Total anthropogenic CO2 production during the period 1800--1935 from carbon-13 measurements in tree rings.

The 13C records in tree ring cellulose have been evaluated in terms of CO2 production rates on the basis of a two box model of atmosphere and ocean. We show that a linear relationship exists between the actual atmospheric excess, deltaM(t), and the actual production rate, P(t), for periods of exponential growth of the production rate. No further calibration data from other sources are needed. The results are certainly depending to some degree on the properties of the used model, but it is demonstrated that even much more complex models have essentially the same property as it has been used here. The analysis covers the perion 1800--1935, where world-wide parallel trends have been found in the tree records. The delta13C shift in atmospheric carbon due to the addition of carbon from the fossil and biospheric reservoir was -1.66% in 1935. The model analysis yields a total production of the order of 100 ppm = 212 . 10(9) tC. Roughly one half of it was produced during the last 25 years of the period. The contribution from the fossil source was 20% of the total. An open question is where the sinks are for those amounts of mobilized carbon.