Dissertations / Theses: 'Climatic constraints'

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Gorst, Ashley. "Assessing climatic and technological constraints to agricultural productivity in South Asia." Thesis, London School of Economics and Political Science (University of London), 2017. http://etheses.lse.ac.uk/3613/.

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This thesis comprises of four essays that seek to advance understanding of the role that climatic constraints have on agricultural productivity in India and Pakistan. This work emphasises that the constraints posed to agricultural production must be understood within the context of an evolving set of environmental and technological conditions. The thesis employs empirical methods to understand these relationships, where particular emphasis is placed on methods suitable for learning about the challenges agriculture will face in the future. The first chapter studies the impact of climate change on rice yields in India by modelling the inter-annual distribution of yield conditional on projected temperature increases. The results suggest a decrease in average yield and a substantial increase in the probability of low yields. It is also shown that yields have become increasingly resilient to heat over time. The second chapter studies the e↵ect of drought on cereal production in India by estimating thresholds of drought impact. By examining thresholds over time, evidence is found of decreasing average impacts, but with evidence of an abrupt increase in average drought impacts in more recent years. Thresholds of precipitation are also estimated, indicating substantial heterogeneity in resilience to drought across crop types and regions of India. The third chapter examines how changes in agricultural technology brought about by the Green Revolution a↵ected the relative importance of agro-climatic factors in determining crop yields. Using a detailed measure of crop suitability it is found that yields increased relatively more in areas of higher suitability, indicating complementarity between agricultural technologies and favourable agro-climatic characteristics. The final chapter uses farm-level data from a specifically-designed survey to assess the impact and determinants of climate change adaptation strategies on crop productivity in Pakistan. Adaptation has a beneficial e↵ect on rice yields, but not on wheat yields. This chapter also finds that a number of household and institutional factors are strongly related to whether households have adapted to climate change.

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Scalici, Giovanni. "Physiological and productive responses of Miscanthus genotypes to different climatic constraints in Mediterranean environment." Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1603.

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Strong global growth and development has increased demand for energy to refine, manufacture and transport products to support the lifestyles of an increasingly developing and globalized world. In recent decades, fossil fuels have become important sources of energy. However, with increasing demand, there has been developing concern over the sustainability of fossil fuels relating to their potential future sources and harmful byproducts of use, specifically large net carbon releases, which has spurred interest towards the use of alternative renewable energy sources. Potential alternatives are available including wind, solar, hydro, and biomass, all of which are touted to have greater environmental benefits relative to fossil fuels. There has been increasing interest in the use of perennial grasses as energy crops in the US and Europe since the mid-1980s. The characteristics which make perennial grasses attractive for biomass production are their high yield potential, the high contents of lignin and cellulose of their biomass and their generally anticipated positive environmental impact. For this purpose, three different researches were carried out with the aim of studying i) the adaptation and biomass production potential of 18 Miscanthus accessions, representing 5 Miscanthus species, collected from a wide geographical range (Numata, 1974) for suitability to semi-arid Mediterranean climates; ii) the effect of harvest time (autumn and winter time) on biomass yield, morph-biometric characters, moisture content, cellulose, hemicelluloses and lignin contents for second generation bioethanol production and ash content for combustion purposes in a long term plantation of Miscanthus x giganteus in a Mediterranean environment; iii) the effect of heat stress, in controlled-environment, on 5 Miscanthus genotypes, coming from the Miscanthus germplasm collection at Institute of Biological, Environmental and Rural Sciences (IBERS) of the Aberystwyth University Wales UK, to identify if the high temperature have a negative effect on the growth, partitioning and physiology of Miscanthus plants. Results suggest that some Miscanthus accessions are suitably adapted to maintain high biomass in a semi-arid Mediterranean environment and that the most commonly available commercial Miscanthus genotypes (M. x giganteus and Goliath) are not well adapted to the Mediterranean climate or environments where water is a limiting factor, and there are other Miscanthus accessions that produce high biomass in water limited semi-arid regions. Long term Miscanthus plantations strictly depend by the thermopluviometric trend of the growing season, decreasing biomass yield as rainfall reduces and the biomass for specific end uses presents higher quality (in terms of more hemicellulose and cellulose content than ash content), with winter harvest. Relative to low temperature, high temperature decreased the plant height (~48%), above-ground dry biomass (~66%), below-ground dry biomass (~26%) and photosynthetic response to absorbed light (~13%). The most widely available and commonly used variety of Miscanthus is sensitive to high temperatures and there are other genotypes that have a higher capacity for carbon assimilation in high temperature environments.

