Anticipating Environmental and Environmental-Health Implications of Extreme Storms: ARkStorm Scenario

American Society of Civil Engineers (ASCE) | July 22nd, 2015

The ARkStorm Scenario predicts that a prolonged winter storm event across California would cause extreme precipitation, flooding, winds, physical damages, and e

The ARkStorm Scenario predicts that a prolonged winter storm event across California would cause extreme precipitation, flooding, winds, physical damages, and economic impacts. This study uses a literature review and geographic information system-based analysis of national and state databases to infer how and where ARkStorm could cause environmental damages, release contamination from diverse natural and anthropogenic sources, affect ecosystem and human health, and cause economic impacts from environmental-remediation, liability, and health care costs. Examples of plausible ARkStorm environmental and health concerns include complex mixtures of contaminants such as petroleum, mercury, asbestos, persistent organic pollutants, molds, and pathogens; adverse physical and contamination impacts on riverine and coastal marine ecosystems; and increased incidences of mold-related health concerns, some vector-borne diseases, and valley fever. Coastal cities, the San Francisco Bay area, the Sacramento-San Joaquin River Delta, parts of the Central Valley, and some mountainous areas would likely be most affected. This type of screening analysis, coupled with follow-up local assessments, can help stakeholders in California and disaster-prone areas elsewhere better plan for, mitigate, and respond to future environmental disasters.

Anticipating responses to climate change and planning for resilience in California’s freshwater ecosystems

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

Appendix for the Development of a Mono Lake Water Level Model and Projections across the 21st Century

University of California, Los Angeles (UCLA) | March 17th, 2026

Main Report: Development of a Mono Lake Water Level Model and Projections across the 21st Century; Summary: Mono Lake in a Changing Climate

Main Report: Development of a Mono Lake Water Level Model and Projections across the 21st Century; Summary: Mono Lake in a Changing Climate

Application of synthetic scenarios to address water resource concerns: A management-guided case study from the Upper Colorado River Basin

Climate Services (Elsevier) | December 9th, 2017

Water managers are increasingly interested in better understanding and planning for projected resource impacts from climate change. In this management-guided study, we u

Water managers are increasingly interested in better understanding and planning for projected resource impacts from climate change. In this management-guided study, we use a very large suite of synthetic climate scenarios in a statistical modeling framework to simultaneously evaluate how (1) average temperature and precipitation changes, (2) initial basin conditions, and (3) temporal characteristics of the input climate data influence water year flow in the Upper Colorado River. The results here suggest that existing studies may underestimate the degree of uncertainty in future streamflow, particularly under moderate temperature and precipitation changes. However, we also find that the relative severity of future flow projections within a given climate scenario can be estimated with simple metrics that characterize the input climate data and basin conditions. These results suggest that simple testing, like the analyses presented in this paper, may be helpful in understanding differences between existing studies or in identifying specific conditions for physically based mechanistic modeling. Both options could reduce overall cost and improve the efficiency of conducting climate change impacts studies.

Aquatic Ecosystem Stressors in the Sacramento-San Joaquin Delta

Public Policy Institute of California (PPIC) | May 5th, 2012

This report presents results from an analysis of the institutional and legal options for more effective ecosystem management in the Sacramento-San Joaquin Delta. It is pa

This report presents results from an analysis of the institutional and legal options for more effective ecosystem management in the Sacramento-San Joaquin Delta. It is part of a wide-ranging study on the management of multiple ecosystem stressors in the Delta. .

Arctic sea-ice loss drives a strong regional atmospheric response over the North Pacific and North Atlantic on decadal scales

Nature Portfolio (Springer Nature) | March 11th, 2025

Previous studies have suggested that Arctic sea-ice loss can have a profound influence on atmospheric circulation far away from the Arctic. However, there is litt

Previous studies have suggested that Arctic sea-ice loss can have a profound influence on atmospheric circulation far away from the Arctic. However, there is little scientific consensus on the features of these remote responses, with the opposite impacts reported. Here we present a multi-model analysis of the decadal climate response to Arctic sea-ice loss using state-of-the-art energy conserving methodologies to isolate the impacts of sea-ice decline. We observe weakening of the Aleutian Low and development of a geopotential ridge in the North Pacific, associated with drier winter conditions over the southwest United States. Over the Atlantic, a negative NAO-like response drives wetter winter conditions across the western Mediterranean. These decadal-scale impacts substantially differ from reported centennial-scale responses to Arctic sea-ice loss simulated using non-energy conserving methodologies. Factors such as the timescale of the response and methodologies used to isolate the impacts of disappearing sea-ice cover should be carefully considered when consolidating scientific understanding on the future impacts of changing Arctic.

