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Caldeira Lab Research:Energy, Global Carbon Cycle, and Climate

Atmospheric Lifetime of Fossil Fuel Carbon Dioxide

David Archer, Michael Eby, Victor Brovkin, Andy Ridgwell, Long Cao, Uwe Mikolajewicz, Ken Caldeira, Katsumi Matsumoto, Guy Munhoven, Alvaro Montenegro, & Kathy Tokos

When carbon dioxide is released from combustion, it equilibriates into the atmosphere, ocean and terrestrial biosphere. There is however, a significant fraction of CO2 which remains in the atmosphere before very slowly returning to solid Earth.


Archer D, Eby M, Brovkin V, Ridgwell, A., Cao, L., Mikolajeicz, Caldeira, K., Matsumoto, K, Munhoven, G., Montenegro, A., and K. Tokos, 2009, Atmospheric Lifetime of Fossil Fuel Carbon Dioxide, Annual Review of Earth and Planetary Sciences 37,117-134.

Atmospheric CO2 trajectories for the 10,000-year duration of the model simulations: Note the split scale that expands the action in the first 1000 years. Colors denote models and line styles denote experiments; the same line style may be used for different experiments in different panels. The pulse has been separated into two panels for clarity and the results represented by the solid lines are repeated for reference. Different line types designate the cases of base (ocean only) simulation, the climate feedback (C), the climate plus sediment feedback (CS), the climate plus sediment plus weathering feedback (CSW), and the climate plus sediment plus weathering plus vegetation feedback (CSWV).

Abstract

CO2 released from combustion of fossil fuels equilibrates among the various carbon reservoirs of the atmosphere, the ocean, and the terrestrial biosphere on timescales of a few centuries. However, a sizeable fraction of the CO2 remains in the atmosphere, awaiting a return to the solid earth by much slower weathering processes and deposition of CaCO3 . Common measures of the atmospheric lifetime of CO2 , including the e-folding time scale, disregard the long tail. Its neglect in the calculation of global warming potentials leads many to underestimate the longevity of anthropogenic global warming. Here, we review the past literature on the atmospheric lifetime of fossil fuel CO2 and its impact on climate, and we present initial results from a model intercomparison project on this topic. The models agree that 20–35% of the CO2 remains in the atmosphere after equilibration with the ocean (2–20 centuries). Neutralization by CaCO3 draws the airborne fraction down further on timescales of 3 to 7 kyr.