• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 437
  • 142
  • 37
  • 34
  • 34
  • 28
  • 7
  • 6
  • 6
  • 5
  • 5
  • 5
  • 4
  • 3
  • 3
  • Tagged with
  • 884
  • 692
  • 265
  • 197
  • 160
  • 138
  • 124
  • 88
  • 88
  • 88
  • 86
  • 74
  • 69
  • 63
  • 62
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
241

Carbon Flux and Weathering Processes in Icelandic Glacial-Fed Rivers

Quiroga, Allison 01 April 2018 (has links)
An investigation into the carbon dynamics and weathering processes occurring in Icelandic glacial-fed streams was conducted during the spring to summer seasonal transition in June of 2017. Four major outlet rives were sampled from the glaciers of Gígjökull, Steinsholtsjökull, Sólheimajökull, and Falljökull. Markarfljót, the major river that Gígjökull, Steinsholtsjökull, and many other glaciers drain into, was also sampled. Longitudinal sampling occurred at all sites to capture downstream trends in the hydrogeochemistry and carbon dynamics. Distinct differences in geochemistry between glacier surface meltwater, sub-glacial waters, pro-glacial lake water, and post-mixed downstream samples were evident in the data. Glacier surface streams were characterized by relatively colder water temperatures, lower specific conductivity, lower total dissolved solids (TDS) and ion concentrations, and more enriched δ13CDIC values than downstream samples. The THINCARB model was used to calculate the total dissolved inorganic carbon (TDIC), excess partial pressure of carbon dioxide (EpCO2), and percent contribution to TDIC by bicarbonate (HCO3), carbonate (CO3), and carbonic acid and dissolved CO2 (H2CO3). All sites showed a slight decreasing trend in DIC and EpCO2 downstream. The calculated CO2 flux ranged from 1.14 × 107 g/yr to 2.80 × 109 g/yr. The DIC flux ranged from 6.81 × 107 g/yr to 8.44 × 109 g/yr. The average carbon within the CO2 fluxing in these rivers accounts for 0.0004% of the annual, global flux of carbon. The δ13C values were the most variable throughout the study and indicate there are multiple sources influencing the river downstream. This study suggests that, despite previous assumptions and estimations, these glacial-fed rivers act as sources of CO2; however, the samples from this study only provide a snapshot into the carbon flux dynamics during the Spring to Summer seasonal transition. In most samples, HCO3 was the dominant species contributing to DIC content within the rivers, suggesting that DIC is being transported to the ocean as HCO3 but sourced to the atmosphere as CO2. By acting as sources of CO2 to the atmosphere, the process of glaciers melting, which drive geochemical processes within the rivers, are contributing to a positive feedback loop with respect to global warming.
242

COAL, GLOBAL WARMING, AND THE CLEAN AIR ACT

Stewart, Terry L. 01 June 2014 (has links)
In the early 1990s many scientists claimed that there was a scientific consensus that the anthropogenic production of greenhouse gases was causing global warming. Carbon dioxide is produced in far greater quantities than other greenhouse gases. Over 80 percent of the carbon dioxide produced in the United States comes from coal-fired power plants. If global warming is a threat to the welfare and survival of future generations, the United States, as one of the greatest producers of greenhouse gases,has an obligation to reduce its production of these gases. In order to determine the most effective way to reduce the production of greenhouse gases in the United States, this study examines recent efforts by the Clinton and Obama administrations to reduce greenhouse gas emissions from coal-fired power plants.The Clinton and Obama administrations were selected for this study because both administrations were Democratic, and both had avowed political agendas to reduce greenhouse gas emissions. For the first two years each administration enjoyed the support of Democratic majorities in both Houses of Congress, and they had similar political support for the remainder of their time in office. This study will show that President Obama’s executive approach to reducing carbon dioxide emissions from coal-fired power plants has been more effective than the legislative approach of the Clinton administration. The study will indicate that a scientific consensus about anthropogenic global warming and the political will to reduce greenhouse gas emissions from coal-fired power plants did not exist during the 1990s. The study also shows that, despite the effectiveness of the Obama administration in reducing carbon dioxide emissions, there are many problems with the executive approach to the problem. The study suggests that the Clean Air Act has ceded to much legislative power to the Executive branch of government, and that success in reducing carbon dioxide emissions from coal-fired power plants is too dependent on the will of the Executive.
243