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Eakin, Hallie Catherine 1970. "Adapting to climatic variability in Tlaxcala, Mexico: Constraints and opportunities for small-scale maize producers." Thesis, The University of Arizona, 1998. http://hdl.handle.net/10150/278686.

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Through semi-structured interviews with Mexican climatologists and farmers and others in the agricultural sector in Tlaxcala, Mexico, this study explored how uncertainties posed by both variable climatic and changing political-economic conditions affect the vulnerability of small-scale maize producers. The objective of my research was to assess whether and how small-scale Tlaxcaltecan farmers could use long-lead forecasts to mitigate climatic uncertainty. The potential effectiveness of the climate forecasts was evaluated within the context of cultural, political, social and economic factors that influence the decision-making of smallholder farmers. This research determined that the vulnerability of small-scale producers in Tlaxcala is more a function of political-economic uncertainty than of physical circumstances. While farmers employ complex methods for anticipating climatic events based on religious beliefs and local knowledge, their ability to adapt is constrained by lack of resources. As a result, the success of the forecasts in mitigating small-farmer vulnerability will be limited.

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Techoro, Prosper Somah Verfasser], and Michael [Akademischer Betreuer] [Schmidt. "Climatic change impacts on subsistence agriculture in the Sudano-Sahel Zone of Cameroon - constraints and opportunities for adaptation / Prosper Somah Techoro. Betreuer: Michael Schmidt." Cottbus : Universitätsbibliothek der BTU Cottbus, 2013. http://d-nb.info/1038211085/34.

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Benzabih, Hosney A. "Environmental and socio-economic constraints on rain-fed agricultural land settlement projects in marginal climatic zones : a case study of the Jabel al-Akhdar Upland, Libya." Thesis, SOAS, University of London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267232.

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Dibacto, Kamwa Stéphane. "Dynamique de construction et démantèlement des volcans tertiaires et quaternaires des Carpates par des approches géomorphologiques et géochronologiques Growth and erosion constraints of the East Carpathians volcanoes by numerical models: tectonic and climatic implications Eruptive history of the Late Quaternary Ciomadul (Csomád) volcano, East Carpathians, part II: magma output rates Eruptive history of the Late Quaternary Ciomadul (Csomád) volcano, East Carpathians I: timing of lava dome activity constrained by the unspiked K-Ar method." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS144.

