Climate Impacts, Climate Policies, and the Role of Adaptation through the Lens of Water Systems

Thursday, December 15, 2016 - 10:20
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Recognizing the critical role of water in human-Earth system interactions, most integrated assessment models are moving to incorporate water within their modeling frameworks and climate change impacts more broadly. However, none of the IA models used in generating the four representative concentration pathways (RCPs) incorporated the potential feedbacks of water limitations on other modeled systems, meaning that these assessments did not consider the joint interactions between hydrologic and human systems simultaneously adapting to and mitigating climate change. Yet, hydrologic systems could impose severe limitations on both energy and land decisions. Also, previous efforts have been limited to taking information from IA and Earth system models and passing that information to global water management and hydrologic models with the implicit assumption that all unmet water demands are taken from non-renewable water resources, generally fossil groundwater. However, extracting and depleting water resources (e.g., aquifers) could have drastic impacts on both energy and land use systems and the ability to mitigate climate change. In this study, we use the Global Change Assessment Model (GCAM), where interactions between population, economic growth, energy, land and water resources interact simultaneously in a dynamically evolving system, to investigate: 1) how water scarcity affects energy and land use decisions as well as mitigation policies, 2) the effects of climate change impacts on the food-energy-water nexus, 3) how these impacts evolve in the context of the shared socioeconomic pathways (SSPs) with specific details on water technologies, 4) the effects of different adaptation measures and their associate investment costs, and 5) the relative contributions of climate and human systems on water scarcity. We find that previous estimates of global water withdrawal projections are overestimated, as our simulations show that it is more economical in some basins to alter agricultural and energy activities rather than utilize non-renewable groundwater or desalinated water. We also find that the human footprints are more pronounced than the climate counterpart for most river basins around the globe, and that adaptation is a viable measure to deal with the water scarcity problem in many regions.

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