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California Drought Increases CO2 Footprint of Energy
Abstract
This Commentary discusses the CO2 footprint of California’s drought during 2012–2014. We show that California drought significantly increased CO2 emissions of the energy sector by around 22 million metric tons, indicating 33% increase in the annual CO2 emissions compared to pre-drought conditions. We argue that CO2 emission of climate extremes deserve more attention, because their cumulative impacts on CO2 emissions are staggering. Most countries, including the United States, do not have a comprehensive a nationwide energy-water plan to minimize their CO2 emissions. We argue that developing a national water-energy plan under a changing climate should be prioritized in the coming years.
... In addition, as variable energy resources like wind and solar expand their share of the power mix, the grid is becoming more sensitive to fluctuations in wind speeds and solar irradiance (Collins et al., 2018;Staffell and Pfenninger, 2018). By influencing supply and demand for electricity, hydrometeorological processes have direct impacts on pollution (e.g., increased greenhouse gas emissions (Collins et al., 2018;Hardin et al., 2017;Tarroja et al., 2016)), wholesale electricity prices (Boogert and Dupont, 2005;Collins et al., 2018;Seel et al., 2018), and the financial standing of suppliers of electricity (e.g., retail utilities, renewable energy producers) and consumers (Bain and Acker, 2018;Boogert and Dupont, 2005;Foster et al., 2015;Kern and Characklis, 2017;Kern et al., 2015). ...
... However, with few exceptions (Turner et al., 2019), previous investigations fall short in assessing the holistic influence of hydrometeorological variability on bulk power systems. Past research efforts assess operational and financial risks from exposure to variability in a more limited set of hydrometeorological processes (Collins et al., 2018;Kern et al., 2015) (e.g., streamflow and temperatures, or wind speeds and solar irradiance); do not consider these effects within the context of large, interconnected power systems ; and/or do not assess impacts probabilistically (Hardin et al., 2017). These shortcomings may be partly attributable to the challenges of modeling bulk electric power systems at sufficient scale and resolution to simulate system operations in a realistic way, and over sufficient time horizons to explore joint uncertainty in multiple, correlated input variables. ...
... During this period, in-state hydropower generation decreased by an average of 40% (Gleick, 2017), forcing the state to rely significantly more on electricity from natural gas power plants. There has been considerable interest in exploring the impacts of this recent drought on pollutant emissions (Hardin et al., 2017), as well as system costs and prices for retail electricity consumers (Gleick, 2017). Particularly when determining the latter, an understanding of impacts on wholesale electricity prices is necessary. ...
Variability (and extremes) in streamflow, wind speeds, temperatures, and solar irradiance influence supply and demand for electricity. However, previous research falls short in addressing the risks that joint uncertainties in these processes pose in power systems and wholesale electricity markets. Limiting challenges have included the large areal extents of power systems, high temporal resolutions (hourly or sub-hourly), and the data volumes and computational intensities required. This paper introduces an open source modeling framework for evaluating risks from correlated hydrometeorological processes in electricity markets at decision relevant scales. The framework is able to reproduce historical price dynamics in high profile systems, while also offering unique capabilities for stochastic simulation. Synthetic generation of weather and hydrologic variables is coupled with simulation models of relevant infrastructure (dams, power plants). Our model will allow the role of hydrometeorological uncertainty (including compound extreme events) on electricity market outcomes to be explored using publicly available models.
... Electricity generation requires water resources to drive turbines in hydroelectric dams and to cool thermoelectric power plants that are fueled by nuclear, coal or natural gas. This dependence on water makes the electricity sector vulnerable to droughts (van Vliet et al 2012, 2016b, Bartos and Chester 2015, Voisin et al 2016, Gleick 2017, Hardin et al 2017, Miara et al 2017, Eyer and Wichman 2018. ...
... The increased use of fossil fuel power plants for peak generation induced by droughts may last from months to years, which can lead to significant increases in pollutant emissions from the electricity sector (Gleick 2017, Hardin et al 2017, Eyer and Wichman 2018. In addition, decreased in-state electricity generation due to droughts may increase the need to import electricity from neighboring states (van Vliet et al 2013, Voisin et al 2016), potentially causing remote increases in pollution. ...
... Recent plant-scale econometric analyses found a positive relationship between water scarcity and emissions from the US electricity sector (Eyer and Wichman 2018), and for the recent California drought (Gleick 2017, Hardin et al 2017. Eyer and Wichman (2018) found that in the Western Interconnection, (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015) of in-state net-generation from hydropower, natural gas, coal, nuclear, petroleum, and solar and wind (combined); and average yearly deficits and surplus of in-state electricity generation compared to total electricity sales. ...
Water is needed for hydroelectric generation and to cool thermoelectric power plants. This dependence on water makes electricity generation vulnerable to droughts. Furthermore, because power sector CO2 emissions amount to approximately one third of total US emissions, droughts could influence the inter- annual variability of state- and national-scale emissions. However, the magnitude of drought-induced changes in power sector emissions is not well understood, especially in the context of climate mitigation policies. Using multivariate linear regressions, we find that droughts are positively correlated to increases in electricity generation from natural gas in California, Idaho, Oregon, and Washington; and from coal in Colorado, Montana, Oregon, Utah, Washington, and Wyoming. Using a statistical model, we estimate that this shift in generation sources led to total increases in regional emissions of 100 Mt of CO2, 45 kt of SO2, and 57 kt of NOx from 2001 to 2015, most of which originated in California, Oregon, Washington, and Wyoming. The CO2 emissions induced by droughts in California, Idaho, Oregon, and Washington amounted to 7%–12% of the total CO2 emissions from their respective power sectors, and the yearly rates were 8%–15% of their respective 2030 yearly targets outlined in the Clean Power Plan (CPP). Although there is uncertainty surrounding the CPP, its targets provide appropriate reference points for climate mitigation goals for the power sector. Given the global importance of hydroelectric and thermoelectric power, our results represent a critical step in quantifying the impact of drought on pollutant emissions from the power sector—and thus on mitigation targets—in other regions of the world.
... Another open question from the 2012-2016 drought has to do with the role of the state's growing reliance on variable renewable energy (wind and solar) in mitigating the environmental impacts of drought. In particular, the substitution of natural gas generation for hydropower during drought is known to increase carbon dioxide (CO 2 ) emissions in California (Fulton and Cooley 2015, Hardin et al 2017, Herrera-Estrada et al 2018. Previous studies have pointed to the state's growing fleet of wind and solar capacity as a counterbalancing force that was able to mitigate increases in CO 2 emissions that would have occurred during the 2012-2016 drought due to a loss of hydropower (Hardin et al 2017, Zohrabian and Sanders 2018, He et al 2019. ...
... In particular, the substitution of natural gas generation for hydropower during drought is known to increase carbon dioxide (CO 2 ) emissions in California (Fulton and Cooley 2015, Hardin et al 2017, Herrera-Estrada et al 2018. Previous studies have pointed to the state's growing fleet of wind and solar capacity as a counterbalancing force that was able to mitigate increases in CO 2 emissions that would have occurred during the 2012-2016 drought due to a loss of hydropower (Hardin et al 2017, Zohrabian and Sanders 2018, He et al 2019. In fact, carbon dioxide (CO 2 ) emissions from California's electric power sector actually decreased over the years 2012-2016 (California Air Resources Board 2019). ...
