VERIFICATION, VALIDATION, AND CONFIRMATION OF NUMERICAL-MODELS IN THEEARTH-SCIENCES

Verification and validation of numerical models of natural systems is impossible. This is because natural systems are never closed and becau se model results are always nonunique. Models can be confirmed by the demonstration of agreement between observation and prediction, but con firmation is inherently partial. Complete confirmation is logically pr ecluded by the fallacy of affirming the consequent and by incomplete a ccess to natural phenomena. Models can only be evaluated in relative t erms, and their predictive value is always open to question. The prima ry value of models is heuristic.