Southeastern South America (SESA), a region encompassing Paraguay, Southern Brazil, Uruguay, and northern Argentina, experienced a 23% increase in austral summer precipitation from 1902-2022, one of the largest precipitation trends observed globally. There is little consensus on the drivers of the precipitation trend, but Atlantic multidecadal variability, stratospheric ozone depletion, and greenhouse gas emissions stand out as key contributing factors. The work presented in this dissertation addresses two main questions. First, what are the historical drivers of the SESA precipitation increase? To address this, I investigate simulations from the Coupled Model Intercomparison Project (CMIP) Phases 3, 5, and 6 and find that not only do fully-coupled climate models simulate positive SESA precipitation trends that are much weaker over the historical interval, but some models persistently simulate negative precipitation trends. The same is true of two atmospheric models forced with observed historical sea surface temperatures. While future 21st-century projections yield positive ensemble mean precipitation trends that grow with increasing greenhouse-gas emissions, the mean forced response never exceeds the observed historical trend. Finally, some pre-industrial control runs occasionally simulate centennial-scale trends that fall within the observational range, but most do not. The second question I address is why climate models struggle to simulate the observed SESA precipitation trend. In an attempt to understand the model bias, I investigate one driver of SESA precipitation variability: the South American low-level jet. By developing a jet index from low-level moisture fluxes into SESA, I find that increased moisture flux through the jet accounts for 20-45% of the observed SESA precipitation trend from 1951-2020 in two reanalysis datasets. While results vary among reanalyses, both point to increased humidity as a fundamental driver of increased moisture flux and precipitation. Increased humidity within the jet is consistent with warming sea surface temperatures driven by anthropogenic forcing, although additional natural climate variations also may have played a role. The jet’s velocity also increased, further enhancing precipitation, but without a clear connection to anthropogenic forcing. These findings indicate that the SESA precipitation trend is partly attributable to jet intensification arising from both natural variability and anthropogenic forcing. In my final research chapter, I explore whether CMIP6 models simulate a realistic relationship between SESA precipitation and the jet, as well as whether inaccuracies in the characterization of the jet could explain muted trends in simulated SESA precipitation. I find that the interannual variability in the simulated jet-precipitation relationship aligns well with results from observations from 1951-2014. Interannual precipitation variability across the models is primarily dominated by the jet’s velocity. The models simulate a forced increase in humidity within the jet, consistent with observations and theory, that contributes a positive trend to SESA precipitation. Given that the models generally simulate realistic jet-precipitation relationships, I conclude that model misrepresentation of the jet is not a likely explanation for the discrepancy between simulated and observed SESA precipitation trends. Despite remaining uncertainties, my work sheds new light on our understanding of SESA precipitation variability and trends. Future work is needed to better understand the large-scale drivers of SESA precipitation outside of the jet and why climate models largely underestimate or fail to reproduce the observed precipitation trend. While Atlantic multidecadal variability is often cited as an important contributor to the SESA precipitation trend, I find austral summer forcing from the Atlantic to be ambiguous with regard to SESA precipitation and requires further analysis. Additionally, I highlight the Pacific South American mode as another contributing factor that warrants further exploration.

