Estimation of Atmospheric Fossil Fuel CO2 Traced by Δ14C: Current Status and Outlook

Fossil fuel carbon dioxide (FFCO2) is a major source of atmospheric greenhouse gases that result in global climate change. Quantification of the atmospheric concentrations and emissions of FFCO2 is of vital importance to understand its environmental process and to formulate and evaluate the efficiency of carbon emission reduction strategies. Focusing on this topic, we summarized the state-of-the-art method to trace FFCO2 using radiocarbon (14C), and reviewed the 14CO2 measurements and the calculated FFCO2 concentrations conducted in the last two decades. With the mapped-out spatial distribution of 14CO2 values, the typical regional distribution patterns and their driving factors are discussed. The global distribution of FFCO2 concentrations is also presented, and the datasets are far fewer than 14CO2 measurements. With the combination of 14C measurements and atmospheric transport models, the FFCO2 concentration and its cross-regional transport can be well interpreted. Recent progress in inverse methods can further constrain emission inventories well, providing an independent verification method for emission control strategies. This article reviewed the latest developments in the estimation of FFCO2 and discussed the urgent requirements for the control of FFCO2 according to the current situation of climate change.