Reassessing the value of regional climate modelling using palaeoclimate simulations

Regional climate models (RCMs) are often assumed to be more skilful compared to lower-resolution general circulation models (GCM). However, RCMs are driven by input from coarser resolution GCMs, which may introduce biases. This study employs versions of the HadAMB3 GCM at three resolutions (>50km) to investigate the added value of higher resolution using identically configured simulations of the pre-industrial (PI), mid-Holocene, and Last Glacial Maximum (LGM). The RCM shows improved PI climatology compared to the coarse-resolution GCM and enhanced palaeo-anomalies in the jet stream and storm tracks. However there is no apparent improvement when compared to proxy reconstructions. In the high-resolution GCM, accuracy in PI climate and atmospheric anomalies are enhanced despite its intermediate resolution. This indicates that synoptic and mesoscale features in a RCM are influenced by its low-resolution input, which impacts the simulated climatology. This challenges the paradigm that RCMs improve the representation of climate conditions and change.