Airborne fraction

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The global carbon dioxide partitioning (atmospheric CO2, land sink, and ocean sink) averaged over the historical period (1900–2020)

The airborne fraction is a scaling factor defined as the ratio of the annual increase in atmospheric CO
to the CO
emissions from human sources.[1] It represents the proportion of human emitted CO2 that remains in the atmosphere. The fraction averages about 45%, meaning that approximately half the human-emitted CO
is absorbed by ocean and land surfaces. There is some evidence for a recent increase in airborne fraction, which would imply a faster increase in atmospheric CO
for a given rate of human fossil-fuel burning.[2] Changes in carbon sinks can affect the airborne fraction.

Observations over the past six decades show that the airborne fraction has remained relatively stable at around 45%.[3] This indicates that the land and ocean's capacity to absorb CO2 has kept up with the rise in human CO2 emissions, despite the occurrence of notable interannual and sub-decadal variability, which is predominantly driven by the land's ability to absorb CO2.

See also[edit]


  1. ^ Forster, P, V Ramaswamy, P Artaxo, et al. (2007) Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S. et al. (eds.)]. Cambridge University Press, Cambridge, UK & New York, USA.[1]
  2. ^ Canadell, Josep G.; Corinne Le Quere; Michael R. Raupach; Christopher B. Field; Erik T. Buitenhuis; Philippe Ciais; Thomas J. Conway; Nathan P. Gillett; R. A. Houghton; Gregg Marland (November 20, 2007). "Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks" (PDF). PNAS. 104 (47): 18866–18870. doi:10.1073/pnas.0702737104. PMC 2141868. PMID 17962418. Retrieved 2010-01-02.
  3. ^ Friedlingstein, Pierre; O'Sullivan, Michael; Jones, Matthew W.; Andrew, Robbie M.; Hauck, Judith; Olsen, Are; Peters, Glen P.; Peters, Wouter; Pongratz, Julia; Sitch, Stephen; Le Quéré, Corinne; Canadell, Josep G.; Ciais, Philippe; Jackson, Robert B.; Alin, Simone (2020). "Global Carbon Budget 2020". Earth System Science Data. 12 (4): 3269–3340. doi:10.5194/essd-12-3269-2020. ISSN 1866-3516.