『Abstract
Critical loads are the basis for policies controlling emissions
of acidic substances in Europe. The implementation of these policies
involves large expenditures, and it is reasonable for policymakers
to ask what degree of certainty can be attached to the underlying
critical load and exceedance estimates. This paper is a literature
review of studies which attempt to estimate the uncertainty attached
to critical loads. Critical load models and uncertainty analysis
are briefly outlined. Most studies have used Monte Carlo analysis
of some form to investigate the propagation of uncertainties in
the definition of the input parameters through to uncertainties
in critical loads. Though the input parameters are often poorly
known, the critical load uncertainties are typically surprisingly
small because of a “compensation of errors” mechanism. These results
depend on the quality of the uncertainty estimates of the input
parameters, and a “pedigree” classification for these is proposed.
Sensitivity analysis shows that some input parameters are more
important in influence critical load uncertainty than others,
but there have not been enough studies to form a general picture.
Methods used for dealing with spatial variation are briefly discussed.
Application of alternative models to the same site or modifications
of existing models can lead to widely differing critical loads,
indicating that research into the underlying science needs to
continue.
Keywords: acid deposition; emission control; environmental policy;
GLUE; Monte Carlo analysis; sensitivity analysis; steady state
mass balance model; steady state water chemistry model; uncertainty
analysis』
1. Introduction
2. Definitions and methodology
2.1. Critical load models
2.2. Uncertainty analysis
3. Full uncertainty analyses
3.1. Critical loads for soils
3.2. Critical loads for waters
3.3. Uncertainties in exceedance
4. Single parameter sensitivity analyses
5. Multiple model applications
6. Changes in model structure
7. Discussion
Acknowledgments
References