3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Volcanic forcing: modelling impacts on southern hemisphere temperatures(2021) Harvey, PamelaConsiderable recent research attention has focussed on volcanic forcing effects on global climate, perhaps due to its cooling effects in what is otherwise an era of global warming. In an attempt to contemplate ways to combat the global warming phenomenon, geoengineering options have been considered, such as the idea to manipulate the climate by injecting sulphate aerosols into the stratosphere and thus simulate a volcanic forcing effect. This was of course a very controversial suggestion, and many argue that attempting to resolve global warming in this way could do more harm than good. The fact is, that there are still too many unknown variables and potential outcomes as a consequence of volcanic forcing on climate, such that the impact of manipulating climate to combat global warming cannot be fully appreciated at this stage. Instead, the focus remains on identifying research gaps and addressing these. While much research attention has focussed on understanding climatic responses to volcanic forcing over the Northern Hemisphere (NH), very little attention has focussed on the Southern Hemisphere (SH) in this regard. This PhD thus aims to address this research gap and establish, in some measure of detail, the temperature responses to major volcanic eruptions over terrestrial regions of the SH. Initially, near-surface temperature responses to eight major eruptions (Krakatau, 1883; Tarawera, 1886; Santa Maria, 1902; Colima, 1913; Quizapu, 1932; Agung, 1963; El Chichón, 1982; Pinatubo 1991) are investigated. Four eruptions (Krakatau, Santa Maria, Agung and Pinatubo) are identified as having caused significant temperature responses over the SH, and thereafter the temperature responses to these eruptions are established at a variety of spatial (hemispheric, continental and sub-regional) and temporal (annual, seasonal and monthly) scales. Model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are used as the main data source to study these climatic impacts. However, a reanalysis dataset (20th Century Reanalysis V2) provided by the NOAA/OAR/ESRL PSL station data, as well as station data for some sub-regions, iv were used to test the reliability of CMIP5 model outputs in its ability to simulate volcanic forcing effects on SH climate. Results from the CMIP5 ensemble used in this study suggest that significant cooling occurs in the SH following four of the eight eruptions (Krakatau, Santa Maria, Agung and Pinatubo), although the response is weaker than what the models suggest for the NH, as expected. The strongest temperature response follows the Krakatau eruption, which emitted the largest amount of SO2 into the lower stratosphere. The weakest responses would follow after either Santa Maria or Agung, varying with the region or the season studied. Overall, it is found that stronger responses occur during austral autumn, followed by austral winter, while the weakest responses occur during austral spring. Exploring the responses at a continental scale reveals that Australia experiences strongest cooling anomalies, which peak earlier (av = 5 months) than both southern African (SAF) and southern South American (SSA) anomalies, while SSA experiences weakest anomalies which also have the most delayed peak response (av = 9 months). Temperature responses in six sub-regions of SAF and eight sub-regions of Australia are then explored to establish responses at a much finer spatial scale. Results show that more northern regions experience stronger cooling than southern regions. Variations of responses appear at the smaller scale, as some regions experience strongest cooling response in one season while other regions experience strongest cooling in another season. Responses can vary depending on the latitude and magnitude of the eruption, the time of year of the eruption, as well as the condition of the atmosphere at the time of the eruption. Investigating variations in the responses to individual eruptions at different spatial and time scales highlights the necessity of studying the impacts of volcanic forcing on an individualistic eruption basis, rather than based on a composite of eruptions. Comparing CMIP5 results to reanalysis and station data reveals that uncertainties exist in the observed temperature responses. It is possible that at least some results are overestimated, as has been found in other CMIP5 studies investigating v volcanic forcing. However, as found in this thesis, at times CMIP5 in fact underestimates the temperature response based on comparisons with reanalysis data (in the Australian sub-regions following the Agung and Pinatubo eruptions). Expecting climate models to perform close to 100% accurately is unrealistic, as large uncertainties also exist when using both reanalysis and station-based instrumental data. Notwithstanding the challenges and limitations when using CMIP5, such model outputs provide a reasonable sense of expected temperature pattern following major volcanic eruptions. Hopefully, such model outputs will continue to improve with the newly established CMIP6Item Perspectives on the effectiveness of green buildings in climate change mitigation: