Exploring CORDEX and driving GCM differences, in the context of time evolving aerosols

An emerging literature has been exploring RCM-GCM differences over Europe and linking many of these differences to the lack (or in a few cases, underestimation) of aerosol “Brightening” in the RCMs (Boe et al, 2019, Gutiérrez et al, 2020, Tarana et al, 2022).  Here we illustrate these differences for mid-century European surface SW, temperature and rainfall projections, with a focus on the spread.  The tendency for the RCMs to underestimate the GCM warming and drying is evident.  For example the RCMs at the lower end show roughly half the warming of the lowest driving CMIP5 GCM and roughly 50% of the RCMs suggest wetter projections that 6 out of 7 driving CMIP5 GCMs.  

We extend this analysis to the wider CORDEX regions and identify where lack of time varying aerosol representation does, and does not matter.   We also use single forcing (AER) CMIP6 experiments, to illustrate how this data can be a useful tool to predict where time varying aerosol representation is (and where it is not) likely to be important in ongoing CMIP6 downscaling.