Corals face serious worldwide population declines due to global climate change in combination with direct anthropogenic impacts. Global climate change is difficult to manage locally, but policy makers can regulate the magnitude of local stressors affecting reefs. The objective of this experiment is to investigate if reducing sedimentation will enable reef corals to better endure global climate change. It has been shown that some coral species can handle climate change stress when provided with additional energy resources. Here I tested if the capacity of corals to cope with climate change can be improved when their ability to feed and photosynthesize was not compromised by increased sedimentation. Sedimentation can impede coral feeding and their ability to photosynthesize due to direct polyp blocking and increased turbidity, which reduces light availability. To evaluate the potential of enhancing coral ability to tolerate climate change by reducing a local stressor, I examined the survival and growth of brooding coral Porites astreoides juveniles when exposed to ambient and elevated water temperatures under differing sedimentation rates. I also assessed if sediment composition has significant impacts on these results. I used sediment from a reef and sediment from a boat basin within a port to mimic natural and anthropogenic sediment types and processes (e.g. dredging). Experiments were conducted to quantitatively assess the synergistic effects of sediment concentration and composition, along with increased temperature on the survival and growth of juvenile P. astreoides. The most detrimental effects were observed with anthropogenic sediment, when both sediment concentration and water temperatures were high. However, increased natural reef sediment was found to be beneficial to juvenile corals. More interestingly, I found that corals capacity to deal with higher temperatures is improved when anthropogenic sedimentation is maintained at minimal levels and turbidity resulting from sedimentation was low. Therefore, this information will aid managers in making decisions that regulate dredging and construction activities to minimize sedimentation, which will contribute to increase coral survival under climate change.

Despite worldwide policy efforts such as the Kyoto Protocol, the emission of greenhouse gases (GHG) remains a negative externality. Economic equilibrium paths in the presence of such an uncorrected externality are inefficient; as a consequence there is no real economic opportunity cost to correcting this externality by mitigating global warming. Mitigation investment using resources diverted from conventional investments can raise the economic well-being of both current and future generations. The economic literature on GHG emissions misleadingly focuses attention on the intergenerational equity aspects of mitigation by using a hybrid constrained optimal path as the "business-as-usual" benchmark. We calibrate a simple Keynes-Ramsey growth model to illustrate the significant potential Pareto-improvement from mitigation investment, and to explain the equilibrium concept appropriate to modeling an uncorrected negative externality.

In this I will explore the ethical challenge of global climate change by analysing three accounts of how responsibility for climate change should be distributed. I explore why it is valuable to view climate change as part of a bigger ethical problem of resources, distribution and global justice. Furthermore, I will argue that a road towards change by a cosmo political theory of justice is the most reasonable option. The theme of my argumentation is that the challenge of global climate change should be understood as a problem between human beings, not between states, or via schemes for distribution or rigid systematic solutions. Many theories of justice fail to do so with challenging and potentially dangerous consequences. / I den här uppsatsen så kommer jag utforska klimatförändringar som etisk utmaning. Jag undersöker varför det är värdefullt att se klimatförändringar som en del av ett större problem som handlar om resurser, distribuering och global rättvisa. Jag kommer undersöka tre möjliga vägar till en lösning på klimatförändringar som etiskt problem och hävda att en kosmopolitisk rättviseteori är det rimligaste alternativet. Klimatförändringens utmaning måste förstås som ett problem människor emellan och inte stater emellan genom planer för distribuering av resurser eller någon annan mer eller mindre regid systematisk lösning. Många rättviseteorier lyckas mindre väl med detta med utmanande och potentiellt farliga konsekvenser som resultat.

In tundra, phosphorus (P) is an important macronutrient for plants and microorganisms. A major fraction of P exists as organic compounds in the topsoil which can be mineralized to bioavailable inorganic P. Since mineralization is positively related to temperature, climate warming is likely to increase P bioavailability but the extend of these changes may also depend on vegetation cover and soil properties. I assessed organic and inorganic P concentrations across an elevation and vegetation gradient in northern Sweden using one dimensional (1D) solution 31P nuclear magnetic resonance spectroscopy. I hypothesized that concentration of labile soil P will decrease with increasing elevation (decreasing temperature) and that soils with meadow vegetation will contain higher concentrations of labile P than heath soils. Concentration of labile P in the form of Resin-P and polyphosphates decreased with elevation whereas less labile orthophosphate monoesters increased. Across vegetation types, polyphosphates were more abundant in heath and meadow contained higher concentrations of monoesters. The inverse response of Resin-P and monoesters to elevation may be best explained by lowered organic P mineralization in colder climate. High concentrations of polyphosphates at the lowest elevation may indicate an increased presence of fungal communities associated with mountain birch forest. Heath seemed to be more dominated by fungal communities than meadow and higher concentration of monoesters in meadow indicated a higher soil sorption capacity. In a broader view, the results may suggest that a warmer climate increases mineralization of organic P in form of orthophosphate monoesters to more labile P forms. This effect might be enhanced by an upward movement of the tree line and might be more pronounced in heath than meadow soils due to a higher fungal activity.

