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 to investigate the added value of higher resolution (>50km) 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.