The CANARI HadGEM3 Large Ensemble: Design, and evaluation of historical experiments

Abstract. This paper introduces the CANARI HadGEM3 Large Ensemble (CANARI LE), a 40-member Single-Model Initial-condition Large Ensemble (SMILE) designed to advance the study of climate variability and change. It is based on HadGEM3-GC3.1, the physical climate model used by the UK Met Office and partners for submissions to CMIP6 (Climate Model Intercomparison Project Phase 6). The CANARI LE simulations span 1950–2100 and are driven by CMIP6 historical and SSP3-7.0 forcings. Compared to existing Large Ensembles, the CANARI LE offers several distinctive features: (i) its resolution (1/4° in the ocean, 60 km in the midlatitude atmosphere), (ii) sub-daily output at the surface and on atmospheric pressure levels, and (iii) the provision of boundary conditions for regional modelling. In this study, the design of the CANARI LE is documented and key aspects of historical model performance are evaluated, while applications of the SSP3-7.0 simulations are left for forthcoming studies. Model evaluations are carried out for global mean surface temperature, North Atlantic jets and storm tracks, Northern Hemisphere stratospheric circulation, Atlantic meridional overturning circulation and subpolar gyre, Arctic sea ice, and El Niño-Southern Oscillation teleconnections. In addition, an example is provided deriving analogues of the North Atlantic 2023 summer marine heatwave showing that the CANARI LE captures unprecedented events of this magnitude and spatial scale. The CANARI LE is a community resource that lends itself for the study of physical coupled climate processes and weather systems in a changing climate. The ability to drive regional models will potentially allow for risk assessments of unprecedented detail in climate impacts and adaptation studies.