The Continental European Suess Effect

Abstract

Observations of 14C in atmospheric CO2 at four different sites in central Europe, Heidelberg, Westerland, Schauinsland and Jungfraujoch have enabled us to determine individual fossil-fuel contributions to atmospheric CO2 concentration. The data clearly show a decrease of fossil-fuel CO2 with distance from anthropogenic source regions. At Heidelberg during winter we observe 14C/12C ratios up to 10% lower than at the clean air mountain station Jungfraujoch in the Swiss Alps, corresponding to an anthropogenic CO2 contamination level of ca 10% at the Heidelberg site. The Schauinsland and Westerland winter fossil-fuel CO2 concentrations are only ca 1.5 and 2% of the mean concentration, respectively. Our results indicate a strong seasonality in the European fossil-fuel CO2 source with ca 50% lower CO2 emissions during summer if compared to winter fossil-fuel CO2 release. This effect may significantly contribute (by 1–2 ppm) to the observed annual cycle of atmospheric CO2 concentration in northern mid-latitudes.