The growing need for risk-based assessments of impacts and adaptation to regional climate change calls for the quantification of the likelihood of regional outcomes and the representation of their uncertainty. Moreover, our global water resources include energy, agricultural and environmental systems, which are linked together as well as to climate. With the prospect of potential climate change and associated shifts in regional hydro-climates and their extremes, the MIT Integrated Global Systems Model (IGSM) framework, has enhanced its capabilities to model impacts (or effects) on the managed water-resource systems.

We first present a hybrid approach that extends the MIT Integrated Global System Model (IGSM)framework to provide probabilistic projections of regional climate changes. This procedure constructs meta-ensembles of the regional hydro-climate, combining projections from the MIT IGSM that represent global-scale uncertainties with regionally resolved patterns from archived climate-model projections. From these, agriculture, river routing, and water-resource impact modules in the IGSM framework can assess water impacts (e.g. drought risk) as well as water allocation among irrigation, hydropower, urban/industrial, and in-stream uses and investigate how society might adapt water resources due to shifts in hydro-climate variations and extremes. We then present examples of how this integrated model framework and downscaling technique are being employed to track changes in the regional hydro-climate over major river basins in southern Africa, Vietnam, and whether adaptive strategies can cope with the more severe climate-related threats to growth and development. In addition, we also present analyses over the United States that quantifies impacts of agricultural productivity and drought-risk - and the degree to which climate policy can avert risk. All this is cast under a probabilistic description of regional climate change encompassed by the IGSM framework.