Browsing by Subject "Global warming"
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Item Combined effects of global warming and a shutdown of the Atlantic meridional overturning circulation on West African and European climate(2012-05) Brown, Meredith Guenevere Longshore; Cook, Kerry Harrison, 1953-; Fu, Rong; Dickinson, Robert E.; Jackson, Charles S.The Atlantic meridional overturning circulation has a vast potential for abrupt climate change due to its large heat transport through the ocean and its nonlinear dynamics. Because of these unique properties, this paper investigates how the climate of West Africa and Europe will respond to a shutdown of the Atlantic meridional overturning circulation at the end of the 21st century. Here we use a regional climate model with 90-km grid spacing is forced by an idealized sea-surface temperature anomaly, based upon coupled atmosphere/ocean global model water hosing experiments, with a business-as-usual global warming scenario to discover how West African and European climate will change. In both the boreal spring and summer, cooling in the eastern Atlantic is associated with a strong intensification and eastward extension of the North Atlantic subtropical high over Europe throughout the depth of the atmosphere, a strengthening of the heat low over West Africa at low levels, and a weakening of the Saharan High in the upper atmosphere. Rainfall rates also decrease markedly throughout most of West Africa and Europe: in spring, rainfall rates decrease by 50-80% over Sahelian Africa, in summer rainfall over Europe decreases by up to 90%, while precipitation over West Africa is reduced by 40%.Item Impacts of simulated climate change on West Texas(Texas Tech University, 1999-05) Kenyon, Jesse DaleClimate records for the four first-class stations of Abilene, Amarillo, Lubbock, and Wichita Falls were statistically analyzed to produce a climatology of the west Texas region. This climatology was used for comparison to the baseline run of a general circulation model to validate its appropriateness in predicting the impacts of global warming in the West Texas area. Statistical analysis was then performed on the doubled CO2 run of the GCM, and a comparison was made to the baseline run. This enabled a determination of the sensitivity of the region to climate change brought about by increased CO2. The effects to the three meteorological variables of temperature, precipitation, and relative humidity are presented.Item Increased temperature effects on fish-mediated nutrient cycling in an East Texas stream(2017-11-07) McWilliams, Jessica Lynn; Hargrave, Chad W.The unprecedented rate of global warming is an inevitable outcome of anthropogenic CO2 release into the atmosphere and complex climatic feedbacks. In ectotherms, increasing temperature may increase metabolic rates, which could enhance the energy demands of individuals and should accelerate resource acquisition. Population size and fish biomass were measured seasonally in a small second order stream over a 10-year period to examine seasonal variation in these parameters. I examined effects of increased temperature on nitrogen and phosphorus excretion in the four most abundant fish in this stream system. These fishes represent three functional feeding guilds common to many temperate stream ecosystems and comprise approximately 80-90% of the fish community. I developed temperature dependent nitrogen and phosphorus excretion models for fishes and applied these models to daily average temperatures in the stream. I then simulated climate warming (+2, +4, & +6°C) to examine the potential effects of increased temperature on fish-mediated nutrient dynamics in a southern temperate stream ecosystem. I found that increased temperature does increase nutrient cycling and nutrient flux within aquatic ecosystems; however, these effects appear to be tied to population size, biomass in addition to seasonal temperature. With increased temperature effects in spring and autumn having the greatest effect, when temperatures are cool and fish abundance and biomass is also greatest.Item Life cycle global warming emissions for natural gas(2012-08) Randel, Tony Lynn; Allen, David T.; Crawford, RichardClimate change is a topic of social and political commentary and controversy, and is a topic that will continue to be addressed by future scientists and laypersons alike. This report contains information and laboratory exercises for use in a greenhouse gas (GHG) and global warming potential (GWP) learning module, to be employed in secondary or entry level university engineering and environmental science curricula. Exercises include a hands-on experience with the greenhouse effect and calculations of GWP for 20-year and 100-year timeframes.Item Local effects of global warming(2007-12) Lu, Jun; Martin, Clyde F.Currently, global warming is a focus of attention. In order to scientifically evaluate evidence about global warming, and prove the existence of global warming, this research analyzes almost 100 years’ daily temperature records in a local weather station (Period: 1/1/1914-12/31/2006, Station: Lubbock International Airport, TX 79403, CoopID: 415411). Since mean and variance are very important in evaluating that the temperature records are inconsistent with an unchanging climate, this research create effective approaches to test the inequality of the variance and the mean of daily temperature in each year, and find their trend over the time. First, it provides the approach to test the normality of daily temperature because a lot of statistical tests are sensitive to normality assumption. Then, based on the results of invalid normality, it gives the detail procedures to test the equality of variances and means using some statistical tests which are robust to departure from normality. In testing the equality of variances, Brown and Forsythe’s test is used. In testing the equality of variances, Kruskal-Wallis nonparametric test and Z-test are used. In addition, “Loess” Smoother