Use of expert elicitation to assign weights to climate and hydrological models in climate impact studies

[摘要] Various methods are available for assessing uncertaintiesin climate impact studies. Among such methods, model weighting by expertelicitation is a practical way to provide a weighted ensemble of models forspecific real-world impacts. The aim is to decrease the influence ofimprobable models in the results and easing the decision-making process. Inthis study both climate and hydrological models are analysed, and the resultof a research experiment is presented using model weighting with theparticipation of six climate model experts and six hydrological model experts.For the experiment, seven climate models are a priori selected from a largerEURO-CORDEX (Coordinated Regional Downscaling Experiment – European Domain) ensemble of climate models, and three different hydrologicalmodels are chosen for each of the three European river basins. The modelweighting is based on qualitative evaluation by the experts for each of theselected models based on a training material that describes the overallmodel structure and literature about climate models and the performance ofhydrological models for the present period. The expert elicitation processfollows a three-stage approach, with two individual rounds of elicitation ofprobabilities and a final group consensus, where the experts are separatedinto two different community groups: a climate and a hydrological modellergroup. The dialogue reveals that under the conditions of the study, mostclimate modellers prefer the equal weighting of ensemble members, whereashydrological-impact modellers in general are more open for assigning weightsto different models in a multi-model ensemble, based on model performanceand model structure. Climate experts are more open to exclude models, ifobviously flawed, than to put weights on selected models in a relativelysmall ensemble. The study shows that expert elicitation can be an efficientway to assign weights to different hydrological models and thereby reducethe uncertainty in climate impact. However, for the climate model ensemble,comprising seven models, the elicitation in the format of this study couldonly re-establish a uniform weight between climate models.

[学科分类] 妇产科学