Over the period 2012–2016, the state of California in the United States (U.S.) experienced a drought considered to be one of the worst in state history. Drought’s direct impacts on California’s electric power sector are understood. Extremely low streamflow manifests as reduced hydropower availability, and if drought is also marked by elevated temperatures, these can increase building electricity demands for cooling. Collectively, these impacts force system operators to increase reliance on natural gas power plants, increasing market prices and emissions. However, previous investigations have relied mostly on ex post analysis of observational data to develop estimates of increases in costs and carbon dioxide (CO 2 ) emissions due to the 2012–2016 drought. This has made it difficult to control for confounding variables (e.g. growing renewable energy capacity, volatile natural gas prices) in assessing the drought’s impacts. In this study, we use a power system simulation model to isolate the direct impacts of several hydrometeorological phenomena observed during the 2012–2016 drought on system wide CO 2 emissions and wholesale electricity prices in the California market. We find that the impacts of drought conditions on wholesale electricity prices were modest (annual prices increased by $0–3 MWh ⁻¹ , although much larger within-year increases are also observed). Instead, it was an increase in natural gas prices, punctuated by the 2014 polar vortex event that affected much of the Eastern U.S., which caused wholesale electricity prices to increase during the drought. Costs from the drought were very different for the state’s three investor owned utilities. Overall, we find that increased cooling demands (electricity demand) during the drought may have represented a larger economic cost ($3.8 billion) than lost hydropower generation ($1.9 billion). We also find the potential for renewable energy to mitigate drought-cased increases in CO 2 emissions to be negligible, standing in contrast to some previous studies.
... Conventional water supplies may be supplemented by nonconventional sources such as desalination of seawater or brackish water, importation of water from adjacent regions, or reuse of treated wastewater (Grant et al., 2013;Gude, 2016). While desalination and imported water are already used to augment potable water supplies, they are associated with high and rising energy costs, a significant greenhouse gas (GHG) footprint, and other environmental concerns (Hardin et al., 2017;Shahabi et al., 2017;Stokes et al., 2014;Tarroja et al., 2014b;Zhou et al., 2014). Treated wastewater has most commonly been used for non-potable purposespartially due to challenges associated with public acceptability (Dolnicar et al., 2011;Hering et al., 2013;WWAP, 2017). ...
... Further possible extensions of WaterSET include scenario-based analysis modelling seasonal or long-term changes in the electricity mix (Hardin et al., 2017;Stokes and Horvath, 2009), simulating the impacts of climate change on chemical and energy requirements of water supply (Mo et al., 2016), as well as optimisation of the overall water supply mix encompassing multiple WSOs (Stokes et al., 2015). Consideration of net impacts of water treatment trains would ideally consider the full urban water cycle including topographic effects, the potential for offsets in pumping of conventional water, and a detailed inclusion of different wastewater treatment stages. ...
... This coincides with severe drought conditions repeatedly experienced in this region. Starting approximately in the 1990s, large parts of the South-Western United States, and in particular the South of California, started to encounter exceptional drought conditions [55,56]. A most recent drought period started in 2011/2012 and is estimated to represent the worst cumulative rainfall deficit on record, resulting in reduced generation of hydroelectricity [57] and a subsequent boost of CO 2 emissions due to increasing consumption of natural gas [55], diminished snowpack, and reduced water levels in the Colorado River as well as in Lake Mead and Lake Powell reservoirs [56]. ...
... Starting approximately in the 1990s, large parts of the South-Western United States, and in particular the South of California, started to encounter exceptional drought conditions [55,56]. A most recent drought period started in 2011/2012 and is estimated to represent the worst cumulative rainfall deficit on record, resulting in reduced generation of hydroelectricity [57] and a subsequent boost of CO 2 emissions due to increasing consumption of natural gas [55], diminished snowpack, and reduced water levels in the Colorado River as well as in Lake Mead and Lake Powell reservoirs [56]. Both reservoirs feed large urban agglomerations, e.g., the rapidly growing Phoenix metropolitan area with an approximate population of 4.5 Mio in 2015, and projected 6.8 Mio in 2040 and 7.7 Mio in 2050 [58]. ...
Over the 20th century, urbanization has substantially shaped the surface of Earth. With population rapidly shifting from rural locations towards the cities, urban areas have dramatically expanded on a global scale and represent crystallization points of social, cultural and economic assets and activities. This trend is estimated to persist for the next decades, and particularly the developing countries are expected to face rapid urban growth. The management of this growth will require good governance strategies and planning. By threatening the livelihoods, assets and health as foundations of human activities, another major global change contributor, climate change, became an equally important concern of stakeholders. Based on the climate trends observed over the 20th century, and a spatially explicit model of urbanization, this paper investigates the impacts of climate change in relation to different stages of development of urban areas, thus evolving a more integrated perspective on both processes. As a result, an integrative measure of climate change trends and impacts is proposed and estimated for urban areas worldwide. We show that those areas facing major urban growth are to a large extent also hotspots of climate change. Since most of these hotspots are located in the Global South, we emphasize the need for stakeholders to co-manage both drivers of global change. The presented integrative perspective is seen as a starting point to foster such co-management, and furthermore as a means to facilitate communication and knowledge exchange on climate change impacts.
... The energy footprint is the energy consumption directly or indirectly caused by an individual, organization, project, or production process [3]. The energy footprint has been increasingly used to measure the impact of human activities on global climate change [4][5][6]. The close link among the wealth gap, energy footprint inequality and energy poverty has been demonstrated [7][8][9]. ...
There are significant differences in energy footprints among individual households. This study uses an environmentally extended input-output approach to estimate the per capita household energy footprint (PCHEF) of 10 different income groups in China's 30 provinces and analyzes the heterogeneity of household consumption categories, and finally measures the energy equality of households in each province by measuring the energy footprint Gini coefficient (EF-Gini). It is found that the energy footprint of the top 10% income households accounted for about 22% of the national energy footprint in 2017, while the energy footprint of the bottom 40% income households accounted for only 24%. With the growth of China's economy, energy footprint inequality has declined spatially and temporally. Firstly, wealthier coastal regions have experienced greater convergence in their energy footprint than poorer inland regions. Secondly, China's household EF-Gini has declined from 0.38 in 2012 to 0.36 in 2017. This study shows that China's economic growth has not only raised household income levels, but also reduced energy footprint inequality.
... For the past 10 years, California has experienced an unprecedented period of drought (22), making the state highly prone to wildfires, most of which occur in the summer months. This presents a mechanism for fine particulate matter (PM 2.5 ) extremes to occur during a time of year when temperature extremes are prevalent, leading to increased chances of exposure to the occurrence of simultaneous extreme episodes. ...
... Drought also impacts the generation of hydroelectricity, a major source of power in California that depends on snowmelt runoff and rainfall. Reductions in hydroelectricity generation during the 2012-2016 drought increased state electricity costs and raised California's carbon footprint until a shift towards different renewable energy sources helped to offset the increased emissions (Gleick, 2016;Hardin et al., 2017;Herrera-Estrada et al., 2018;Szinai et al., 2020;Zohrabian and Sanders, 2018). ...
The Indicators of Climate Change in California report is prepared by the Office of Environmental Health Hazard Assessment (OEHHA) and documents observed changes in the state’s climate and its impacts. Indicators are scientific measurements that track trends and conditions relating to climate change. Collectively, the indicators portray a statewide picture of how climate change has been impacting the environment and people of California. Through these indicators, the report tells the state’s climate change story, starting with the human influences on climate, or “drivers,” followed by the changes in climate Californians have been experiencing, and then their consequences on the physical environment, on plant and animal species, and on human health.
The fourth edition of the report contains a new section highlighting how California Tribes have witnessed climate change. Eight Tribes provide accounts of their unique experiences. Information about OEHHA’s ongoing work with Tribes to document the impacts of climate change can be found here: https://oehha.ca.gov/climate-change/general-info/indicators-climate-change-impacts-california-tribes
Suggested citation:
Office of Environmental Health Hazard Assessment (OEHHA, 2022). Indicators of Climate Change in California, Fourth Edition, California Environmental Protection Agency, OEHHA.
