Browsing by Subject "Climate change"
Now showing 1 - 20 of 57
Results Per Page
Sort Options
Item Addressing water availability and climate change issues in the Cordillera Blanca, Peru through technical analysis and community building strategies(2010-12) Read, Laura K.; McKinney, Daene C.; Maidment, DavidAccelerated tropical glacial melt on the order of 15-18 meters per year since the 1980's in Peru's Cordillera Blanca region is alarming rural communities and urban authorities, causing them to seek technical support for risk management and adaptation actions. Melting glaciers coupled with changing seasonal rainfall patterns has left many rural communities in the upper Rio Santa basin lacking sufficient fresh water supply to support livestock, irrigation and human consumption. In response to these concerns, a Water Evaluation And Planning (WEAP) model was created by the Stockholm Environmental Institute for simulating glacial melt and flow in the Santa River. Through input parameters of climate, glacial runoff, water use, crop acreage, soil type and groundwater interactions, WEAP has the flexibility to model scenarios for different operation schemes. These schemes allow users to determine the most effective ways to regulate their resources and explore adaptation actions (e.g. altering farming practices and building reservoirs) for future planning. This project improved the existing model by including observed water demand data for irrigation, and evaluating the Climate Forecast System Reanalysis (CFSR) dataset to serve as a potential source for filling gaps in the historic climate record. These improvements added robustness to the model and correlated well with historic stream flow at La Balsa (R² = 0.78 , Nash = 0.68). Two scenarios were explored where (1) a 50% reduction in potato crop was replaced with maize for each sub-basin, and (2) a 10% reduction in precipitation was applied over the upper basin. Results show that the WEAP model is sensitive to changes in crop type and rainfall at the sub-basin scale, an encouraging finding for future exploration. This investigation enables communities to base future decisions on technical evidence and provides a basis for educating citizens on the importance of evaluating their available resources under climate change projectionsItem An Economic Study of Carbon Capture and Storage System Design and Policy(2012-10-19) Prasodjo, DarmawanCarbon capture and storage (CCS) and a point of electricity generation is a promising option for mitigating greenhouse gas emissions. One issue with respect to CCS is the design of carbon dioxide transport, storage and injection system. This dissertation develops a model, OptimaCCS, that combines economic and spatial optimization for the integration of CCS transport, storage and injection infrastructure to minimize costs. The model solves for the lowest-cost set of pipeline routes and storage/injection sites that connect CO2 sources to the storage. It factors in pipeline costs, site-specific storage costs, and pipeline routes considerations involving existing right of ways and land use. It also considers cost reductions resulting from networking the pipelines segment from the plants into trunk lines that lead to the storage sites. OptimaCCS is demonstrated for a system involving carbon capture at 14 Texas coal-fired power plants and three potential deep-saline aquifer sequestration sites. In turn OptimaCCS generates 1) a cost-effective CCS pipeline network for transporting CO2 from all the power plants to the possible storage sites, and 2) an estimate of the costs associated with the CO2 transport and storage. It is used to examine variations in the configuration of the pipeline network depending on differences in storage site-specific injection costs. These results highlight how various levels of cooperation by CO2 emitters and difference in injection costs among possible storage sites can affect the most cost-effective arrangement for deploying CCS infrastructure. This study also analyzes CCS deployment under the features in a piece of legislation the draft of American Power Act (APA) - that was proposed in 2010 which contained a goal of CCS capacity for emissions from 72 Gigawatt (GW) by 2034. A model was developed that simulates CCS deployment while considering different combinations of carbon price trajectories, technology progress, and assumed auction prices. The model shows that the deployment rate of CCS technology under APA is affected by the available bonus allowances, carbon price trajectory, CCS incentive, technological adaptation, and auction process. Furthermore it demonstrates that the 72GW objective can only be achieved in a rapid deployment scenario with quick learning-by-doing and high carbon price starting at 25 dollars in 2013 with a 5 percent annual increase. Furthermore under the slow and moderate deployment scenarios CCS capacity falls short of achieving the 72 GW objective.Item Antarctic Circumpolar Current System and its Response to Atmospheric Variability(2012-08-16) Kim, Yong Sun 1976-The Antarctic Circumpolar Current (ACC) is well known for its multiple bands with large meridional property gradients in the upper waters, each associated with a deep-reaching current core. A revised nineteen-year time series (1992?2011) of altimeter data from the CNES/CLS AVISO is analyzed to identify and trace the spatial distribution of ACC fronts. Specific contours of sea surface height (SSH) are selected within narrow continuous bands of relative maxima SSH slope in the Southwest Atlantic Ocean sector, where they closely follow the distribution of ACC fronts derived from inspection of concurrent high-resolution profile data at hydrographic stations. When applied to the full circumpolar belt, the frontal distribution derived from these new altimeter-based indicators