21st century United States emissions mitigation could increase water stress more than the climate change it is mitigating

Abstract

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...

A framework for modelling the complexities of food and water security under globalisation

“…In addition, the energy sector itself requires considerable water resources (Bijl et al, 2016). Fossil fuel extraction such as coal mining and shale gas fracking are highly water intensive, whilst biofuel production competes with food production for land and water resources (Bonsch et al, 2016;Hejazi et al, 2015). Failure to capture sectoral interdependencies means we may fail to identify synergistic solutions; or worse still, policies in one sector may have unintended negative consequences in another.…”

“…An integrated approach has also been applied by Bonsch et al (2016) using MAgPIE (Lotze-Campen et al, 2008, a global land and water use allocation model, to understand the trade-off between agricultural expansion and intensification via water abstraction to meet biofuel targets. Like Hejazi et al (2015), their integrated approach showed that changes in the energy sector can lead to competition for water resources within the food sector. The MAgPIE approach also underlined the importance of capturing dynamic vegetation and hydrological processes in the same modelling framework as the two are intrinsically intertwined, with changes in vegetation impacting water resources and vice versa Konar et al, 2013;Lotze-Campen et al, 2008).…”

“…Given the complexity of the food system, it is challenging to develop effective food and water management strategies because policies can leak across regions, sectors and scales (Eakin et al, 2009;Hejazi et al, 2015;Meyfroidt et al, 2013). Models and decision tools exist to inform policymakers on these issues.…”

Tethys – A Python Package for Spatial and Temporal Downscaling of Global Water Withdrawals

“…235 water basins [21]). GCAM is often used as a boundary condition and coupled to sectoral models, such as the Community Land Model and Xanthos, which typically operate at finer spatial and temporal scales than GCAM [19,20]. For example, Xanthos is a globally gridded hydrology model that operates at monthly scale.…”

“…3. Electricity: Temporal downscaling of electricity water withdrawal from annual to monthly was based on the assumption that the amount of water withdrawal for electricity generation is proportional to the amount of electricity generated [19,20]. 4.…”