Dilution of Atmospheric Radiocarbon CO2 by Fossil Fuel Emissions

Abstract

Post bomb period data for 14C in atmospheric carbon dioxide from seven measurement stations are available in small samples up to and including the year 2007. They do not support the theory that dilution by 14C-free fossil fuel emissions is responsible for falling levels of 14C in atmospheric CO2. We find instead that the observed decline of 14C in atmospheric CO2 is consistent with the exponential decay of bomb 14C. We also find that the attribution to fossil fuel emissions of the pre-bomb dilution of 14C in atmospheric CO2 in the period 1900-1950 found by Stuiver and Quay in tree-ring data is inconsistent with total emissions and changes in atmospheric CO2 during that period. We conclude that the data for 14C in atmospheric CO2 do not serve as empirical evidence that the observed increase in atmospheric CO2 since the Industrial Revolution is attributable to fossil fuel emissions.