Mitigation and Adaptation Strategies for Global Change

, Volume 7, Issue 1, pp 19–30

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


  • Philip M. Fearnside

DOI: 10.1023/A:1015885027530

Cite this article as:
Fearnside, P.M. Mitigation and Adaptation Strategies for Global Change (2002) 7: 19. doi:10.1023/A:1015885027530


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 accountingdeforestation avoidanceglobal warmingKyoto Protocolland-use changeton-year accounting

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© Kluwer Academic Publishers 2002