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Book Climate Change and California Surface Hydrology

Download or read book Climate Change and California Surface Hydrology written by Marla Ann Schwartz and published by . This book was released on 2016 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding 21st century changes in California surface hydrology is critical to ensuring enough freshwater resources for the state's municipal, ecological and agricultural purposes and assessing future ecosystem health and wildfire risk. To project 21st century surface hydrology over California - a region with highly complex topography that is not well captured by global climate models (GCMs) - downscaling is necessary. This work projects future changes in surface hydrology over the Los Angeles and Sierra Nevada regions through dynamical and statistical downscaling techniques. Dynamical downscaling is employed over Los Angeles to produce 2-km resolution regional projections for the mid-21st-century under an aggressive warming scenario. These projections reveal annual mean runoff and actual evapotranspiration are nearly insensitive to warming. This insensitivity is an artifact of the region's Mediterranean-type climate: Because the warm season receives almost no precipitation, the strongest warming-induced potential evapotranspiration enhancement coincides with dry soils, severely constraining actual evapotranspiration increases. This surprising result highlights that this important semi-arid region is less susceptible to long-term changes in runoff and soil moisture due to its Mediterranean climate. Over the Sierra Nevada Mountains, dynamical downscaling is used to produce high-resolution (3-km) simulations of end-of-21st-century surface hydroclimate. The high resolution and physical realism of these simulations provides unprecedented detail into the elevational dependence of hydroclimate changes and allows us to examine hydroclimate changes at the watershed level. These downscaled simulations reveal future warming leads to a shift toward significantly earlier snowmelt-driven surface runoff timing at each elevation throughout the Sierra Nevada, particularly in mid-elevations (2000-2750m) in the western and northern Sierra. Moreover, these projections show that any precipitation increases are outweighed by warming induced snowpack reductions and evapotranspiration increases, resulting in statistically significant drying of spring and summer soils and a substantial lengthening of the summer dry period. Relationships and patterns that emerge through dynamical downscaling over the Sierra Nevada are exploited to build simple statistical models that mimic dynamical model behavior. Using this hybrid dynamical-statistical downscaling model, high-resolution end-of-21st-century runoff timing and soil moisture changes are projected for all available GCMs from phase 5 of the Coupled Model Intercomparison Project and the four forcing scenarios adopted by the Intergovernmental Panel on Climate Change's Fifth Assessment Report. These multi-model projections allow us to quantify and characterize ensemble-mean changes and the associated uncertainty due to inter-model GCM spread, as well as the consequences associated with choice of emissions scenario. Averaged across the Sierra, April-September soil moisture is projected to decrease 17.1% in the 35-model ensemble mean under RCP8.5 (with an approximate intermodel range of -12.9% to -21.0%), but only 9.1% with an approximate intermodel range of -5.7% to -12.9%) under RCP4.5, a reasonable mitigation scenario.

Book Projections of Potential Flood Regime Changes in California

Download or read book Projections of Potential Flood Regime Changes in California written by and published by . This book was released on 2009 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Simulating the Cold Season Snowpack

Download or read book Simulating the Cold Season Snowpack written by and published by . This book was released on 2009 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book 2009 California Climate Adaptation Strategy

Download or read book 2009 California Climate Adaptation Strategy written by and published by . This book was released on 2009 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Advancing the Science of Climate Change

    Advancing the Science of Climate Change

    Book Details:
  • Author : National Research Council (U.S.). Board on Atmospheric Sciences and Climate
  • Publisher : National Academies Press
  • Release : 2010-12-24
  • ISBN : 9780309145886
  • Pages : 532 pages

Download or read book Advancing the Science of Climate Change written by National Research Council (U.S.). Board on Atmospheric Sciences and Climate and published by National Academies Press. This book was released on 2010-12-24 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt: Climate change is occurring, is caused largely by human activities, and poses significant risks for--and in many cases is already affecting--a broad range of human and natural systems. The compelling case for these conclusions is provided in Advancing the Science of Climate Change, part of a congressionally requested suite of studies known as America's Climate Choices. While noting that there is always more to learn and that the scientific process is never closed, the book shows that hypotheses about climate change are supported by multiple lines of evidence and have stood firm in the face of serious debate and careful evaluation of alternative explanations. As decision makers respond to these risks, the nation's scientific enterprise can contribute through research that improves understanding of the causes and consequences of climate change and also is useful to decision makers at the local, regional, national, and international levels. The book identifies decisions being made in 12 sectors, ranging from agriculture to transportation, to identify decisions being made in response to climate change. Advancing the Science of Climate Change calls for a single federal entity or program to coordinate a national, multidisciplinary research effort aimed at improving both understanding and responses to climate change. Seven cross-cutting research themes are identified to support this scientific enterprise. In addition, leaders of federal climate research should redouble efforts to deploy a comprehensive climate observing system, improve climate models and other analytical tools, invest in human capital, and improve linkages between research and decisions by forming partnerships with action-oriented programs.