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Dans cette thèse, 47 nouveaux âges ont été obtenus par la technique Cassignol-Gillot. La très bonne reproductibilité des âges obtenus, ajoutée à une stricte cohérence observée entre les édifices volcaniques, supporte l'utilisation de la méthode K-Ar dans la datation des laves des Carpates orientales (Călimani-Gurghiu-Harghita ; CGH) et des dépôts d'ignimbrite du Miocène des Carpates occidentales (les monts de Mátra et Bükk). Dans la partie orientale de la chaîne, les données géochronologiques ont été combinées avec des analyses géomorphologiques pour contraindre l'histoire volcanique et calculer leur taux de construction et d'érosion. Parallèlement, dans la partie occidentale de la chaîne, les données géochronologiques obtenues ont été combinées aux données paléomagnétiques disponibles pour affiner leur stratigraphie. La chaîne des Carpates orientales a connu une migration de son activité éruptive le long de l’arc du Miocène au Quaternaire. Ici, une méthodologie novatrice et complexe apporte de nouvelles contraintes géochronologiques et géomorphologiques sur l'évolution des 20 volcans de la chaîne. Les nouveaux âges ont permis de contraindre leur durée d’activité Par exemple Seaca-Tătarca (6,79-6,47 Ma), Vârghiş (5,47-4,61 Ma) ou de dater l’activité volcanique la plus récente de Călimani. Pour le complexe volcanique de Ciomadul, composé d'une douzaine de dômes de lave, l’activité volcanique a été contrainte entre 704±18 et 28±1ka (<1 Ma) interrompue de périodes de repos. En parallèle, des reconstructions numériques de paléo-topographies volcaniques ont été réalisées dans le but de quantifier leur forme à la fin de leur construction. Les résultats déduits de nos reconstructions ont donné un volume total de matériel émis de 2300km3 sur toute la chaîne avec, à l’échelle de chaque volcan, une large gamme de variation de leur taille (3±3 à 592±115 km³). Ces volumes montrent une nette diminution du nord au sud de la chaîne avec des valeurs de 910, 880, 279 et 165 km³ pour des secteurs géographiques de Călimani, Gurghiu, North Harghita et South Harghita respectivement. Combinés aux âges, ces volumes ont permis de calculer un taux de construction moyen de 200km³/Ma pour toute la chaîne, représenté par deux groupes distincts ; un groupe caractérisé par des taux de construction de 137 km³/Ma caractéristiques des vieux volcans (11-3,6 Ma) suivi d'un groupe avec des taux de construction de 28km³/Ma pour les volcans Plio-Quaternaires. La comparaison des volcans reconstruits et ceux actuels a permis de calculer un volume érodé total de 524±125km³, correspondant à une dénudation moyenne de 22% et à un taux d'érosion moyen de 20m/Ma pour la chaîne de CGH. Suite aux fluctuations climatiques enregistrées le long de cette chaîne, les taux d'érosion caractéristiques de ces grandes périodes climatiques ont été calculés dans le but de montrer le rôle qu’a joué le climat sur les taux d’érosion. Le taux d'érosion le plus élevé de 38m/Ma a été obtenu pour la période régie par un climat continental subtropical modéré transitionnel (9,5-8,2 Ma). Pour la période climatique continentale modérée (8,2-6,8 Ma), caractérisée par des conditions climatiques beaucoup moins humides, un taux d'érosion de 14 m/Ma est proposé. Pour la période correspondant à un climat continental avec identification de périodes semi-arides (6,8-5,8 Ma), un taux d'érosion de 7 m/Ma a été calculé. Pour les volcans Plio-Quaternaires ayant connus des cycles interglaciaires/glaciaires, un taux d'érosion de 28m/Ma a été obtenu. Une telle approche morphométrique et géochronologique quantitative démontre son efficacité à étudier le dynamisme volcanique, y compris les processus de construction et d'érosion au fil du temps. Dans la partie occidentale des Carpates, les âges obtenus sur les coulées de lave de Börzsöny contraignent sa période d'activité entre 14,3-15,1 Ma. Pour les dépôts ignimbritiques de Bükk, les résultats K-Ar évoluent entre 12,7-16,5 Ma