Arctic sea-ice loss is projected to lead to more frequent strong El Niño events

Nature Portfolio (Springer Nature) | August 23rd, 2022

Arctic sea ice has decreased substantially and is projected to reach a seasonally ice-free state in the coming decades. Little is known about whether dwindling Arctic sea

Arctic sea ice has decreased substantially and is projected to reach a seasonally ice-free state in the coming decades. Little is known about whether dwindling Arctic sea ice is capable of influencing the occurrence of strong El Niño, a prominentmode of climate variability with global impacts. Based on time slice coupled model experiments, here we show that no significant change in the occurrence of strong El Niño is found in response to moderate Arctic sea-ice loss that is consistent with satellite observations to date. However, as the ice loss continues and the Arctic becomes seasonally ice-free, the frequency of strong El Niño events increases bymore than one third, as defined by gradientbased indices that remove mean tropical Pacific warming induced by the seasonally ice-free Arctic. By comparing our time slice experiments with greenhouse warming experiments, we conclude that at least 37–48% of the increase of strong El Niño near the end of the 21st century is associated specifically with Arctic sea-ice loss. Further separation of Arctic sea-ice loss and greenhouse gas forcing only experiments implies that the seasonally ice-free Arctic might play a key role in driving significantly more frequent strong El Niño events.

Are Atmospheric Models Too Cold in the Mountains? The State of Science and Insights from the SAIL Field Campaign

American Meteorological Society (AMS) | July 16th, 2024

Are Modern Droughts Unprecedented?

American Geophysical Union (AGU) | August 8th, 2026

Global drought variability of past centuries remains poorly understood due to sparse instrumental records and limited paleoclimate reconstructions. Yet, quantifying long-

Global drought variability of past centuries remains poorly understood due to sparse instrumental records and limited paleoclimate reconstructions. Yet, quantifying long-term forced and unforced variability is key for assessing the extremeness of modern (2000–2024) drought events. Here, we combine 20 ensemble members from a 600-year climate simulation (ModE-Sim, 1420–2009) and modern reanalysis data (ERA5-Land, 1950–2024) to place recent droughts in a multi-century context. Drought magnitude and timing are measured using the annual maximum potential cumulative water deficit (PCWD), which integrates atmospheric moisture demand and supply, the daily timing of precipitation events, snow melt, and radiation. We analyze the deviation of modern annual, multi-year mean, and 30-year extreme PCWD from alternative reference periods that sample forced and unforced variability to a variable extent. We find a strong decline in the number of regions with unprecedented modern (2000–2024) single-year and 25-year mean PCWD as the reference is extended into the past and with the additional consideration of unforced atmospheric variability. This is not the case for extreme droughts. 30-year extreme PCWD has increased beyond the range of variability of the last 600 years in over half of all regions globally. This suggests that drought extremes are intensifying more rapidly beyond the range experienced in the past than mean conditions. While individual droughts in the modern era may not appear unprecedented when viewed against a century-long record, the shift in their frequency distribution indicates a rising risk of damaging impacts and an increasing likelihood of droughts reaching unprecedented magnitudes in the near future.

ARTMIP-early start comparison of atmospheric river detection tools: how many atmospheric rivers hit northern California’s Russian River watershed?

Climate Dynamics (Springer) | September 10th, 2018

Many atmospheric river detection tools (ARDTs) have now been developed. However, their relative performance is not well documented. This paper compares a diverse set of A

Many atmospheric river detection tools (ARDTs) have now been developed. However, their relative performance is not well documented. This paper compares a diverse set of ARDTs by applying them to a single location where a unique 12-year-long time-series from an atmospheric river observatory at Bodega Bay, California is available. The study quantifies the sensitivity of the diagnosed number, duration, and intensity of ARs at this location to the choice of ARDT, and to the choice of reanalysis data set. The ARDTs compared here represent a range of methods that vary in their use of different variables, fixed vs. percentile-based thresholds, geometric shape requirements, Eulerian vs. Lagrangian approaches, and reanalyses. The ARDTs were evaluated first using the datasets documented in their initial publication, which found an average annual count of 19 ± 7. Applying the ARDTs to the same reanalysis dataset yields an average annual count of 19 ± 4. Applying a single ARDT to three reanalyses of varying grid sizes (0.5°, 1.0°–2.5°) showed little sensitivity to the choice of reanalysis. While the annual average AR event count varied by about a factor of two (10–25 per year) depending on the ARDT, average AR duration and maximum intensity varied by less than ± 10%, i.e., 24 ± 2 h duration; 458 ± 44 kg m− 1 s− 1maximum IVT. ARDTs that use a much higher threshold for integrated vapor transport were compared separately, and yielded just 1–2 ARs annually on average. Generally, ARDTs that include either more stringent geometric criteria or higher thresholds identified the fewest AR events.