WMO Greenhouse Gas Bulletin - No.15: The State of Greenhouse Gases in the Atmosphere Based on Global Observations through 2018

Measurements of the content of radiocarbon (14C) in atmospheric carbon dioxide (CO2) provide a unique way to discriminate between fossil fuel combustion and natural sources of CO2. Simultaneous observations of CO2 and 14C demonstrate the decline of 14C content in atmospheric CO2 caused by CO2 addition from fossil fuel combustion. This finding illustrates the importance of long-term measurements of atmospheric composition by laboratories involved in the WMO Global Atmosphere Watch (GAW) Programme in helping identify greenhouse gas emission sources.