Model responses to aerosol forcing, 1850-2014

Bjorn Stevens’ team has developed a “simple plume” aerosol model, MACv2-SP, which prescribes optical properties of anthropogenic aerosol and aerosol indirect (Twomey) effect. Because different climate models use different aerosol schemes, the response to aerosol forcing has not historically been easy to evaluate. By using consistent aerosol climatologies, each model’s aerosol response can be compared. The MACv2-SP Fortran code is available as a supplement to the GMD paper that describes the model. For this component of RFMIP, centres using MACv2-SP as their anthropogenic aerosol model require no additional simulations to be run.

For piClim-SpAer-anthro and piClim-SpAer-aer, modelling groups should use year-2014 aerosol climatologies for consistency with CMIP6. This differs from the prescription in the RFMIP protocol paper which stated a mean from 1985-2005.

It has come to our attention that the piClim-SpAer-anthro experiment is described differently in ES-Doc. Please follow the guidelines on this website. Clarifications, but where the protocol agrees with ES-Doc, are given in orange. – CS, 8 April 2019
Table 1: Specified aerosol experiments

Experiment title Tier Years Parallel experiment
hist-spAer-all 1 1850-2014 CMIP6 historical (note: fully coupled atmosphere-ocean model)
hist-spAer-aer 2 1850-2014 Historical-Aer (DAMIP) (note: fully coupled atmosphere-ocean model)
piClim-SpAer-anthro 2 30 piClim-anthro (using year-2014 aerosol) (note: present day ozone)
piClim-SpAer-aer 2 30 piClim-aer (using year-2014 aerosol and ozone fixed at pre-industrial concentrations)
piClim-spAer-histall 2 1850-2014 piClim-histall
piClim-spAer-histaer 2 1850-2014 piClim-histaer (ozone fixed at pre-industrial concentrations)