of a few decades around mid-century, as represented in SSP5-3.4OS, does not affect the end outcome of temperature and precipitation changes by 2100, which return to the same levels as those reached by the gradually increasing SSP4-3.4 (not erasing the possibility, however, that other aspects of the system may not be as easily reversible). Central estimates of the time at which the ensemble means of the different scenarios reach a given warming level might be biased by the inclusion of models that have shown faster warming in the historical period than the observed. Those estimates show all scenarios reaching 1.5 ∘C of warming compared to the 1850–1900 baseline in the second half of the current decade, with the time span between slow and fast warming covering between 20 and 27 years from present. The warming level of 2 ∘C of warming is reached as early as 2039 by the ensemble mean under SSP5-8.5 but as late as the mid-2060s under SSP1-2.6. The highest warming level considered (5 ∘C) is reached by the ensemble mean only under SSP5-8.5 and not until the mid-2090s.
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Dates and versions

meteo-03490791 , version 1 (17-12-2021)

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Claudia Tebaldi, Kevin Debeire, Veronika Eyring, Erich Fischer, John Fyfe, et al.. Climate model projections from the Scenario Model Intercomparison Project (ScenarioMIP) of CMIP6. Earth System Dynamics, 2021, 12 (1), pp.253-293. ⟨10.5194/esd-12-253-2021⟩. ⟨meteo-03490791⟩
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