also agrees well with the traces of current jets and in-situ dynamic height fields calculated from concurrent Argo profile data. The temporal variability of ACC fronts is analyzed in relation to dominant modes of atmospheric forcing variability in the Southern Ocean. All three ACC fronts have experienced large seasonal to decadal variability throughout the satellite altimetry era. The general seasonal tendency for each of these jets, with respect to long-term mean positions, is to be located farther to the south during the austral summer and to north in the winter. Circumpolar-mean annual frontal locations show a consistent linear trend of southward migration. However, the estimated decadal variability of the frontal distributions is highly localized, and due to selective response mechanisms to atmospheric variability. A persistent poleward drift of ACC fronts is observed in the Indian sector consistent with increasing sea surface temperature trends. In contrast, a vacillation in the meridional location of ACC fronts is observed in the Pacific sector in association to minor sea surface cooling trends. Therefore, unlike in the Indian sector, the regional Pacific Ocean response is significantly sensitive to dominant atmospheric forcing indices. Mesoscale eddies derived from instabilities at strong current cores are successfully identified with specific SSH gradient criteria. The new estimates of rings population in the Southern Ocean are tightly linked to interannual to decadal atmospheric variability. Increased number of mesoscale eddies correlate with positive SAM forcing about two years earlier, or negative ENSO forcing two to three months earlier. These cross-correlations might explain a prominent peak in rings abundance estimated during 2000 and 2001, and the short-lived maximum that appeared in 2010. There are no persistent trends in the estimated sea surface slope across Drake Passage, and therefore neither in the transport of the ACC. High cross-correlation between the abundance of mesoscale eddies and atmospheric forcing suggests that the overall ACC system is in an eddy-saturated state. However, Drake Passage positive sea level slope anomalies were two-year lagged with negative SAM forcing and with positive ENSO events. These regional responses are characteristic of eastward-propagating signals from a buoyancy-dominated Pacific sector of the Southern Ocean.Item Assessing GCM performance for use in greenhouse gas forced climate change predictions using multivariate empirical orthogonal functions(2012-08) Picton, Jeffrey; Jackson, Charles S., doctor of geophysical science; Ghattas, Omar N.Due to factors such as spatial discretization and the parameterization of certain processes, the presence of bias in models of the Earth's atmosphere is unavoidable. Whether we are selecting a model to explain past phenomenon, forecast weather patterns, or make inferences about the future, the target of any selection process is to minimize the discrepancies between model output and observations. Some discrepancies have a greater effect on the scatter of model predictions though. We exemplify this in the case of CO2 forced warming using multivariate empirical orthogonal functions (EOF), created using an ensemble of plausible parameter configurations of CAM3.1. When subjecting this ensemble to a doubling of atmospheric CO2, some EOFs exhibit significantly higher correlation than others with the resulting increase in mean global surface temperature. Therefore, there are discernible bias patterns that effect its predictive scatter. By targeting these patterns in the model evaluation process, it is plausible to use this information to constrain the resulting range of predictions. We take a first step towards showing this by creating a metric to evaluate model skill based on these EOFs and their correlation to a model's sensitivity to CO2 forcing. Using model output, for which we know the resulting temperature increase, as a surrogate for observations in this metric, the resulting distribution of skill scores indeed agreement in sensitivity to CO2 forcing.Item Assessing the Impacts of Climate Change on Cotton Production in the Texas High Plains and Rolling Plains(2014-12-11) Modala, Naga RaghuveerThe Texas Plains, which include the Texas High Plains and Rolling Plains, is one of the largest cotton growing areas in the world. Cotton cultivation in this region is facing severe challenges from rapidly declining groundwater levels and increasing number of droughts. Projected changes in climate are expected to further add to the uncertainty of cotton production in this region. The overall goal of this research was to study the effects of climate change on cotton yield using the CROPGRO-Cotton Cropping System Model (CSM) within the Decision Support System for Agrotechnology Transfer (DSSAT). The future (2041-2070) climate data generated by three Regional Climate Models (RCMs), namely RCM3-GFDL, RCM3-CGCM3 and CRCM-CCSM was obtained from the North American Regional Climate Change Assessment Program (NARCCAP) and was bias corrected using Distribution mapping techniques. The CROPGRO-Cotton model was calibrated, validated and further evaluated using the observed data collected from cotton experiments at Chillicothe in the Texas Rolling Plains during the years 2008 and 2012. A GIS-based distributed modeling approach was used to predict cotton yields across major cotton-growing counties in the Texas Plains under historic and future climate scenarios using the calibrated CROPGRO-Cotton CSM. The RCMs predicted an overall decrease in the average rainfall (30 to 127 mm), increase in the intensity of extreme rainfall events (4% to 14% as per RCM3-GFDL), and increase in both minimum (1.9 to 2.9 ?C) and maximum temperatures (2.0 to 3.2 ?C) (as per three RCMs) in the future. Deficit