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National Assessment of Ecosystem Carbon Sequestration and Greenhouse Gas Fluxes


Understanding Uncertainties

An evaluation of uncertainty is a critical component of resource assessments and is necessary in order for an assessment to be translated into information that is useful for formulating policy. Insufficient data, limits in modeling capabilities, interactions between ecological phenomena and the scientific understanding of these complex interactions can lead to uncertainties in the assessment. Although validation methods will be used for assessing current carbon stocks, carbon sequestration and greenhouse gas fluxes, uncertainties in the assessment will be limited to scenarios, data, and methods related to future potential conditions. The basis for estimating uncertainties in the assessment is defined within Intergovernmental Panel on Climate Change (IPCC) guidelines on uncertainties.

There are two general sources of uncertainty for the assessment: uncertainty related to the IPCC storyline framework, which may yield unpredictable results; and uncertainty related to data and methods, which may be quantified and reported.

Addressing Uncertainty from the Use of the Storylines and Scenarios:

The strategy for treating scenario-related uncertainties involve the following steps:

Communicating the sources of uncertainty:

  • Potential sources of uncertainty include choices of storylines or scenarios and the downscaling process

Reducing the unknown uncertainties:

  • Downscaling the IPCC SRES storylines based on data and studies rather than on global-scale model outputs
  • Standardizing the downscaling methods, which will be accomplished through consultation sessions with regional experts
  • Increasing the consistency of the scenario framework by using the same design criteria for each alternative scenario and aligning it with the IPCC SRES storylines

Addressing Uncertainty to Data and Assessment Methods

The sources of uncertainty related to the assessment data and methods include:

  • Input data
  • Scarcity of data that pertains to the assessment methods (such as greenhouse-gas flux data for different ecosystems)
  • The process-model structure and associated parameters that are used to estimate carbon stocks, carbon sequestration and greenhouse-gas fluxes
  • The interactions between components of the assessment (such as projecting LULC change and evaluating the effects)

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