Net flux of carbon dioxide into the atmosphere results in rising atmospheric concentration, which is calculated endogenously in the FeliX model. Gross emissions are released during primary energy production; as a result of LULUC; and during to the natural decay of biomass and humus.
Carbon is withdrawn from the atmosphere in the following processes:
- Biomass increments for biofuel production and by unmanaged portions of the biosphere
- Uptake of carbon by the oceans
All of these fluxes are factored into the calculation of atmospheric carbon dioxide concentration, which is projected to rise monotonically through 2100. The BAU scenario result is shown below with RCP projections as well as the consequences of high and low population predictions (shaded red). Historical data, shown in grey, is taken from the CDIAC .
 Etheridge, D.M., Steele, L.P., Langenfelds, R.L., Francey, R.J., Barnola, J.-M., Morgan, V.I. 1998. Historical CO2 records from the Law Dome DE08, DE08-2, and DSS ice cores. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A