irrigation simulations indicated that the maximum seed cotton yields under normal and dry weather conditions could be achieved at 100% and 110% ET replacement scenarios, respectively. The cotton yield at Chillicothe was projected to decrease within a range of 2% to 14.9% under the three RCM future climate scenarios. Majority of the counties in the Texas Plains showed a decline in average cotton yield within a range of 2% to 20% under RCM3-GFDL projected future climate scenario, with the counties in the Texas Rolling Plains being the most affected. A combination of early planting and adoption of no-till practices can minimize the climate change-induced yield losses to some extent.Item Assessment of Water Resources in A Humid Watershed and A Semi-arid Watershed; Neches River Basin, TX and Canadian River Basin, NM(2013-07-16) Heo, JoonghyeokWater is the most important resource on Earth. Climate and land cover changes are two important factors that directly influenced water resources. This research provides important information for water resources management and contributes on understanding of the responses of water resources to climate and land cover changes in two different climates. The Neches River watershed located in a humid subtropical climate had a 0.7 ?C increase in temperature and a 16.3 % increase in precipitation. Developed and crop land covers increased whereas vegetation cover decreased, as a result of human activities. Hydrologic responses to climate and land cover changes resulted in the increases of surface runoff (15.0 %), soil water content (2.7 %), evapotranspiration (20.1 %), and a decrease of groundwater discharge (9.2 %). Surface runoff had an increasing trend with precipitation whereas soil water content was sensitive to changes in land cover, especially human intervention. The Canadian River watershed, a semi-arid watershed, experienced a 0.9 ?C increase in temperature and a 10.9 % decrease in precipitation. Land cover was converted from developed and crop lands into barren land and grass covers, as a result of the decrease in human activity. The change of grass and forest covers into bush/shrub cover is thought to be linked to climate change. Surface runoff, groundwater discharge, soil water content, and evapotranspiration were all decreased by 10.2 %, 10.0 %, 7.7 %, and 9.4%, respectively. Hydrologic parameters generally follow similar patterns to that of precipitation. The trend in water resources followed a similar trend of precipitation for the two watersheds with different climates; a humid watershed and a semi-arid watershed. The humid climate watershed, the Neches River watershed, experienced increasing trends in temperature and precipitation. Groundwater discharge was sensitive to changes in land cover caused by human activities. The semi-arid watershed, the Canadian River watershed, had an increase in precipitation and a decrease in precipitation. Conversion of developed and crop land covers into barren and grass land covers was thought to be the result of the decrease in human activity. The volume of soil water was relatively offset by a combination of precipitation changes and land-cover changes.Item Atmospheric emissions and air quality impacts of natural gas production from shale formations(2014-08) Zavala Araiza, Daniel; Allen, David T.; Webber, Michael; McDonald-Buller, Elena; Hildebrandt Ruiz, Lea; Edgar, ThomasNatural gas is at the core of the energy supply and security debates; new extraction technologies, such as horizontal drilling and hydraulic fracturing, have expanded natural gas production. As with any energy system, however, natural gas has an environmental footprint and this thesis examines the air quality impacts of natural gas production. Greenhouse gas (GHG), criteria pollutant, and toxic emissions from natural gas production have been subject to a great amount of uncertainty, largely due to limited measurements of emission rates from key sources. This thesis reports direct and indirect measurements of emissions, assessing the spatial and temporal distributions of emissions, as well as the role of very high emitting wells and high emitting sources in determining national emissions. Direct measurements are used to identify, characterize and classify the most important sources of continuous and episodic emissions, and to analyze mitigation opportunities. Methods are proposed and demonstrated for reconciling these direct measurements of emissions from sources with measurements of ambient concentrations. Collectively, the direct source measurements, and analyses of ambient air pollutant measurements in natural gas production regions reported in this work improve the estimation, characterization, and methods for monitoring air quality implications of shale gas production.Item Beyond the annual book sale : a model for an environmentally sustainable post-weeding process(2012-05) Halpern, Rebecca Katharine; Feinberg, Melanie, 1970-; Roy, LorieneSocial activism is a foundation in librarianship. As community stewards,librarians regularly develop solutions to complex social issues from discrimination in the workplace to open source academic publishing. Increasingly, one of those issues is climate change. As the reality of climate change becomes more apparent, libraries are faced with their role in supporting healthy communities and environmental sustainability through activities like reducing carbon emissions. There has been much work on how to build greener collections and improve library facilities, but little attention has been paid to the role of weeding—specifically, what happens to deaccessioned materials. The Austin (Texas) Public Library developed an innovative, creative, and long-term model for recycling their core commodity. The Recycled Reads bookstore offers a useful example of how an urban