In this PhD thesis, 47 new ages have been obtained by the Cassignol-Gillot technique. The very good reproducibility of the ages obtained in this study, added to a strict consistency observed between the volcanic edifices, support the use of the K-Ar method in the dating of the East Carpathian lavas (Călimani-Gurghiu-Harghita) and ignimbrite deposits of the North Hungarian (Mátra and Bükk Mts. [western Carpathians]). In the Eastern part, this new geochronological dataset has been combined with geomorphological analyses to constrain the volcanic history as well as to compute construction and erosion rates of those volcanoes. In parallel, in the western part geochronological dataset has been combined with available paleomagnetic data to refine their stratigraphy. The East Carpathian volcanic range experienced an along-arc, Late Miocene to Quaternary migration of eruptive activity. Here, a novel and complex methodology are presented that yields new geochronological and geomorphological constraints on the evolution of the 20 volcanic edifices. New unspiked K-Ar ages either constrain their lifespan (6.79- 6.47 Ma for Seaca-Tătarca; 5.47- 4.61 Ma for Vârghiş) or date the youngest volcanic activity (central Călimani). For Ciomadul volcanic complex composed by a dozen of lava domes, which hosts the recent volcanic activity since the last 1 Ma, its activity has been constrained between 704± 18 ka and 28 ± 1 ka with several quiescence periods. In parallel, numerical reconstructions of volcanic paleo-topographies were performed to quantify their shape at the end of their construction stage. The inferred initial volcano size shows a wide range (3±3 to 592±115 km³), making up the four main successive volcanic segments (910, 880, 279 and 165 km³ for Călimani, Gurghiu,North Harghita and South Harghita segment, respectively) totalizing 2300 km³. Volume and age constraints allowed computing an average growth rate of 200 km³/Ma for the whole range, characterized by an initial moderate growth rate (137 km³/Ma) of the older volcanoes (11-3.6 Ma) followed by a lower growth rate (28 km³/Ma) obtained for the Plio-Quaternary volcanoes. Comparing reconstructed and current topographies yielded a total eroded volume of 524±125 km³, defining averaged denudation of 22% and a 20 m/Ma erosion rate. Erosion rates for major climatic periods were computed, which highlight the contrasting climatic contexts since 11 Ma. The highest erosion rate (38 m/Ma) occurred during a transitional moderate subtropical continental climate period (9.5-8.2 Ma). An intermediate erosion rate (14m/Ma) characterized a moderate continental climate period (8.2-6.8 Ma) when conditions became less humid. The lowest erosion rate (7 m/Ma) reflects the prevailing continental but occasionally semi-arid climate (6.8-5.8 Ma). The highest erosion rate (28m/Ma) was obtained for Plio-Quaternary times during the interglacial/glacial cycles. Such a quantitative morphometric and geochronological approach demonstrates its efficiency to study volcanic dynamism, including both constructional and erosional processes, through time. In the western part of the Carpathian range, the new ages obtained on the lava flows of Börzsöny made it possible to constraint its period of activity between 14.27 - 15.11 Ma. For the Miocene ignimbrite of Bükk foreland, the new K-Ar results range between 12.7 - 16.5 Ma

