The authors are critically revisiting the Carbon Cycle and find for the stock-to-outflow ratio of CO2 in the atmosphere a residence time of about five years. Accordingly, only about 5.5% of the atmospheric CO2 stock comes from fossil fuel emissions not yet absorbed by vegetation or oceans, while 94.5% originates from natural outgassing of oceans and soils. This interpretation is supported by multiple lines of observations like the d13C or D14C records and the strong month-by-month correlation over nearly 800 months between the CO2 growth rate at Mauna Loa Observatory and the sea-surface temperature anomaly in the inter-tropical zone.
