The Airborne Fraction of Anthropogenic CO2 Emissions
Knorr, W. 2009. Is the airborne fraction of anthropogenic CO2 emissions increasing? Geophysical Research Letters 36: 10.1029/2009GL040613.
In an effort to determine the likelihood of this concern, Knorr constructed a new-and-improved history of AF values stretching all the way back to 1850 by utilizing data on CO2 emissions arising from fossil-fuel use, cement production and changes in land use, as well as atmospheric CO2 concentrations measured at Mauna Loa and the South Pole, plus those derived from Law Dome and Siple ice-core data, together with their associated uncertainties. Based upon that reconstruction, the UK researcher reports that "despite the predictions of coupled climate-carbon cycle models, no trend in the airborne fraction can be found [italics added]." Or as he writes in the concluding section of his study, "the hypothesis of a recent or secular trend in the AF cannot be supported on the basis of the available data and its accuracy," which indicates that not only has the global ocean been increasing its uptake rate of anthropogenic carbon in such a way as to successfully "keep up" with the rate at which the air's CO2 content has risen in response to historical anthropogenic carbon inputs - as has concurrently been demonstrated by Khatiwala et al. (2009) - so also have Earth's terrestrial ecosystems been "keeping up" in this regard.
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