a study of the City of Johannesburg(2021) Makgalemele, Malesotse CeciliaIt has been proved that anthropogenic activities globally have resulted in accelerated climate change and global warming, beginning with the industrial revolution, through the release of greenhouse gases of which Carbon Dioxide is the most prevalent. Estimations indicate that up to 40% of greenhouse gases are emitted from the construction and building sector hence the urgency for climate change mitigation. The aim of this study was to determine the effectiveness of retrofitted certified green buildings of office use in the City of Johannesburg in terms of climate change mitigation during their operational lifecycle. The study utilized semi-structured interviews which were conducted with various stakeholders as well as existing literature. Their purpose was to gather the information needed to examine the various perspectives on green buildings in terms of climate change mitigation. Parallel to the human perceptions, energy consumption data was also collected from the property companies and meteorological data was collected from the South African Weather Services. These two data sets as well as calculated Carbon emission data were analysed against each other to examine whether climate, particularly temperature, impacted how buildings consume energy and emit Carbon emissions. The empirical evidence suggests that despite factors contributing to increased energy consumption and Carbon emissions in buildings existing, retrofitting and certifying existing office buildings in the City of Johannesburg generally mitigates this. The process of certification, like the majority of the legislation and institutional frameworks in existence countrywide governing green buildings, is voluntary and act more as a guide. Challenges in governance and implementation of legislation present an obstacle to realising the full potential of green buildings. Generally, the building sector in the country has been positively impacted by the green building phenomena with incentives from various economic sectors playing a significant role and other potential ones identifiedItem Long-term reconstruction of rainfall and fire for the Kavango-East and Zambezi regions, Namibia and the impact of people on past fire regimes(2020) Hamilton, TamrynAfrican savanna structure is driven by climate and fire, which have been well documented in modern observations and palaeo-studies, but is lacking on intermediate (decades to centuries) timescales where much of the ecosystem dynamics occur. Long term rainfall and fire records were generated from environmental proxies from the semi-arid Kavango-Zambezi region of South-Central Africa. The records were radiocarbon dated in high resolution and modelled with Bayesian accumulation models to generate ~600year chronologies. The proxy time series were analysed in time-frequency space to elucidate the relationship between rainfall and fire at different timescales within local and regional fire histories. Wavelet analysis shows periods of time in the past when fire had a positive relationship with rainfall, and also a negative relationship, and a switch from local to regional-scale fire response to rainfall is observed in the Little Ice Age (1700-750). A shift to regionally dominated fire regime thereafter is attributed to human population increase and associated land-use change. The results show that over time savanna landscapes can shift between load-limited and moisture-limited fire regimes and that savanna structure has been affected by human activities both directly, and via changes in fire regimesItem SYMBIOSEAS - Connecting man and sea: preserving our oceans through built form(2020) Cachalia, AyeshaCurrently our oceans are at great risk of losing species and habitats due to global warming, pollution and over fishing. Marine conservationists are fighting to maintain the biodiversity in our oceans however, these efforts are futile if the global population does not acknowledge the damaging impact of their activities on the ocean. It is through awareness and understanding of marine life that humans can be more conscious of their actions. Human interaction with the ocean is limited and often superficial. This research works towards establishing a meaningful connection between man and sea through a multitude of interactions. To achieve this in the form of a building proposal, a site in Hermanus was chosen due to pre-existing eco-tousrim infrastructure which supports the cause. In this environment it is possible to create up-close encounters with marine life, in nature, providing a more intimate experience than what is already available. The proposed design, facilitating meaningful access to the ocean, includes a shark research centre and a much needed visitor centre, connected by an education centre which includes an underwater observatory. A journey through these spaces, ending in the local historic harbour, will be the source of different experiential relationships between people and the oceanItem Ecosystem-based adaptation of urban hydrology to climate change in three South African cities(2019) Goodbrand, Sarah AmyThere can be no doubt that the world is experiencing climate change. Urban areas suffer intensified impacts thereof, including