Aerosol Radiative Forcing time development in the CMIP6 historical experiment

Abstract

In this study, radiative forcing time series on a component basis from the historical experiment in CMIP6 are presented. For each aerosol component (sulphate, black carbon, organic aerosols, nitrate) aerosol radiative forcing for aerosol-radiation interaction (RFari) is calculated from 1850 to 2014 using a radiative kernel and modelled changes in aerosol mass. The radiative kernel has been generated using the DISORT radiative transfer model. Aerosol radiative forcing for aerosol-cloud interaction (RFaci) is calculated offline based on the monthly fields from CMIP6 and simulate changes in the effective radius. For the individual models the time development of total aerosol radiative forcing is compared to aerosol effective radiative forcing (ERF) time series calculated within RFMIP, that take into account the adjustments. The radiative forcing trend will be presented on a global and a regional scale. The calculations are also done for the AeroCom phase III historical experiment. Both the AeroCom phase III and CMIP6 historical experiment use the CMIP6 CEDS emissions. These emissions are recently updated and extended. Using results from a chemistry transport model (OsloCTM3) we show how the updated emissions have changed the radiative forcing trends in the model. The emissions used to drive the models play an important role for determining the time development of the aerosol radiative forcing. At the end we will discuss uncertainties in the trend based on available historical global emission inventories for aerosol and aerosol precursors.