Projected Regional Climate Change in the Context of Recent Observed Changes

Abstract:

Since 1950 most of the north-central U.S. has seen an increase in warm-season precipitation. In contrast, the ensemble mean of CMIP5 global model projections suggest that warm season precipitation will decrease over the region during the coming decades. Given that this is one of the most productive agricultural regions in the world the discrepancy between observations and simulations is important to understand from societal and economic perspectives. We explore some of the reasons for this discrepancy by focusing on results from regional climate model simulations over the CORDEX North America domain. We show that results from RCM simulations agree better with observed trends compared to the CMIP5 global models and discuss the reasons for this improved agreement, namely the role of organized mesoscale convection. We also show that trends in extreme precipitation intensity are more robust than trends in mean precipitation, in that precipitation intensity trends are more consistent among global models, regional models and observations. We discuss the reasons for this seeming contradiction between mean and extreme precipitation.Since 1950 most of the north-central U.S. has seen an increase in warm-season precipitation. In contrast, the ensemble mean of CMIP5 global model projections suggest that warm season precipitation will decrease over the region during the coming decades. Given that this is one of the most productive agricultural regions in the world the discrepancy between observations and simulations is important to understand from societal and economic perspectives. We explore some of the reasons for this discrepancy by focusing on results from regional climate model simulations over the CORDEX North America domain. We show that results from RCM simulations agree better with observed trends compared to the CMIP5 global models and discuss the reasons for this improved agreement, namely the role of organized mesoscale convection. We also show that trends in extreme precipitation intensity are more robust than trends in mean precipitation, in that precipitation intensity trends are more consistent among global models, regional models and observations. We discuss the reasons for this seeming contradiction between mean and extreme precipitation.