The 2020 Hersbach reference for ERA5 refers to the 2015 Hersbach paper on ERA-20CM as a reference for how aerosols are prescribed. The 2015 paper indicates that CMIP5 forcing is used for sulfate aerosols, but it is not clear to me which RCP was used to extend the CMIP5 historical data for ERA5. What sulfate aerosol concentrations are used in ERA5 post-2005?
In addition, are there any updated references about aerosol forcing in ERA5, or does the 2015 paper provide the most up-to-date information?