floods, severe storms, droughts and heat waves. Urban populations are increasing exponentially, forcing local governments to investigate functional, alternate ways to adapt cities to the negative risks of climate change, thereby becoming more resilient and ultimately suffering less catastrophe. Conventional hard infrastructure methods have proven to be insufficient against the impact of climate change. A method which has been considered positively is Ecosystem-based Adaptation (EbA), which makes use of natural processes, including biodiversity and ecosystem services (the benefits people derive from nature), to assist people in adapting to the adverse effects of climate change. EbA actions identified in literature range from maintaining rivers and wetlands to promoting natural vegetation. This dissertation aimed to critically explore the practice and presence of EbA within the climate change adaptation plans of three cities in South Africa (also referred to as metropolitan municipalities), namely: Cape Town, Durban and Johannesburg. The assessment of the adaptation plans was further supported by semi-structured interviews conducted with city officials and experts in the field. High-level water balances were calculated for these cities, so that the potential of EbA to contribute to reducing the vulnerability of urban water systems to the negative effects of climate change could be critically examined. The water balances were also used to identify the different types of water related infrastructure, either ‘soft’ (also called ‘green’ - e.g. wetlands, parks, rivers) or ‘hard’ ( also called ‘grey’ - e.g. storm water drains, sewers, roads). I found that the inclusion of EbA related solutions within the adaptation plans was sparse, often only vaguely making reference to EbA through ecosystem services or soft infrastructure. There is uncertainty as to whether the implemented EbA actions, were in fact implemented with EbA as the driver, or if they were merely projects undertaken for other reasons, rebranded as EbA. Determining the proportion of the water balance managed by soft infrastructure, proved difficult, due to the challenges in defining and categorising the different components of the water balance as either hard or soft. It was noted however, that rainfall was the main quantitative contributor to the all three of the cities’ water balance. EbA methods to manage a future reduction in rainfall include maintaining green spaces by growing drought resistant plants, and managed aquifer recharge. EbA methods to manage too much rainfall (for instance, floods resulting from increased rainfall intensity) include maintaining rivers and wetlands through river clean-up programmes to remove litter and alien vegetation. The suggestion that the resilience of urban water management can be supported by soft infrastructure using EbA approaches receives quantitative support from this study, since the natural water flows are of similar magnitude to the manages ‘hard’ infrastructure flows, but are currently only partially considered in the urban adaptation plans. However, the uncritical championing of EbA as a sole or dominant solution is premature. Further research is required into the efficacy of EbA actions in managing urban water.Item A Palaeolimnological determination of a regional industrial signal in the sediments of Mpumalanga Highveld Pans(2020) Spratt, Jesse PatrickFresh water endorheic wetlands are a scarce resource in South Africa and are threatened by human activities such as mining, abstraction, farming and other industry. The Mpumalanga Lake District (MLD) is a unique region comprising of over 300 endorheic pans differing in type. This provided the ideal regional setting for a pilot palaeolimnological study. The overall aim was to identify a regional industrial signal for anthropogenic influence by understanding the uniqueness of these pans through a palaeolimnological approach using historical lake sediments. A historical sediment record was established in order to identify any temporal changes in physiochemical characteristics over the last approximately 130 years. Four sites were selected so as to analyse a spatial aspect of contamination and to compare physical characteristics of pans in the MLD. Sediment samples were collected in the form of four lake sediment cores which were sub-sampled at 0.5 cm in order to understand down core trends. A bathymetric approach was adopted in which GPS, depth and water quality data were obtained in order to understand the physiochemical characteristics and morphology of these pans. Analyses performed included radio-isotopic dating through 210Pb, organic carbon content analysis through Loss on Ignition methods, sediment grain size analysis using laser diffraction and the analysis of the composition of major elements in these lake sediments using x-ray fluorescence (XRF) spectrometry. Bathymetry data was used to produce maps representing the physical morphological characteristics of these pans. Sediment data including major elements, organic carbon content and grain size data was analysed statistically and represented graphically in order to understand down core trends. Identified was the uniqueness of these pans and the MLD region as a whole. The pans differed in