library system recycles weeded print and media materials in such a way that 100 percent of their materials are diverted away from landfills. Through stakeholder buy-in and working closely with community and corporate partners, Austin Public Library's Recycled Reads facility is a model any library system could adopt to address environmentally responsible weeding policies.Item Black mangrove (Avicennia sp.) colony expansion in the Gulf of Mexico with climate change : implications for wetland health and resistance to rising sea levels(2010-12) Comeaux, Rebecca Suzanne; Allison, Mead A. (Mead Ashton); Bianchi, Thomas S.; Mohrig, David; Wilson, Clark R.Populations of black mangroves (Avicennia sp.) are hypothesized to expand their latitudinal range with global climate change in the 21st century, induced by a reduction in the frequency and severity of coastal freezes, which are known to limit mangrove colony extent and individual tree size, as well as an overall warmer climate. The Gulf of Mexico is located at the northward limit of black mangrove habitat and is therefore a prime candidate for population expansion with global warming. This expansion may come at the expense of existing Gulf coastal saline wetlands that are dominantly Spartina spp. marsh grasses. The present study was conducted to focus, not on the extent to date of this replacement, but to examine the potential implications of a marsh to mangrove transition in Gulf wetlands, specifically 1) resistance to accelerating eustatic sea level rise (ESLR) rates, 2) wetland resistance to wave attack in large storms (increased cyclonic storm frequency/intensity is predicted with future climate warming), and 3) organic carbon sequestration and wetland soil geochemistry. Field sites of adjacent and intergrown Avicennia mangrove and Spartina marsh populations in similar geomorphological setting were selected in back-barrier areas near Port Aransas and Galveston, TX (two sites each) as part of a larger-scale planned study of the full latitudinal transition of the western Gulf funded by the National Institute for Climate Change Research (U.S. Department of Energy). The reconnaissance conducted for site surveys show that black mangrove populations in this part of Texas are clustered near inlet areas, suggesting seed transport vectors are a major control on colony establishment, and likely, on the potential rapidity of wetland habitat replacement. Resistance to ESLR was tested by 1) creating high-accuracy (±1 cm) elevation maps over ~5,000 m² areas of adjacent mangrove and marsh areas, and 2) measuring mineral and organic matter accumulation rates (Pb/Cs radiotracer geochronology, loss on ignition) from auger cores. Elevation surveys in Port Aransas indicate mangrove vegetated areas are 4 cm higher in elevation than surrounding marsh on an average regional scale, and 1 to 2 cm higher at the individual mangrove scale: at the Galveston sites, any trend is complicated by the area's pre-existing geomorphology and the relative youth of the mangrove colonies. ¹³⁷Cs accumulation rates and loss on ignition data indicate that mineral trapping is 4.1 times higher and sediment organics are 1.7 times lower in mangroves at Port Aransas; no such definable trends exist at the Galveston sites or in calculated ²¹⁰Pb sediment accumulation rates. This additional mineral particle trapping in mangroves does not differ in grain size character from marsh mineral accumulation. Elevation change may also be effected by root volume displacement: live root weight measurements in the rooted horizon (~0 to 20 cm depth) are consistently higher in mangrove cores from Port Aransas and the site at the west end of Galveston Island. Port Aransas porosities are lower in mangrove rooted horizons, with a corresponding increase in sediment strength (measured by shear vane in the cores), suggesting mangrove intervals may be more resistant to wave-induced erosion during storm events. Port Aransas mangroves exhibit higher pore water redox potentials and salinities over entire core depths and depressed pH over rooted intervals, suggesting a distinct diagenetic environment exists relative to marsh sites. Increased salinities and higher redox potentials may be a function of the rooting network, which introduces oxygen into the sediment and focuses evapo-transpiration and salt exclusion within this zone: this may prove advantageous when competing with marsh grasses by elevating salinities to levels that are toxic for Spartina. Trends observed in the more mature systems of Port Aransas are generally absent at the Galveston sites, suggesting the youth and physically shorter stature of these systems means they have not yet established a unique sediment signature.Item Carbon capture and storage potential contribution to mitigate climate change(2009-12) Baca, Angel Mario; Bickel, J. Eric; Duncan, Ian J.; Gutierrez, Genaro J.Carbon Capture and Storage Potential Contribution to Mitigate Climate Change By Angel Mario Baca, M.A. The University of Texas at Austin, 2009 Supervisor: Dr. Eric Bickel This thesis evaluates the potential of the Carbon Capture and Storage technologies to mitigate climate change. This work emerged from the current debate regarding when CCS technologies are going to be ready in a commercial-scale, or whether they are going to be economically viable. Geologically, the world contains enough room for storing CO2 emissions, but it is still unsolved if leakage can be controlled and monitored. This research focuses on the development of an economic model to estimate the value of CCS.. This model uses equations from the DICE (Dynamic Integrated model on Climate and the Economy). Then, it estimates what change in temperature could occur, and computes the present value of damages to the economy. Moreover, emissions are simulated using the 40 