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Open Access Publications from the University of California
Cover page of Effects of Climate Change on the Inland Fishes of California:  With Emphasis on the San Francisco Estuary Region

Effects of Climate Change on the Inland Fishes of California: With Emphasis on the San Francisco Estuary Region

(2012)

California’s native inland fish fauna is in steep decline, a pattern which is reflected in the status of fishes native to streams flowing into the San Francisco Estuary and in the estuary itself. Climate change will further reduce the distribution and abundance of these mostly endemic fishes and expand the distribution and abundance of alien fish species. The decline and likely extinction of many native fishes reflects dramatic shifts in the state’s aquatic ecosystems; shifts which are being accelerated by climate change. Fishes requiring cold water, such as salmon and trout, will especially suffer from climate change impacts of warmer water and reduced summer flows. Additionally, desirable species living in the San Francisco Estuary and the lower reaches of its streams will have to contend with the effects of rising sea level along with changes in flows and temperature. This paper: (1) briefly describes the environment of California and its fish fauna, (2) summarizes the projected general effects of climate change on its aquatic environments, (3) discusses likely interactions of climate with other stressors of fish populations, (4) describes possible effects on fishes of the San Francisco Estuary, and (5) suggests elements of a conservation strategy for the native fish fauna, focusing on the San Francisco Estuary.

Cover page of Identifying and Overcoming Barriers to Climate Change Adaptation in San Francisco Bay:  Results from Case Studies

Identifying and Overcoming Barriers to Climate Change Adaptation in San Francisco Bay: Results from Case Studies

(2012)

The research goals of this project were threefold: (1) to systematically identify the adaptation barriers encountered by local government entities in San Francisco Bay; (2) to test empirically the robustness and usefulness of a diagnostic framework (previously developed by the authors) so as to modify or refine its components; and (3) to draw larger lessons about the adaptation process and the importance of adaptation barriers—even in highly developed nations—for the scientific community in terms of future research priorities and for policy‐makers. To fulfill these goals, an in‐depth study of five California case studies in the San Francisco Bay region (Hayward, San Francisco, Santa Clara and Marin Counties, and the regional adaptation process) was undertaken. Relevant data were collected through key informant interviews, public documents, observation of and/or participation in public meetings, and a statewide survey.   The study found growing, but still very limited activities in the case studies. Institutional and attitudinal barriers dominate, but economic barriers are also important, even in wealthy locales. Leadership emerged as a critical factor in moving them forward on adaptation. Science mattered some, but policy and planning opportunities were more significant in motivating or launching the adaptation process. The study also found that communities have assets, aids, and advantages that can help them avoid barriers and that there is significant opportunity to affect and overcome the barriers that are being encountered in the “here and now.” However, local communities need outside intervention to address “legacy” and “remote” barriers. With still very little visible adaptation activity “on the ground,” the study concluded that a big portion of what communities are doing to date is working on overcoming the barriers to adaptation instead

Cover page of Development and Application of Downscaled Hydroclimatic Predictor Variables for Use in Climate Vulnerability and Assessment Studies

Development and Application of Downscaled Hydroclimatic Predictor Variables for Use in Climate Vulnerability and Assessment Studies

(2012)

This paper outlines the production of 270 meter grid‐scale maps for 14 climate and derivative hydrologic variables for a region that encompasses the State of California and all the streams that flow into it. The paper describes the Basin Characterization Model (BCM), a map‐based, mechanistic model used to process the hydrological variables. Three historic and three future time periods of 30 years (1911–1940, 1941–1970, 1971–2000, 2010–2039, 2040–2069, and 2070– 2099) were developed that summarize 180 years of monthly  historic and future climate values. These comprise a standardized set of fine‐scale climate data that were shared with 14 research groups, including the U.S. National Park Service and several University of California groups as part of this project. The paper presents three analyses done with the outputs from the Basin Characterization Model: trends in hydrologic variables over baseline, the most recent 30‐year period; a calibration and validation effort that uses measured discharge values from 139 streamgages and compares those to Basin Characterization Model‐derived projections of discharge for the same basins; and an assessment of the trends of specific hydrological variables that links historical trend to projected future change under four future climate projections. Overall, increases in potential evapotranspiration dominate other influences in future hydrologic cycles. Increased potential evapotranspiration drives decreasing runoff even under forecasts with increased precipitation, and drives increased climatic water deficit, which may lead to conversion of dominant vegetation types across large parts of the study region, as well as have implications for rain‐fed agriculture. The potential evapotranspiration is driven by air temperatures, and the Basin Characterization Model permits it to be integrated with a water balance model that can be derived for landscapes and summarized by watershed. These results show the utility of using a process‐based model with modules representing different hydrological pathways that can be interlinked

Cover page of Climate Change Scenarios for the San Francisco Region

Climate Change Scenarios for the San Francisco Region

(2012)

