Precipitation shifts over western North America as a result of declining Arctic sea ice cover: The coupled system response

American Meteorological Society (AMS) | July 21st, 2009

Changes in Arctic sea ice cover have the potential to impact midlatitude climate. A previous sensitivity study utilizing the National Center for Atmospheric Resea

Changes in Arctic sea ice cover have the potential to impact midlatitude climate. A previous sensitivity study utilizing the National Center for Atmospheric Research’s (NCAR) atmospheric general circulation model [AGCM; Community Climate Model, version 3 (CCM3)] to explore climate sensitivity to declining Arctic sea ice cover suggested that, as Arctic sea ice cover is reduced, precipitation patterns over western North America will shift toward dryer conditions in southwestern North America and wetter conditions in northwestern North America. Here, three complementary lines of research validate and explore the robustness of this possible climate change impact: 1) repetition of the previous sensitivity study (specified constant Arctic sea ice cover and atmospheric CO2) with an updated version of the NCAR AGCM [third Community Atmosphere Model (CAM3)], 2) investigation of the climate response to dynamically reduced Arctic sea ice cover (driven by a quadrupling of atmospheric CO2) in the coupled NCAR Community Climate System Model.

Precipitation variability increases in a warmer climate

Nature Portfolio (Springer Nature) | December 21st, 2017

Understanding changes in precipitation variability is essential for a complete explanation of the hydrologic cycle’s response to warming and its impacts. Whil

Understanding changes in precipitation variability is essential for a complete explanation of the hydrologic cycle’s response to warming and its impacts. While changes in mean and extreme precipitation have been studied intensively, precipitation variability has received less attention, despite its theoretical and practical importance. Here, we show that precipitation variability in most climatemodels increases over a majority of global land area in response to warming (66% of land has a robust increase in variability of seasonal-mean precipitation). Comparing recent decades to RCP8.5 projections for the end of the 21st century, we find that in the global, multi-model mean, precipitation variability increases 3–4% K−1 globally, 4–5% K−1 over land and 2–4% K−1 over ocean, and is remarkably robust on a range of timescales from daily to decadal. Precipitation variability increases by at least as much as mean precipitation and less than moisture and extreme precipitation for most models, regions, and timescales. We interpret this as being related to an increase in moisture which is partially mitigated by weakening circulation. We show that changes in observed daily variability in station data are consistent with increased variability.

Predicting Streamflow Elasticity Based on Percolation Theory and Ecological Optimality

American Geophysical Union (AGU) | July 20th, 2023

Preparing for New Risks: Addressing Climate Change in California’s Urban Water Management Plans

California Department of Water Resources (DWR) | June 20th, 2013

Urban Water Management Plans (UWMPs) are a central component of California’s efforts to assure reliable water supplies, particularly during drought conditions that are

Urban Water Management Plans (UWMPs) are a central component of California’s efforts to assure reliable water supplies, particularly during drought conditions that are frequently experienced in the state. Prepared by water suppliers every five years, UWMPs include supply and demand projections for the next 20 years, and describe strategies to assure adequate supplies during average, single-­year, and multi-­year drought conditions. UWMPs also contain plans to implement a 20% reduction in per capita urban water use by the year 2020, as required under the Water Conservation Act of 2009 (SBX7-­7). Climate change is introducing new risks in water planning, such as increasing temperatures, reduced snowpack, changing precipitation patterns, and accelerating sea level rise, which are already being observed in the state. It is increasingly important for water suppliers to consider how these trends are impacting water supply, demand, and drought patterns. Water suppliers can also make important contributions to reducing greenhouse gas emissions (GHGs), through energy savings from water conservation as well as other measures. In its guidance to water suppliers for preparing 2010 UWMPs, the California Department of Water Resources (DWR) included an optional section focused on consideration of climate change impacts and GHG emissions. This study assesses how water suppliers have incorporated these factors into their 2010 plans. Drawing upon a sample of 2010 UWMPs, it examines the nature and extent of climate change discussion and analysis, and assesses how climate change risks have been incorporated into water supply and demand projections. The report also provides recommendations for how DWR could improve its guidance for 2015 UWMPs to support water suppliers in addressing climate change. All public and investor-­owned utilities serving 3,000 customers or supplying at least 3,000 acre-­feet of water annually are required to submit an Urban Water Management Plan to DWR every five years. Of the approximately 400 agencies submitting UWMPs, most are relatively small, with 90% serving less than 300,000 people, and 40% serving less than 50,000.  Most are public entities, but some are private companies, including three investor-­owned utilities with multiple service areas across the state. Large and small water suppliers tend to differ in their access to resources for planning and analysis of issues such as climate change. For many small suppliers, UWMP preparation serves as their primary long-­term planning process. Suppliers also vary in the nature of their vulnerability to drought and the impacts of climate change. Larger suppliers usually have multiple sources of supply, while small suppliers are more likely to rely on a single source, especially groundwater. These small utilities are less likely to have relationships with other suppliers, thereby reducing their options for coping with severe droughts. This study is based on an analysis of 49 individually submitted UWMPs, seven regional UWMPs, and UWMPs from three investor-­owned utilities with multiple service areas across the state. The sample was stratified so that it represents water suppliers of all sizes. It includes all large suppliers (serving 300,000 or more customers), and 10% of medium-­sized and small suppliers (serving 50,000 – 300,000 and less than 50,000 customers, respectively). Each UWMP was analyzed for its content related to climate change, and classified according to the degree and focus of discussion. This report is also informed by informal consultations with representatives of water supply agencies of different sizes.

