COMPARISON OF CLIMATE-CHANGE SCENARIO CONSTRUCTION METHODOLOGIES FOR IMPACT ASSESSMENT STUDIES

This paper explores three important aspects of studies that assess the possible effects of climatic change on agricultural productivity at r egional spatial scales. First, long-term historic and stochastically g enerated (WGEN) weather records are compared in terms of their statist ical attributes using the climate conditions found in central France. Second, our results show that the use of CERES-wheat coupled with WGEN produced weather data provides an efficient method for assessing the impacts of changing climate on average agricultural production. Less c onfidence can be placed, however on the estimation of future agricultu ral risk and variability assessment, Finally, time series of climate v ariables with changed mean and variability are either constructed acco rding to the methodology proposed by Mearns et al. (1992) or simulated with WGEN using the approach suggested by Riha et al. (1996). The cli mate change scenarios are compared in terms of their effects on wheat development and predicted yield with CERES-wheat using daily data from the sulphate integration of the HadCM2 General Circulation Model to d rive the crop model. The comparison of the different approaches for th e construction of climate change scenario demonstrates the relative im portance of changes in the mean climate and short/long-term variabilit y in the prediction of crop yield on a regional basis. The results als o indicate that the strength of the yield response to such combined sc enarios and sometimes even its sign, depends on the qualitative nature of the change, Therefore, assessments of future agricultural producti vity based on this methodological approach must be regarded as specula tive. (C) 1998 Elsevier Science B,V. All rights reserved.