Modelling uncertainty in Critical Load Models
The aim of the project was to examine the uncertainties in critical load assessments and develop a practical methodology for such assessments within the EA's regulatory role. This work built on an earlier Environment Agency project which developed methods for assessing the uncertainty in critical loads due to uncertainty in the input parameters to critical load models, and applied it to a forested site in southern England.
A Monte Carlo approach was used together with Critical Load models to assess parameter sensitivity and model uncertainty. An extensive programme of testing uncertainties in the acidity critical load model used for terrestrial ecosystems was carried out.
The sensitivities to choice of input parameters, their statistical distribution type and their intercorrelation were calculated and the methods applied to other coniferous forest sites. It was hoped that this would identify parameters which could be selectively targeted for research to narrow output uncertainties, but almost any input parameter proved potentially important.
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