... For the past 10 years, California has experienced an unprecedented period of drought (22), making the state highly prone to wildfires, most of which occur in the summer months. This presents a mechanism for fine particulate matter (PM 2.5 ) extremes to occur during a time of year when temperature extremes are prevalent, leading to increased chances of exposure to the occurrence of simultaneous extreme episodes. ...
Rationale:
Extremes of heat and particulate air pollution threaten human health and are becoming more frequent due to climate change. Understanding health impacts of co-exposure to extreme heat and air pollution is urgent.
Objectives:
To estimate association of acute co-exposure to extreme heat and ambient fine particulate matter (PM2.5) with all-cause, cardiovascular, and respiratory mortality in California from 2014-2019.
Methods:
We used a case-crossover study design with time-stratified matching using conditional logistic regression to estimate mortality associations with acute co-exposures to extreme heat and PM2.5. For each case day (date of death) and its control days, daily average PM2.5, maximum and minimum temperature were assigned (0-3-day lag) based on decedent's residence census tract.
Main results:
All-cause mortality risk increased 6.1% (95%confidence interval, CI: 4.1, 8.1) on extreme maximum temperature only days and 5.0% (95%CI: 3.0, 8.0) on extreme PM2.5 only days, compared to non-extreme days. Risk increased 21.0% (95%CI: 6.6, 37.3) on days with exposure to both extreme maximum temperature and PM2.5. Increased risk of cardiovascular and respiratory mortality on extreme co-exposure days was 29.9% (95%CI: 3.3, 63.3) and 38.0% (95%CI:-12.5, 117.7), respectively, and were more than the sum of individual effects of extreme temperature and PM2.5 only. A similar pattern was observed for co-exposure to extreme PM2.5 and minimum temperature. Effect estimates were larger over age 75 years.
Conclusion:
Short-term exposure to extreme heat and air pollution alone were individually associated with increased risk of mortality, but their co-exposure had larger effects beyond the sum of their individual effects. This article is open access and distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
... Hydrometeorology, including extreme events like droughts and heatwaves, is known to be a significant driver of emmisions from power plants 2 . This is especially true in California's electric power system. ...
Droughts reduce hydropower production and heatwaves increase electricity demand, forcing power system operators to rely more on fossil fuel power plants. However, less is known about how droughts and heat waves impact the county level distribution of health damages from power plant emissions. Using California as a case study, we simulate emissions from power plants under a 500-year synthetic weather ensemble. We find that human health damages are highest in hot, dry years. Communities of color and communities with high pollution burden are disproportionately impacted by increased emissions from power plants during droughts and heat waves. Taxing power plant operations based on each plant’s contribution to health damages significantly reduces average exposure. However, emissions taxes fail to reduce air pollution damages on the worst polluting days, becasuse supply scarcity (caused by severe heat waves) forces system operators to use every power plant available to avoid causing a blackout.
... Air temperatures (which influence heating and cooling demands) are the primary driver of day-to-day and seasonal changes in electricity demand [54]. By influencing both supply and demand for electricity, hydrometeorological processes can directly affect GHG emissions [52,61,65], wholesale electricity prices [52,66,67], and costs for power utilities and consumers [55,66,68,69]. Deeper understanding of the effects of hydrometeorological variability on power system operations can help inform operational decisionmaking and related agents. ...
Power grid operations increasingly interact with environmental systems and human systems such as transportation, agriculture, the economy, and financial markets. Our objective is to discuss the modelling gaps and opportunities to advance the science for multisector adaptation and tradeoffs. We focus on power system operational models, which typically represent key physical and economic aspects of grid operations over days to a year and assume a fixed power grid infrastructure. Due to computational burden, models are typically customized to reflect regional resource opportunities, data availability, and applications of interest. We conceptualize power system operational models with four core processes: physical grid assets (generation, transmission, loads, and storage), model objectives and purpose, institutions and decision agents, and performance metrics. We taxonomize the representations of these core processes based on a review of 23 existing models. Using science questions around grid and short term uncertainties, long term global change, and multisectoral technological innovation as examples, we report on tradeoffs in process fidelity and tractability that have been adopted by the research community to represent multisectoral interactions in power system operational models. Our recommendations for research directions are model-agnostic, focusing on core processes, their interactions with other human systems, and consider computational tradeoffs.
... The work by Chowdhury et al. (2021) facilitates an interesting discussion on the role of water resources management in electricity production and subsequent greenhouse gas emissions under hydrologic uncertainty. Chowdhury et al. (2021) compliment work regarding the electricity sector in California, which showed the 2012-2016 drought in California caused an estimated increase of carbon emissions by 10%-33% compared to predrought conditions (Gleick, 2015;Hardin et al., 2017;Kern et al., 2020). The drought in California resulted in reduced water availability, which impacted the production of hydroelectricity and forced increased reliance on carbon intensive fuel-based generation. ...
Water resources are required for cooling of thermoelectric power plants and in the production of hydroelectricity. Scarcity of water resources impacts the ability to generate electricity in grids across the globe. There is extensive literature and research on the electricity‐water nexus, spanning hydrology, policy, and energy sectors. Existing research often focuses on quantifying a static relationship and rarely accounts for expectations of annual, seasonal, and subseasonal water variability in nexus research. This omission leaves an important, unanswered question in the field: how can the water footprinting framework be operationalized in the electricity‐water nexus with hydroclimatic forecasts? Building off the work by Chowdhury et al. (https://doi.org/10.1029/2020EF001814), we comment on the opportunities for climate‐informed, seasonal, or subannual assessments of the electricity‐water nexus to facilitate decision‐making.
... VRE production is sensitive to fluctuations in wind speeds and solar irradiance(59,60), representing a growing concern as power systems increase their reliance on these resources(69,70). Air temperatures (which influence heating and cooling demands) are the primary driver of day-to-day and seasonal changes in electricity demand(64).By influencing both supply and demand for electricity, hydrometeorological processes can directly affect GHG emissions(60,65,71), wholesale electricity prices(60,72,73), and costs for power utilities and consumers(61,72,74,75)). Deeperunderstanding of the effects of hydrometeorological variability on power system operations can help inform operational decision-making and feed into long-term planning efforts in the power sector and other areas. The effects of hydrometeorological uncertainty on power system operations have been explored either by subjecting a deterministic power system model to an ensemble of exogenous weather-based stressors (34, 61, 76) or by embedding stochastic representations of generation and load within the optimization itself (77, 78) (Figure 3). ...
Power grid operations increasingly interact with environmental systems and human systems such as transportation, agriculture, the economy, and financial markets. Our objective is to discuss the modelling gaps and opportunities to advance the science for multisector adaptation and tradeoffs. We focus on power system operational models, which typically represent key physical and economic aspects of grid operations over days to a year and assume a fixed power grid infrastructure. Due to computational burden, models are typically customized to reflect regional resource opportunities, data availability, and applications of interest. While there are model intercomparison papers, there is however no model-agnostic characterization and systematic overview of the state-of-the-art process representations in operational power system models. To address our objective, we conceptualize power system operational models with four core processes: physical grid assets (generation, transmission, loads, and storage), model objectives and purpose, institutions and decision agents, and performance metrics. We taxonomize the representations of these core processes based on a review of 23 existing open-source and commercial models. As we acknowledge the computational burden of certain representations, we leverage this taxonomy to describe tradeoffs in process fidelity and tractability that have been adopted by the research community to address interactions between the power grid and hydrometeorological uncertainties, global change, and/or technological innovation. The core process taxonomy along with the existing computational tradeoffs are used to identify technical gaps and recommend future model development needs and research directions to better represent power grid operations as part of integrated multisector dynamics modeling and interdisciplinary research.
