Considerations for Selecting Climate Projections for Water Resources, Planning, and Environmental Analyses

U.S. Bureau of Reclamation (USBR) | March 2nd, 2016

For over a century, Reclamation’s mission has focused on managing water resources in the Western United States. Water resources, planning, and environmental studies car

For over a century, Reclamation’s mission has focused on managing water resources in the Western United States. Water resources, planning, and environmental studies carried out to support Reclamation’s mission have routinely considered hydrologic variability, including variability of water supplies and demands from season to season and year to year. Because weather and climate are two of the primary drivers of water supply and demand, Reclamation studies have also routinely considered weather and climate variability. The SECURE Water Act directs Reclamation to evaluate the risks and impacts of climate change in long-range planning and decision making (see Section 1.1. of the main report), including: •Water resources and environmental analyses •Planning studies •Design and analysis of current and proposed infrastructure and operating plans Considering climate change involves analyzing projected changes in weather and climate conditions as well as the effects of these changes on water supplies, demands, and management.  This document provides an overview of the primary considerations relevant to selecting climate projection information for use in a given water resources, planning, or environmental analysis. Audience For technical specialists involved in selecting and using climate projections for a given study—e.g., climatologist, hydrologists, and water resources engineers— this document provides a brief overview of the models and methods used to develop climate projections (Section 2.) and relevant considerations for selecting an appropriate climate projection dataset and set of climate projections to meet their specific study objectives (Section 3.). This document also provides a detailed summary of available climate projection datasets (Section 4.) and established methods for selecting climate projections for use in a detailed analysis (Section 5.). For other study team members involved in interpreting and documenting the use of climate change information in a given study—e.g., planners, environmental specialists, and resource managers—this document provides an overview of how climate projections are developed (Section 2.) and the choices and considerations involved in selecting climate projections for analysis in the study (Section 3.).

Consumption Change Detection for Urban Planning: Monitoring and Segmenting Water Customers During Drought

American Geophysical Union (AGU) | March 11th, 2020

Demand management is a powerful way for water utilities to address the challenges of population growth and climate change. Although active conservation efforts have been

Demand management is a powerful way for water utilities to address the challenges of population growth and climate change. Although active conservation efforts have been studied extensively, recent evidence suggests households respond to many external events beyond a utility's control, including political responses to extreme climatic episodes and corresponding mass media coverage. Despite their importance, these external factors are difficult to analyze in a controlled setting, and few tools exist to evaluate their influence on customers. Here, we present a consumption change detection (CCD) method that offers new insights into how climate‐related mass media and policy events affect conservation by pinpointing the timing and magnitude of customer‐level water use shifts. We use CCD to monitor and segment the responses of residential water customers to policy and media events in Costa Mesa, California, during the severe 2012–2016 drought. Our results show consumption reductions among 75% of customers. Of these, 80% reduced water use before mandatory restrictions were imposed, coincident with intensifying state policy responses and spikes in media coverage that affected all customer types during 2014. Analysis of standardized drought consumption trajectories indicates that 16% of conserving customers increased consumption in 2015–2016. Conservation and rebound were both more likely among affluent and educated customers, suggesting that CCD can identify engaged and informed water savers who make suitable targets for water‐efficient retrofit incentive schemes. This study demonstrates CCD's potential as a novel demand analysis tool in an interconnected world where external social, political, and climatic stressors can exert an important influence on customer behavior.

