Abstract
Abstract. The Canadian Earth System Model version 5 (CanESM5) is a global model developed to simulate historical climate change and variability, to make centennial-scale projections of future climate, and to produce initialized seasonal and decadal predictions. This paper describes the model components and their coupling, as well as various aspects of model development, including tuning, optimization, and a reproducibility strategy. We also document the stability of the model using a long control simulation, quantify the model's ability to reproduce large-scale features of the historical climate, and evaluate the response of the model to external forcing. CanESM5 is comprised of three-dimensional atmosphere (T63 spectral resolution equivalent roughly to 2.8∘) and ocean (nominally 1∘) general circulation models, a sea-ice model, a land surface scheme, and explicit land and ocean carbon cycle models. The model features relatively coarse resolution and high throughput, which facilitates the production of large ensembles. CanESM5 has a notably higher equilibrium climate sensitivity (5.6 K) than its predecessor, CanESM2 (3.7 K), which we briefly discuss, along with simulated changes over the historical period. CanESM5 simulations contribute to the Coupled Model Intercomparison Project phase 6 (CMIP6) and will be employed for climate science and service applications in Canada.
Highlights
A multitude of evidence shows that human influence is driving accelerating changes in the climate system, which are unprecedented in millennia (IPCC, 2013)
The increase in crop area over the historical period is based on LUH2 v2h product of the land use harmonization (LUH) effort produced for Coupled Model Intercomparison Project phase 6 (CMIP6) (Hurtt et al, 2011)
Objective global skill metrics show that Canadian Earth System Model version 5 (CanESM5) improves the simulation of observed largescale climate patterns, relative to CanESM2, for most variables surveyed
Summary
A multitude of evidence shows that human influence is driving accelerating changes in the climate system, which are unprecedented in millennia (IPCC, 2013). As the impacts of climate change are increasingly being felt, so is the urgency to take action based on reliable scientific information (UNFCCC, 2015) To this end, the Canadian Centre for Climate Modelling and Analysis (CCCma) is engaged in an ongoing effort to improve modelling of the global Earth system, with the aim of enhancing our understanding of climate system function, variability, and historical changes, and making improved quantitative predictions and projections of future climate. The resolution of CanESM5 (T63 or ∼ 2.8◦ in the atmosphere and ∼ 1◦ in the ocean) remains similar to CanESM2 and is at the lower end of the spectrum of CMIP6 models The advantage of this coarse resolution is a relatively high model throughput given the complexity of the model, which enables many years of simulation to be achieved with available computational resources. We investigate the sensitivity of the model to external forcings
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