Climate model simulations were used to investigate possible changes in regional climate over California. To accomplish this, the model simulations were downscaled from the coarse global climate model resolution (usually 150 kilometers [km] or greater horizontal grid spacing) to about 12 km horizontal grid spacing over the California region, using statistical techniques. The global model output was used in a statistical modeling scheme to produce sea-level projections for selected California coastal sites. Six global climate models and two greenhouse emissions scenarios, the medium-high emissions Special Report on Emissions Scenarios (SRES) A2 and the lower emissions SRES B1 were considered. By the end of the twenty-first century, the envelope of warming in the models projections, as an annual average, ranges from about 2°C to 6°C (about 3.5 °F to 11°F). On average, mean annual temperature of the A2 scenarios is about 1.5°C (about 3°F) greater than that of the B1 scenario. There is greater warming in summer than in winter. All simulations indicate that hot daytime and nighttime temperatures (heat waves) increase in frequency, magnitude, and duration from the historical period and during the projected period through the first half of the twenty-first century. Projected precipitation is marked by considerable variability between years and decades. In the southern half of California, the models show a decline in annual precipitation. Sea level, at hourly intervals for the historical through the projected twenty-first century, is estimated for selected tide gage sites along the California coast, with rises in the sample of simulations considered here ranging from 27 to 48 centimeters (cm) (11 to 19 in) over historical levels by 2050, and ranging from 77 cm to 140 cm (30 to 55 in) over historical levels by 2100. The rise of mean sea level would provoke an increase in extreme events, as gaged by exceedances above a relatively high or rare historical threshold. Such events become much more frequent and have longer durations than has been seen historically.

Cover page of Urban Growth in California:  Projecting Growth in California (2000-2050) Under Six Alternative Policy Scenarios and Assessing Impacts to Future Dispersal Corridors, Fire Threats, and Climate-Sensitive Agriculture

Urban Growth in California: Projecting Growth in California (2000-2050) Under Six Alternative Policy Scenarios and Assessing Impacts to Future Dispersal Corridors, Fire Threats, and Climate-Sensitive Agriculture

(2012)

This paper documents the development of land use models that represent different urban growth policy scenarios for California, a contribution to the Public Interest Energy Research (PIER) Climate Vulnerability and Assessment Project of 2010–2011. The research team produced six UPlan model runs that portray the following policies as footprint scenarios to 2050: Business as Usual, Smart Growth, Fire Adaptation, Infill, Conservation of Projected Connectivity for Plant Movement under Climate Change, and Conservation of Vulnerable Agricultural Lands. This paper compares the outputs from these six scenarios on outputs from three other PIER vulnerability studies: biodiversity, fire return interval, and agricultural sensitivity. While not directly targeting any conservation or agricultural objective, the Infill scenario preserved more open space for other use than any of the other scenarios. The results suggest that combining Infill objectives with other open space goals will produce better conservation goals for those objectives than merely directing growth away from landscape elements of conservation interest.

Cover page of The Impacts of Sea Level Rise on the San Francisco Bay

The Impacts of Sea Level Rise on the San Francisco Bay

(2012)

Over the past century, sea level has risen nearly eight inches along the California coast, and general circulation model scenarios suggest very substantial increases in sea level as a significant impact of climate change over the coming century. This study includes a detailed analysis of the current population, infrastructure, and property along the San Francisco Bay that are at risk from projected sea level rise if no actions are taken to protect the coast. The sea level rise scenario was developed by the State of California from medium to high greenhouse gas emissions scenarios from the Intergovernmental Panel on Climate Change but does not reflect the worst‐case sea level rise that could occur. If development continues in the areas at risk, all of these estimates will rise. No matter what policies are implemented in the future, sea level rise will inevitably change the character of the San Francisco Bay. We estimate that a 1.0 meter (m) sea level rise will put 220,000 people at risk of a 100‐year flood event, given today’s population. With a 1.4 m increase in sea levels, the number of people at risk of a 100‐year flood event would rise to 270,000. Among those affected are large numbers of low‐ income people and communities of color, which are especially vulnerable. Critical infrastructure, such as roads, hospitals, schools, emergency facilities, wastewater treatment plants, power plants, and more will be at increased risk of inundation, as will vast areas of wetlands and other natural ecosystems. In addition, the cost of replacing property at risk of coastal flooding with a 1.0 m rise in sea levels is $49 billion (in year 2000 dollars). A rise of 1.4 m would increase the replacement cost to $62 billion (in year 2000 dollars). Continued development in vulnerable areas will put additional areas at risk and raise protection costs. A number of structural and non‐structural policies and actions, which are described qualitatively, could be implemented to reduce these risks.

Cover page of Climate Change Effects on the High-Elevation Hydropower System with Consideration of Warming Impacts on Electricity Demand and Pricing

Climate Change Effects on the High-Elevation Hydropower System with Consideration of Warming Impacts on Electricity Demand and Pricing

(2012)

While only about 30 percent of California’s usable water storage capacity lies at higher elevations, high‐elevation hydropower units generate, on average, 74 percent of California’s in‐ state hydroelectricity. In general, high‐elevation plants have small man‐made reservoirs and rely mainly on snowpack. Their low built‐in storage capacity is a concern with regard to climate warming. Snowmelt is expected to shift to earlier in the year, and the system may not be able to store sufficient water for release in high‐demand periods. Previous studies have explored the climate warming effects on California’s high‐elevation hydropower system by focusing on the supply side (exploring the effects of hydrological changes on generation and revenues) but they have ignored the warming effects on hydropower demand and pricing. This study extends the previous work by simultaneous consideration of climate change effects on high‐elevation hydropower supply and demand in California. Artificial Neural Network models were developed as long‐term price estimation tools, to investigate the impact of climate warming on energy prices. California’s Energy‐Based Hydropower Optimization Model (EBHOM) was then applied, to estimate the adaptability of California’s high‐elevation hydropower system to climate warming, considering the warming effects on hydropower supply and demand. The model was run for dry and wet warming scenarios, representing a range of hydrological changes under climate change. The model’s results relative to energy generation, energy spills, reservoir energy storage, and average shadow prices of energy generation and storage capacity expansion are examined and discussed. The modeling results are compared with previous studies to emphasize the need to consider climate change effects on hydroelectricity demand and pricing when exploring the effects of climate change on California’s hydropower system.