technique is used to find the trend of the variance and the mean of daily temperature over time. The results show that the equality of variances and means are both invalid, and their trends are increasing over time. These results suggest global warming really exists in the local place, and they also provides evidences that support global warming Furthermore, the probability of maximum temperature is found to be a Weibull distribution by applying Extreme Value Theory. Based on fitting data to the distribution, some useful predictions are made, such as estimation of 100-year return level which predicts what the annual maximum temperature will be on average every 100 years. Overall, this research scientifically estimates the local effect of global warming. It gives a good reference for the study of global warming, climate change, weather prediction, or time series data.Item MEASURING THE EFFECT OF MISCONCEPTIONS INSTRUCTION ON THE(2011-05) Mccuin, John L.; Lichti, Roger L.; Hayhoe, Katharine; Lan, William; Leary, Colleen; Lamp, Carl D.Global warming is an important scientific issue. As the result of anthropogenic carbon emissions, global warming is already affecting life on this planet and will likely have even more significant impacts on economies, species, and human life in future decades.1 As potential solutions to global warming require economy-wide measures, global warming is also a prominent issue discussed in politics and the media. While there is not much debate regarding the fundamental science of global warming and the greenhouse effect among active, publishing researchers in the field,2 scientific misconceptions abound across broad age ranges and education levels, including politicians and journalists. These misconceptions give rise to a great deal of debate over issues such as the greenhouse effect that have been viewed as settled by the scientific community for decades and sometimes even centuries.3-17 The present science education research was designed with the specific goal of investigating the potential for increasing scientific understanding of a fundamental yet relatively basic physical phenomenon underlying global warming, namely the greenhouse effect. This research lies within the category of science learning in general, and conceptual change research in particular, as this is an area where significant misconceptions are documented to exist.4, 7, 11, 18 For example, a common misconception is that global warming is due to a hole in the ozone layer.4, 19 The Conceptual Change Hypothesis (CCH) holds that misconceptions interfere with the learning of correct concepts and that misconceptions are resistant to the traditional mode of correct instruction alone. According to the CCH, special instruction that effectively addresses learner misconceptions should be added. In the present study, this specialized form of instructional intervention will be called Misconceptions Instruction. The present study examines the relative effects of Traditional Instruction (TI) and Misconceptions Instruction (MI) on the learning of fundamental physics concepts related to the greenhouse effect. In the present study, approximately 200 students in intact course sections of a first-year Atmospheric Sciences course at Texas Tech University were quasi-randomly assigned to one of two instructional treatments: Traditional Instruction or Misconceptions Instruction. Both treatment groups received a pretest, an immediate posttest following treatment, and a delayed posttest approximately 14 days after the treatment. Raw scores were calculated, and mean scores for both groups were subjected to a repeated-measures ANOVA to determine if participants in each group improved over time and if there was a statistically significant difference in their assessment performances. The results of the repeated measures ANOVA reveal no improvement over time and no statistically significant difference between groups for performance on concept questions and on the assessment as a whole, although there was a statistically significant difference between groups for performance on the misconception questions only. The results carry significant implications for the quantity and type of instruction utilized in this study, as well as implications about the nature of the most common misconceptions about the greenhouse effect and global warming. For example, short reading passages about the greenhouse effect were found inadequate for bringing about conceptual change, in contrast with other studies that had longer exposure times and varied instructional methods.11, 20 Also, the nature of the most common misconceptions concerning the greenhouse effect was found to be categorical, meaning that students used the entirely wrong mental model as opposed to isolated misconceptions about the correct mental model, and thus refutational instructional methods were ineffective. These implications are discussed in light of previous findings related to science education research in general and to research on misconceptions-based instruction in specific. Appendix G: Global circulation models (GCMs) capture the large-scale trends of climate variables, but GCMs operate on a grid size that cannot account for local features which modify the climate and thus the global trend in a region. While the climate is warming globally, many effects are felt locally. Therefore, the GCM output needs to be downscaled to provide regional climate scenarios, and one approach for doing this is empirical statistical downscaling (ESD). There are a few different software packages and methods for performing ESD, one of which is SDSM 4.2, which computes the parameters of multiple linear regression optimized using ordinary least squares or dual simplex algorithms. In this study, the Statistical Downscaling Model software package (SDSM) was evaluated using data from 20 different weather stations and three different atmosphere-ocean general circulation models (AOGCMs) for two variables in order to determine