Wine ethanol 14 C as a tracer for fossil fuel CO 2 emissions in Europe: Measurements and model comparison

14 C (radiocarbon) in atmospheric CO 2 is the most direct tracer for the presence of fossil‐fuel‐derived CO 2 (CO 2 ‐ff). We demonstrate the 14 C measurement of wine ethanol as a way to determine the relative regional atmospheric CO 2 ‐ff concentration compared to a background site (“regional CO 2 ‐ff excess”) for specific harvest years. The carbon in wine ethanol is directly back traceable to the atmospheric CO 2 that the plants assimilate. An important advantage of using wine is that the atmosphere can be monitored annually back in time. We have analyzed a total of 165 wines, mainly from harvest years 1990–1993 and 2003–2004, among which is a semicontinuous series (1973–2004) of wines from one vineyard in southwest Germany. The results show clear spatial and temporal variations in the regional CO 2 ‐ff excess values. We have compared our measured regional CO 2 ‐ff excess values of 2003 and 2004 with those simulated by the REgional MOdel (REMO). The model results show a bias of almost +3 parts per million (ppm) CO 2 ‐ff compared with those of the observations. The modeled differences between 2003 and 2004, however, which can be used as a measure for the variability in atmospheric mixing and transport processes, show good agreement with those of the observations all over Europe. Correcting for interannual variations using modeled data produces a regional CO 2 ‐ff excess signal that is potentially useful for the verification of trends in regional fossil fuel consumption. In this fashion, analyzing 14 C from wine ethanol offers the possibility to observe fossil fuel emissions back in time on many places in Europe and elsewhere.