Editing IPCC:AR6/WGI/Chapter-10 (section)

==== 10.3.2.1 Transient Simulations and Time-slice Experiments ====

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Transient simulations intend to represent the evolving climate state of the Earth system (Chapter 4). They are typically based on coupled global model simulations, such as those in the Diagnostic, Evaluation and Characterization of Klima (DECK) and ScenarioMIP part of CMIP6 covering the period 1850–2100 ( [[#Eyring--2016a|Eyring et al., 2016a]] ), and HighResMIP (1950–2050; [[#Haarsma--2016|Haarsma et al., 2016]] ). Global transient climate simulations may be further downscaled by either dynamical or statistical downscaling. Currently available CORDEX RCM simulations (1950–2100) are based on CMIP5 ( [[#Gutowski%20Jr.--2016|Gutowski Jr. et al., 2016]] ).

In contrast, time-slice experiments are designed to represent only a specific period of time (typically 30 years). They are often run using global and regional models in atmosphere-only mode, forced by SSTs derived either from observations, as AMIP experiments, or from historical simulations and future projections of coupled global models. Compared to transient simulations, they offer advantages in being computationally cheaper (due to the lack of coupled ocean and short duration), which allows for the number of ensemble members(T. [[#Zhang--2016|]] [[#Zhang--2016|]] [[#Zhang--2016|Zhang et al., 2016]] ), and/or the resolution ( [[#Haarsma--2013b|Haarsma et al., 2013b]] ; [[#Davini--2017|Davini et al., 2017]] ) to be increased. Convection-permitting simulations, both covering the globe or particular regions, are currently conducted for short time slices only ( [[#Kendon--2017|Kendon et al., 2017]] ; [[#Hewitt--2018|Hewitt and Lowe, 2018]] ; [[#Coppola--2020|Coppola et al., 2020]] ; [[#Pichelli--2021|Pichelli et al., 2021]] ). Another high-resolution time-slice data base is d4PDF ( [[#Mizuta--2017|Mizuta et al., 2017]] ; [[#Ishii--2020|Ishii and Mori, 2020]] ). Experiments covering a limited integration period have been carried out for coupled ocean–atmosphere RCMs ( [[#Sein--2015|Sein et al., 2015]] ; [[#Zou--2016b|Zou and Zhou, 2016b]] , 2017). However, long spin-up periods are required to reach a stable stationary state in the deep ocean that otherwise might lead to invalid projections ( [[#Planton--2012|Planton et al., 2012]] ; [[#Soto-Navarro--2020|Soto-Navarro et al., 2020]] ).

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