size, depth and in terms of the sediment properties of organic carbon, carbonate and sediment grain size distribution. Results showed a distinct difference between sites TPE compared to the other three sites in terms of bathymetry and limnology. It was determined that there are multiple fluctuations throughout the sediment record which represents a seasonal variation in climatic conditions. An attempt to observe trends of environmental and climatic change was made with varied success. An identification of a possible regional industrial signal was made with respect to major element compositional changes however the distinction between natural and anthropogenic sources was difficult to determineItem A Southern Hemisphere tropical cyclone climatology: analysis of variability under a changing climate(2019) Pillay, Micheal TeronTropical cyclones are becoming more intense and the locations at which they form and attain their lifetime maximum intensities are migrating poleward, exposing more regions to tropical cyclone impacts. This study investigated a new climatology for Southern Hemisphere tropical cyclones, aimed to update and re-examine the previous tropical cyclone climatology from the canonical works of Gray (1968, 1979). The optimal and minimum ranges of thermodynamic and dynamic climate variables during tropical cyclogenesis were determined, to define the conditions at which the majority of Southern Hemisphere tropical cyclones are generated. The change over time of tropical cyclone activity and the magnitude of the climate drivers at the 1000and 850mb levels was also examined. The sea surface temperatures of 27.5-28.5°C is observed as the optimal range at which a majority of storms undergo genesis. However, the lowest observed magnitude at which genesis was possible is 24°C. This challenges the 26.5°C threshold for genesis in the Southern Hemisphere. Based on factor analysis weightings and multivariate regression, sea surface temperature, air temperature and relative humidity also account for a relatively large amount of variability in the formation process of tropical cyclones, compared to the other climate variables examined. Over 1980-2016, an increase for Southern Hemisphere tropical cyclone maximum intensity of 2.4 m.s-1 per decade is observed. Of the climate drivers measured at the point of genesis; omega, meridional shear, sea surface temperature and solar flux display statistically significant correlations with tropical cyclone intensity. Sea surface temperature, air temperature, solar flux and vertical shear at the point of genesis for Southern Hemisphere tropical cyclones, demonstrate statistically significant increases in magnitude, while omega and relative humidity indicate a decreasing trend. The increase in thermodynamic variables and their relationship to storm intensity infers that a warming climate is capable of influencing tropical cyclone intensity. The El Niño Southern Oscillation, Indian Ocean Dipole, Southern Annular Mode and volcanic eruption events indicated a statistically significant relationship to metrics of tropical cyclone activity, mainly intensity and longitude of storm genesis. The tropical cyclone climatology established here by providing an up to date seasonality and background of Southern Hemisphere tropical cyclone activity, can assist impact and risk assessment studies in areas potentially vulnerable to tropical cyclone impacts within the Southern Hemisphere.Item Early South African newspaper reporting of climate change(2019) McCarthy, Jarred DeanMass media is a medium used for scientific knowledge dissemination, informing society, and therefore shaping society’s perspectives. A highly popularised aspect of scientific discourse in the media is climate change, given its potential threat to livelihoods, the environment, and related political and economic agendas. For the aforementioned reasons, qualitative research was undertaken to examine the diachronic portrayal, and subsequent development, of early climate change by several English South African newspapers, including The Rand Daily Mail and The Star. The undertaking of this research is made possible given an existing newspaper clippings archive at the South African Weather Service, 1906-present. The period under examination, 1906-1956 (50 years), represents significant shifts in environmental, and political agendas. Articles that contained early climate change as their point of interest were further analysed using discourse analysis and thematic content analysis by means of a coding process as well as utilising a narrative analysis. By researching diachronically, it became possible to document and describe the development of early climate change, and the development of the South African media’s technique(s), and process(es) of how early climate change was portrayed. Findings suggest that without Professor Schwarz professing that South Africa was undergoing ‘climatic changes’, a progressive decrease in rainfall, early climate change would not have been covered as extensively as it was throughout the 1906-1955 time period analysed. This debate divided ordinary citizens and experts who agreed with Professor Schwarz and the South African scientific community, who did not agree that a progressive decrease in rainfall