The majority of lakes on Earth are shallow, unproductive and located at high latitudes. These lakes are experiencing big changes due to climate change, where two environmental drivers operate simultaneously, browning and warming. How they affect lake ecosystems is not well understood. Here, I addressed this issue by using a theoretical and an experimental approach. In particular, I generated model predictions and compared them with the results of a realistic large-scale experiment, where browning and warming were manipulated in a factorial design. In addition, model outcomes were compared with data from 12 unproductive lakes sampled along a gradient of browning. Another novelty of my thesis is that it integrates benthic and pelagic food web components in the model and experimental approaches. I found that browning affected the resources availability for benthic and pelagic producers in the model and in the experiment. With browning, benthic primary producers became increasingly light limited and declined, while pelagic producers became less nutrient limited and increased. Pelagic nutrient limitation was alleviated by two non-exclusive mechanisms. Browning directly enriched the water with nutrients, and browning indirectly increased the nutrient flowing from the sediment to the pelagic habitat via suppression of benthic producers. To tease apart these two mechanisms I applied structural equation modeling (SEM). The indirect evidence by SEM suggests that both mechanisms contributed equally to the pelagic nutrient concentration in the experiment. Interestingly, a model food web with only primary producers shows similar qualitative behavior as a food web with grazers and carnivores included. This happens because carnivorous fish exert strong top-down control in the more productive habitat, which relaxes grazing pressure on primary producers and increases resource limitation in the adjacent habitat. Biomass of benthic and pelagic consumers followed the same pattern as their resources. The lake data were largely congruent with model expectations and supported the findings of the experiment. Furthermore, the model also predicted a negative relationship between total phosphorus and both primary and fish production, which was observed across the 12 lakes. Warming effects were more complex. The model predicts that warming effects should depend on browning and are expected to be strongest in the more productive of the two (benthic and pelagic) habitats. For example, at low levels of browning the biomasses of benthic algae and fish are expected to decline with warming, which was observed in the experiment. In contrast, observed warming effects at high levels of browning deviated from model expectations. The mechanisms by which browning and warming interactively affect lake food webs are still poorly understood. This thesis offers a conceptual foundation for their further study through the integration of within- and between-habitat interactions.

Typically, multi-model ensemble studies show mixed responses of El Nino Southern Oscillation (ENSO) under global warming, so it is currently unknown how, or even if, global warming will impact ENSO and its teleconnections. ENSO is governed by various ocean-atmosphere interactions in the equatorial Pacific, which provide either positive amplifying or negative damping feedbacks and are not always accurate in models. This results in uncertainty in projected ENSO responses. In a flux adjusted HadCM3 perturbed physics ensemble, the Bjerknes' stability index (BJ index), a measure of ENSO stability, has been used to analyse the strength of ENSO feedbacks and their response under the SRES A1B warming scenario with respect to mean climate conditions. Despite mean sea surface temperature biases being minimised by flux adjustment, the important dominant feedbacks, namely the latent heat flux feedback, shortwave flux feedback, the thermocline feedback and the zonal advective feedback are found to be too weak in the ensemble. Common model biases cause weak ocean-atmosphere interactions such as a weak response of ocean currents to wind stress anomalies, a weak thermocline slope response to wind stress anomalies and weak thermodynamic dampings. These biases are linked to overly strong zonal surface ocean currents and convective response biases. Under global warming, a large increase in thermodynamic damping, caused by increasing shortwave damping, is found. This increase is linked to a strong convective response and overrides other feedback responses, resulting in a weakening BJ index in contrast to increasing ENSO amplitude. Positive feedback responses are also found but counteract each other, so have relatively little impact on total ENSO stability. Results here show that common model biases, such as the cold tongue bias, are linked to persistent ENSO feedback biases pointing to areas of improvement in future models. Results also suggest that caution must be exercised when using the BJ index to assess ENSO, as the BJ index is not always representative of ENSO amplitude. This may be caused by non-linearities in ENSO feedbacks which are not accounted for by the linear approximations used in the BJ index, or by ENSO feedbacks not being directly comparable in magnitude, as assumed by the BJ index calculation.