Given the current policies in place, the world is not on track to achieve net-zero emissions by the year 2050 as greenhouse gas (GHG) emissions continue to rise. Though fossil fuels are heavily linked to GHG emissions, they are a staple in both energy applications and chemical production. Reducing the barriers associated with producing fossil fuel alternatives, such as hydrogen (H₂), will allow society to shift towards net-zero emissions and mitigate anthropogenic driven climate change. At present the majority of H₂ is produced from fossil fuels, making H₂ production from water electrolysis (green H₂), which can be GHG emissions free, an attractive solution. This dissertation studies alternative electrocatalysts for the production of green H₂ that traditionally rely on materials that are scarce, expensive, and associated with relatively large GHG emissions. Furthermore, this work explores applications where green H₂ can be impactful in reducing GHG emissions such as in the upcycling of polyethylene and in the sequestration of biogas into useful solid materials. First, Pt- and Pd-modified molybdenum nitride (Mo₂N) was explored as an alternative for the traditional Pt electrocatalyst in the hydrogen evolution reaction (HER) for water electrolysis. Hydrogen binding energy (HBE) has been used as a descriptor for potential electrocatalysts and in Chapter 3, the HBE of both Pt- and Pd-modified Mo2N was determined experimentally using temperature-programmed desorption (TPD). This was then correlated with electrochemical measurements in both acidic and alkaline electrolyte. The established trend revealed that the similar activity of Pt/Mo2N, in both media, to Pt(111) is linked to their similar HBE values. Density functional theory (DFT) calculations further verified the trends established in this chapter and provided insight into the electronic structure of these modified Mo₂N surfaces. In Chapter 4, the binding strength of two more Pt-modified transition metal nitride (TMN) surfaces, titanium nitride and vanadium nitride, were explored for their potential use as electrocatalysts in green H₂ production. The desorption of H₂O from Pt-modified titanium nitride and tantalum nitride were also studied to understand their binding affinity to H₂O, which is an important factor in alkaline HER. Second, the tunability of the product distribution for polymer upcycling was investigated in Chapter 5. Low-density polyethylene (LDPE) was converted using H₂, via hydrogenolysis, into smaller hydrocarbon products with bimetallic RuM₃/CeO₂ (M = Fe, Ni, Co) catalysts. The formation of bimetallic alloys resulted in a shift in product distribution, away from unwanted methane (CH₄) and towards longer chain, value-added products. X-ray absorption fine structure measurements, electron microscopy imaging, and H₂ temperature-programmed reduction were used to characterize the catalysts. Furthermore, n-hexadecane was included as a model compound for polyolefins to determine the effects of H₂ pressure and reaction time on the product distribution. Of the three bimetallic catalysts, RuCo₃/CeO₂ was the most promising and was capable of suppressing C-C bond scission of shorter chain alkanes into CH₄. Lastly, Chapter 6 reports the successful conversion of biogas (CH₄ and CO₂) into syngas (CO and H₂ followed by carbon nanofiber (CNF) formation using a tandem reactor. This work combined a non-thermal plasma reactor, which can be easily integrated with renewable electricity, for the breakdown of biogas and a thermal reactor, operating at relatively mild temperatures (450 °C), to convert syngas into CNF. Different parameters were varied to determine their impact on CNF formation and biogas conversion. Higher residence times, which were achieved using lower total flow rates and longer plasma lengths, resulted in more CNF growth compared to lower residence times. The production of C₂ and C₃ alkanes and alkenes were also reported as side products from the plasma-assisted conversion of biogas. Chapter 7 highlighted future applications of TPD and non-thermal plasma in H₃ production and utilization as well as suggestions for improving the work presented in this dissertation.

A static chamber technique was used to measure methane emissions in July and August, 1995 from peatland sites in the Fort Simpson area, Northwest Territories, at the southern fringe of the discontinuous permafrost zone. Sites were classified ecologically and geomorphologically, and water table and temperature regimes were monitored. / Methane emissions ranged from $-$3.3 to 1144.2 mg/m$ sp2 cdot$d, from raised frozen sites to pond sites, respectively, similar to emissions recorded from other boreal regions. Water table was the strongest predictor of CH$ sb4$ emission. Although peat temperature is significantly correlated to methane flux, it did not significantly improve the flux-water table relationship. Methane storage within the saturated portion of the peat profile ranged from 0.2 to 4.2 g/m$ sp2$ over depths ranging from 30 to 76 cm, and did not play a large role in surficial emissions. The zone immediately above and below the water table appears to regulate methane diffusion to the surface. Residence times (storage/flux) ranged from 12 to 30 days in poor fens, and from 6 to 5789 days in fens. / Ranges and mean fluxes of methane were determined according to landform and water table position. Based on the geomorphology of the area, overall flux determined for the Fort Simpson area, map NTS 95H, NW1/4, is estimated to be 19 mg/m$ sp2 cdot$d.

No description available.