scenario emissions from the Intergovernmental Panel on Climate Change. As the main conclusion of this model, CCS has to be deployed in almost in the entire number of fossil fuel plants around the world and has to be done in the next 30 years to see CCS having an impact, otherwise it would be relatively small and not worth it. Moreover, CCS technologies are part of the components to reduce climate change, but not the main one. It is required that governments, companies, and institution focus their efforts in working collaboratively towards the enforcement of new policies and development of more technologies.Item Climate change framing in the New York Times : the media’s impact on a polarized public(2015-12) Goff, Paepin D.; Jensen, Robert, 1958-; Wilson, KristopherWhile the threat of climate change grows stronger along with the consensus of scientists about the certainty of anthropogenic causes, researchers observe an opposite effect in the public’s acceptance of climate science. While climate change is a salient topic in society, the media’s presentation of climate change has varied over time and the public remains politically divided on the issue. This content analysis of 134 New York Times’ climate change articles between 2001 and 2013 identified six different types of media frames associated with climate change coverage and investigated the presentation of scientific information within those frames. This study also investigated the congruence between scientific consensus regarding climate change, the public’s perception of current scientific knowledge and the way climate change is talked about in the media.Item Climate change impacts and water security in the Cordillera Blanca, Peru(2016-08) Chisolm, Rachel Elizabeth; McKinney, Daene C.; Catania, Ginny; Gilbert, Robert; Hodges, Ben R; Passalacqua, PaolaThis dissertation addresses two aspects of climate change impacts on water resources in the Cordillera Blanca mountain range in Ancash, Peru: glacial lake outburst floods (GLOFs) and water availability. Peru is one of the countries most impacted by climate change, largely due to the abundance of glaciers that play an integral role in the water resources systems of the Peruvian Andes and the coastal region. A warming climate has resulted in the accelerated retreat of many of these glaciers in recent decades. The two greatest impacts of climate change on water security in the Cordillera Blanca are GLOFs and water scarcity during the dry season. This dissertation studies both of these facets of water security in the Cordillera Blanca, Peru. As new glacial lakes emerge and existing lakes continue to grow, they pose an increasing risk of GLOFs that can be catastrophic to the communities living downstream. In this work, particular emphasis is placed on the upper watershed processes that typically comprise a GLOF event. Dynamics of avalanche-generated impulse waves are investigated through three-dimensional hydrodynamic lake simulations of potential GLOF scenarios at Lake Palcacocha, Peru. At Artesonraju Glacier, an emerging lake has recently formed and continues to grow as the glacier retreats. Future lake volumes are projected from ground penetrating radar measurements of ice thickness. With these projections of future lake conditions, possible future hazard conditions are studied at vi Artesonraju, and a new analytical method is presented for calculating approximate overtopping volumes from avalanche-generated waves. Climate change impacts on water availability have been studied through the analysis of approximately 50 years of precipitation data from a weather station in the Cordillera Blanca. These data have been analyzed for trends and changes in variability in precipitation patterns. As a foundation for climate-resilient development, precipitation trends and changes in variability have been linked to possible impacts on agricultural projects. The results of the precipitation data analysis were compared to studies of local perceptions of climate change, and it was concluded that people’s perceptions of change in precipitation patterns often do not reflect the trends observed in the gauged data.Item Coenzyme B, amino acid, and iron-sulfur cluster biosynthesis in methanogenic archaea(2009-08) Drevland, Randy Michael; Graham, David E.Methane is a greenhouse gas and a major contributor to climate change. Methanogenic Archaea produce more than 1 billion tons of this gas each year through methanogenesis, the anaerobic reduction of CO₂ to methane. Coenzyme B (CoB) is one of eight coenzymes required for methanogenesis and it is unique to methanogens. Therefore, this coenzyme is a potential target for inhibiting methanogenesis. To further elucidate the CoB biosynthetic pathway, genes from Methanocaldococcus jannaschii were cloned and expressed in an effort to identify the CoB homoaconitase. From this study, the MJ0499-MJ1277 pair of proteins was identified as the methanogen isopropylmalate isomerase involved in leucine and isoleucine biosynthesis. The MJ1003-MJ1271 pair of proteins was characterized as the homoaconitase required for CoB biosynthesis. This enzyme exhibited broad substrate specificity, catalyzing the isomerization of cis-unsaturated tri-carboxylates with [gamma]-chains of 1-5 methylenes in length. Previously characterized homoaconitases only catalyzed half of the predicted reactions in the isomerization of homocitrate. The MJ1003-MJ1271 proteins function as the first homoaconitase described to catalyze the full isomerization of homocitrate to homoisocitrate. Also, the CoB homoaconitase was identified as specific for (R)-homocitrate and cis-unsaturated intermediates, contrary to a previous study that suggested the substrate specificity of this enzyme included (S)-homocitrate and trans-homoaconitate. The M. jannaschii isopropylmalate isomerase