Direct Effects of Warming Increase Woody Plant Abundance in a Subarctic Wetland

Carlson, Lindsay G. 01 December 2017 (has links)
Climate change is expected to continue to cause large increases in temperature in Arctic and sub-Arctic ecosystems which has already resulted in changes to plant communities; for example, increased shrub biomass and range. It is important to understand how warmer temperatures could affect the plant community in a wetland system because this region provides crucial high-quality forage for migratory herbivores during the breeding season. One mechanism by which warming could cause change is directly, where warming influences the vital rates of a species; these effects may be either positive or negative. Warmer temperatures may also affect a species indirectly, by impacting neighboring plants which compete with, or facilitate that species. Altering interspecific interactions may affect the abundances of the surrounding species. Recent research shows these ‘indirect’ effects which are mediated by biotic interactions may be important enough to reverse ‘direct’ effects of climate change in some plant communities. Furthermore, herbivores have been shown to mediate the effects of warming, in some systems, even preventing shrub expansion. However, the abundance of herbivores may change because of climate change so it is important to understand the role of herbivores in mitigating climate change effects to inform management strategy. Therefore, we aimed to determine the importance of direct and indirect effects of warming on this plant community while considering changing herbivore pressures. We conducted a two-year field experiment in the coastal wetlands of western Alaska to investigate how warming and herbivory will impact the abundances of two common species, a sedge and a dwarf shrub. We used the results from the experiment to predict the equilibrium abundances of the two species under different climate and herbivory scenarios and determine the contribution of direct and indirect effects to predicted community change. The sedge, Carex ramenskii, remained dominant in under ambient conditions, but the dwarf shrub, Salix ovalifolia, became dominant in warmed treatments. Herbivory mediated some of the effects of warming; where grazing was present community composition did not change as much as where it was not grazed. Results suggest that in the absence of goose herbivory, a 2°C increase could cause a shift from sedge to woody plant dominance on the coast of western Alaska. However, if grazing pressure by geese continues at the present rate, it may help retain the current community composition, though herbivory pressure was not sufficient to entirely reverse the effect of warming. Finally, we found that direct effects were more important than indirect effects in causing changes to this plant community.
244

Trend Analysis and Modeling of Health and Environmental Data: Joinpoint and Functional Approach