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Duhamel, Maxence. "Restitution des changements de l’hydrologie des masses d’eaux intermédiaires et profondes de la Méditerranée au cours des derniers 145 ka à partir de la mesure de la composition isotopique du Nd de foraminifères Variations in eastern Mediterranean hydrology during the last climatic cycle as inferred from neodymium isotopes in foraminifera Changes in the intermediate water masses of the Mediterranean Sea during the last climatic cycle - new constraints from neodymium isotopes in foraminifera." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS120.

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Cette thèse vise à faire progresser notre connaissance de l’hydrologie des masses d’eaux intermédiaires et profondes de la Méditerranée au cours du dernier cycle climatique (derniers 145 ka), et de contraindre les modèles de circulation océanique ayant permis les dépôts de niveaux riches en matière organique (ORL et sapropèles). La composition isotopique en Nd (εNd) d’échantillons de foraminifères de carottes localisées à des bathymétries intermédiaires et profondes de la mer Tyrrhénienne, de l’Adriatique, de la mer Ionienne et du bassin Levantin ont été analysées. Ce travail a permis de mettre en évidence que les eaux intermédiaires et profondes de la Méditerranée Orientale sont systématiquement plus radiogéniques durant les périodes glaciaires que durant les interglaciaires. Nous avons démontré que ces changements ne peuvent pas être attribuée entièrement aux variations des apports éoliens et fluviatiles du Nord de l’Afrique mais à d’importantes modifications dans la quantité d’eau Atlantique (AW) pénétrant en Méditerranéen. Les périodes de bas niveaux marins glaciaire sont associées à une réduction des flux d’eau Atlantique à travers les détroits de Gibraltar et Siculo-tunisien en induisant des masses d’eau profonde plus radiogéniques en Méditerranée orientale. Surimposées à ces fluctuations glaciaires-interglaciaires, les périodes humides Africaines et de dépôts de sapropèles sont systématiquement caractérisées par des valeurs εNd plus radiogéniques. Cela a été attribué à l’arrêt de la convection profonde des eaux moins radiogéniques de surface associée à une augmentation du temps de contact des masses d’eaux profondes avec les sédiments radiogéniques des marges continentales du bassin Levantin. Nos résultats mettent en évidence durant les terminaisons I et II une augmentation de la contribution d’eau moins salées d’origine Nord Atlantique (MAW) d’environ 55 % pouvant avoir pré-conditionné la Méditerranée orientale plusieurs milliers d’année avant le dépôt des sapropels S1 et S5.La comparaison des enregistrements d’εNd obtenus dans les bassins Orientale et Occidentale sur le dernier cycle climatique montre un gradient d’εNd plus fort entre les deux bassins aux profondeurs intermédiaires et profondes durant les stades glaciaires. Cela est cohérent avec un échange d’eau plus faible de part et d’autre du détroit Siculo-tunisien durant les périodes de bas niveau marin glaciaire. Durant les hauts niveaux marins des périodes les interglaciaires les échanges d’eau sont au contraires plus forts entre les deux bassins induisant un transfert à la mer Tyrrhénienne des variations de la composition isotopique en Nd observée en Méditerranée orientale. Ainsi, les périodes humides africaines induisant une stratification des masses d’eaux et les dépôts de sapropèles à l’est, sont associées à des signatures d’eaux plus radiogéniques qui sont alors transportées par la LIW en Mer Tyrrhénienne. Surimposé à ces variations orbitales, des variations rapides de l’εNd ont pu être mises en évidence dans le chenal de Corse. Chaque événements froids des hautes latitudes de l’hémisphère Nord (Younger Dryas et événements de Heinrich) se caractérisent par une LIW plus radiogénique dans la mer Tyrrhénienne impliquant une réduction de la formation d’eau intermédiaire dans le Golfe du Lion (lié à de plus forts apports d’eaux douces depuis l’Atlantique lors des événements de Heinrich) et/ou une production plus importante de LIW en Méditerranée orientale (lié à un refroidissement de la surface du Nord de la Méditerranée lors des événements de Heinrich)
This thesis aims to advance our knowledge of the hydrology of the intermediate and deep water masses of the Mediterranean during the last climatic cycle (last 145 ka), and to constrain the ocean circulation models that allowed the deposition of organic matter-rich sediments (ENT and sapropels). The Nd isotopic composition (εNd) of foraminifera samples in cores located at intermediate and deep bathymetries of the Tyrrhenian Sea, the Adriatic Sea, the Ionian Sea and the Levantine Basin were analyzed. This work allowed to highlight that the intermediate and deep waters of the Eastern Mediterranean are systematically more radiogenic during the glacial stadiums than during the interglacials. We have shown that these changes cannot be entirely attributed to variations in dust and river inputs from northern Africa but to significant changes in the amount of Atlantic (AW) water entering the Mediterranean. Periods of low sea ice levels are associated with a reduction in Atlantic water flows through the straits of Gibraltar and Siculo-Tunisia by inducing more radiogenic deep-water masses in the eastern Mediterranean. Superimposed on these glacial-interglacial fluctuations, African humid periods and sapropel deposits are systematically characterized by more radiogenic εNd values. This has been attributed to the cessation of deep convection of less radiogenic surface water associated with an increase in the contact time of deep-water bodies with radiogenic sediments from the continental margins of the Levantine basin. Our results highlight during terminations I and II an increase in the contribution of less salty water of North Atlantic origin (MAW) of around 55% which may have pre-conditioned the eastern Mediterranean several thousand years before the deposit S1 and S5 sapropels. A comparison of the εNd recordings obtained in the Eastern and Western basins over the last climate cycle shows a stronger gradient of εNd between the two basins at intermediate and deep depths during the glacial stadiums. This is consistent with a weaker water exchange across the Siculo-Tunisian Strait during periods of low sea ice. On the contrary, during the high sea levels of the interglacial periods, water exchanges are stronger between the two basins, inducing a transfer to the Tyrrhenian Sea of variations in the isotopic composition of Nd observed in the eastern Mediterranean. Thus, the African wet periods inducing a stratification of the water masses and the deposits of sapropels in the east, are associated with signatures of more radiogenic waters which are then transported by the LIW in the Tyrrhenian Sea. Superimposed on these orbital variations, rapid variations in εNd could be highlighted in the Corsica channel. Each cold event in the high latitudes of the Northern Hemisphere (Younger Dryas and Heinrich events) is characterized by a more radiogenic LIW in the Tyrrhenian Sea involving a reduction in the formation of intermediate water in the Gulf of Lion (linked to more strong freshwater inflows from the Atlantic during the Heinrich events) and / or a greater production of LIW in the eastern Mediterranean (linked to a cooling of the northern Mediterranean surface during the Heinrich events)

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Sansom, Philip George. "Statistical methods for quantifying uncertainty in climate projections from ensembles of climate models." Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/15292.