SDSMs ability to meet modern downscaling needs. It was found that as a software package, SDSM was not suitable for projects involving the need to perform many runs of the system. With regard to performance, SDSM was found to perform worse than two of the newer methods against which it was compared.Item Petrophysical modeling and simulatin study of geological CO₂ sequestration(2014-05) Kong, Xianhui; Delshad, Mojdeh; Wheeler, Mary F. (Mary Fanett)Global warming and greenhouse gas (GHG) emissions have recently become the significant focus of engineering research. The geological sequestration of greenhouse gases such as carbon dioxide (CO₂) is one approach that has been proposed to reduce the greenhouse gas emissions and slow down global warming. Geological sequestration involves the injection of produced CO₂ into subsurface formations and trapping the gas through many geological mechanisms, such as structural trapping, capillary trapping, dissolution, and mineralization. While some progress in our understanding of fluid flow in porous media has been made, many petrophysical phenomena, such as multi-phase flow, capillarity, geochemical reactions, geomechanical effect, etc., that occur during geological CO₂ sequestration remain inadequately studied and pose a challenge for continued study. It is critical to continue to research on these important issues. Numerical simulators are essential tools to develop a better understanding of the geologic characteristics of brine reservoirs and to build support for future CO₂ storage projects. Modeling CO₂ injection requires the implementation of multiphase flow model and an Equation of State (EOS) module to compute the dissolution of CO₂ in brine and vice versa. In this study, we used the Integrated Parallel Accurate Reservoir Simulator (IPARS) developed at the Center for Subsurface Modeling at The University of Texas at Austin to model the injection process and storage of CO₂ in saline aquifers. We developed and implemented new petrophysical models in IPARS, and applied these models to study the process of CO₂ sequestration. The research presented in this dissertation is divided into three parts. The first part of the dissertation discusses petrophysical and computational models for the mechanical, geological, petrophysical phenomena occurring during CO₂ injection and sequestration. The effectiveness of CO₂ storage in saline aquifers is governed by the interplay of capillary, viscous, and buoyancy forces. Recent experimental data reveals the impact of pressure, temperature, and salinity on interfacial tension (IFT) between CO₂ and brine. The dependence of CO₂-brine relative permeability and capillary pressure on IFT is also clearly evident in published experimental results. Improved understanding of the mechanisms that control the migration and trapping of CO₂ in the subsurface is crucial to design future storage projects for long-term, safe containment. We have developed numerical models for CO₂ trapping and migration in aquifers, including a compositional flow model, a relative permeability model, a capillary model, an interfacial tension model, and others. The heterogeneities in porosity and permeability are also coupled to the petrophysical models. We have developed and implemented a general relative permeability model that combines the effects of pressure gradient, buoyancy, and capillary pressure in a compositional and parallel simulator. The significance of IFT variations on CO₂ migration and trapping is assessed. The variation of residual saturation is modeled based on interfacial tension and trapping number, and a hysteretic trapping model is also presented. The second part of this dissertation is a model validation and sensitivity study using coreflood simulation data derived from laboratory study. The motivation of this study is to gain confidence in the results of the numerical simulator by validating the models and the numerical accuracies using laboratory and field pilot scale results. Published steady state, core-scale CO₂/brine displacement results were selected as a reference basis for our numerical study. High-resolution compositional simulations of brine displacement with supercritical CO₂ are presented using IPARS. A three-dimensional (3D) numerical model of the Berea sandstone core was constructed using heterogeneous permeability and porosity distributions based on geostatistical data. The measured capillary pressure curve was scaled using the Leverett J-function to include local heterogeneity in the sub-core scale. Simulation results indicate that accurate representation of capillary pressure at sub-core scales is critical. Water drying and the shift in relative permeability had a significant impact on the final CO₂ distribution along the core. This study provided insights into the role of heterogeneity in the final CO₂ distribution, where a slight variation in porosity gives rise to a large variation in the CO₂ saturation distribution. The third part of this study is a simulation study using IPARS for Cranfield pilot CO₂ sequestration field test, conducted by the Bureau of Economic Geology (BEG) at The University of Texas at Austin. In this CO₂ sequestration project, a total of approximately 2.5 million tons supercritical CO₂ was injected into a deep saline aquifer about ~10000 ft deep over 2 years, beginning December 1st 2009. In this chapter, we use the simulation capabilities of IPARS to numerically model the CO₂ injection process in Cranfield. We conducted a corresponding history-matching study and got good agreement with field observation. Extensive sensitivity studies were also conducted for CO₂ trapping, fluid phase behavior, relative permeability, wettability, gravity and buoyancy, and capillary effects on sequestration. Simulation results are consistent with the observed CO₂ breakthrough time at the first observation well. Numerical results are also consistent with bottomhole injection flowing pressure for the first 350 days before the rate increase. The