Kafle, Ram C. 04 June 2014 (has links)
The present study is divided into two parts: the first is on developing the statistical analysis and modeling of mortality (or incidence) trends using Bayesian joinpoint regression and the second is on fitting differential equations from time series data to derive the rate of change of carbon dioxide in the atmosphere. Joinpoint regression model identifies significant changes in the trends of the incidence, mortality, and survival of a specific disease in a given population. Bayesian approach of joinpoint regression is widely used in modeling statistical data to identify the points in the trend where the significant changes occur. The purpose of the present study is to develop an age-stratified Bayesian joinpoint regression model to describe mortality trends assuming that the observed counts are probabilistically characterized by the Poisson distribution. The proposed model is based on Bayesian model selection criteria with the smallest number of joinpoints that are sufficient to explain the Annual Percentage Change (APC). The prior probability distributions are chosen in such a way that they are automatically derived from the model index contained in the model space. The proposed model and methodology estimates the age-adjusted mortality rates in different epidemiological studies to compare the trends by accounting the confounding effects of age. The future mortality rates are predicted using the Bayesian Model Averaging (BMA) approach. As an application of the Bayesian joinpoint regression, first we study the childhood brain cancer mortality rates (non age-adjusted rates) and their Annual Percentage Change (APC) per year using the existing Bayesian joinpoint regression models in the literature. We use annual observed mortality counts of children ages 0-19 from 1969-2009 obtained from Surveillance Epidemiology and End Results (SEER) database of the National Cancer Institute (NCI). The predictive distributions are used to predict the future mortality rates. We also compare this result with the mortality trend obtained using joinpoint software of NCI, and to fit the age-stratified model, we use the cancer mortality counts of adult lung and bronchus cancer (25-85+ years), and brain and other Central Nervous System (CNS) cancer (25-85+ years) patients obtained from the Surveillance Epidemiology and End Results (SEER) data base of the National Cancer Institute (NCI). The second part of this study is the statistical analysis and modeling of noisy data using functional data analysis approach. Carbon dioxide is one of the major contributors to Global Warming. In this study, we develop a system of differential equations using time series data of the major sources of the significant contributable variables of carbon dioxide in the atmosphere. We define the differential operator as data smoother and use the penalized least square fitting criteria to smooth the data. Finally, we optimize the profile error sum of squares to estimate the necessary differential operator. The proposed models will give us an estimate of the rate of change of carbon dioxide in the atmosphere at a particular time. We apply the model to fit emission of carbon dioxide data in the continental United States. The data set is obtained from the Carbon Dioxide Information Analysis Center (CDIAC), the primary climate-change data and information analysis center of the United States Department of Energy. The first four chapters of this dissertation contribute to the development and application of joinpiont and the last chapter discusses the statistical modeling and application of differential equations through data using functional data analysis approach.
245

Profiling plants to predict range dynamics under climate warming

Radny, Janina 22 July 2019 (has links)
No description available.
246

Putting the spin on wind energy: risk management issues associated with wind energy project development in Australia

Finlay-Jones, Richard Unknown Date (has links)
The debate on global warming is over (Stix, 2006 p24). The global community must now find ways to reduce greenhouse emissions, particularly from energy generation. Wind energy provides one of the potential solutions to generate renewable energy without creating harmful greenhouse gases. Wind energy is the fastest growing energy generation industry globally (‘Operating wind power capacity' 2006a). This rapid growth is being driven by increasing global energy demand, commitment from governments globally to international agreements including the Kyoto Protocol (UNFCCC 1997) to reduce the emission of greenhouse gases, as well as individual country commitments to mandatory renewable energy targets. Australia, whilst being a signatory to the United Nations Framework Convention on Climate Change (UNFCCC) commitment to reduce greenhouse gas emissions, has so far failed to ratify the Kyoto Protocol. In Australia, wind energy development to date has been driven primarily by the development of the Mandatory Renewable Energy Target (MRET) under the Renewable Energy (Electricity) Act 2000. This requires a commitment to 2% of total electricity generation (9,500GW) to be derived from renewable energy sources by the year 2010 (Warwryk, undated). It is now understood, that the current federal obligation to renewable energy is now oversubscribed, and consequently the likelihood of further wind energy projects being developed is highly limited (Brazzale 2005). External to the government commitment to renewable energy, the development of wind energy projects requires a range of inputs including, but not limited to; an understanding of the wind resource, security of land, access to suitable electricity transmission grid, a market for the electricity, access to suitable technology and a level of community support. Whilst the literature related to project management and risk management is extensive, the literature related to the risks associated with wind energy development in Australia is limited. This research then seeks to fill a void that asks the question; How can project managers minimise the risk associated with wind energy developments in Australia? To investigate this research problem, comparative case study analysis was adopted as a methodology utilising a structured interview process of project managers responsible for the development of 8 Australian wind energy projects. This research shows that the greatest risk to Australian projects is the lack of security associated with the current federal legislation and the consequent loss of market value of the power from wind energy projects. A number of additional primary and secondary risks are identified by the interview participants, and the research is able to draw out three common themes of risk management strategies. These three themes were categorised as conservatism, due diligence and proactivism. This study contributes to the research associated with project management, risk management and wind energy development. This insight into the Australian wind energy industry provides policy makers, educators and stakeholders with information to assist in improving the political, economic and social environment for further wind energy development, in order to mitigate against further greenhouse gas emission and combat global warming.
247

