With a lidar system that was installed in Lindenberg/Germany, we observed inJune 2003 an extended aerosol layer at 13~\unit{km} altitude in the lowermoststratosphere. This layer created an inelastic backscatter signal that wedetected with a water vapour Raman channel, but that was not produced by Ramanscattering. Also, we find evidence for inelastic scattering from a smoke plumefrom a forest fire that we observed in the troposphere. We interpret theunexpected properties of these aerosols as fluorescence induced by the laserbeam at organic components of the aerosol particles. Fluorescence from ambientaerosol had not yet been considered detectable by lidar systems. However,organic compounds such as polycyclic aromatic hydrocarbons sticking to theaerosol particles, or bioaerosol such as bacteria, spores or pollen fluorescewhen excited with UV-radiation in a way that is detectable by our lidar system.Therefore, we conclude that fluorescence from organic material released bybiomass burning creates, inelastic backscatter signals that we measured with ourinstrument and thus demonstrate a new and powerful way to characterize aerosolsby a remote sensing technique. The stratospheric aerosol layer that we haveobserved in Lindenberg for three consecutive days is likely to be a remnant fromSiberian forest fire plumes lifted across the tropopause and transported aroundthe globe.