There is evidence that warming leads to greater evapotranspiration and surface drying, thus contributing to increasing intensity and duration of drought and implying that mitigation would reduce water stresses. However, understanding the overall impact of climate change mitigation on water resources requires accounting for the second part of the equation, i.e., the impact of mitigationinduced changes in water demands from human activities. By using integrated, high-resolution models of human and natural system processes to understand potential synergies and/or constraints within the climate-energy-water nexus, we show that in the United States, over the course of the 21st century and under one set of consistent socioeconomics, the reductions in water stress from slower rates of climate change resulting from emission mitigation are overwhelmed by the increased water stress from the emissions mitigation itself. The finding that the human dimension outpaces the benefits from mitigating climate change is contradictory to the general perception that climate change mitigation improves water conditions. This research shows the potential for unintended and negative consequences of climate change mitigation.climate change | mitigation | water deficit | Earth system model | integrated assessment E arlier work addressing the impact of emissions mitigation on water supply and demand has produced conflicting results (1-5). The reasons are complex. Earth system models (ESMs) and climate models are generally in agreement that a lack of climate change mitigation would lead to greater warming and intensification of the global water cycle (6), increasing precipitation intensity (7), changes in runoff that amplify the existing wet/dry patterns (8), and increasing flood risk (9) as well as aridity (10). However, changes in seasonal patterns and the increasing probability of extreme events may complicate the general patterns of wet/dry trends (11). Additionally, changes in water demands caused by socioeconomic drivers alone may surpass the effects of climate change on water availability (12). Several studies (1-5) have assessed the consequences of mitigation on some measure of water deficit. Each study used its own integrated assessment and global hydrologic models, generally with varying underlying socioeconomic and technological assumptions, climate inputs, measures of water deficit, and a wide range of spatial and temporal resolutions. A key distinction of the study presented here is its coupling of regional ESMs and human systems models using finer spatial and/or temporal resolutions than previous efforts.Extending the work of Hejazi et al. (4) and Voisin et al. (13), integrated regional models of human and natural systems with enhanced capabilities are used at high temporal and spatial resolution while maintaining consistency with regional and global climate and economic modeling. In this modeling framework, a regional integrated assessment model (IAM) simulates water demand for both irrigation and nonirrigation sectors (a resu...

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a b s t r a c tThis paper presents the results of numerous commercial and residential building simulations, with the purpose of examining the impact of climate change on peak and annual building energy consumption over the portion of the EIC (Eastern Interconnection) located in the United States. The climate change scenario considered includes changes in mean climate characteristics as well as changes in the frequency and duration of intense weather events. Simulations were performed using the BEND (Building ENergy Demand) model which is a detailed building analysis platform utilizing EnergyPlus™ as the simulation engine. Over 26,000 building configurations of different types, sizes, vintages, and characteristics representing the population of buildings within the EIC, are modeled across the three EIC time zones using the future climate from 100 target region locations, resulting in nearly 180,000 spatially relevant simulated demand profiles for three years selected to be representative of the general climate trend over the century. This approach provides a heretofore unprecedented level of specificity across multiple spectrums including spatial, temporal, and building characteristics. This capability enables the ability to perform detailed hourly impact studies of building adaptation and mitigation strategies on energy use and electricity peak demand within the context of the entire grid and economy.

A new large-scale stream temperature model has been developed within the Community Earth System Model (CESM) framework. The model is coupled with the Model for Scale Adaptive River Transport (MOSART) that represents river routing and a water management model (WM) that represents the effects of reservoir operations and water withdrawals on flow regulation. The coupled models allow the impacts of reservoir operations and withdrawals on stream temperature to be explicitly represented in a physically based and consistent way. The models have been applied to the Contiguous United States driven by observed meteorological forcing. Including water management in the models improves the agreement between the simulated and observed streamflow at a large number of stream gauge stations. It is then shown that the model is capable of reproducing stream temperature spatiotemporal variation satisfactorily by comparing against the observed data from over 320 USGS stations. Both climate and water management are found to have important influence on the spatiotemporal patterns of stream temperature. Furthermore, it is quantitatively estimated that reservoir operation could cool down stream temperature in the summer low-flow season (August-October) by as much as 128C due to enhanced low-flow conditions, which have important implications to aquatic ecosystems. Sensitivity of the simulated stream temperature to input data and reservoir operation rules used in the WM model motivates future directions to address some limitations in the current modeling framework.