and homoaconitase share more than 50% sequence identity and catalyze analogous reactions. Site directed mutagenesis of the MJ1271 protein was used to identify residues involved in substrate specificity. Arg26 of MJ1271 was critical for the specificity of the CoB homoaconitase. Mutation of this residue to the analogous residue in the M. jannaschii isopropylmalate isomerase, Val28, altered the substrate specificity of the homoaconitase to include the substrates of isopropylmalate isomerase. These homologs of aconitase require a [4Fe-4S] cluster for coordinating their respective substrates at the enzyme active site. However, methanogens lack most of the proteins required for iron-sulfur cluster assembly. Therefore, genes homologous to the Salmonella enterica ApbC iron-sulfur scaffold protein were characterized from methanogens. The MMP0704, MJ0283, and SSO0460 proteins from Methanococcus maripaludis, M. jannaschii, and Solfolobus solfataricus, respectively, were identified as scaffold proteins involved in methanogen iron-sulfur cluster biosynthesis.Item Contemporary high-level political rhetoric surrounding climate change — how Gore, Bush, and Obama approach the issue.(2012-08-08) Vint, Kyle J.; Gerber, Matthew G.; Communication Studies.; Baylor University. Dept. of Communication Studies.Climate change has become a hot button issue spanning the fields of economics, politics, religion, race, ethics, and identity. This thesis provides a rhetorical criticism analyzing how three high-level politicians, namely Al Gore, George W. Bush, and Barack Obama, navigate the intense contours of climate change discussions and articulate their own rhetorical understanding of the phenomena. Presidents and major political figures influence and shape the evolution of climate change rhetoric within American politics. One of the ways high-level politicians shape understandings of climate change is by articulating different rhetorical frames of climate change. This thesis analyzes how political leaders employ different frames in the face of political, economic, and rhetorical constraints. This thesis argues that the ways Gore, Bush, and Obama framed climate change, its consequences, and its solutions, hold important implications for the discussions and policy formulations surrounding climate change.Item Decision analysis and risk management : application to climate change and risk detection(2011-08) Agrawal, Shubham; Bickel, J. Eric; Bickel, J. Eric; Morton, DavidWe have analyzed the application of decision analysis and risk management tools to solve practical problems associated with Climate Change and Risk Detection in the financial services industry. Geoengineering, which is described as an intentional modification of earth’s environment to mitigate the harmful effects of climate change, is evaluated as a policy alternative using the aforementioned tools. We compared the performance of geoengineering with optimal emission controls and a business as usual strategy under various scenarios and found that geoengineering passes the cost benefit test for a majority of the scenarios. We modified the DICE model (Nordhaus, 2008) and used it to evaluate the performance of different environmental policies. Our results show geoengineering as a potential alternative to solve climate change problems. Through this application, and by comparing our findings against Goes et al. (2011), we showed that how framing of the decision problem can lead to completely different results. We also analyzed the application of risk management in the financial services industry. The industry faces three main types of risk: Market risk, Credit risk and Operational risk. Market risk is managed using a diversified portfolio, derivatives, insurance and contracts. More challenging is the task of preventing credit and fraud risk. Statistical models used by the industry to detect and prevent these types of risk are explained in the thesis.Item Dissolved organic matter in major rivers across the Pan-Arctic from remote sensing(2016-05) Griffin, Claire Genevieve; McClelland, James W.; Frey, Karen E; Gardner, Wayne S; Liu, Zhanfei; Shank, Gerald CClimate-driven changes in Arctic hydrology and biogeochemistry are impacting transport of water and water-borne material from land to ocean. This includes massive amounts of organic matter that are mobilized and exported from the pan-Arctic watershed via rivers each year. Dissolved organic matter (DOM), an important part of the Arctic carbon cycle, has received growing attention in recent years, yet long-term studies of riverine biogeochemistry remain rare in these remote and logistically challenging regions. Remote sensing of chromophoric dissolved organic matter (CDOM, the portion of the DOM pool that absorbs light), provides a unique opportunity to investigate variations in DOM in major Arctic rivers over multiple decades. CDOM is a useful proxy for dissolved organic carbon (DOC) and is essential to photochemical processes in surface waters. This dissertation presents the development and application of remote sensing regression models across six major Arctic rivers: the Kolyma, Lena, Mackenzie, Ob’, Yenisey and Yukon. Frozen, archival samples of CDOM were used to develop calibration data for remote sensing regressions. Remote sensing methods estimated CDOM with R2 of 85% across all rivers, although individual rivers varied in their predictability in association with sediment loading and hydrology. As with previous studies of Arctic systems, concentrations and export of CDOM and DOC were highest during spring freshet in most of these rivers. Interannual variability in DOM export may be linked to the Arctic Oscillation. Within the Mackenzie, Ob’, and Yenisey rivers, observations of DOM concentration and export were extended back to the 1980s, the first known empirical