Climate change and California drought in the 21st century

National Academy of Sciences (NAS) | March 31st, 2015

Climate science has advanced over decades from an initial focus on the development and use of numerical models of Earth’s climate and compilation of rich netw

Climate science has advanced over decades from an initial focus on the development and use of numerical models of Earth’s climate and compilation of rich networks of obser- vational data, to now being in a position to“detect” and “attribute” specific impacts and events to anthropogenic climate change. Recent analyses have thus established the“fingerprint” of anthropogenic climate change in an increasingly diverse array of meteorological and hydrological phenomena around the world, from heat waves to coastal damages during extreme tides and storms, flooding from more intense precipitation events, and severe drought. In a new study published in PNAS, Diffenbaugh et al. now add weight to the accumulating evidence that anthropogenic climatic changes are already influencing the frequency, magnitude, and duration of drought in California. The authors show that the increasing co-occurrence of dry years with warm years raises the risk of drought despite limited evidence of a trend in precipitation itself, highlighting the critical role of elevated temperatures in altering water availability and increasing overall drought intensity and impact.

Climate Change and Flooding in Central Appalachia

Pacific Institute | November 30th, 2023

Climate Change and Future Water Availability in the United States, Chapter E of U.S. Geological Survey Integrated Water Availability Assessment—2010–20

U.S. Geological Survey (USGS) | January 15th, 2025

The following are the key points of this chapter:  The steady rise in global temperature as a result of human activity is causing changes in Earth’s water cycle.

The following are the key points of this chapter:  The steady rise in global temperature as a result of human activity is causing changes in Earth’s water cycle. The amount of water stored within and moving between vapor, liquid and frozen components of the water cycle is shifting, with significant consequences for water availability. Climatic drivers underlie regional or local changes in water supply and their socioeconomic impacts. Threats to the quantity and quality of water available for humans and ecosystems in North America include increases in drought, aridification, and fire weather; heavy precipitation and flooding; cryosphere decline; rising surface-water temperatures; and saltwater intrusion in coastal areas. An understanding of how changes in the major climatic drivers impact the water cycle and the accurate simulation of impacts in hydrological models are crucial to predicting future water availability and developing adaptation strategies to ensure human and ecosystem water supplies. Companion chapters: U.S. Geological Survey Integrated Water Availability Assessment—2010–20, Chapter A Water Supply in the Conterminous United States, Alaska, Hawaii, and Puerto Rico, Water Years 2010–20, Chapter B Status of Water-Quality Conditions in the United States, 2010–20, Chapter C  Water Use Across the Conterminous United States, Water Years 2010–20, Chapter D  Integrated Water Availability in the Conterminous United States, 2010–20, Chapter F 

Climate Change and Integrated Regional Water Management in California: A Preliminary Assessment of Regional Approaches

California Department of Water Resources (DWR) | June 6th, 2012

This report examines the initial steps that IRWM regions are taking in response to new requirements to address climate change vulnerabilities and consider greenhouse gas

This report examines the initial steps that IRWM regions are taking in response to new requirements to address climate change vulnerabilities and consider greenhouse gas emissions in IRWM plans. Given our evolving understanding of climate change impacts and appropriate adaptation strategies, effectively integrating climate change into planning is a challenging task. This report seeks to learn from initial steps by IRWM regions in order to inform future guidance and support. It also identifies key considerations for DWR and IRWM regions in analyzing and adapting to climate change risks within an adaptive management framework. Specifically, this report seeks to: 1. Assess the manner and degree to which the climate change requirements in the 2010 IRWM Guidelines are met in Round 1 Proposition 84 Planning and Implementation grant proposals, and in recently approved IRWM plans 2. Assess current IRWM regional approaches to analyzing and adapting to climate change risks, in light of the overall goal to promote an adaptive management approach 3. Provide recommendations on key steps for DWR and IRWM regions to support the development of informative climate change analyses and mechanisms for adaptive management at regional and state levels This assessment is based on a review of the current IRWM climate change requirements, existing IRWM plans, and Planning and Implementation grant proposals funded in 2011. It is also informed by interviews conducted by DWR regional climate change specialists with representatives of IRWM regions regarding their plans to address climate change.

Climate change and its influence on water systems increases the cost of electricity system decarbonization

Nature Portfolio (Springer Nature) | November 25th, 2024

Climate Change and Rural Water for Frontline Communities in the Southwest United States

Pacific Institute | March 26th, 2024

Climate change is threatening rural water supply and quality in the Southwest United States and will intensify water challenges in the coming years. Climate impacts such

Climate change is threatening rural water supply and quality in the Southwest United States and will intensify water challenges in the coming years. Climate impacts such as prolonged drought conditions and extreme high temperatures paired with groundwater depletion and reduced mountain snowpack are increasing the risk of water supply shortages in the region. Climate change models project an increase in temperature and an overall decline in average annual precipitation in the Southwest, though punctuated with extreme precipitation and more damaging flooding events.

