NE - RWU 4104

Last modified 11/09/2005

Heath, L.S., and J. E. Smith. 2000.

An assessment of uncertainty in forest carbon budget projections.

Environmental Science & Policy 3: 73-82.


Estimates of uncertainty are presented for projections of forest carbon inventory and average annual net carbon flux on private timberland in the US using the model FORCARB. Uncertainty in carbon inventory was approximately 9% (2000 million metric tons) of the estimated median in the year 2000, rising to 11% (2800 million metric tons) in projection year 2040, with this range covering 95% of the distribution. Relative uncertainties about net flux were higher and more variable than relative uncertainty estimates of carbon inventory. Results indicated that relatively high correlations among projected carbon budgets for the regional forest types led to greater total uncertainty than under assumptions of independence among types, indicating that an accurate portrayal of correlations is important. Uncertainty in soil carbon, closely followed by uncertainty in tree carbon, were most influential in estimating uncertainty in carbon inventory, but uncertainties in projections of volume growth and volume removals were most important in estimating uncertainty in carbon flux. This implies the most effective ways of reducing uncertainty in carbon flux are different from those required to reduce uncertainties in carbon inventory. Analyses as presented here are necessary prerequisites to identify and reduce uncertainty in a systematic and iterative way.

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