Jet stream dynamics, hydroclimate, and fire in California from 1600 CE to present

National Academy of Sciences (NAS) | March 4th, 2019

Moisture delivery in California is largely regulated by the strength and position of the North Pacific jet stream (NPJ), winter high-altitude winds that influence regiona

Moisture delivery in California is largely regulated by the strength and position of the North Pacific jet stream (NPJ), winter high-altitude winds that influence regional hydroclimate and forest fire during the following warm season. We use climate model simulations and paleoclimate data to reconstruct winter NPJ characteristics back to 1571 CE to identify the influence of NPJ behavior on moisture and forest fire extremes in California before and during the more recent period of fire suppression. Maximum zonal NPJ velocity is lower and northward shifted and has a larger latitudinal spread during presuppression dry and high-fire extremes. Conversely, maximum zonal NPJ is higher and southward shifted, with narrower latitudinal spread during wet and low-fire extremes. These NPJ, precipitation, and fire associations hold across pre–20th-century socioecological fire regimes, including Native American burning, postcontact disruption and native population decline, and intensification of forest use during the later 19th century. Precipitation extremes and NPJ behavior remain linked in the 20th and 21st centuries, but fire extremes become uncoupled due to fire suppression after 1900. Simulated future conditions in California include more wet-season moisture as rain (and less as snow), a longer fire season, and higher temperatures, leading to drier fire-season conditions independent of 21st-century precipitation changes. Assuming continuation of current fire management practices, thermodynamic warming is expected to override the dynamical influence of the NPJ on climate–fire relationships controlling fire extremes in California. Recent widespread fires in California in association with wet extremes may be early evidence of this change.

LandFlex Grant Program Guidelines

California Department of Water Resources (DWR) | January 14th, 2023

The California Department of Water Resources (DWR) is administering the LandFlex Grant Program (LandFlex) through DWR’s Sustainable Groundwater Management (SGM) Grant P

The California Department of Water Resources (DWR) is administering the LandFlex Grant Program (LandFlex) through DWR’s Sustainable Groundwater Management (SGM) Grant Program. LandFlex (referred to as Ag Drought Relief) will award funds authorized by the California Budget Act of 2021 (Stats. 2021, ch. 44, § 25). This document contains DWR’s Guidelines and scoring criteria (Guidelines) for LandFlex. Climate change means that California needs to plan for a hotter, drier future. Long-term drought, fueled by climate change, has adversely affected the State’s water supplies, which includes groundwater availbility. In response to the Governor’s California’s Water Supply Strategy, Adapting to a Hotter, Drier Future, DWR will launch the LandFlex Program as a new and innovative tool to protect vulnerable drinking water wells. LandFlex will provide incentives to farmers to limit groundwater pumping in areas near communities reliant on vulnerable drinking water wells before they go dry. LandFlex combines traditional short-term fallowing incentives with the elimination of long-term unsustainable groundwater pumping, a unique approach to groundwater resilience. LandFlex is a program that will provide $25 million in block grants to local government agencies to grant to farmers who limit agricultural water use. Local government agencies will work directly with farmers in critically overdrafted (COD) basins (as identified in Bulletin 118) to identify lands that would reduce pumping impacts to nearby drinking water wells. Through financial incentives to farmers, LandFlex will provide multiple community benefits such as drinking water well relief, groundwater overdraft prevention, and climate resilience.

Landslide-channel feedbacks amplify channel widening during floods

Nature Portfolio (Springer Nature) | January 24th, 2025

Large contribution from anthropogenic warming to an emerging North American megadrought

American Association for the Advancement of Science (AAAS) | April 17th, 2020

Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogen

Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogenic climate change. We use hydrological modeling and new 1200-year tree-ring reconstructions of summer soil moisture to demonstrate that the 2000–2018 SWNA drought was the second driest 19-year period since 800 CE, exceeded only by a late-1500s megadrought. The megadrought-like trajectory of 2000–2018 soil moisture was driven by natural variability superimposed on drying due to anthropogenic warming. Anthropogenic trends in temperature, relative humidity, and precipitation estimated from 31 climate models account for 47% (model interquartiles of 35 to 105%) of the 2000–2018 drought severity, pushing an otherwise moderate drought onto a trajectory comparable to the worst SWNA megadroughts since 800 CE.

Large-Scale Environments of Successive Atmospheric River Events Leading to Compound Precipitation Extremes in California

American Meteorological Society (AMS) | February 18th, 2022

Successive atmospheric river (AR) events—known as AR families—can result in prolonged and elevated hydrological impacts relative to single ARs due to the lack of reco

Successive atmospheric river (AR) events—known as AR families—can result in prolonged and elevated hydrological impacts relative to single ARs due to the lack of recovery time between periods of precipitation. Despite the outsized societal impacts that often stem from AR families, the large-scale environments and mechanisms associated with these compound events remain poorly understood. In this work, a new reanalysis-based 39-yr catalog of 248 AR family events affecting California between 1981 and 2019 is introduced. Nearly all (94%) of the interannual variability in AR frequency is driven by AR family versus single events. Using k-means clustering on the 500-hPa geopotential height field, six distinct clusters of large-scale patterns associated with AR families are identified. Two clusters are of particular interest due to their strong relationship with phases of El Niño–Southern Oscillation (ENSO). One of these clusters is characterized by a strong ridge in the Bering Sea and Rossby wave propagation, most frequently occurs during La Niña and neutral ENSO years, and is associated with the highest cluster-average precipitation across California. The other cluster, characterized by a zonal elongation of lower geopotential heights across the Pacific basin and an extended North Pacific jet, most frequently occurs during El Niño years and is associated with lower cluster-average precipitation across California but with a longer duration. In contrast, single AR events do not show obvious clustering of spatial patterns. This difference suggests that the potential predictability of AR families may be enhanced relative to single AR events, especially on subseasonal to seasonal time scales.