Climate Change and Sea Level Rise Scenarios for California Vulnerability and Adaptation Assessment

California Energy Commission (CEC) | July 31st, 2012

This white paper provides an evaluation of physical elements of climate change and sea level rise that are contained in the California Climate Change Vulnerability and Ad

This white paper provides an evaluation of physical elements of climate change and sea level rise that are contained in the California Climate Change Vulnerability and Adaptation Assessment. The analyses use six global climate models, each run under the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios B1 and A2 scenarios. From the global climate models and associated downscaled output, these scenarios contain a range of warming, continued interannual and decadal variation of precipitation with incremental changes by the middle and end of twenty-first century, substantial loss of mountain snow pack, and a range of sea level rise along the California coast.

Climate Change and the Agricultural Sector in the San Francisco Bay Area: Changes in Viticulture and Rangeland Forage Production Due to Altered Temperature and Precipitation Patterns

California Energy Commission (CEC) | July 31st, 2012

Climate change has the potential to alter the San Francisco Bay Area’s agricultural production, a $2 billion industry. Two of the top sectors, wine and ranching, are ex

Climate change has the potential to alter the San Francisco Bay Area’s agricultural production, a $2 billion industry. Two of the top sectors, wine and ranching, are examined in this paper. Downscaled models suggest that forage production in Bay Area rangelands may be enhanced by future conditions in most years, at least in terms of peak standing crop. However, the timing of production is as important as its peak, and altered precipitation patterns could mean delayed germination and earlier senescence, resulting in shorter growing seasons. An increase in the frequency of extremely dry years also increases the uncertainty of forage availability. Similarly, wine grape yields are projected to increase throughout much of the Bay Area, but wine grape quality may decline substantially under future climate conditions, as the crop ripens earlier during hotter months. The implications for these shifts in wine grape and forage production are that the aspects of Bay Area agriculture most sensitive to climate change are not yields, but subtler nuances of production such as quality and timing. Adaptive measures will need to be taken to maintain the economic viability of these enterprises.

Climate change and the aridification of North America

National Academy of Sciences (NAS) | May 19th, 2020

Discussions of droughts and their impacts often center on the lack of precipitation, just as assessments of hydrologic impacts under a changing climate most ofte

Discussions of droughts and their impacts often center on the lack of precipitation, just as assessments of hydrologic impacts under a changing climate most often focus on how average precipitation in a given locale is likely to change in the future. Within climate science, however, focus has begun to include the growing role warming temperatures are playing as a potent driver of greater aridity: hotter climate extremes; drier soil conditions; more severe drought; and the impacts of hydrologic stress on rivers, forests, agriculture, and other systems. This shift in the hydrologic paradigm is most clear in the American Southwest, where declining flows in the region’s two most important rivers, the Colorado and Rio Grande, have been attributed in part to increasing temperatures caused by human activities, most notably the burning of fossil fuels. Warmer summers are also likely to reduce flows in the Columbia River, as well as in rivers along the Sierra Nevada in California. Now, an important study [Increased drought severity tracks warming in the United States’ largest river basin, J.T. Martin et al] documents how warming is also causing flow declines in the northern Rocky Mountains and in the largest river basin in the United States, the Missouri. This work further highlights the mechanisms behind the temperature-driven river flow declines and places more focus on how anthropogenic climate warming is progressively increasing the risk of hot drought and more arid conditions across an expanding swath of the United States.

Climate Change and the Delta

University of California, Davis (UC Davis) | October 1st, 2016

Climate change amounts to a fast approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic

Climate change amounts to a fast approaching, “new” stressor in the Sacramento–San Joaquin Delta system. In response to California’s extreme natural hydroclimatic variability, complex water-management systems have been developed, even as the Delta’s natural ecosystems have been largely devastated. Climate change is projected to challenge these management and ecological systems in different ways that are characterized by different levels of uncertainty. Future precipitation changes are less certain, with as many climate models projecting wetter conditions as drier. Warmer temperatures will likely enhance evaporation and raise water temperatures. Consequently, climate change is projected to yield both more extreme flood risks and greater drought risks. Effects on the Delta ecosystem that are traceable to warming include sea level rise, reduced snowpack, earlier snowmelt and larger storm-driven streamflow, warmer and longer summers, warmer summer water temperatures, and water-quality changes. These changes and their uncertainties will challenge the operations of water projects and uses throughout the Delta’s watershed and delivery areas. Although the effects of climate change on Delta ecosystems may be profound, the end results are difficult to predict, except that native species will fare worse than invaders. Successful preparation for the coming changes will require greater integration of monitoring, modeling, and decision-making across time, variables, and space than has been historically normal.