California Institute for Energy and Environment (CIEE)

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

We examine a macro-scaled perspective of fire and climate for California and highlight landscapes where sensitivity and exposure to climate change has the potential to induce alteration of future fire activity. This research presents just one method of proposing a future of fire and includes many caveats and assumptions. Using statistical models, we relate the probability of burning in 1080-m landscapes over a 30-year baseline period of 1971–2000 to climate variables for the same period. These climate variables aim to represent spatial variation in vegetation growth conditions and the seasonal dryness necessary for burning. A metric of distance to human development is used to examine human influence on fire activity via ignition and/or suppression. We quantify how the risk of relatively long-term tendency for burning might change with climate over the next 100 years based on projections from two Global Climate Models and two emissions scenarios. Model outcomes suggest varying degrees of increased future fire activity in more productive regions of California however by 2070–2099, the two GCMs selected for the study disagree in the polarity in response for drier, less productive regions. The second component of this study is retrospective. We test the temporal transferability of baseline models by back-casting using 1971–2000 model parameters but incorporating climate and development data from 1941–1970. These baseline back-casts were compared against model outcomes developed using data from the 30-year period from 1941–1970. Though fire records from before 1950 were not kept as reliably as in more recent periods, this method helps to understand how well projections of future fire might reflect actual future events. Baseline models are then also used with observed climate records for periods 1911–1940, which allows us to consider differences among future projections of fire and climate in the context of the range estimated for the last century.

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.

To build public support for adapting to and mitigating climate change, it will be necessary to develop greater awareness of a broad set of biophysical and socioeconomic factors that influence agricultural vulnerability and resilience. First, the study developed a spatially explicit agricultural vulnerability index for California derived from 22 climate, crop, land use, and socioeconomic variables. Results of the agricultural vulnerability index suggest that the Sacramento‐San Joaquin Delta, the Salinas Valley, the corridor between Merced and Fresno, and the Imperial Valley merit special consideration due to their high agricultural vulnerability. The underlying factors contributing to vulnerability and resilience differ among these regions, indicating that future studies and responses could benefit from adopting a contextualized “place based” approach. As an example of this approach, the research team summarized the findings from a recent study on climate change adaptation in Yolo County. The Yolo County study consists of: (1) an econometric analysis of crop acreages under future climate change projections; (2) a hydrologic model of the Cache Creek watershed that simulates the impact of future climate and crop acreage projections on local water supplies; (3) a countywide inventory of agricultural greenhouse gas (GHG) emissions and how it might be used to inform local Climate Action Plans; (4) a survey of farmers’ views on climate change, its impacts and what adaptation and mitigation strategies they might be inclined to adopt; and (5) an urban growth model that evaluates various future development scenarios and the impact on Yolo County farmland and GHG emissions. Since farmland throughout the state is vulnerable to urbanization, the study also used urban growth projections for 2050 to examine the possible impacts on statewide agricultural production, land use patterns, and soils. Lastly, the study examined two on‐farm case studies (Fetzer/Bonterra Vineyards and Dixon Ridge Farms) that highlight the possible benefits of innovative agricultural practices (for example, vineyard carbon storage and renewable energy production from crop residues) that link adaptation and mitigation. 

To provide an updated synoptic assessment of vertical land motion rates in the Sacramento-San Joaquin Delta, the research team performed synthetic aperture radar interferometry (InSAR) on 35 radar scenes from the Envisat platform acquired from 2006–2010. The study used contemporaneously collected continuous global positioning system data to tie the InSAR results to an absolute reference frame. In accord with the researchers’ previous study from 1995–2000 (VLM00), the new results (VLM10) demonstrate general subsidence of the Delta with respect to its margins. The average rates of ~1-2 millimeters per year (mm/yr) are slightly lower than the ~3-5mm/yr rates from 1995–2000. An unexpected finding is the uplift associated with Roberts Island, in the Delta’s southeastern sector. The time- and space-varying differences between the two solutions (VLM00 and VLM10) highlights the need to develop a physical model for the Delta. The study used the updated ground-motion rate map and the most current twenty-first century sea-level rise predictions to project when Delta levees will subside below high-water design thresholds. The study showed that the time period between 2050–2075 is a critical time period, when levees will start to fall below design thresholds, and by 2100 most Delta levees will probably do so.

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.

The San Francisco Bay Area contains a rich array of plant and animal biodiversity and an extensive open space network, embedded within a major metropolitan area. Terrestrial habitats in the San Francisco Bay Area support a wide range of ecosystem services, including carbon storage, forage production, enhanced water supply and quality, crop pollination, and outdoor recreation. The distribution of habitats and plant and animal species is strongly influenced by spatial variation in climate, and is thus expected to change in response to changes in regional and global climate. Current research suggests that most vegetation types will shift toward the coast, especially under scenarios with warmer and drier conditions; range contractions and reduced diversity are projected for California endemic plants in the Bay Area. Bird communities are projected to undergo significant reorganization, leading to altered interactions and community structure. Improved modeling at fine spatial scales represents an important priority to reduce uncertainty in these projections. Climate change is expected to strongly affect ecosystem services. Carbon storage in soils and vegetation could contribute to California’s carbon emissions reduction strategy, but current models project reduced carbon storage in trees due to climate change. Altered agricultural management strategies, including conversion to perennial crops, have the potential to increase soil carbon storage. Climate change impacts on vegetation, hydrology and habitat integrity may negatively affect fire regimes, forage production, water supplies, crop pollination services, and outdoor recreation and quality of life in the San Francisco Bay Area, but few specific projections are available. Strategic conservation planning in the Bay Area is under way to enhance biodiversity conservation through continued open space acquisition. Conservation of heterogeneous landscapes will provide resilience in the face of climate change. Improved understanding of projected climate change impacts on natural habitats will contribute to the development of regional adaptation strategies.