Contraction of the World's Storm-Cloud Zones the Primary Contributor to the 21st Century Increase in the Earth's Sunlight Absorption

American Geophysical Union (AGU) | June 8th, 2025

Recent Earth energy budget observations show an increase in the sunlight absorbed by the Earth of 0.45 W/m2 per decade, caused primarily by a decrease in cloud reflectio

Recent Earth energy budget observations show an increase in the sunlight absorbed by the Earth of 0.45 W/m2 per decade, caused primarily by a decrease in cloud reflection. Here we decompose the solar radiative budget trends into general circulation and cloud controlling process components. Regimes representing the midlatitude and tropical storm zones are defined, and the trends in the areal coverage of those regimes which are potentially induced by circulation changes are separated from trends in the cloud radiative effect within each regime which are potentially induced by changes in local cloud controlling processes. The regime area change component, which manifests itself as a contraction of the midlatitude and tropical storm regimes, constitutes the largest contribution to the solar absorption trend, causing decreased sunlight reflection of 0.37 W/m2 per decade. This result provides a crucial missing piece in the puzzle of the 21st century increase of the Earth's solar absorption.

Contraction of the World's Storm‐Cloud Zones the Primary Contributor to the 21st Century Increase in the Earth's Sunlight Absorption

American Geophysical Union (AGU) | June 8th, 2025

Recent Earth energy budget observations show an increase in the sunlight absorbed by the Earth of 0.45 W/m2 per decade, caused primarily by a decrease in cloud reflectio

Recent Earth energy budget observations show an increase in the sunlight absorbed by the Earth of 0.45 W/m2 per decade, caused primarily by a decrease in cloud reflection. Here we decompose the solar radiative budget trends into general circulation and cloud controlling process components. Regimes representing the midlatitude and tropical storm zones are defined, and the trends in the areal coverage of those regimes which are potentially induced by circulation changes are separated from trends in the cloud radiative effect within each regime which are potentially induced by changes in local cloud controlling processes. The regime area change component, which manifests itself as a contraction of the midlatitude and tropical storm regimes, constitutes the largest contribution to the solar absorption trend, causing decreased sunlight reflection of 0.37 W/m2 per decade. This result provides a crucial missing piece in the puzzle of the 21st century increase of the Earth's solar absorption.

Contribution of Changes in Atmospheric Circulation Patterns to Extreme Temperature Trends

Nature Portfolio (Springer Nature) | July 24th, 2015

Surface weather conditions are closely governed by the large-scale circulation of the Earth’s atmosphere. Recent increases in the occurrence of some extreme wea

Surface weather conditions are closely governed by the large-scale circulation of the Earth’s atmosphere. Recent increases in the occurrence of some extreme weather phenomena have led to multiple mechanistic hypotheses linking changes in atmospheric circulation to increasing probability of extreme events. However, observed evidence of long-term change in atmospheric circulation remains inconclusive. Here we identify statistically significant trends in the occurrence of atmospheric circulation patterns, which partially explain observed trends in surface temperature extremes over seven mid-latitude regions of the Northern Hemisphere. Using self-organizing map cluster analysis, we detect robust circulation pattern trends in a subset of these regions during both the satellite observation era (1979–2013) and the recent period of rapid Arctic sea-ice decline (1990–2013). Particularly substantial influences include the contribution of increasing trends in anticyclonic circulations to summer and autumn hot extremes over portions of Eurasia and North America, and the contribution of increasing trends in northerly flow to winter cold extremes over central Asia. Our results indicate that although a substantial portion of the observed change in extreme temperature occurrence has resulted from regional- and global-scale thermodynamic changes, the risk of extreme temperatures over some regions has also been altered by recent changes in the frequency, persistence and maximum duration of regional circulation patterns.

Contribution of historical precipitation change to US flood damages

Publisher not available | January 26th, 2021

Precipitation extremes have increased across many regions of the United States, with further increases anticipated in response to additional global warming. Quantifying

