File:Carbon Stabilization Scenarios.png

From Global Warming Art



Carbon dioxide emissions scenarios considered by the Intergovernmental Panel on Climate Change for different possible population and economic growth scenarios for the 21st century in the absence of explicit actions to control greenhouse gas emissions.

This figure shows a range of simulated trajectories for carbon dioxide (CO2) that would result in stabilization of the atmospheric carbon dioxide concentration at between 450 and 1000 parts per million by volume (ppmv), and the variations in industrial emissions (expressed in gigatonnes carbon per year [GtC/yr]) that would be required to realize those trajectories.

As is illustrated here, stabilization at 1000 ppmv or less is likely to require that CO2 emissions reach a maximum during the course of this century and are subsequently reduced to levels below present day. The oceans and atmosphere are presently able to absorb ~40% of modern emissions made each year, so immediate stabilization at present day levels (380 ppmv) would require an immediate 60% reduction in emissions. Further, as the available carbon sinks in the oceans and biosphere (e.g. forests) become acclimated to high CO2 levels, their ability to absorb emissions declines, thus requiring further reductions in carbon emissions. However, full adjustment would take a few thousand years of constant emissions.

Because the global warming effects of CO2 are generally associated with its accumulated concentration, greater emissions in the near future can be partially offset by deeper cuts in future emissions (Wigley et al. 1996).

Model details

These curves are based on a simple inverse carbon cycle box model by Wigley (1991, 1993) that simulates carbon exchange between 5 reservoirs via 14 fluxes that incorporate the ocean, atmosphere, and biosphere with carbon fertilization feedbacks. Unlike some more sophisticated models, it does not consider the impact of temperature change or the spatial structure of the Earth's continents. The model was adjusted so that the oceanic and atmospheric fluxes more closely agree with recent measurements (Bender et al. 2005). Substantial uncertainties are currently associated with this sort of analysis, though the qualitative conclusions are generally considered to be reliable (IPCC 2001a, [1]).


This figure was prepared by Robert A. Rohde from a new implementation of the model described by Wigley (1991, 1993). The figure is licensed under the Global Warming Art license.

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  • [abstract] [DOI] Bender, Michael L., David T. Ho, Melissa B. Hendricks, Robert Mika, Mark O. Battle, Pieter P. Tans, Thomas J. Conway, Blake Sturtevant, Nicolas Cassar (2005). "Atmospheric O2/N2 changes, 1993-2002: Implications for the partitioning of fossil fuel CO2 sequestration". Global Biogeochemical Cycles 19: GB4017. 
  • [full text] IPCC (2001a). Houghton, J.T.,Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson (eds.): Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge University Press. ISBN 0521807670. 
  • Wigley, TML (1991). "A simple inverse carbon cycle model". Global Biogeochemical Cycles 5: 373-382. 
  • [abstract] [full text] [DOI] Wigley, TML (1993). "Balancing the carbon budget. Implications for projections of future carbon dioxide concentration changes". Tellus 45B: 409-425. 
  • [abstract] [DOI] Wigley, T.M.L., Richels, R., and Edmonds, J.A. (1996). "Economic and environmental choices in the stabilization of CO2 concentrations: choosing the 'right' emissions pathway". Nature 379: 240-243. 

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