records of this length for Arctic rivers that span both continents. Although no pan-Arctic trends in CDOM export were detected, there is some evidence of long-term changes in riverine DOM. For example, discharge-specific CDOM concentrations decreased in the Yenisey River and increased in the Ob’ River. Additionally, CDOM concentrations increased over the past ~30 years within the Mackenzie River. This dissertation also includes results from experiments used to quantify the effects of cryopreservation on CDOM analyses, and potential approaches for ameliorating freezing effects. These experiments showed that freezing for preservation introduces some error into CDOM measurements, although these effects vary between river systems. Sonication may improve CDOM measurements in some river systems, but the effects of both cryopreservation and sonication should be quantified on a case-by-case basis. Overall, this dissertation work demonstrates that 1) remote sensing of CDOM is a viable tool for tracking fluvial DOM in the major Arctic rivers, 2) only the Mackenzie River showed significant increases in CDOM concentration from the 1980s to present and 3) long-term changes in discharge-specific CDOM concentrations have occurred in the Yenisey and Ob’ rivers. These long-term trends cannot be definitively linked to climate change, but may be related to effects of warming on permafrost, hydrology, and biogeochemistry within in Arctic watersheds with consequences for carbon cycling on both regional and global scales.Item Ecological and evolutionary analyses of range limits and biodiversity patterns(2011-12) Behrman, Kathrine Delany; Keitt, Timothy H.; Kirkpatrick, Mark, 1956-The goal of this dissertation is to further our understanding of how spatially heterogeneous landscapes may impact the formation of range boundaries that then aggregate to form large-scale biodiversity patterns. These patterns have been analyzed from many different perspectives by ecologists, evolutionary biologist, and physiologists using a variety of different theoretical, statistical, and mechanistic models. For some species, there is an obvious abrupt change in the environment causing a range boundary. Other environments change gradually, and it is unclear why species fail to adapt and expand their range. The first chapter develops a novel theoretical model of how the establishment of new mutations allows for adaptation to an environmental gradient, when there is no genetic variation for the trait that limits the range. Shallow environmental gradients favor mutations that arise nearer to the range margin, have smaller phenotypic effects, and allow for proportionately larger expansions than steep gradients. Mutations that allow for range expansion tend to have large phenotypic effects causing substantial range expansions. Spatial and temporal variation in climatic and environmental variables is important for understanding species response to climate change. The second chapter uses a mechanistic model to simulate switchgrass (Panicum virgatum L.) productivity across the central and eastern U.S. for current and future climate conditions. Florida and the Gulf Coast of Texas and Louisiana have the highest predicted current and future yields. Regions where future temperature and precipitation are anticipated to increase, larger future yields are expected. Large-scale geographic patterns of biodiversity are documented for many taxa. The mechanisms allowing for the coexistence of more of species in certain regions are poorly understood. The third chapter employs a newly developed wavelet lifting technique to extract scale-dependent patterns from irregularly spaced two-dimensional ecological data and analyzes the relationship between breeding avian richness and four energy variables. Evapotranspiration, temperature, and precipitation are significant predictors of richness at intermediate-to-large scales. Net primary production is the only significant predictor across small-to-large scales, and explains the most variation in richness (~40%) at an intermediate scale. Changes in the species-energy relationship with scale, may indicate a shift in the mechanism governing species richness.Item Ecological mechanisms underlying soil microbial responses to climate change(2013-12) Waring, Bonnie Grace; Hawkes, Christine V.Soil microbes influence the global carbon cycle via their role in the decomposition and formation of soil organic matter. Thus, rates of ecosystem processes such as primary production, soil respiration, and pedogenesis are sensitive to changes in the aggregate functional traits of the entire microbial community. To predict the magnitude and direction of microbial feedbacks on climate change, it is necessary to identify the physiological, ecological, and evolutionary mechanisms that underlie microbes’ responses to altered temperature and rainfall. Therefore, I examined microbial community composition and function in relation to manipulations of resource availability and precipitation in two contrasting ecosystems: a tropical rainforest at La Selva Biological Station, Costa Rica, and a semi-arid grassland in central Texas. I conducted a leaf litter decomposition experiment at La Selva to identify the physiological constraints on microbial allocation to extracellular enzymes, which degrade organic matter. I found strong evidence that microbial enzyme production is decoupled from foliar stoichiometry, consistent with weak links between leaf litter nutrients and decomposition rates at the pan-tropical scale. Next, to examine whether ecological trade-offs within microbial communities may drive shifts in carbon cycling at local spatial scales, I quantified changes in soil fungal and bacterial community composition in response to an in situ precipitation exclusion experiment I established at La