Book Climate Extreme Heat and Electricity Demand in California

Download or read book Climate Extreme Heat and Electricity Demand in California written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Climate projections from three atmosphere-ocean climate models with a range of low to mid-high temperature sensitivity forced by the Intergovernmental Panel for Climate Change SRES higher, middle, and lower emission scenarios indicate that, over the 21st century, extreme heat events for major cities in heavily air-conditioned California will increase rapidly. These increases in temperature extremes are projected to exceed the rate of increase in mean temperature, along with increased variance. Extreme heat is defined here as the 90 percent exceedance probability (T90) of the local warmest summer days under the current climate. The number of extreme heat days in Los Angeles, where T90 is currently 95 F (32 C), may increase from 12 days to as many as 96 days per year by 2100, implying current-day heat wave conditions may last for the entire summer, with earlier onset. Overall, projected increases in extreme heat under the higher A1fi emission scenario by 2070-2099 tend to be 20-30 percent higher than those projected under the lower B1 emission scenario, ranging from approximately double the historical number of days for inland California cities (e.g. Sacramento and Fresno), up to four times for previously temperate coastal cities (e.g. Los Angeles, San Diego). These findings, combined with observed relationships between high temperature and electricity demand for air-conditioned regions, suggest potential shortfalls in transmission and supply during T90 peak electricity demand periods. When the projected extreme heat and peak demand for electricity are mapped onto current availability, maintaining technology and population constant only for demand side calculations, we find the potential for electricity deficits as high as 17 percent. Similar increases in extreme heat days are suggested for other locations across the U.S. southwest, as well as for developing nations with rapidly increasing electricity demands. Electricity response to recent extreme heat events, such as the July 2006 heat wave in California, suggests that peak electricity demand will challenge current supply, as well as future planned supply capacities when population and income growth are taken into account.

Book Climate Scenarios for California

Download or read book Climate Scenarios for California written by and published by . This book was released on 2006 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Possible future climate changes in California are investigated from a varied set of climate change model simulations. These simulations, conducted by three state-of-the-art global climate models, provide trajectories from three greenhouse gas (GHG) emission scenarios. These scenarios and the resulting climate simulations are not "predictions," but rather are a limited sample from among the many plausible pathways that may affect California's climate. Future GHG concentrations are uncertain because they depend on future social, political, and technological pathways. In all of the simulations, most precipitation continues to occur in winter, with virtually all derived from North Pacific winter storms. Relatively little change in overall precipitation is projected. Climate warming has a profound influence in diminishing snow accumulations, because there is more rain and less snow, and earlier snowmelt. These snow losses increase as the warming increases, so that they are most severe under climate changes projected by the more sensitive model with the higher GHG emissions.

Book Simulating and Understanding Variability in Runoff from the Sierra Nevada

Download or read book Simulating and Understanding Variability in Runoff from the Sierra Nevada written by Alex Hall and published by . This book was released on 2010 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Climate Change Effects on California Precipitation and Soil Moisture

Download or read book Climate Change Effects on California Precipitation and Soil Moisture written by Neil Elliott Berg and published by . This book was released on 2015 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Projecting 21st century changes in California precipitation and soil moisture is accomplished through examining global climate model simulations alongside dynamical and statistical downscaling techniques. Over the Los Angeles region, a novel hybrid statistical-dynamical downscaling procedure is developed to project mid- and end-of-21st century changes to local precipitation according to 36 global climate models under an aggressive warming scenario. For both time slices, large uncertainty exists on the sign of mean precipitation change, though the spread of these changes is only around 0.2 to 0.4 times as large as natural interannual variability in the historical period. Uncertainty in these precipitation projections can be attributed to varying model placements of the jet stream and storm tracks over the eastern Pacific Ocean. While mean precipitation changes over the Los Angeles region are projected to be small compared to natural variability levels, global climate models project significant changes to interannual extreme precipitation events over central and northern California. The strongest and most statistically significant changes are found by the second half of the 21st century, 2060--2100. During this time period, dry extremes become 1.5 to 2 times more common than historical levels, while wet extremes generally triple in their historical frequency. The mechanism behind this signal of increased extremes is rooted in large increases to interannual precipitation variability seen in a clear majority of global climate models. Finally, the hybrid statistical-dynamical downscaling technique is used to provide for a high-resolution multi-model projection of soil moisture changes over the California Sierra Nevada. Large spatial heterogeneity is found across the region, as the central and northern Sierra Nevada experience drier end-of-century soils and the highly-elevated southeastern peaks experience wetter soils. These signals reflect the complex effects of a much warmer future climate acting on snow-dominated landscapes. Across the entire Sierra Nevada, multiple lines of evidence indicate that the region will experience a net decline in soil moisture on the order of 2-3% per year by the end of the 21st century.

Book Extreme Hydrological Changes in the Southwestern US Drive Reductions in Water Supply to Southern California by Mid Century

Download or read book Extreme Hydrological Changes in the Southwestern US Drive Reductions in Water Supply to Southern California by Mid Century written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Southwestern United States has a greater vulnerability to climate change impacts on water security due to a reliance on snowmelt driven imported water. The State of California, which is the most populous and agriculturally productive in the United States, depends on an extensive artificial water storage and conveyance system primarily for irrigated agriculture, municipal and industrial supply and hydropower generation. Here we take an integrative high-resolution ensemble approach to examine near term climate change impacts on all imported and local sources of water supply to Southern California. While annual precipitation is projected to remain the same or slightly increase, rising temperatures result in a shift in precipitation type towards more rainfall, reducing cold season snowpack and earlier snowmelt. Associated with these hydrological changes are substantial increases in both dry and flood event frequency and intensity. On one hand, the greater probability of drought decreases imported water supply availability. On the other hand, earlier snowmelt and significantly stronger winter precipitation events pose increased flood risk requiring water releases from reservoirs for flood control, also potentially decreasing water availability. As a result, lack of timely local water resource expansion coupled with climate change projections and population increases may leave the area in extended periods of shortages.