Implementing global and geographical education

Bliss, Sue, 1944-, University of Western Sydney, College of Arts, School of Education January 2006 (has links)
This portfolio documents the development and application of a new conceptual framework for the effective implementation of Global Education knowledge, perspectives, values and citizenship in the New South Wales Geography curricula for Years 7-8 (Stage 4), Years 9-10 (Stage 5), and Years 11-12 (Stage 6) (Board of Studies, 1998; 1999; 2003), related teaching and learning resources, and pre-service and in-service courses for teachers. The New South Wales Secondary Global Education Project, funded by the Australian Agency for International Development (AusAID), is managed by the researcher for the Geography Teachers’ Association of New South Wales. The researcher, as manager, was required to publish refereed papers and teaching and learning resources. As such, this portfolio represents a synergistic bringing together of scholarly academic work and professional practice. / Doctor of Education (Ed. D.)
248

Benchmarking climate change strategies under constrained resource usage.

Nettleton, Stuart John January 2010 (has links)
This doctoral dissertation presents evidence based research into climate change policy. The research technique of political economy is used to investigate policy development. A major change in the Anglo-American growth paradigm from unconstrained to constrained growth is identified. The implications of this change for climate change policy are identified. The political economy of climate change policies is expressed in a new Spatial Climate Economic Policy Tool for Regional Equilibria (Sceptre). This is an innovative bechmarking approach to computable general equilibrium (CGE) that provides a spatial analysis of geopolitical blocs and industry groupings within these blocs. It includes international markets for carbon commodities and geophysical climate effects. It is shown that climate constrained growth raises local policy issues in managing technology diffusion and dysfunctional resource expansive specialisations exacerbated by the creation of global carbon markets.
249

Benchmarking climate change strategies under constrained resource usage.

Nettleton, Stuart John January 2010 (has links)
This doctoral dissertation presents evidence based research into climate change policy. The research technique of political economy is used to investigate policy development. A major change in the Anglo-American growth paradigm from unconstrained to constrained growth is identified. The implications of this change for climate change policy are identified. The political economy of climate change policies is expressed in a new Spatial Climate Economic Policy Tool for Regional Equilibria (Sceptre). This is an innovative bechmarking approach to computable general equilibrium (CGE) that provides a spatial analysis of geopolitical blocs and industry groupings within these blocs. It includes international markets for carbon commodities and geophysical climate effects. It is shown that climate constrained growth raises local policy issues in managing technology diffusion and dysfunctional resource expansive specialisations exacerbated by the creation of global carbon markets.
250

Tradable permits for greenhouse gas emissions : a primer with particular reference to Europe

11 1900 (has links)
This paper is written as part of a two-year study of climate change policy choices facing Sweden, conducted under the auspices of the Center for Business and Policy Studies in Stockholm. As such, it aims to be a primer on emissions trading as an instrument for limiting greenhouse gas (GHG) emissions under the Kyoto Protocol to the Framework Convention on Climate Change. The first section notes general considerations concerning emissions trading, particularly in relation to climate policy. The second section explains the many forms of emissions trading included in the Kyoto Protocol. The third section provides a brief review of emissions trading proposals that have been advanced in Europe as of mid-2000. The fourth section addresses issues in the design and implementation of a national GHG emissions trading system. The brief conclusion is followed by an appendix, which draws applicable lessons concerning the choice and design of a cap and trade system from the U.S. SO2 emissions trading program. / Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/) / Includes bibliographical references (p. 38-39).

Page generated in 0.0921 seconds