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  • Modelling of climate indicators - IMAGE

Change in atmospheric gas concentrations also changes the amount of radiation absorbed or transmitted by the atmosphere, and thus changes the earth’s energy balance and temperature. The energy balance change is expressed as radiative forcing per gas, measured in W/m2. In MAGICC, concentrations of long-lived greenhouse gases are translated into radiative forcing values using radiative efficiency estimates from the IPCC (Myhre et al., 2013), and radiative forcing of tropospheric ozone is calculated based on ozone sensitivity factors from MAGICC 6.0 (Meinshausen et al., 2011a; Meinshausen et al., 2011b).

However, other processes also lead to changes in the atmospheric energy balance, which are also modelled and assigned a radiative forcing value. Aerosols, such as SO2, NOx, and organic carbon, have a direct cooling effect by reflecting more radiation back into space (direct aerosol effect). They also interact with clouds and precipitation in many ways (indirect aerosol effect); this cloud feedback is the largest source of uncertainty in estimating climate sensitivity (Denman et al., 2007). Although also an aerosol, black carbon has a strong direct warming effect (WMO/UNEP, 2013).

Direct and indirect aerosol effects are approximated in MAGICC by scaling the radiative forcing in a reference year (mostly 2005) with the relative increase in future emissions with respect to emissions in the reference year. As MAGICC assumes radiative forcing by albedo and mineral dust to stay constant over the scenario period (Meinshausen et al., 2011a), this is also assumed in IMAGE.


A brief overview is presented here, for more information see the IMAGE 3.0 web page.

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