Why a 100-Year Time Horizon should be used for GlobalWarming Mitigation Calculations

  • Philip M. Fearnside


Global warming mitigation calculationsrequire consistent procedures for handlingtime in order to compare `permanent' gainsfrom energy-sector mitigation options with`impermanent' gains from many forest-sectoroptions. A critical part of carbonaccounting methodologies such as thosebased on `ton-years' (the product of thenumber of tons of carbon times the numberof years that each ton is held out of theatmosphere) is definition of a timehorizon, or the time period over whichcarbon impacts and benefits are considered. Here a case is made for using a timehorizon of 100 years. This choice avoidsdistortions created by much longer timehorizons that would lead to decisionsinconsistent with societal behavior inother spheres; it also avoids a rapidincrease in the implied value of time ifhorizons shorter than 100 years are used.Selection of a time horizon affectsdecisions on financial mechanisms andcarbon credit. Simple adaptations canallow a time horizon to be specified andused to calculate mitigation benefits andat the same time reserve a given percentageof weight in decision making forgenerations beyond the end of the timehorizon. The choice of a time horizon willheavily influence whether mitigationoptions such as avoided deforestation areconsidered viable.

carbon accounting deforestation avoidance global warming Kyoto Protocol land-use change ton-year accounting 


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  1. Arrhenius, E.A. and Waltz, T.W.: 1990, The Greenhouse Effect: Implications for Economic Development, World Bank Discussion Paper No. 78, Washington, DC, World Bank, 18 pp.Google Scholar
  2. Azar, C. and Sterner, T.: 1996, 'Discounting and distributional considerations in the context of global warming', Ecol. Econ. 19(2), 169–184.Google Scholar
  3. Blanco, J.T. and Forner, C.: 2000, Expiring CERs: A Proposal to Addressing the Permanence Issue for LUCF Projects in the CDM, Unpublished manuscript, Bogotá, Colombia. Economic and Financial Analysis Group, Ministry of the Environment, 4 pp. FCCC/SB/2000/MISC.4/Add.2/Rev.1, 14 September 2000. (available at http// Scholar
  4. Dutschke, M.: 2001, Permanence of CDM Forests or Non-Permanence of Land Use Related Carbon Credits?, HWWADiscussion paper 134, Hamburgisches Welt-Wirtschafts-Archiv (HWWA), Hamburg, Germany, 34 pp. (available from Scholar
  5. Fearnside, P.M.: 1997, 'Greenhouse-gas emissions from Amazonian hydroelectric reservoirs: The example of Brazil's Tucuruí Dam as compared to fossil fuel alternatives', Envir. Conserv. 24(1), 64–75.Google Scholar
  6. Fearnside, P.M.: 2000, 'Uncertainty in land-use change and forestry sector mitigation options for global warming: plantation silviculture versus avoided deforestation', Biomass & Bioenergy 18(6), 457–468.Google Scholar
  7. Fearnside, P.M.: nd-a, 'Saving tropical forests as a global warming countermeasure: An issue that divides the environmental movement', Ecol. Econ. (in press).Google Scholar
  8. Fearnside, P.M.: nd-b, Time Preference in Global Warming Calculations: A Proposal for a Unified Index, (manuscript).Google Scholar
  9. Fearnside, P.M., Lashof, D.A. and Moura-Costa, P.: 2000, 'Accounting for time in mitigating global warming', Mit. Adapt. Strat. Gl. Change 5(3), 239–270.Google Scholar
  10. Heal, G.: 1997, 'Discounting and climate change', Climatic Change 37(2), 335–343.Google Scholar
  11. Lashof, D.A. and Ahuja, D.R.: 1990, 'Relative global warming potentials of greenhouse gas emissions', Nature 344, 529–531.Google Scholar
  12. Marland, G., Fruit, K. and Sedjo, R.: nd, Accounting for Sequestered Carbon: The Question of Permanence, (manuscript).Google Scholar
  13. Moura-Costa, P. and Wilson, C.: 2000, 'An equivalence factor between CO2 avoided emissions and sequestration — description and applications in forestry', Mit. Adapt. Strat. Gl. Change 5(1), 51–60.Google Scholar
  14. Noble, I. and 34 others: 2000, 'Implications of Different Definitions and Generic Issues', in R.T. Watson, I.R. Noble, B. Bolin, N.H. Ravindranath, D.J. Verardo and D.J. Dokken (eds.), Land Use, Land-Use Change and Forestry: A Special Report of the Intergovernmental Panel on Climate Change (IPCC), Cambridge, Cambridge University Press, pp. 53–126.Google Scholar
  15. Schimel, D. and 75 others: 1996, 'Radiative Forcing of Climate Change', in J.T. Houghton, L.G. Meira Filho, B.A. Callander, N. Harris, A. Kattenberg and K. Maskell (eds.), Climate Change 1995: The Science of Climate Change, Cambridge, Cambridge University Press, pp. 65–131.Google Scholar
  16. Shine, K.P. and 19 others: 1990, 'Radiative forcing of climate', in J.T. Houghton, G.J. Jenkins and J.J. Ephraums (eds.), Climate Change: The IPCC Scientific Assessment, Cambridge, Cambridge University Press, pp. 41–68.Google Scholar
  17. UN-FCCC (United Nations Framework Convention on Climate Change): 1992, United Nations Framework Convention on Climate Change, (available at Scholar
  18. UN-FCCC (United Nations Framework Convention on Climate Change): 1997, Addendum to the Protocol, Decision 2/CP.3, para. 3', (available at Scholar

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© Kluwer Academic Publishers 2002

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  • Philip M. Fearnside

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