Preparing Scientists, Policy-Makers, and Managers for a Fast-Forward Future

University of California, Davis (UC Davis) | June 15th, 2021

Priorities for California's Water: Responding to the Changing Climate

Public Policy Institute of California (PPIC) | November 18th, 2021

Water is central to how California adapts to a changing climate. To those of us steeped in the complexities of managing the state’s water resources, the current fast-mo

Water is central to how California adapts to a changing climate. To those of us steeped in the complexities of managing the state’s water resources, the current fast-moving drought—coming on the heels of the record-breaking 2012–16 drought—is a stark reminder that we must accelerate preparation for the disruptive changes underway. Californians have taken steps to address major threats to our water resources. But a recent IPCC report underscored that the climate is changing faster than anticipated, and that many of these changes are already locked in. Rising temperatures are making our winters shorter and our droughts more intense, outpacing our ability to manage water supplies and the natural environment. We need to act with urgency to adapt to these changes. And we need to rethink how we store water. This brief examines how the current drought and a changing climate are affecting California’s ability to manage water and lays out priority actions to address major challenges—including some urgent short-term actions should the drought continue into next year.

Priorities for California’s Water

Public Policy Institute of California (PPIC) | November 14th, 2022

This report considers the state of water in California: What changes are we seeing now, and what should we expect in the near future? Then it examines how these climate s

This report considers the state of water in California: What changes are we seeing now, and what should we expect in the near future? Then it examines how these climate shifts will impact urban and rural communities, agriculture, and the environment. Finally, it explores wet-year strategies that will help Californians get through the dry years.

Priorities for California’s Water: Are We Ready for Climate Change?

Public Policy Institute of California (PPIC) | November 12th, 2024

California faces many immediate challenges around water management, but as the record-breaking heat of 2024 makes clear, temperatures are rising—and Californians are co

California faces many immediate challenges around water management, but as the record-breaking heat of 2024 makes clear, temperatures are rising—and Californians are contending with the consequences. In a PPIC poll earlier this year, residents named climate change, forest fires and wildfires, and water supply and drought as the most important environmental issues facing the state. 

Procedures to evaluate sea-level change: impacts, responses, and adaptation

U.S. Army Corps of Engineers (USACE) | June 30th, 2014

Productive wetlands restored for carbon sequestration quickly become net CO2 sinks with site-level factors driving uptake variability

PLOS | March 25th, 2021

Inundated wetlands can potentially sequester substantial amounts of soil carbon (C) over the long-term because of slow decomposition and high primary productivity, partic

Inundated wetlands can potentially sequester substantial amounts of soil carbon (C) over the long-term because of slow decomposition and high primary productivity, particularly in climates with long growing seasons. Restoring such wetlands may provide one of several effective negative emission technologies to remove atmospheric CO2 and mitigate climate change. However, there remains considerable uncertainty whether these heterogeneous ecotones are consistent net C sinks and to what degree restoration and management methods affect C sequestration. Since wetland C dynamics are largely driven by climate, it is difficult to draw comparisons across regions. With many restored wetlands having different functional outcomes, we need to better understand the importance of site-specific conditions and how they change over time. We report on 21 site-years of C fluxes using eddy covariance measurements from five restored fresh to brackish wetlands in a Mediterranean climate. The wetlands ranged from 3 to 23 years after restoration and showed that several factors related to restoration methods and site conditions altered the magnitude of C sequestration by affecting vegetation cover and structure. Vegetation established within two years of re-flooding but followed different trajectories depending on design aspects, such as bathymetry-determined water levels, planting methods, and soil nutrients. A minimum of 55% vegetation cover was needed to become a net C sink, which most wetlands achieved once vegetation was established. Established wetlands had a high C sequestration efficiency (i.e. the ratio of net to gross ecosystem productivity) comparable to upland ecosystems but varied between years undergoing boom-bust growth cycles and C uptake strength was susceptible to disturbance events. We highlight the large C sequestration potential of productive inundated marshes, aided by restoration design and management targeted to maximise vegetation extent and minimise disturbance. These findings have important implications for wetland restoration, policy, and management practitioners.