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Appropriate and defensible statistical frameworks are required in order to make credible inferences about future climate based on projections derived from multiple climate models. It is shown that a two-way analysis of variance framework can be used to estimate the response of the actual climate, if all the climate models in an ensemble simulate the same response. The maximum likelihood estimate of the expected response provides a set of weights for combining projections from multiple climate models. Statistical F tests are used to show that the differences between the climate response of the North Atlantic storm track simulated by a large ensemble of climate models cannot be distinguished from internal variability. When climate models simulate different responses, the differences between the re- sponses represent an additional source of uncertainty. Projections simulated by climate models that share common components cannot be considered independent. Ensemble thinning is advocated in order to obtain a subset of climate models whose outputs are judged to be exchangeable and can be modelled as a random sample. It is shown that the agreement between models on the climate response in the North Atlantic storm track is overestimated due to model dependence. Correlations between the climate responses and historical climates simulated by cli- mate models can be used to constrain projections of future climate. It is shown that the estimate of any such emergent relationship will be biased, if internal variability is large compared to the model uncertainty about the historical climate. A Bayesian hierarchical framework is proposed that is able to separate model uncertainty from internal variability, and to estimate emergent constraints without bias. Conditional cross-validation is used to show that an apparent emergent relationship in the North Atlantic storm track is not robust. The uncertain relationship between an ensemble of climate models and the actual climate can be represented by a random discrepancy. It is shown that identical inferences are obtained whether the climate models are treated as predictors for the actual climate or vice versa, provided that the discrepancy is assumed to be sym- metric. Emergent relationships are reinterpreted as constraints on the discrepancy between the expected response of the ensemble and the actual climate response, onditional on observations of the recent climate. A simple method is proposed for estimating observation uncertainty from reanalysis data. It is estimated that natural variability accounts for 30-45% of the spread in projections of the climate response in the North Atlantic storm track.

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Nettleton, Stuart John. "Benchmarking climate change strategies under constrained resource usage /." Electronic version, 2009. http://utsescholarship.lib.uts.edu.au/iresearch/scholarly-works/handle/2100/1012.

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Häckner, Lina. "Climate Change and Agriculture in Babati : Awareness Strategies Constrains." Thesis, Södertörn University College, School of Life Sciences, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-2685.

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Climate change caused by green house gas emissions, mainly carbon dioxide, is today’s most debated environmental issue. The United Nations Framework Convention on Climate Change, with the legally binding Kyoto protocol, is the emission regulatory framework. Tanzania has ratified both the conventions supporting carbon reductions.

Tanzania has a very varied climate with two rainfall regimes dominating the country, bimodal and unimodal. Scientific literature predicts a 2,2-4°C average increase in temperature for Tanzania, all studies also predict a higher increase in the cooler period and lower in the warm period. Rainfall predictions are less certain but in general a 10 % average increase is expected but the distribution uneven, both between rain periods and geographically. Tanzanian reports estimate a 5-45 % increase in rainfall in bimodal regions and a 5-15 % decrease in unimodal regions. The distribution of increase in bimodal regions will be uneven, with an increase in the long rain period and a decrease in the short rain period.

Agriculture is indisputably the most important source of income in Tanzania standing for 80% of employment and 50% of GNP. Climate change will therefore inevitably affect the economy and livelihood of people. Developing countries are also more vulnerable due to lower adaptation capacity. Effects on Tanzania are predicted to be both positive and negative. Maize production, the major staple, is predicted an average 33% decline while cash crops like coffee and cotton are predicted to increase. To be able to adapt there first has to be a perception of need to adapt, adaption strategies then have to be developed and barriers worked through. The purpose of this thesis is to investigate the level of awareness, strategies and barriers existing for adaption to climate change on national, regional and local level, Tanzania nationally and Babati regionally and locally. The research questions are; How do people perceive climate change? What are the strategies for adapting to climate change? What are the barriers for adaption to climate change? At national level policy framework and strategies were used to answer the research questions. At regional and local level a field study was conducted in Babati to answer the research questions at these levels.