D.Phil. / Global society has evolved into a complex multi-dimensional system in which it has become increasingly difficult to construct and maintain a systemic model of cause and effect. Specialisation and abstraction in the various disciplines of scientific and societal complexity has led to divergent theories of sustainability. Failure to integrate real life problems across disciplines poses a threat to modern society because the causal links between disciplines are unattended in many instances and events in one dimension could lead to catastrophic unintended consequences in another. In light of the above, this thesis contributes towards the multi-disciplinary integration of some of the most important sustainability concerns of modern society, namely Energy Security, Economic Growth and Global Warming. Analysing these real-life sustainability issues in a multi-disciplinary context leads to conclusions that are controversial in terms of established philosophical worldviews and policy trends. Firstly, the thesis establishes deterministic expectations of an imminent era of declining Energy Security resulting from the exhaustion of non-renewable fossil fuel resources, despite optimistic expectations of technology improvements in alternative energy sources such as renewable and nuclear. Secondly, the exhaustion of non-renewable fossil fuel resources imposes limits to the potential sources of anthropogenic carbon emissions that render the more pessimistic emissions cases considered in the global warming debate irrelevant. The lower level of attainable carbon emissions challenges the merits of the conventional carbon feedback cycle with the result that the predicted global warming is within acceptance limits of the contemporary global warming debate. Thirdly, the consequences of declining Energy Security on socio-economic welfare is a severe divergence from historical trends and demands the reassertion of the role of energy in human development, including Economic Growth theory. The thesis develops a novel economic growth model that treats energy as an explicit and Autonomous Factor of Production, thereby facilitating plausible predictions of future Economic Growth potential. The results challenge the sustainability of the current free-market capitalist economic system and demand strong policy responses to avoid the collapse of modern society.

Doctor Educationis / Analysis of temperature, rainfall and evaporation records over a 44-year period spanning the years 1964 to 2008 indicates changes in the climate around Lake Kariba. Mean annual temperatures have increased by approximately 1.5oC, and pan evaporation rates by about 25%, with rainfall having declined by an average of 27.1 mm since 1964 at an average rate of 6.3 mm per decade. At the same time, lake water temperatures, evaporation rates, and water loss from the lake have increased, which have adversely affected lake water levels, nutrient and thermal dynamics. The most prominent influence of the changing climate on Lake Kariba has been a reduction in the lake water levels, averaging 9.5 m over the past two decades. These are associated with increased warming, reduced rainfall and diminished water and therefore nutrient inflow into the lake. The warmer climate has increased temperatures in the upper layers of lake water, the epilimnion, by an overall average of 1.9°C between 1965 and 2009. The warmer epilimnion has led to a more stable thermocline in the lake, and its upward migration from a previously reported 20 m depth to the current 2 to 5 m depth reported in the lake’s Sanyati Basin. A consequence of the more stable thermocline has been the trapping of greater amounts of nutrients in the deep, cold bottom waters of the lake, the hypolimnion, and this coupled with a shorter mixing (turnover) period is leading to reduced nutrient availability within the epilimnion. This is evident from a measured 50% reduction in nitrogen levels within the epilimnion, with phosphorus levels displaying a much smaller net decline due to localised sources of pollution inflows into the lake. These changes in lake thermal dynamics and density stratification have reduced the volume of the lake epilimnion by ~50%, which includes the well mixed, oxygenated euphotic zone leading to more acidic waters (lower pH) and increased water ionic concentrations (conductivity), and decreased dissolved oxygen levels, which have resulted in a 95% reduction in phytoplankton biomass and a 57% decline in primary production rates since the 1980s. The reduced nitrogen levels especially have contributed to a proliferation of nitrogen-fixing Cyanophyceae, the dominant Cylindrospermopsis raciborskii comprising up to 66% of the total phytoplankton biomass and 45.6% of the measured total phytoplankton cellular concentrations. Also, shifts in seasonal dominance of different phytoplankton groups have been observed in the lake during turnover, the Cyanophyceae having increased in dominance from 60% of the total phytoplankton biomass in the early 1980’s to the current 75%. In contrast, the Bacillariophyceae have declined substantially, from 18% of the total phytoplankton biomass in the early 1980’s to the current 1.7%. The diminished phytoplankton biomass of more palatable phytoplankton, and the proliferation of smaller, less palatable phytoplankton taxa, has resulted in reduced zooplankton biomass and species richness and altered zooplankton species composition. Concentrations of large Cladocera and Copepoda especially have declined substantially in the lake by up to 93.3% since the mid 1970s, with small Rotifera currently comprising 64% of the total zooplankton biomass. The reductions in zooplankton biomass correspond with recorded decreases in catches per unit effort for the sardine Limnothrissa miodon (Kapenta), which have been steadily declining in the lake since 1986.

