Papers published in Science of Climate Change by Harde and Salby (2021),
and by Berry (2021) contend that the well documented growth of
atmospheric CO2 in recent decades is predominantly a natural phenomenon
rather than human caused. Both papers are wrong on two counts. First,
they focus only on their own (suspect) calculations of anthropogenic
atmospheric carbon levels, rather than on measured total carbon levels.
The present concentration of anthropogenic carbon in the atmosphere,
even correctly calculated, does not establish the human contribution to
the rise in total atmospheric carbon. Second, the models these authors
develop for determining present anthropogenic atmospheric carbon levels
are incompatible with 14C data. The sources of background “anomalous
14C” postulated by Harde and Salby fall well short of being large
enough to salvage their model. A highly questionable assumption built
into Harde and Salby’s model is explicitly identified.