The study showed that Tanzania nationally has declared their conviction in climate change and state that the issue has to be addressed. Agriculture is identified as one of the most vulnerable areas however climate change is not mainstreamed into agricultural and environmental policy framework. In Babati district no policy was found on climate change and official perception varied. Concerns were related to timing and amount of rainfall, the results were the same for farmers. Global climate change was also known for both studied groups and existed as a parallel truth with the local reason for changes. A number of adaption strategies are also identified nationally, both used and potential, where small scale irrigation is the primary adaptive step. Switching to draught resistant crops is also prioritized in the North eastern region. In Babati adaption strategies were promoted, even though there was not a general policy or perception, by officials to switch to short-term crops and planting of trees. Switching cops was also the most commonly used strategy by farmers along with traditional diversification. Nationally a large number of barriers are also identified including, lack of funding, poverty, HIV, lack of infrastructure and analytic capacity. Officials in Babati also mentioned the lack of money, deforestation, lack of clouds, education, irrigation and seeds. The farmers in Babati were not so clear about what they needed to adapt, irrigation, livestock backup, diversification and switching crops were mentioned, not differing much from used strategies.

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Koper, Nicola. "Ecological constraints on growth of painted turtles, Chrysemys picta, in northern climates." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ31843.pdf.

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Pascale, Salvatore. "Maximum entropy production as a constraint on the climate system." Thesis, University of Reading, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541950.

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Georgian, Sam Ellis. "ENVIRONMENTAL AND ENERGETIC CONSTRAINTS ON COLD-WATER CORALS." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/382890.

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Biology
Ph.D.
Cold-water corals act as critical foundation species in the deep sea by creating extensive three-dimensional habitat structures that support biodiversity hotspots. There is currently a paucity of data concerning the environmental requirements and physiology of cold-water corals, severely limiting our ability to predict how resilient they will be to future environmental change. Cold-water corals are expected to be particularly vulnerable to the effects of ocean acidification, the reduction in seawater pH and associated changes to the carbonate system caused by anthropogenic CO2 emissions. Here, the ecological niche and physiology of the cold-water coral Lophelia pertusa is explored to predict its sensitivity to ocean acidification. Species distribution models were generated in order to quantify L. pertusa’s niche in the Gulf of Mexico with regard to parameters including seafloor topography, the carbonate system, and the availability of hard substrate. A robust oceanographic assessment of the Gulf of Mexico was conducted in order to characterize the current environmental conditions at benthic sites, with a focus on establishing the baseline carbonate system in L. pertusa habitats. Finally, an experimental approach was used to test the physiological response of biogeographically separated L. pertusa populations from the Gulf of Mexico and the Norwegian coast to ocean acidification. Based on my findings, it appears that L. pertusa already persists near the edge of its viable niche space in some locations, and therefore may be highly vulnerable to environmental change. However, experimental results suggest that some populations may be surprisingly resilient to ocean acidification, yielding broad implications for the continued persistence of cold-water corals in future oceans.
Temple University--Theses

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Kishimoto, Paul Natsuo. "Passenger transport in China under climate constraints : general equilibrium analysis, uncertainty, and policy." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78492.