Selva. Although drought-induced shifts in community structure were small, large increases in biomass-specific respiration rates were observed under dry conditions. These findings suggest that physiological adjustments to drought may constitute an important feedback on climate change in wet tropical forests. Finally, I focused on microbial community responses to climate change within a meta-community framework, using a reciprocal transplant experiment to investigate how dispersal shapes bacterial community structure along a natural rainfall gradient in central Texas. I found that soils from the wet end of the precipitation gradient exhibited more plastic functional responses to altered water availability. However, soil bacterial community composition was resistant to changes in rainfall and dispersal, preventing functional acclimatization to precipitation regime. Together, the results of these experiments emphasize the potential for physiological plasticity or microevolutionary shifts within microbial populations to drive ecosystem carbon cycling under climate change.Item Effect of Urbanization and Climate Change on Hydrological Processes over the San Antonio River Basin, Texas(2014-11-18) Zhao, GangWith the rapid population growth and economic development in the State of Texas, a fast urbanization process has occurred over the past several decades. The direct consequences of the increased impervious area are greater surface runoff and higher flood peaks. Meanwhile, climate change has led to more frequent extreme events. Therefore, a thorough understanding of the hydrological processes under urbanization and climate change is indispensable for sustainable water management. In this investigation, a case study was conducted by applying the Distributed Hydrology Soil Vegetation Model (DHSVM) to the San Antonio River Basin (SARB), Texas. Hosting the seventh largest city in the U.S. (i.e., City of San Antonio), the SARB is vulnerable to both floods and droughts. A set of historical and future land cover maps were assembled to represent the urbanization process. Two forcing datasets were employed to drive the DHSVM model. The first is a long-term observation based dataset (1915-2011), which was used as inputs for calibrating and validating DHSVM, as well as evaluating the urbanization effect. The second is the statistically downscaled climate simulations (1950-2099) from the Coupled Model Intercomparison Project Phase 5 (CMIP5), which were applied for understanding impacts related to climate change. Results show that urbanization exerts a much larger influence on streamflow than climate change does. Under the same observed forcings, annual average streamflow increased from 28.12 m^3/s (with 1929 land cover) to 50.34 m^3/s (with 2011 land cover). As for climate change, results suggest that it will exacerbate the drought severity ? with reduced evapotranspiration and soil moisture caused by decreased precipitation. However, the projected future streamflow does not show a clear increasing or decreasing trend. Regarding the combined effect from urbanization and climate change, the results indicate that the seasonal streamflow magnitude will be notably changed. Furthermore, with significantly decreased evapotranspiration and slightly increased soil moisture, more water will be available for streamflow, increasing the possibility of flood risk in the region.Item Effect of Warming and Precipitation Distribution on Soil Respiration and Mycorrhizal Abundance in Post Oak Savannah(2012-07-16) Cartmill, Andrew DavidProjected climate change may alter soil carbon dioxide (CO2) efflux from terrestrial ecosystems; yet disentangling effect of plant species from climate drivers remains a key challenge. We explored the effects of the dominant plant species, warming, and precipitation distribution on soil CO2 efflux, its underlying components, and mycorrhizal abundance in southern post oak savannah. Post oak savannah in the south-central US are dominated by three contrasting plant functional types: Schizachyrium scoparium (Michx.) Nash. (little bluestem) a C4 grass, Quercus stellata Wangenh.(post oak)a C3 deciduous tree, and Juniperus virginiana L. (eastern redcedar) a C3 evergreen tree. Monocultures and tree-grass plots were warmed using infrared heaters and precipitation events were manipulated to intensify summer drought and augment cool season precipitation. Soil CO2 efflux, the root, bacterial and hyphal components of CO2 efflux, and mycorrhizal abundance were measured. Soil CO2 efflux varied with seasonal changes in soil VWC and temperature, with higher soil CO2 efflux rates in the spring and lower rates in both the cooler winter season and at the end of the dry summer period. There was no relationship between root length density or root mass density and soil CO2 efflux during the short term precipitation distribution campaigns. Partitioning of root, fungal, and bacterial component contribution to soil CO2 efflux indicated a substantial contribution of bacterial respiration to soil CO2 efflux within this system. There was no relationship between microbial biomass [microbial dissolved organic carbon (DOC)] and soil CO2 efflux, or root length (or mass) density and microbial biomass. This suggests that species and climatic effects on root and microbial activity drive soil CO2 efflux. As plant species within this system differed in their association with mycorrhizal fungi and had a strong effect on the individual components of soil CO2 efflux, we conclude that shifts in vegetation cover and growth and the response of vegetation to long term warming and potential future extreme precipitation events (e.g., large preciptation events, prolonged drought) will be major drivers of changes in soil carbon (C) dynamics and associated soil CO2 efflux.
- «
- 1 (current)
- 2
- 3
- »