Laudato si - Encyclical letter of the Holy Father Francis on Care for our Common Home*

Holy See | May 24th, 2015

*Also commonly known as the Pope's encyclical on climate change. 1. “Laudato si’, mi’ Signore” – “Praise be to you, my Lord”. In the words of this

*Also commonly known as the Pope's encyclical on climate change. 1. “Laudato si’, mi’ Signore” – “Praise be to you, my Lord”. In the words of this beautiful canticle, Saint Francis of Assisi reminds us that our common home is like a sister with whom we share our life and a beautiful mother who opens her arms to embrace us. “Praise be to you, my Lord, through our Sister, Mother Earth, who sustains and governs us, and who produces vari-ous fruit with coloured flowers and herbs”. 2. This sister now cries out to us because ofthe harm we have inflicted on her by our irre- sponsible use and abuse of the goods with which God has endowed her. We have come to see ourselves as her lords and masters, entitled to plunder her at will.

Law and Policies that Address Equitable, Climate-Resilient Water and Sanitation (Part 2)

Pacific Institute | October 21st, 2024

In the United States, federal, tribal, state, and local laws and policies exist to govern the provision of water and sanitation services to communities and homes. The law

In the United States, federal, tribal, state, and local laws and policies exist to govern the provision of water and sanitation services to communities and homes. The laws are designed to ensure the protection of public health and the environment; deliver sufficient, safe water for drinking, bathing, cooking, and other household needs; and remove and treat domestic (i.e., household) waste. People without complete plumbing or safe water live within the “water access gap.” As explored in the first report in this series, climate change—from extreme temperatures to droughts, floods, extreme storms, and wildfires—is making it hard to close this gap and keep it from growing. Water and sanitation systems in frontline communities already feel the disproportionate “first and worst” impacts of climate change to these systems and to their access to water and sanitation. Laws and policies should help anticipate and plan for the incremental and catastrophic impacts of climate change and protect those most harmed by the effects. Unfortunately, in most cases, the climate is changing faster than the law can respond, thereby leaving frontline communities’ water and sanitation systems vulnerable to damage or destruction. (Click here for Part 1)

Levee Decisions and Sustainability for the Sacramento-San Joaquin Delta

University of California, Davis (UC Davis) | August 15th, 2010

Leveraging Wetlands for a Better Climate Future

San Francisco Estuary Institute (SFEI) | July 15th, 2022

Managing Natural and Working Lands (NWL) to enhance carbon sinks and limit greenhouse gas (GHG) emissions is a key component of California’s ambitious strategy to achie

Managing Natural and Working Lands (NWL) to enhance carbon sinks and limit greenhouse gas (GHG) emissions is a key component of California’s ambitious strategy to achieve net carbon neutrality by 2045. The California Air Resources Board (CARB) Climate Change Scoping Plan includes 7 NWL categories in its GHG emission reduction scenarios, one of which is wetlands. Coastal wetlands in California are a high- leverage NWL type for GHG management relative to their small spatial footprint. These ecosystems have high rates of carbon sequestration and can accumulate large stocks of carbon, due to high productivity, efficient sediment trapping, and low decomposition rates (Chmura et al. 2003, Mcleod et al. 2011). In the absence of management interventions focused on wetland conservation, however, conversion of coastal wetlands to other land uses such as agriculture, grazing, development, impounded wetlands, or subtidal or upland habitat can halt or reverse carbon sequestration, and can shift these ecosystems from long-term GHG sinks to large GHG sources (Hatala et al. 2012, Tan et al. 2019). Filling of wetlands for infrastructure and development was a common practice throughout the early 20th century (Goals Project 1999), dramatically reducing the state’s coastal wetland area and associated carbon sink.

Limiting fossil fuel production as the next big step in climate policy

Nature Portfolio (Springer Nature) | November 26th, 2018

Despite the current ambivalence of the United States towards the Paris Agreement, national and local jurisdictions across the globe remain committed, and they are seeking

Despite the current ambivalence of the United States towards the Paris Agreement, national and local jurisdictions across the globe remain committed, and they are seeking ways to increase the ambition and effectiveness of their climate policies. One way forwards could be limiting the production — not just the consumption — of coal, gas and oil. Here we describe the rationale for, and CO2 emissions implications of, limiting oil production. Seven countries have recently imposed such limits, and we develop a case study for a potential addition to this group, the US state of California. We find that by ceasing the issuance of permits for new oil wells, California could reduce global CO2 emissions substantially and also enhance environmental justice in the state.