Using a Tree Ring δ 13C Annual Series to Reconstruct Atmospheric CO 2 Concentration over the Past 300 Years

Abstract

The annual series of δ^13C were measured in tree rings of three Cryptomeria fortunei disks (CF-1, CF-2, and CF3) collected from West Tianmu Mountain, Zhejiang Province, China, according to cross-dating tree ring ages. There was no obvious decreasing trend of the δ^13C annual time series of CF-2 before 1835. However, from 1835 to 1982 the three tree ring δ^13C annual series exhibited similar decreasing trends that were significantly (P≤0.001) correlated. The distribution characteristics of a scatter diagram between estimated δ^13C series of CF-2 from modeling and the atmospheric CO2 concentration extracted from the Law Dome ice core from 1840 to 1978 were analyzed and a curvilinear regression equation for reconstructing atmospheric CO2 concentration was established with R^2=0.98. Also, a test of independent samples indicated that between 1685 and 1839 the reconstructed atmospheric CO2 concentration using the δ^13C series of CF-2 had a close relationship with the Law Dome and Siple ice cores, with a standard deviation of 1.98. The general increasing trend of the reconstructed atmospheric CO2 concentration closely reflected the long-term variation of atmospheric CO2 concentration recorded both before and after the Industrial Revolution. Between 1685 and 1840 the evaluated atmospheric CO2 concentration was stable, but after 1840 it exhibited a rapid increase. Given a longer δ^13C annual time series of tree rings, it was feasible to rebuild a representative time series to describe the atmospheric CO2 concentration for an earlier period and for years that were not in the ice core record.