Precipitation extremes have increased across many regions of the United States, with further increases anticipated in response to additional global warming. Quantifying the impact of these precipitation changes on flood damages is necessary to estimate the costs of climate change. However, there is little empirical evidence linking changes in precipitation to the historically observed increase in flood losses. We use >6,600 reports of state-level flood damage to quantify the historical relationship between precipitation and flood damages in the United States. Our results show a significant, positive effect of both monthly and 5-d state-level precipitation on state-level flood damages. In addition, we find that historical precipitation changes have contributed approximately one-third of cumulative flood damages over 1988 to 2017 (primary estimate 36%; 95% CI 20 to 46%), with the cumulative impact of precipitation change totaling $73 billion (95% CI 39 to $91 billion). Further, climate models show that anthropogenic climate forcing has increased the probability of exceeding precipitation thresholds at the extremely wet quantiles that are responsible for most flood damages. Climate models project continued intensification of wet conditions over the next three decades, although a trajectory consistent with UN Paris Agreement goals significantly curbs that intensification. Taken together, our results quantify the contribution of precipitation trends to recent increases in flood damages, advance estimates of the costs associated with historical greenhouse gas emissions, and provide further evidence that lower levels of future warming are very likely to reduce financial losses relative to the current global warming trajectory.

Contribution of the Pacific Decadal Oscillation to global mean sea level trend

American Geophysical Union (AGU) | October 3rd, 2013

Understanding and explaining the trend in global mean sea level (GMSL) have important implications for future projections of sea level rise. While measurements from sa

Understanding and explaining the trend in global mean sea level (GMSL) have important implications for future projections of sea level rise. While measurements from satellite altimetry have provided accurate estimates of GMSL, the modern altimetry record has only now reached 20 years in length, making it difficult to assess the contribution of decadal to multi-decadal climate signals to the global trend. Here, we use a sea level reconstruction to study the 20 year trends in sea level since 1950. In particular, we show that the Pacific Decadal Oscillation (PDO) contributes significantly to the 20 year trends in GMSL. We estimate the PDO contri-bution to the GMSL trend over the past 20 years to beapproximately 0.49 ± 0.25 mm/year and find that removing the PDO contribution reduces the acceleration in GMSL estimated over the past 60 years. 

Contributions of Climate Change and ENSO Variability to Future Precipitation Extremes Over California

American Geophysical Union (AGU) | June 14th, 2023

Coupling a spatiotemporally distributed soil water budget with stream‐depletion functions to inform stakeholder‐driven management of groundwater‐dependent ecosystems

American Geophysical Union (AGU) | November 12th, 2013

Groundwater pumping, even if only seasonal, may significantly impact groundwater‐dependent ecosystems through increased streamflow depletion, particularly in semiarid a

Groundwater pumping, even if only seasonal, may significantly impact groundwater‐dependent ecosystems through increased streamflow depletion, particularly in semiarid and arid regions. The effects are exacerbated, under some conditions, by climate change. In social sciences, the management of groundwater‐dependent ecosystems is generally considered a “wicked” problem due to the complexity of affected stakeholder groups, disconnected legal frameworks, and a divergence of policies and science at the cross road between groundwater and surface water, and between ecosystems and water quality. A range of often simplified scientific tools plays an important role in addressing such problems. Here we develop a spatiotemporally distributed soil water budget model that we couple with an analytical model for stream depletion from groundwater pumping to rapidly assess seasonal impacts of groundwater pumping on streamflow during critical low flow periods. We demonstrate the applicability of the tool for the Scott Valley in Northern California, where protected salmon depend on summer streamflow fed by cool groundwater. In this example, simulations suggest that increased recharge in the period immediately preceding the critical low streamflow season, and transfer of groundwater pumping away from the stream are potentially promising tools to address ecosystem concerns, albeit raising difficult infrastructure and water trading issues. In contrast, additional winter recharge at the expense of later spring recharge, whether intentional or driven by climate may reduce summer streamflows. Comparison to existing detailed numerical groundwater model results suggests that the coupled soil water mass balance—stream depletion function approach provides a viable tool for scenario development among stakeholders, to constructively inform the search for potential solutions, and to direct more detailed, complex site‐specific feasibility studies. The tool also identifies important field monitoring efforts needed to improve the understanding and quantification of site‐specific groundwater‐stream interactions.

Cultivating climate resilience in California agriculture: Adaptations to an increasingly volatile water future

National Academy of Sciences (NAS) | July 29th, 2024