The composition of volcanic plumes contains information on dynamic processes in the volcano interior and on the volcanic contribution to geochemical constituent cycles. In particular, the partitioning between carbon dioxide and sulfur dioxide emitted by volcanoes holds the promise to be indicative for future volcanic activity and thus, to enable forecasting eruptions. So far, monitoring volcanic carbon dioxide has been mostly limited to in-situ techniques deployed in the direct proximity of the crater coming along with overwhelming logistics effort and various hazards for instruments and operators. A field campaign in the vicinity of Mt. Etna, Sicily, demonstrates the feasibility of remote sensing volcanic carbon dioxide in the volcanic plume several kilometers downwind of the source. Our robust and versatile spectroscopic instrumentation overcomes the major challenge to detect the minute volcanic carbon dioxide enhancements on top of a large atmospheric background. Simultaneous observations of sulfur dioxide allow for correlating Mt. Etna’s carbon and sulfur emissions. We recommend our approach for future use in volcano monitoring on the way toward forecasting eruptive activity.