was occurring. Results also suggest that journalists played a central and critical role in the development of early climate change and in the development of a scientific consensus thereon. Journalists pushed for clarity on the underlying causes that resulted in ‘climatic changes’, which subsequently expanded the debate to include both anthropogenic and natural facets of early climate change such as solar variability, ENSO and land-use change among others.Item Assessing the poverty-environment nexus in three rural South African villages: environmental degradation, vulnerability and perceptions(2018) Ramatshimbila, Tshifhiwa VioletPoverty and environmental degradation are two serious challenges facing developing countries. The poor are often blamed for causing degradation, and degradation is assumed to worsen poverty. This relationship between the two has been referred to as the Poverty Environment Nexus (PEN). The PEN is known to be complex and multidimensional, and is surrounded by a number of theories and controversies. Although the co-occurrence of poverty and degradation has been well explored across the developing world, it has received modest attention in the literature especially on how wealth differentiation within these communities shapes the way in which local people conceptualise, experience, and cope with degradation. The intersection between the PEN and local environmental governance is also under-studied. This study addresses these knowledge gaps by investigating how household wealth status influences 1) local perceptions about woodland degradation, 2) household vulnerability to degradation, and 3) awareness and attitudes about local environmental governance, in three rural villages in Limpopo Province, South Africa. A mixed-methods approach was used, combining focus groups, a household survey (n=213), an individual survey (n=213) and key informant interviews. The influence of household wealth status score (derived from assets and income sources using Principal Component Analysis (PCA)) on individual perceptions, awareness, and attitudes, and household vulnerability to degradation, after controlling for confounding factors, was analysed statistically using multivariate logistic regression models. Focus groups and key informant interviews were useful for identifying themes and adding qualitative insights to the quantitative results. Perceptions: Woodland degradation was perceived both in terms of physical aspects, such as reduction in large trees, and experiential aspects, namely having to travel further to collect resources. The latter perception was influenced by wealth status. Perceived causes of degradation included environmental, socio-economic, and governance factors, and these perceptions were mostly associated with increasing wealth status. However, poorer respondents were more aware of their own household’s contribution to local degradation. For potential solutions, wealthier respondents focussed on using alternatives to harvested resources (such as other energy sources), while the poorer respondents focussed on reducing daily resource consumption. Vulnerability: Poorer households were more likely to use most of 13 woodland resources. Poorer households were thus more likely to report being impacted by degradation, especially by having to travel further to collect resources. Coping responses of the poor were typically inward-looking, focusing on modifying their natural resource use, such as by reducing quantities used or harvesting around other villages. By contrast, the wealthy were more outward-looking and focused on external coping mechanisms such as seeking employment and buying commercial alternatives from shops. The use of social capital to cope with degradation emerged as an important response strategy cross wealth status. Governance: Traditional authorities were widely recognised as important institutional structures for local woodland management. Awareness of relevant government agencies was relatively low. Poorer respondents were more aware of customary environmental laws and penalties, while wealthier respondents were more aware of those of government agencies. Wealth status also influenced attitudes about the benefits of the various institutions for managing local communal woodlands. It was widely agreed that local woodland governance could be improved by delegating more power to traditional authorities and communities, and improving monitoring by government agencies. These views were not influenced by wealth status Key insights from this study include: Even within poor communities, there is wealth differentiation in environmental perceptions that has consequences for addressing the poverty-environment nexus. The poor are hit by a “double whammy” when it comes to vulnerability to degradation – first, they are more at risk to impacts because they are more dependent on natural resources, and secondly, they are less able to adapt in ways which do not undermine human wellbeing or environmental sustainability. Despite their weaknesses, traditional governance structures and institutions have an important role to play in managing the poverty-environment nexus in common property systems, but they need support from government.
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