The global threat of climate change is one of the most crucial environmental issues facing the world in modern times. In response to this threat, international governments have drafted the Kyoto Protocol which included the Clean Development Mechanism (CDM). The CDM is a scheme which invited developing countries, like South Africa, to become involved in climate change mitigation projects. While South Africa has been identified as an attractive host country for CDM projects, research has revealed that it lags behind other developing countries in this regard. This study provides a theoretical background to the CDM and grounds the subject within the field of Environmental Economics. Following a literature review of factors that could influence the involvement of a municipality in CDM projects, this thesis undertook a case study of the barriers and drivers to CDM implementation within the Nelson Mandela Bay Municipality (NMBM). Use was made of semi-structured interviews, where a questionnaire was used to guide the researcher’s interview process. Five NMBM officers, who were likely to have been involved with CDM project implementation, were interviewed. Data collected was analyzed using a coding technique and was compared and contrasted to the literature in a process of explanation building. It was possible to elicit 14 factors that acted as CDM-barriers; seven that acted as CDM-drivers; and 10 that were required to change within the NMBM to encourage greater CDM involvement. Of the barriers, lack of awareness, poor political will and lack of funding emerged as the most inhibiting. Of the CDM-drivers, the potential financial benefits; ownership of infrastructure capable of producing carbon assets; and technology transfer emerged as the factors most likely to promote CDM involvement. With regards the factors that require change, it emerged that a positive response would result from a proactive stance by National Government on the CDM; the use of Public-Private-Partnerships to facilitate CDM projects; and improved communication and capacity building within the NMBM and the Nelson Mandela Bay business community. The main recommendation offered to the NMBM was for it to draft a Sustainable Development Policy as well as a formal sustainable development strategy to drive a coherent and consolidated approach to the Municipality’s involvement with CDM projects. Further, it was proposed that the NMBM should, lobby National Government for it to promulgate enabling legislation and a framework which would encourage CDM investment in South Africa; and engage with local business to promote the active involvement of the Nelson Mandela Bay with the implementation of CDM projects. Keywords: Global Warming, Kyoto Protocol, Clean Development Mechanism, Sustainable Development, Environmental Economics, Public Sector, Nelson Mandela Bay Municipality.

Climate change is regarded as the greatest threat facing the world today. The Intergovernmental Panel on Climate Change (IPCC) concluded that climate change is caused by human activities, as a result of greenhouse gases (GHGs) being emitted into the atmosphere. Scientific literature on the impact of climate change is well documented, especially for the health sector. The mission of the Gauteng Department of Health (GDoH) is to “contribute towards the reduction of the burden of diseases in all the communities in Gauteng”. Ekurhuleni Health District is part of GDoH and shares a similar mission. However, this mission is under threat due to the direct and indirect impact of climate change on the public health sector. Therefore, it is essential for Ekurhuleni Health District and Provincial Clinics to take measures to reduce their contribution to climate change in the light of improving the health of their constituent. This study estimates the carbon footprint of the employees of Ekurhuleni Health District and Provincial Clinics and determines the knowledge and perception of climate change among managers and operational employees. The methodologies of the Greenhouse Gas Protocol (GHGP) and the Department of Environmental Forestry and Rural Affairs (DEFRA) were used to quantify the carbon footprints of the employees of the Ekurhuleni Health District and Provincial Clinics. A content analysis was applied to determine the knowledge and perception of climate change. The study revealed that Scope 2, indirect emissions (electricity), accounts for 92% (35150 t CO2e) of the total carbon footprints for the period of five years, 2010-2014. Scope 1, direct emission (vehicles), is responsible for 4% (1362 t CO2e) and Scope 3, indirect emissions for ICT, for 2% (862 t CO2e), office paper 1% (181 t CO2e) and air conditioners 1% (458 t CO2e). The majority of employees demonstrated basic knowledge of climate change. However, the concept of GHGs was unfamiliar to most of the employees. In terms of perceptions of climate change, the majority of employees were concerned about the future of the planet and climate change and believed that climate change will impact their job description. The study recommends the following mitigation measures, among others, to reduce carbon footprints: (1) electrical vehicles; (2) substituting personal desktops with laptops; and (3) substituting HFC-23 air conditioner refrigerant with R410A. These recommendations have the potential to reduce the carbon emissions by 2445 t CO2e for the period of five (5) years and save R7 875 089 from fuel and power consumption. Furthermore, the District Office and Provincial Clinics can generate a revenue of R293 400 by registering for a CMD project for five years or R1 173 600 for the duration of the project (20 years). / Environmental Sciences / M. Sc. (Environmental Management)