Twenty Years of Atmospheric 14Co2 Observations At Schauinsland Station, Germany

We present and discuss quasi-continuous long-term 14 CO 2 observations from the continental background station Schauinsland (48°N, 8°E, 1205 m asl, Black Forest, southern Germany). The observed steady decline of atmospheric 14 CO 2 from 1977 to 1996 can be described by a single exponential function with an e-folding time of (16.3 ± 0.2) yr. Summer means (May to August) in atmospheric 14 CO 2 at Schauinsland compare within Δ 14 C = ±4‰ with measurements made on individual rings from a tree grown in the near vicinity of the Schauinsland site. Both data sets are slightly depleted by up to 5‰ if compared to maritime background measurements of atmospheric 14 CO 2 made at Izaña, Tenerife. This is due to the influence of fossil fuel CO 2 emissions over the European continent as well as generally in mid latitudes of the Northern Hemisphere. δ 13 C analyses from the Schauinsland samples show mean seasonal variations with an amplitude of ±0.4‰, caused by atmosphere-biosphere exchange, and a mean decrease from 1977 to 1996 of δ 13 C = −0.017‰ yr −1 . This trend is mainly due to an increasing quantity of fossil fuel CO 2 in the atmosphere, depleted in 13 C/ 12 C ratio, and compares well to trends measured at other stations in mid-to-high northern latitudes.