... Recent droughts foreshadow how the state's energy-water nexus may fare under these impacts of climate change [19]. California's water sector's drought responses transferred and compounded vulnerability to its electricity sector-increased groundwater pumping spiked electricity consumption, while hydropower deficits were replaced by greenhouse gas (GHG)emitting fossil generation [37,42]. In addition, the state has already seen several unprecedented climaterelated impacts to the electricity grid, such as the August 2020 West-wide heat wave that triggered California's rolling blackouts [43]. ...
Electricity and water systems are inextricably linked through water demands for energy generation, and through energy demands for using, moving, and treating water and wastewater. Climate change may stress these interdependencies, together referred to as the energy-water nexus, by reducing water availability for hydropower generation and by increasing irrigation and electricity demand for groundwater pumping, among other feedbacks. Further, many climate adaptation measures to augment water supplies—such as water recycling and desalination—are energy-intensive. However, water and electricity system climate vulnerabilities and adaptations are often studied in isolation, without considering how multiple interactive risks may compound. This paper reviews the fragmented literature and develops a generalized framework for understanding these implications of climate change on the energy-water nexus. We apply this framework in a case study to quantify end-century direct climate impacts on California's water and electricity resources and estimate the magnitude of the indirect cross-sectoral feedback of electricity demand from various water adaptation strategies. Our results show that increased space cooling demand and decreased hydropower generation are the most significant direct climate change impacts on California's electricity sector by end-century. In California's water sector, climate change impacts directly on surface water availability exceed demand changes, but have considerable uncertainty, both in direction and magnitude. Additionally, we find that the energy demands of water sector climate adaptations could significantly affect California's future electricity system needs. If the worst-case water shortage occurs under climate change, water-conserving adaptation measures can provide large energy savings co-benefits, but other energy-intensive water adaptations may double the direct impacts of climate change on the state's electricity resource requirement. These results highlight the value of coordinated adaptation planning between the energy and water sectors to achieve mutually beneficial solutions for climate resilience.
... For instance, a sound FEW nexus analysis can remediate the intertwined issues of local air pollution, urban heat island (UHI) effect, regional air pollution, and global climate change, which are directly related to fossil derived fuels combustion for energy supply and transportation in urban areas. Interdisciplinary sustainability solutions in a sustainable city for counteracting different scales of such impacts can, in turn, mitigate climate change impacts on regional water, carbon, and ecosystem footprints that can affect water supplies directly and food production indirectly (Bibri, 2018;Chang et al., 2020a, 2020b, Hardin et al., 2017Tsolakis & Anthopoulos, 2015). ...
The integration of food-energy-water (FEW) sectors is essential for addressing the co-evolution of urban infrastructure systems during urban growth. But how these evolutionary pathways can affect an urban growth model is unclear. This review paper offers a synthesis of the current philosophy of a FEW nexus in connection with the realm of urban growth models (UGMs) to signify the paradigm collision and shift with interdisciplinary sustainability insights. Findings indicate that urban metabolism and urban ecology in relation to FEW sectors can be incorporated into UGMs with scales via multi-criteria decision analysis as FEW technology hub integration can play a critical role in UGMs via a common cellular automata (CA) architecture for both model construction and solution procedure. Synergies between FEW sectors and CA-based UGMs as well as tradeoffs across FEW technology hub integration are highlighted to reflect the cascade effects and higher order impact on urban metabolism and urban ecology. This concept was confirmed with a case study in Miami, Florida, the United States for demonstration.Such synergistic framework is helpful for fostering more sustainable, green,smart,forward-looking, environmentally-sound, socially equitable, risk-informed, resilient,and cost-effective urban growth simulations. It is anticipated that the proposed hybrid FEW-CA-based UGMs can fully account for interactions of context-and culture-driven issues for multi-scale and multi-agent urban planning and design in different countries.
... They reported that this relation might be due to cheap and wasteful energy use in this sector. Likewise, high energy consumption, particularly electricity in the agricultural sector will increase the vulnerability of the electric power industry and increasing electricity production is to be linked with enhanced greenhouse gas emissions (Hardin et al., 2017). In the same vein, Mirzaei et al. (2019) stated that increasing energy consumption underscore dysfunctional feedback relations between agricultural water and energy price and groundwater withdrawal in an inefficient agronomic sector. ...
The increasing demands of the population and the need for development obliged the optimal use and adaptive management of the watershed resources. Accordingly, it is necessary to adopt comprehensive measures to reach sustainable development goals. This objective can be achieved by the application of interdisciplinary and professional approaches through establishing dynamic and optimal balance in supply and demand resources. However, such important optimization approaches have been rarely practiced at the watershed scale. The present study has been therefore formulated to apply a linear water-energy-food nexus optimization for the Shazand watershed, Markazi Province, Iran. This approach was applied for planning 14 crops planted in orchard, irrigated farms, and rain-fed farms, between 2006 and 2014, and targeting water-energy-food nexus index (WEFNI) maximization. The connections among the water, energy, and food were then evaluated through determining the amount of consumption, mass productivity, and economic productivity of water and energy. The results of WEFNIs revealed that almond has the highest WEFNI with values of 0.92, 0.76, 0.76, 0.83, 0.86, 0.86, 0.87, 0.87, and 0.88. Whilst, potato with WEFNI of 0.05, 0.05, 0.05, 0.06, 0.09, 0.10 and 0.11, sugar cane with WEFNI of 0.10 and cucumber with WEFNI of 0.13 had the lowest scores and the corresponding lowest performance among the study crops. The outcomes of optimization study explained that the current situation of land use in the Shazand Watershed is unsuitable to minimize water and energy consumption and maximize benefit. The results can be used as an effective tool for designating proper soil and water resource management strategies in the region.
... They reported that this relation might be due to cheap and wasteful energy use in this sector. Likewise, high energy consumption, particularly electricity in the agricultural sector will increase the vulnerability of the electric power industry and increasing electricity production is to be linked with enhanced greenhouse gas emissions (Hardin et al., 2017). In the same vein, Mirzaei et al. (2019) stated that increasing energy consumption underscore dysfunctional feedback relations between agricultural water and energy price and groundwater withdrawal in an inefficient agronomic sector. ...
The increasing demands of the population and the need for development obliged the optimal use and adaptive management of the watershed resources. Accordingly, it is necessary to adopt comprehensive measures to reach sustainable development goals. This objective can be achieved by the application of interdisciplinary and professional approaches through establishing dynamic and optimal balance in supply and demand resources. However, such important optimization approaches have been rarely practiced at the watershed scale. The present study has been therefore formulated to apply a linear water-energy-food nexus optimization for the Shazand watershed, Markazi Province, Iran. This approach was applied for planning 14 crops planted in orchard, irrigated farms, and rain-fed farms, between 2006 and 2014, and targeting water-energy-food nexus index (WEFNI) maximization. The connections among the water, energy, and food were then evaluated through determining the amount of consumption, mass productivity, and economic productivity of water and energy. The results of WEFNIs revealed that almond has the highest WEFNI with values of 0.92, 0.76, 0.76, 0.83, 0.86, 0.86, 0.87, 0.87, and 0.88. Whilst, potato with WEFNI of 0.05, 0.05, 0.05, 0.06, 0.09, 0.10 and 0.11, sugar cane with WEFNI of 0.10 and cucumber with WEFNI of 0.13 had the lowest scores and the corresponding lowest performance among the study crops. The outcomes of optimization study explained that the current situation of land use in the Shazand Watershed is unsuitable to minimize water and energy consumption and maximize benefit. The results can be used as an effective tool for designating proper soil and water resource management strategies in the region.