abnormal pressure response with rate increase on day 350 indicates possible geomechanical issues, which can be represented in simulation using an induced fracture near the injection well. The recorded injection well bottomhole pressure data were successfully matched after modeling the fracture in the simulation model. Results also illustrate the importance of using accurate trapping models to predict CO₂ immobilization behavior. The impact of CO₂/brine relative permeability curves and trapping model on bottom-hole injection pressure is also demonstrated.Item The risk of ending a solar radiation management program abruptly(2009-12) Agrawal, Shubham; Bickel, J. Eric; Lasdon, LeonClimate change as a result of anthropogenic activities calls for reduction of greenhouse gas emissions to avoid dangerous consequences on society. However, abatement of emission is a costly process and adversely affects the economic growth. Recent proposals, therefore, suggested a different approach i.e. Geoengineering. Instead of controlling emissions, Geoengineering modifies the climate by changing global energy fluxes either by increasing the amount of outgoing infrared radiation through reduction of greenhouse gases (GHGs) or by decreasing the amount of solar radiation falling upon the earth’s surface by increasing the albedo (reflectivity) of the atmosphere. Most popular geoengineering strategies are Air Capture (AC) and Solar Radiation Management (SRM) and many economic studies have shown large net monetary benefits with their application. But, these studies neglected the risks which can arise due to potential failure to sustain SRM after few decade of its deployment. There is a concern that application of SRM will lead to increase in concentration of carbon-dioxide in atmosphere and its abrupt turning off can lead to rise in temperature and thereby huge monetary losses. In this report, consequences of abruptly turning off of SRM have been analyzed. A modified version of DICE (Dynamic Integrated model of Climate and the Economy) model that incorporates negative SRM forcing and a two phase optimization procedure has been used for the study. Different outcomes such as net change in NPV of climate damage and abatement costs, maximum mean temperature of earth surface, increase in temperature, emissions control rate, carbon taxes, etc due to abrupt ending of SRM have been analyzed. Results show that application of SRM with a risk of abrupt turnoff is still more profitable compared to not using it at all.Item Study of extreme values in weather(2008-05) Kliewer, Anton; Martin, Clyde; Neusel, Mara D.; Ghosh, Bijoy K.This thesis is an attempt to find any sign of global warming by studying weather data on the local level. For this weather data for three cities is analyzed, using statistical methods based on extreme values. Extreme values means that extraordinary situations can be predicted, or in this thesis, quantified. To understand what the analysis of the weather data means, numerous experiments were performed to understand the nature of extreme values. The study of extreme values began with Emil Gumbel in the mid-20th century and is best understood through the application of the Generalized Extreme Value distribution. It is with an applied-math approach that this thesis attempts to understand how local climate changes can be quantified.Item Understanding preciptation changes over West Africa and North America under global warming and identifying a Congo Basin Walker circulation(2015-05) Neupane, Naresh; Cook, Kerry Harrison, 1953-; Dickinson, Robert E.; Fu, Rong; Jackson, Charles S.; Scanlon, Bridget R.Studies have shown that the Atlantic Ocean affects West African rainfall. However, the response of the West African monsoon to Atlantic warming is not understood clearly. My dissertation explores this by analyzing idealized simulations with a regional climate model. Below 1.5 K warming of the Atlantic, rainfall increase by 30-50% over the Sahel. In contrast, above 2 K, rainfall decreases substantially. Atlantic warming is accompanied by decreases in low-level geopotential heights in the Atlantic decreasing the large-scale meridional geopotential height gradient across West Africa. This leads to easterly wind anomalies in the Sahel. Below 2 K, these easterly anomalies allow moisture transport to the Sahel. Above 2 K, the easterly anomalies reverse the westerly flow and reduce precipitation in the Sahel. Models predict increases of precipitation in the future under global warming. Theoretical understanding of this is founded in the Clausius-Clapeyron equation. I compare precipitation from the theory with the model simulations over the U.S. for the mid-21st century and investigate the physics of the departure of the model from theory. In the spring and fall precipitation increases, up to 30%/ K, and the modeled precipitation matches the theoretical prediction. In contrast, rainfall lowers and prediction fails in the summer. These differences are associated with the soil moisture distributions. Associated with the increased soil moisture, model follows theoretical prediction in the spring and fall, while reduced soil moisture is associated with failure of the theoretical prediction in the summer. The Gulf of Guinea in the eastern Atlantic shows subsidence. This subsidence becomes well established in the low-level from July-September. Using observations, I contribute to understanding its cause and relationship with the regional precipitation and circulation. This subsidence is associated with the subsiding-branch of a Congo basin Walker circulation identified here. The circulation has a rising-branch over the Congo basin, and is driven by temperature gradient. Basin temperature remains almost uniform throughout the year, but in association with the Atlantic cold tongue formation, Guinean temperature cools up to -4 K in the summer. This gradient drives the circulation. A strong Walker circulation is associated with enhanced northward moisture transport.