Radiative forcing by stratospheric aerosol from volcanoes and major fires for the last 3 decades

We present instantaneous forcing computed in a transient simulation with the chemistry climate model EMAC considering more than 600 explosive eruptions and plumes of major forest fires observed by limb scanning satellites in the period 1991 to 2021. If not available directly, perturbations of SO₂ in the volcanic plumes, which we use as alternative to the "point source approach", were derived from observed extinctions. For the fires, black and organic carbon is injected at the top of the pyro-cumulonimbus and the resulting increase in extinction is compared with satellite data. Medium sized volcanic eruptions cause a total forcing of up to -0.35W/m² at the top of the atmosphere while for the fires the forcing there can be positive (about 0.2W/m²).