... They reported that this relation might be due to cheap and wasteful energy use in this sector. Likewise, high energy consumption, particularly electricity in the agricultural sector will increase the vulnerability of the electric power industry and increasing electricity production is to be linked with enhanced greenhouse gas emissions (Hardin et al., 2017). In the same vein, Mirzaei et al. (2019) stated that increasing energy consumption underscore dysfunctional feedback relations between agricultural water and energy price and groundwater withdrawal in an inefficient agronomic sector. ...
... In California, utilities increased fossil fuel generation of electricity to compensate for the drought-driven decline in hydroelectricity, increasing state carbon dioxide emissions in the first year of the drought (2011 to 2012) by 1.8 million tons of carbon, the equivalent of emissions from roughly 1 million cars. 338,339 A drop in the price of natural gas also contributed to the increase, although the shift from hydroelectric to fossil fuels cost California an estimated $2.0 billion (in 2015 dollars). 340 Other southwestern states also shifted some generation from hydropower to fossil fuels. ...
... This will likely increase the vulnerability of the electric power industry, which should prepare to absorb the additional agricultural energy load. In addition, increased electricity production is likely to be associated with increased greenhouse gas emissions (as observed in other parts of the world, e.g., California [50]). From a long-term sustainability perspective, however, it is critical to recognize the extensive and widespread groundwater table decline as a serious warning signal to implement adaptive agricultural water management measures to mitigate, or better yet, prevent future socioeconomic repercussions (e.g., job losses) associated with exhausting high-quality or marginal-quality groundwater. ...
This paper presents the first groundwater‒energy‒food (GEF) nexus study of Iran’s agronomic crops based on national and provincial datasets and firsthand estimates of agricultural groundwater withdrawal. We use agronomic crop production, water withdrawal, and energy consumption data to estimate groundwater withdrawal from electric-powered irrigation wells and examine agronomic productivity in Iran’s 31 provinces through the lens of GEF nexus. The ex-post GEF analysis sheds light on some of the root causes of the nation’s worsening water shortage problems. Access to highly subsidized water (surface water and groundwater) and energy has been the backbone of agricultural expansion policies in Iran, supporting employment in agrarian communities. Consequently, water use for agronomic crop production has greatly overshot the renewable water supply capacity of the country, making water bankruptcy a serious national security threat. Significant groundwater table decline across the country and increasing energy consumption underscore dysfunctional feedback relations between agricultural water and energy price and groundwater withdrawal in an inefficient agronomic sector. Thus, it is essential to implement holistic policy reforms aimed at reducing agricultural water consumption to alleviate the looming water bankruptcy threats, which can lead to the loss of numerous agricultural jobs in the years to come.
... The projected hydrological impacts on surface water reservoirs can affect the ability of hydropower plants to counterbalance wind and solar variability. The reduction or absence of hydropower resources may result in the increased reliance on available conventional natural gas power plants to balance electric loads and generation, which occurred during the recent 2015 drought [17]. ...
This study investigates how hydropower generation under climate change affects the ability of the electric grid to integrate high wind and solar capacities. Using California as an example, water reservoir releases are modeled as a function of hydrologic conditions in the context of a highly-renewable electric grid in the year 2050. The system is perturbed using different climate models under the Representative Concentration Pathway 8.5 climate scenario. The findings reveal that climate change impact on hydropower can increase greenhouse gas emissions up to 8.1% due to increased spillage of reservoir inflow reducing hydropower generation, but with minimal effects (<1%) on renewable utilization and levelized cost of electricity. However, increases in dispatchable power plant capacity of +2.1 to +6.3% and decreases in the number of start-up events per power plant unit up to 3.1%, indicate that the majority of dispatchable natural gas power plant capacity is offline for most of the climate change scenarios. While system-wide performance metrics experience small impacts, climate change effects on hydropower generation increase both the need for dispatchable generation and the costs of electricity from these power plants to support large-scale wind and solar integration on the electric grid.
... This followed the Federal Energy Policy Act (FEPA) of 2005, which called for the development of at least 10,000 megawatts of renewable energy generation on public lands by 2015. Due to these pieces of legislation, and other policy and economic incentives [1,2], solar and wind power generation in California has increased relatively rapidly (by 270%) since 2011 [3]. As covered 400,000 km 2 of land, more than in Germany and 188 other countries [4]. ...
In 2010, The Nature Conservancy completed the Mojave Desert Ecoregional Assessment, which characterizes conservation values across nearly 130,000 km² of the desert Southwest. Since this assessment was completed, several renewable energy facilities have been built in the Mojave Desert, thereby changing the conservation value of these lands. We have completed a new analysis of land use to reassess the conservation value of lands in two locations in the Mojave Desert where renewable energy development has been most intense: Ivanpah Valley, and the Western Mojave. We found that 99 of our 2.59-km² planning units were impacted by development such that they would now be categorized as having lower conservation value, and most of these downgrades in conservation value were due to solar and wind development. Solar development alone was responsible for a direct development footprint 86.79 km²: 25.81 km² of this was primarily high conservation value Bureau of Land Management lands in the Ivanpah Valley, and 60.99 km² was privately owned lands, mostly of lower conservation value, in the Western Mojave. Our analyses allow us to understand patterns in renewable energy development in the mostly rapidly changing regions of the Mojave Desert. Our analyses also provide a baseline that will allow us to assess the effectiveness of the Desert Renewable Energy Conservation Plan in preventing development on lands of high conservation value over the coming decades.
... Climate change is projected to shift the temporal and spatial availability of water across the globe (IPCC 2013). Shifts in regional hydrology may have significant impacts on electricity generation dispatch, electric grid reliability, and regional emissions (Hardin et al. 2017). In California, where hydroelectric capacity mainly resides in the Sierra Nevada, inflow to reservoirs has historically been regulated by the melting snowpack. ...
Climate change is expected to significantly reshape hydropower generation in California. However, the impact on the ability of hydropower to provide reserve capacity that can provide on-demand, back-up electricity generation to stabilize the grid in the case of a contingency has not been explored. This study examined the impact of climate change-driven hydrologic shifts on hydropower contributions to generation and ancillary services. We used projections from four climate models under Representative Concentration Pathways (RCP) RCP4.5 and RCP8.5 to evaluate the impact of climate change conditions, comparing the future period 2046–2055 to the baseline 2000–2009, and observed a net increase of inflow into large hydropower units in northern California. However, as extreme events yield greater spillage, increased overall inflow did not necessarily yield increased generation. Additionally, higher winter generation and summer reservoir constraints resulted in decreases in the spinning reserve potential for both RCP scenarios. We also examined a regionally downscaled “long drought” scenario under RCP8.5 to assess the impact of an extended dry period on generation and spinning reserve bidding. The long drought scenario, developed as part of the California 4th Climate Assessment, involves rainfall congruent with 20-year historical dry spells in California under increased temperatures. In addition to decreased generation, the long drought scenario yielded a 41% reduction in spinning reserve bidding tied to a decline in reservoir levels. The decreased spinning reserve bidding from hydropower may require increased reliance on other electricity resources that can provide the same dynamic support to maintain grid stability under climate change.
... In recent years, California has experienced a series of flooding events (Vahedifard et al., 2017) on the heels of a 5-year drought (e.g., AghaKouchak et al., 2014;Hardin et al., 2017;Shukla et al., 2015). In 2017, a major flood in Northern California led to structural failure of Oroville Dam's spillway that triggered the evacuation of about 200,000 people. ...