Magister Artium - MA / The concern that weather variability and climate change has raised nowadays puts every society or community on the alert. This is arguably the most persistent environmental threat to global stability in vulnerable communities in recent times. City dwellers are now experiencing increased variable weather episodes such as frequent flooding, heat waves and drought with increased wind and storm activities. Unfortunately, the aftermath of these weather irregularities are felt most severely by vulnerable urban poor residents with the least mechanisms to cope. This study focused on the residents of Enkanini in Makhaza, an informal settlement in the greater Khayelitsha Township of Cape Town, South Africa. It documented the challenges they encounter with respect to weather, seeking to understand their adaptive strategies. Emphasis was also placed on the vulnerable nature of their dwellings and their ingenuity in coping with the variable weather pattern in Cape Town. Qualitative and quantitative methods were used to analyse field data, using codes derived from themes and SPSS respectively. Ethnographic methodology guided the researcher to participate overtly in the activities of the community over an extended period, watching what happened, listening to what was said and asking questions pertaining to their vulnerability to the vicissitudes of the prevailing weather in the informal settlement. Findings from the study revealed that over 62% of the dwellings do not conform to the City‟s Disaster Risk Management Centre and Fire & Rescue safety regulations and that over 80% of the residents do not adapt very well to weather-related episodes. It also identifies the most challenging weather episodes to be floods during winter and shack fires during summer; amidst other health concerns that occur all year round.

Scientists started to study the relationship between changing weather patterns and the emission of carbon dioxide (CO2) and other harmful gasses. They soon discovered compelling evidence that CO2 concentration and other gases have been increasing and it was causing temperatures to increase in certain areas on the earth, which disturb historic weather patterns. Climate change has become a very popular field of study in the modern science. Europe first introduced measures to reduce carbon emissions but it was the Kyoto in 1997 where global leaders were asked to participate in a joint protocol to reduce greenhouse gases. South Africa responded to climate change challenges in 2008 with the Long term Mitigation Scenarios (LTMS). The Integrated Resource Plan for electricity to 2030 was developed from the LTMS scenarios and after some major amendments it was accepted and promulgated by Government and has recently been included in the National Development Plan to 2030 (NDP). There are concerns about the achievability of some of the objectives listed in the NDP and this study explored the IRP2010 as the proposed strategy to meet energy demand and reduce emissions. The purpose for this study was to answer this question: Is there an optimum climate change mitigation strategy for South Africa and how can the effect thereof be simulated on economic growth? Through primary and secondary research during the study it was possible to define some 32 categories of energy producing assets that are commercially active or nearly market-ready. The characteristics of the various assets and the relevant fuel are defined in mathematical equations. It was found that the three portfolios that matched the 450TWh electricity requirement would perform substantially better than the NDP portfolio in terms of cost and similar on emissions with marginally fewer employment opportunities created. The proposed electricity strategy in this study was 390TWh and 33.5 Million tonnes of oil consumption by 2030. This strategy was substantially more affordable than the 450TWh strategy. Trends in the Supply and Use tables since 1993 were studied and then forecasted to 2030 to determine consumption levels on electricity and liquid fuel into the future. It was found that electricity demand is seriously overestimated and South Africa would end up with large excess capacity in electricity infrastructures if the NDP energy strategy (IRP2010) is implemented. It is concluded that the NDP energy strategy to 2030 is based on an incorrect electricity demand forecast. It would lead to excessive investment in an electricity infrastructure. Government has confirmed that part of the new infrastructure would be nuclear. It is also found that NDP has not clearly supported nuclear as part of the strategy. Nuclear is partly the reason why the capital requirement of the NDP portfolio is so much higher than the other portfolios. It is the conclusion of this study that South Africa do not need to invest in a nuclear build programme as the electricity demand would be adequately covered by adding the new Medupi and Kusile power stations, Ingula pump storage scheme, some wind and solar renewables, electricity from cogeneration, biogas, biomass, small hydro and imported hydro from neighbour countries. To invest in electricity capacity to generate 450TWh annually by 2030 would result in excessive energy cost, GDP growth could be up to 1% lower due to underperforming capital investments in the electricity infrastructure and higher energy cost would lead to a decline in global competitiveness.