First Analysis of Climate Forcing and Response to Updated Historical Anthropogenic Aerosol With the New CMIP7 Model ICON XPP

Kurzfassung

The simple plumes (SP) parameterization for anthropogenic aerosol effects on radiation and clouds has been used in the Coupled Model Intercomparison Project phase six (CMIP6) and beyond. This study documents the new SP forcing data in preparation for use in CMIP phase seven (CMIP7) and its first application in the newly developed coupled atmosphere‐ocean‐river model ICON XPP. We assess historical trends and spatio‐temporal differences for the aerosol optical depth of SP and find moderate differences compared to the CMIP6 data variant of SP. Radiative effects of anthropogenic aerosols from SP are estimated with atmosphere‐ only experiments of ICON XPP. The global all‐sky effective radiative forcing (ERFall) is − 0.33 Wm− 2 for the 2014 anthropogenic aerosols against the pre‐industrial level. Using either the CMIP6 version of SP or the different climate state of present‐day compared to pre‐industrial yield a similar ERFall of anthropogenic aerosol in ICON XPP, with global mean differences of 0.05 Wm− 2. Climate responses to the anthropogenic aerosols are computed with three‐member ensembles of fully‐coupled historical experiments with ICON XPP. ICON XPP shows no apparent differences in global mean responses for outgoing shortwave radiation, temperature, and precipitation when the updated SP data are prescribed in comparison to experiments that use the CMIP6 variant of SP. Such small present‐day differences suggest that future extensions of historical data for SP, not an update of the entire historical period, might be sufficient for climate studies, unless larger revisions of past emissions will be made.