In this study, we investigate changes in future streamflows in California using bias-corrected and routed streamflows derived from global climate model (GCM) simulations under two representative concentration pathways (RCPs): RCP4.5 and RCP8.5. Unlike previous studies that have focused mainly on the mean streamflow, annual maxima or seasonality, we focus on projected changes across the distribution of streamflow and the underlying causes. We report opposing trends in the two tails of the future streamflow simulations: lower low flows and higher high flows with no change in the overall mean of future flows relative to the historical baseline (statistically significant at 0.05 level). Furthermore, results show that streamflow is projected to increase during most of the rainy season (December to March) while it is expected to decrease in the rest of the year (i.e., wetter rainy seasons, and drier dry seasons). We argue that the projected changes to streamflow in California are driven by the expected changes to snow patterns and precipitation extremes in a warming climate. Changes to future low flows and extreme high flows can have significant implications for water resource planning, drought management, and infrastructure design and risk assessment.
... Affluence and trade openness cause to increase and decrease in energy consumption, respectively. The study by Hardin et al. (2017) shows that drought can significantly increase the speed of CO 2 emissions in the energy sector. Rafindadi and Ozturk (2017) illustrate that there is a relationship 2 Middle East and North Africa 3 Middle East and North Africa region 4 Greenhouse gas 5 Gulf Cooperation Council countries 6 Environmental Kuznets Curve 7 Association of South East Asian Nations between consumption of renewable energy and economic growth. ...
Iran should pay special attention to its excessive consumption of energy and air pollution due to the limited availability of water resources. This study explores the effects of the consumption of energy and water resources on air pollution in Iran from 1971 to 2014. It utilizes the non-linear autoregressive distributed lag approach to establish a robust relationship between the variables which show that both long- and short-run coefficients are asymmetrical. The positive and negative aspects of the long-run coefficients of energy consumption and water resources were found to be 0.19, − 1.63, 0.18, and 2.36, respectively, while only the negative ones were significant for energy consumption. Based on the cumulative effects, it can be established that there are important and significant differences in the responses of air pollution to positive and negative changes in water productivity and energy consumption. In particular, CO2 gas emissions are affected by negative changes in H2O productivity both in terms of the total and the GDP per unit of energy use in Iran. In regard to short-run results, considerable asymmetric effects occur on all the variables for CO2 emissions. Based on the results obtained, some recommendations are presented, which policymakers can adopt in efforts to address the issues of pollution and consumption.
... The opposite is also plausible; heavy rains in the arid west of the United States connected to the 1997-1998 El Niño event are thought to have contributed to increased hydropower output, leading to reduced energy costs (Changnon 1999). Although regional impact may be relatively small, the cumulative impact can be staggering (Hardin et al 2017), especially when multiple regions are affected by ENSO simultaneously. The scale of these impacts is likely to depend on both the magnitude of the hydropower production shortfall and the relative importance of hydropower in regional energy supplies. ...
El Niño Southern Oscillation (ENSO) strongly influences the global climate system, affecting hydrology in many of the world's river basins. This raises the prospect of ENSO-driven variability in global and regional hydroelectric power generation. Here we study these effects by generating time series of power production for 1593 hydropower dams, which collectively represent more than half of the world's existing installed hydropower capacity. The time series are generated by forcing a detailed dam model with monthly-resolution, 20th century inflows - the model includes plant specifications, storage dynamics and realistic operating schemes, and runs irrespectively of the dam construction year. More than one third of simulated dams exhibit statistically significant annual energy production anomalies in at least one of the two ENSO phases of El Niño and La Niña. For most dams, the variability of relative anomalies in power production tends to be less than that of the forcing inflows - a consequence of dam design specifications, namely maximum turbine release rate and reservoir storage, which allows inflows to accumulate for power generation in subsequent dry years. Production is affected most prominently in Northwest United States, South America, Central America, the Iberian Peninsula, Southeast Asia and Southeast Australia. When aggregated globally, positive and negative energy production anomalies effectively cancel each other out, resulting in a weak and statistically insignificant net global anomaly for both ENSO phases.
The western United States has experienced severe drought in recent decades, and climate models project increased drought risk in the future. This increased drying could have important implications for the region's interconnected, hydropower-dependent electricity systems. Using power-plant level generation and emissions data from 2001 to 2021, we quantify the impacts of drought on the operation of fossil fuel plants and the associated impacts on greenhouse gas (GHG) emissions, air quality, and human health. We find that under extreme drought, electricity generation from individual fossil fuel plants can increase up to 65% relative to average conditions, mainly due to the need to substitute for reduced hydropower. Over 54% of this drought-induced generation is transboundary, with drought in one electricity region leading to net imports of electricity and thus increased pollutant emissions from power plants in other regions. These drought-induced emission increases have detectable impacts on local air quality, as measured by proximate pollution monitors. We estimate that the monetized costs of excess mortality and GHG emissions from drought-induced fossil generation are 1.2 to 2.5x the reported direct economic costs from lost hydro production and increased demand. Combining climate model estimates of future drying with stylized energy-transition scenarios suggests that these drought-induced impacts are likely to remain large even under aggressive renewables expansion, suggesting that more ambitious and targeted measures are needed to mitigate the emissions and health burden from the electricity sector during drought.
In recent years, the Mojave Desert, which is known for its unique and endemic plant and animal diversity, has become a preferred area for renewable energy developments. However, an environmental impact that is not calculated into the production of green energy has emerged that not only puts an additional burden on already endangered species but also affects the quality of life for residents living in disadvantaged and underserved communities. Using the example of just another solar farm to be built on 2,300 acres of pristine desert land, we point out the negative impacts of unsustainable land development on community health and environmental justice, driven by the administration of Kern County, which promotes and prioritizes economic growth over residents’ concerns. In the eyes of the local population, several promises by the County to the community, as documented in the 2017–2020 County of Kern Strategic Goals, were broken. This study investigates the effects of unsustainable land development, particularly the threat to iconic Joshua trees (Yucca brevifolia), the increase in PM10 pollution, and the risk of contracting Valley fever for residents of two small desert communities, Boron, and Desert Lakes, in Kern County, California. This study focused on environmental justice issues due to the implementation of an ambitious renewable energy transition plan supported by the administration. This is the first study that documented the presence of the causative agent of Valley fever in soils to be disturbed for ambitious renewable energy development in eastern Kern County using a molecular, culture-independent, approach.
Droughts reduce hydropower production and heatwaves increase electricity demand, forcing power system operators to rely more on fossil fuel power plants. However, less is known about how droughts and heat waves impact the county level distribution of health damages from power plant emissions. Using California as a case study, we simulate emissions from power plants under a 500-year synthetic weather ensemble. We find that human health damages are highest in hot, dry years. Counties with a majority of people of color and counties with high pollution burden (which are somewhat overlapping) are disproportionately impacted by increased emissions from power plants during droughts and heat waves. Taxing power plant operations based on each plant’s contribution to health damages significantly reduces average exposure. However, emissions taxes do not reduce air pollution damages on the worst polluting days, because supply scarcity (caused by severe heat waves) forces system operators to use every power plant available to avoid causing a blackout.
The ambition and effectiveness of climate policies will be essential in determining greenhouse gas emissions and, as a consequence, the scale of climate change impacts1,2. However, the socio-politico-technical processes that will determine climate policy and emissions trajectories are treated as exogenous in almost all climate change modelling3,4. Here we identify relevant feedback processes documented across a range of disciplines and connect them in a stylized model of the climate–social system. An analysis of model behaviour reveals the potential for nonlinearities and tipping points that are particularly associated with connections across the individual, community, national and global scales represented. These connections can be decisive for determining policy and emissions outcomes. After partly constraining the model parameter space using observations, we simulate 100,000 possible future policy and emissions trajectories. These fall into 5 clusters with warming in 2100 ranging between 1.8 °C and 3.6 °C above the 1880–1910 average. Public perceptions of climate change, the future cost and effectiveness of mitigation technologies, and the responsiveness of political institutions emerge as important in explaining variation in emissions pathways and therefore the constraints on warming over the twenty-first century. A stylized model of the climate–social system could help to understand policy and emissions futures.
