T. Trickl and co-authors have just published an ACP paper looking at 35 years of stratospheric aerosol measurements taken at Garmisch-Partenkirchen, Germany. They focused largely on the volcanically quiescent period of 1995-2006 to investigate the processes maintaining a residual lower stratospheric aerosol layer. Their results indicate that the influence of air traffic on stratospheric aerosol loading is small and that although single, large forest-fire events could be noticed, overall biomass burning also seems to have a limited impact on the stratospheric background aerosol. Post 2008 they observed an increase in backscatter coefficients largely due to mid-sized (explosivity index 4) volcanic eruptions, most of which occurred in the mid-latitudes. Find the full abstract here.