Presentation and Evaluation of the IPSL‐CM6A‐LR Climate Model

TLDR

The study introduces IPSL‑CM6A‑LR, a CMIP6 global climate model developed at IPSL to investigate natural climate variability and responses to natural and anthropogenic forcings. The model integrates updated physical components, a global carbon cycle, and a large historical ensemble of over 30 members, with additional scenario ensembles up to 2300, and its design is compared to earlier IPSL models. Compared to its predecessor, IPSL‑CM6A‑LR shows markedly improved climatology across radiation, temperature, precipitation, and wind, though residual biases such as a double ITCZ, wintertime blocking, and ENSO dynamics persist, and both equilibrium climate sensitivity and transient climate response are higher.

Abstract

Abstract This study presents the global climate model IPSL‐CM6A‐LR developed at Institut Pierre‐Simon Laplace (IPSL) to study natural climate variability and climate response to natural and anthropogenic forcings as part of the sixth phase of the Coupled Model Intercomparison Project (CMIP6). This article describes the different model components, their coupling, and the simulated climate in comparison to previous model versions. We focus here on the representation of the physical climate along with the main characteristics of the global carbon cycle. The model's climatology, as assessed from a range of metrics (related in particular to radiation, temperature, precipitation, and wind), is strongly improved in comparison to previous model versions. Although they are reduced, a number of known biases and shortcomings (e.g., double Intertropical Convergence Zone [ITCZ], frequency of midlatitude wintertime blockings, and El Niño–Southern Oscillation [ENSO] dynamics) persist. The equilibrium climate sensitivity and transient climate response have both increased from the previous climate model IPSL‐CM5A‐LR used in CMIP5. A large ensemble of more than 30 members for the historical period (1850–2018) and a smaller ensemble for a range of emissions scenarios (until 2100 and 2300) are also presented and discussed.