Jaworowski et al. (1992 a, 1992 b) reviewed published CO2 measurements from ice cores, and
emphasized that the pre-industrial atmospheric CO2 concentration, according to early accurate
analyses, was many times larger (measurements up to 2450 ppmv) than the present atmospheric
value. They also pointed out that CO2 variations in ice is mainly an artificial effect of a large
number of natural physical-chemical processes in ice and the recovered ice cores. These effects
dominate over the eventual traces of anthropogenic CO2. Criticism of the methodology has also
independently been presented by Heyke (1992 a, 1992 b, 1992 c).
Jaworowski et al. (1992 a) have presented a number of criticisms regarding the methodology of
atmospheric CO2 measurements, including spectroscopic instrumental peak overlap errors (from
N2O, CH4, and CFCs in the air). They also pointed out that the CO2 measurements at current
CO2observatories use a procedure involving a subjective editing (Keeling et al., 1976) of
measured data, only representative of a few tens of percent of the total data. There are also
fundamental problems connected with the use of stable carbon isotopes (13C/12C) in tree rings for
model calculations of earlier atmospheres' CO2 concentration, a method which now seems to have
been abandoned (Jaworowski et al., 1992 a).
The third evidence, based on carbon isotopes, will be discussed below in Section 5.
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