the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
Dynamics of global atmospheric CO2 concentration from 1850 to 2010: a linear approximation
Abstract. The increase in anthropogenic CO2 emissions largely followed an exponential path between 1850 and 2010, and the corresponding increases in atmospheric CO2 concentration were almost constantly proportional to the emissions by the so-called "airborne fraction". These observations suggest that the dynamics of atmospheric CO2 concentration through this time period may be properly approximated as a linear system. We demonstrate this hypothesis by deriving a linear box-model to describe carbon exchanges between the atmosphere and the surface reservoirs under the influence of disturbances such as anthropogenic CO2 emissions and global temperature changes. We show that the box model accurately simulates the observed atmospheric CO2 concentrations and growth rates across interannual to multi-decadal time scales. The model also allows us to analytically examine the dynamics of such changes/variations, linking its characteristic disturbance-response functions to bio-geophysically meaningful parameters. In particular, our results suggest that the elevated atmospheric CO2 concentrations have significantly promoted the gross carbon uptake by the terrestrial biosphere. However, such "fertilization" effects are partially offset by enhanced carbon release from surface reservoirs promoted by warmer temperatures. The result of these interactions appears to be a decline in net efficiency in sequestering atmospheric CO2 by ∼30% since 1960s. We believe that the linear modeling framework outlined in this paper provides a convenient tool to diagnose the observed atmospheric CO2 dynamics and monitor their future changes.
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- RC C6416: 'referee comment on Dynamics of Global Atmospheric CO2 Concentration ...', Ian Enting, 02 Nov 2014
- RC C6933: 'further comment', Ian Enting, 23 Nov 2014
- RC C6950: 'Referee report of Dynamics of Global Atmospheric CO2 Concentration from 1850 to 2010: a Linear Approximation', Anonymous Referee #2, 24 Nov 2014
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AC C7237: 'Responses to Dr. Enting's and another anonymous reviewer's comments', Weile Wang, 10 Dec 2014
- RC C7420: 'comments on 'Dynamics of global atmospheric CO2 concentration from 1850 to 2010: a linear approximation'', Andrew Jarvis, 17 Dec 2014
- RC C7623: 'Additional Comment 2: On committed warming', Ian Enting, 26 Dec 2014
- RC C7625: 'Additional comment 3: On inverse problems.', Ian Enting, 26 Dec 2014
- RC C7629: 'Additonal comment 4: on ambiguity and feedback', Ian Enting, 26 Dec 2014
- AC C8247: 'Final responses to reviewers' comments and the revised manuscript', Weile Wang, 23 Jan 2015
- RC C6416: 'referee comment on Dynamics of Global Atmospheric CO2 Concentration ...', Ian Enting, 02 Nov 2014
- RC C6933: 'further comment', Ian Enting, 23 Nov 2014
- RC C6950: 'Referee report of Dynamics of Global Atmospheric CO2 Concentration from 1850 to 2010: a Linear Approximation', Anonymous Referee #2, 24 Nov 2014
-
AC C7237: 'Responses to Dr. Enting's and another anonymous reviewer's comments', Weile Wang, 10 Dec 2014
- RC C7420: 'comments on 'Dynamics of global atmospheric CO2 concentration from 1850 to 2010: a linear approximation'', Andrew Jarvis, 17 Dec 2014
- RC C7623: 'Additional Comment 2: On committed warming', Ian Enting, 26 Dec 2014
- RC C7625: 'Additional comment 3: On inverse problems.', Ian Enting, 26 Dec 2014
- RC C7629: 'Additonal comment 4: on ambiguity and feedback', Ian Enting, 26 Dec 2014
- AC C8247: 'Final responses to reviewers' comments and the revised manuscript', Weile Wang, 23 Jan 2015
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