During the 2011 drought, Texas electricity prices rose as generators with water intensive cooling technologies cut back production. We investigate the effect of exceptional drought on electricity supply and emissions using a fixed-effects model on intra-hourly ERCOT data from 2010 to 2017. We find that the effect of exceptional drought on electricity supply varies with the cooling technology type used by the generator. Generators with water-intensive cooling technologies respond to exceptional drought conditions by raising their average offer prices. However, generators that use dry cooling technologies do not raise offer prices but do increase the total quantity offer during exceptional drought periods. These changes in offer prices lead to lower emissions plants being dispatched during exceptional drought in ERCOT. Given that exceptional drought intensity and duration are forecasted to increase over the coming decades, our findings provide valuable insights for state policymakers seeking to regulate the electricity market in our study area.
Traditional, mainstream definitions of drought describe it as deficit in water-related variables or water-dependent activities (e.g., precipitation, soil moisture, surface and groundwater storage, and irrigation) due to natural variabilities that are out of the control of local decision-makers. Here, we argue that within coupled human-water systems, drought must be defined and understood as a process as opposed to a product to help better frame and describe the complex and interrelated dynamics of both natural and human-induced changes that define anthropogenic drought as a compound multidimensional and multiscale phenomenon, governed by the combination of natural water variability, climate change, human decisions and activities, and altered micro-climate conditions due to changes in land and water management. This definition considers the full spectrum of dynamic feedbacks and processes (e.g., land-atmosphere interactions and water and energy balance) within human-nature systems that drive the development of anthropogenic drought. This process magnifies the water supply demand gap and can lead to water bankruptcy, which will become more rampant around the globe in the coming decades due to continuously growing water demands under compounding effects of climate change and global environmental degradation. This challenge has de facto implications for both short-term and long-term water resources planning and management, water governance, and policymaking. Herein, after a brief overview of the anthropogenic drought concept and its examples, we discuss existing research gaps and opportunities for better understanding, modeling, and management of this phenomenon.
Hydrometeorological conditions influence the operations of bulk electric power systems and wholesale markets for electricity. Streamflow is the “fuel” for hydropower generation, wind speeds and solar irradiance dictate the availability of wind and solar power production, and air temperatures strongly affect heating and cooling demands. Despite growing concern about the vulnerability of power systems to hydrometeorological uncertainty, including “compound” extremes (multiple extremes occurring simultaneously), quantifying baseline probabilistic risks remains difficult even without factoring in climate change. Here, we use newly developed power system simulation software to show how uncertainties in spatially and temporally correlated hydrometeorological processes affect market prices and greenhouse gas emissions in California’s wholesale electricity market. Results highlight the need for large synthetic datasets to access rare, yet plausible system states that have not occurred in the recent historical record. We find that time scale strongly controls which combinations of hydrometeorological variables cause extreme outcomes. Although scarcity caused by low streamflows and high air temperatures has long been considered a primary concern in Western power markets, market prices are more profoundly impacted by weather and streamflow conditions that lead to an overabundance of energy on the grid.
Characterizing the advantages and disadvantages of different electricity resource mixes in meeting electricity decarbonization goals is an active area of research. Many system-level assessments, however, evaluate different mixes on the basis of minimizing electricity costs without accounting for regional environmental externalities. California represents a highly populated region with both aggressive electricity decarbonization policies and water scarcity issues that are projected to worsen under climate change, representing an interesting case study for assessing the tradeoffs between the costs of electricity decarbonization and water resource consumption. This study therefore combines electric grid dispatch modeling and regional life cycle freshwater consumption data to compare in-state freshwater consumption and levelized cost of electricity for four electricity mix scenarios designed to achieve zero-carbon electricity in California by 2045, compliant with current law (California Senate Bill 100). In modeled scenarios, we find that the lowest costs occurred for mixes with lower energy storage capacity needs enabled by high capacity factor and dispatchable renewables. However these mixes also resulted in high freshwater consumption due largely to heavy reliance on geothermal resources. By contrast, the mix with the lowest freshwater consumption relied exclusively on wind, solar, and hydropower and reduced water consumption by an order of magnitude compared to that of the lowest cost mix. Due to lower capacity factors and greater difficulty in matching supply to demand (increasing energy storage needs), this mix increased the levelized cost of electricity by 30%. Overall, our results show that prioritizing low electricity costs as well as other climate-relevant criteria, such as freshwater consumption, in meeting zero-carbon electricity goals will result in a very different electricity mix than simply considering costs alone.
Generally, atmospheric evaporation demand (AED) shows a positive correlation with actual evaporation (AE) in the Yangtze River basin. In order to explore whether and why abnormal correlation exits in its five sub-basins, the temporal changes between AED and AE were compared, and then the impacts of climate change and human activities on abnormal correlations were assessed using the sensitivity method of Penman equation and the decomposition method of Budyko equation. The results indicated: (1) Pan evaporation and potential evaporation (indicators of AED) decreased at rates of up to -0.04 and -0.06 mm d⁻¹ decade⁻¹, respectively. In contrast, the water budget-derived evaporation (an indicator of AE) increased at the rate of 0.09 mm d⁻¹ decade⁻¹ in the Fuhe River basin and remained stable in other basins. Abnormal correlations (nonpositive correlations) were observed. (2) Decreasing net radiation and wind speed were major climate factors resulting in simultaneous temporal decreases in AED and AE. In contrast, afforestation was a major human factor leading to an increase in annual AE of 78 mm, but had no effect on AED. Afforestation was the primary driving force of the abnormal correlation. These results could provide water-energy guidance for urban climate change mitigation and flood/drought disaster management.
With recent advances in artificial intelligence (AI), built environment (BE) is getting more and more closely linked to energy. A macroscopic view of smart energy (SE) and smart built environment (SBE) is provided in this paper. Categories of smart energy systems (SESs) are divided according to the trade forms. Objectives of SBE include minimizing non-renewable energy to maintain sustainable BE, minimizing carbon exhausted to guarantee green BE, and minimizing capital cost to provide economically affordable BE. The transient fraction of power (FP) in SESs has to be controlled to obtain the optimal fraction of energy (FE). The optimal FE values depend not only on system size and time scales but also on SBE objectives. A weighted maximum volume criterion is proposed to take sustainability, green, and affordability into account. Results are compared with those optimization results based on a single objective. Methodologies for promotion of SESs from technology, system optimization, demand forecasting, and holistic design views are presented. The corresponding solution for SBE is illustrated. Challenges for future SESs for SBE are also discussed.
Ultra-low PtCu loading on carbon nanotubes (CNT) catalysts were synthesized by a novel galvanic displacement (GD) method under sonication conditions. The influence of the type of copper template, reaction time, and Pt concentration in the galvanic displacement bath and their correlation to electrocatalytic activity of the catalysts for oxygen reduction reaction in acidic media were studied. Among the catalysts synthesized, the best catalyst identified through electrochemical analysis was used to prepare Membrane Electrode Assembly and evaluated in a hydrogen fuel cell. The maximum power density of the PtCu/CNT and commercial catalyst (20% Pt/C) in the fuel cell were 452 mW cm⁻² at 0.424 V and 358 mW cm⁻² at 0.475 V, respectively, clearly showing the superior electrocatalytic capability of the PtCu/CNT catalyst synthesized in this study when compared with the commercial catalyst.
Iran is currently experiencing serious water problems. Frequent droughts coupled with over-abstraction of surface and groundwater through a large network of hydraulic infrastructure and deep wells have escalated the nation’s water situation to a critical level. This is evidenced by drying lakes, rivers and wetlands, declining groundwater levels, land subsidence, water quality degradation, soil erosion, desertification and more frequent dust storms. This paper overviews the major drivers of Iran’s water problems. It is argued that while climatic changes and economic sanctions are commonly blamed as the main drivers of water problems, Iran is mainly suffering from a socio-economic drought—i.e. “water bankruptcy,” where water demand exceeds the natural water supply. In theory, this problem can be resolved by re-establishing the balance between water supply and demand through developing additional sources of water supply and implementing aggressive water demand reduction plans. Nevertheless, the current structure of the water governance system in Iran and the absence of a comprehensive understanding of the root causes of the problem leave minimal hope of developing sustainable solutions to Iran’s unprecedented water problems.
California's current extreme drought must be a lesson for managing water in a warmer, more densely populated world, say Amir AghaKouchak and colleagues.
In the Southwest and Central Plains of Western North America, climate change is expected to increase drought severity in the coming decades. These regions nevertheless experienced extended Medieval-era droughts that were more persistent than any historical event, providing crucial targets in the paleoclimate record for benchmarking the severity of future drought risks. We use an empirical drought reconstruction and three soil moisture metrics from 17 state-of-the-art general circulation models to show that these models project significantly drier conditions in the later half of the 21st century compared to the 20th century and earlier paleoclimatic intervals. This desiccation is consistent across most of the models and moisture balance variables, indicating a coherent and robust drying response to warming despite the diversity of models and metrics analyzed. Notably, future drought risk will likely exceed even the driest centuries of the Medieval Climate Anomaly (1100-1300 CE) in both moderate (RCP 4.5) and high (RCP 8.5) future emissions scenarios, leading to unprecedented drought conditions during the last millennium.
Significance
California ranks first in the United States in population, economic activity, and agricultural value. The state is currently experiencing a record-setting drought, which has led to acute water shortages, groundwater overdraft, critically low streamflow, and enhanced wildfire risk. Our analyses show that California has historically been more likely to experience drought if precipitation deficits co-occur with warm conditions and that such confluences have increased in recent decades, leading to increases in the fraction of low-precipitation years that yield drought. In addition, we find that human emissions have increased the probability that low-precipitation years are also warm, suggesting that anthropogenic warming is increasing the probability of the co-occurring warm–dry conditions that have created the current California drought.
Climate change and climate variability, population growth, and land use change drive the need for new hydrologic knowledge and understanding. In the mountainous West and other similar areas worldwide, three pressing hydrologic needs stand out: first, to better understand the processes controlling the partitioning of energy and water fluxes within and out from these systems; second, to better understand feedbacks between hydrological fluxes and biogeochemical and ecological processes; and, third, to enhance our physical and empirical understanding with integrated measurement strategies and information systems. We envision an integrative approach to monitoring, modeling, and sensing the mountain environment that will improve understanding and prediction of hydrologic fluxes and processes. Here extensive monitoring of energy fluxes and hydrologic states are needed to supplement existing measurements, which are largely limited to streamflow and snow water equivalent. Ground-based observing systems must be explicitly designed for integration with remotely sensed data and for scaling up to basins and whole ranges.
Potential global climate change impacts on hydrology pose a threat to water resources systems throughout the world. The California
water system is especially vulnerable to global warming due to its dependence on mountain snow accumulation and the snowmelt
process. Since 1983, more than 60 studies have investigated climate change impacts on hydrology and water resources in California.
These studies can be categorized in three major fields: (1) Studies of historical trends of streamflow and snowpack in order
to determine if there is any evidence of climate change in the geophysical record; (2) Studies of potential future predicted
effects of climate change on streamflow and; (3) Studies that use those predicted changes in natural runoff to determine their
economic, ecologic, or institutional impacts. In this paper we review these studies with an emphasis on methodological procedures.
We provide for each category of studies a summary of significant conclusions and potential areas for future work.
Recently the Southwest has experienced a spate of dryness, which presents a challenge to the sustainability of current water use by human and natural systems in the region. In the Colorado River Basin, the early 21st century drought has been the most extreme in over a century of Colorado River flows, and might occur in any given century with probability of only 60%. However, hydrological model runs from downscaled Intergovernmental Panel on Climate Change Fourth Assessment climate change simulations suggest that the region is likely to become drier and experience more severe droughts than this. In the latter half of the 21st century the models produced considerably greater drought activity, particularly in the Colorado River Basin, as judged from soil moisture anomalies and other hydrological measures. As in the historical record, most of the simulated extreme droughts build up and persist over many years. Durations of depleted soil moisture over the historical record ranged from 4 to 10 years, but in the 21st century simulations, some of the dry events persisted for 12 years or more. Summers during the observed early 21st century drought were remarkably warm, a feature also evident in many simulated droughts of the 21st century. These severe future droughts are aggravated by enhanced, globally warmed temperatures that reduce spring snowpack and late spring and summer soil moisture. As the climate continues to warm and soil moisture deficits accumulate beyond historical levels, the model simulations suggest that sustaining water supplies in parts of the Southwest will be a challenge.
The severity of damaging human-induced climate change depends not only on the magnitude of the change but also on the potential for irreversibility. This paper shows that the climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop. Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do not drop significantly for at least 1,000 years. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450-600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the "dust bowl" era and inexorable sea level rise. Thermal expansion of the warming ocean provides a conservative lower limit to irreversible global average sea level rise of at least 0.4-1.0 m if 21st century CO(2) concentrations exceed 600 ppmv and 0.6-1.9 m for peak CO(2) concentrations exceeding approximately 1,000 ppmv. Additional contributions from glaciers and ice sheet contributions to future sea level rise are uncertain but may equal or exceed several meters over the next millennium or longer.
How anthropogenic climate change will affect hydroclimate in the arid regions of southwestern North America has implications
for the allocation of water resources and the course of regional development. Here we show that there is a broad consensus
among climate models that this region will dry in the 21st century and that the transition to a more arid climate should already
be under way. If these models are correct, the levels of aridity of the recent multiyear drought or the Dust Bowl and the
1950s droughts will become the new climatology of the American Southwest within a time frame of years to decades.
Observations have shown that the hydrological cycle of the western United States changed significantly over the last half of the 20th century. We present a regional, multivariable climate change detection and attribution study, using a high-resolution hydrologic model forced by global climate models, focusing on the changes that have already affected this primarily arid region with a large and growing population. The results show that up to 60% of the climate-related trends of river flow, winter air temperature, and snow pack between 1950 and 1999 are human-induced. These results are robust to perturbation of study variates and methods. They portend, in conjunction with previous work, a coming crisis in water supply for the western United States.
Climate warming is expected to alter hydropower generation in California through affecting the annual stream-flow regimes and reducing snowpack. On the other hand, increased temperatures are expected to increase hydropower demand for cooling in warm periods while decreasing demand for heating in winter, subsequently altering the annual hydropower pricing patterns. The resulting variations in hydropower supply and pricing regimes necessitate changes in reservoir operations to minimize the revenue losses from climate warming. Previous studies in California have only explored the effects of hydrological changes on hydropower generation and revenues. This study builds a long-term hydropower pricing estimation tool, based on artificial neural network (ANN), to develop pricing scenarios under different climate warming scenarios. Results suggest higher average hydropower prices under climate warming scenarios than under historical climate. The developed tool is integrated with California's Energy-Based Hydropower Optimization Model (EBHOM) to facilitate simultaneous consideration of climate warming on hydropower supply, demand and pricing. EBHOM estimates an additional 5% drop in annual revenues under a dry warming scenario when climate change impacts on pricing are considered, with respect to when such effects are ignored, underlining the importance of considering changes in hydropower demand and pricing in future studies and policy making.
Temperature impacts on the water year 2014 drought in California
- Shukla
Developing a module for estimating climate warming effects on hydropower pricing in California
- Guégan
Climate change 2013: The physical science basis
- IPCC