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Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 69-76).
Vehicle sales and road travel volume in China have grown rapidly in recent years, and with them energy demand, greenhouse gas emissions and local air pollution. Aviation and rail travel have also grown, while ceding a large share to private vehicles. What path will household transport demand in China take in the future? How might it interact with policies which limit greenhouse gases, and what are the implications for energy use, the environment and the economy? To contribute policy insights and a foundation for future study in this area, I undertake a new calibration of the Chinese household transport sector in the MIT Emissions Prediction & Policy Analysis (EPPA) computable general equilibrium (CGE) model, implementing income elasticities of demand for vehicle travel and vehicle stock growth based on historical data. To bracket uncertainty in the literature, I impose three scenarios of future growth in demand for purchased (air, rail and marine) and vehicle modes. These are explored under a no-policy baseline, a climate-stabilization policy, and with a policy that extends the emissions-intensity goal of China's Twelfth Five-Year Plan-both policies are modelled as caps creating prices on carbon. Examining the results, I find that trends in growth are only modesty affected by policy continuing present energy-intensity goals, with small decreases in travel activity and energy intensity of vehicles combining for a reduction in refined oil use; such a policy has modest cost and affects household transport less than other sectors. In contrast, my results show that a stringent emissions cap has large impacts on vehicle efficiency, limits vehicle ownership and general travel activity levels. Compared to the no-policy baseline, a smaller vehicle fleet (250 million total, or 200 per 1000 capita). Sixteen percent of the fleet is new energy vehicles (plug-in hybrid-electrics), while total refined oil use increases by 2050 to nearly three times its 2010 level. However, these effects come with a reduction in total primary energy as the policy is introduced, and large costs economy-wide. Chinese national and municipal policies include objectives of promoting vehicle ownership and mobility on the one hand, and of reducing dependence on carbon-intensive refined oil on the other. My findings illustrate that these goals are at odds, and offer inputs to policy design related to vehicle sales, public transit, congestion, pollution and energy security.
by Paul Natsuo Kishimoto.
S.M.in Technology and Policy

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15

Sarofim, Marcus C. "Climate policy design : interactions among carbon dioxide, methane, and urban air pollution constraints." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39257.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 176-189).
Limiting anthropogenic climate change over the next century will require controlling multiple substances. The Kyoto Protocol structure constrains the major greenhouse gases and allows trading among them, but there exist other possible regime architectures which may be more efficient. Tradeoffs between the market efficiency of all-inclusive policies and the benefits of policies targeted to the unique characteristics of each substance are investigated using an integrated assessment approach, using the MIT Emissions Prediction and Policy Analysis model, the Integrated Global Systems Model, and political analysis methods. The thesis explores three cases. The first case addresses stabilization, the ultimate objective of Article 2 of the UN Framework Convention on Climate Change. We highlight the implications of imprecision in the definition of stabilization, the importance of non-CO2 substances, and the problems of excessive focus on long-term targets. The results of the stabilization analysis suggest that methane reduction will be especially valuable because of its importance in low-cost mitigation policies that are effective on timescales up to three centuries. Therefore in the second case we examine methane, demonstrating that methane constraints alone can account for a 15% reduction in temperature rise over the 21st century.
(cont.) In contrast to conventional wisdom, we show that Global Warming Potential based trading between methane reductions and fossil CO2 reductions is flawed because of the differences in their atmospheric characteristics, the uncertainty in methane inventories, the negative interactions of CO2 constraints with underlying taxes, and higher political barriers to constraining CO2. The third case examines the benefits of increased policy coordination between air pollution constraints and climate policies. We calculate the direct effects of air pollution constraints to be less than 8% of temperature rise over the century, but ancillary reductions of GHGs lead to an additional 17% decrease. Furthermore, current policies have not had success coordinating air pollution constraints and CO2 constraints, potentially leading to a 20% welfare cost penalty resulting from separate implementation. Our results lead us to recommend enacting near term multinational CH4 constraints independently from CO2 policies as well as supporting air pollution policies in developing nations that include an emphasis on climate friendly projects.
by Marcus C. Sarofim.
Ph.D.

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16

Zakaria, Mohamad. "Possibilities and Constraints Facing the International Cooperation in Negotiating Global Climate Change Regimes." Thesis, Malmö högskola, Fakulteten för kultur och samhälle (KS), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-23331.

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This thesis analysis the problems facing the negotiators during their international efforts to create global climate change regimes. Without understanding why such negotiations failed in the past, it is difficult to learn how to negotiate them successfully in the future. The US and China are responsible for emitting almost half of the greenhouse emissions to the atmosphere. However, they are still laggards in the efforts to create an effective global climate change regime and are running away from their global responsibility by blaming each other for the failure to reach a global climate change deal. The EU has been taking the leadership in efforts to negotiate global climate change regimes. However, they can not influence and force the main two hegemonic powers to follow their leadership. This is because the EU is not hegemony in the global political arena. The EU persistence to find compromises during negotiations for future global climate change regimes is a source of hope to humankind. Flexibility during negotiations, openness to consider the views of other global actors to find optimum solutions, and the understanding that no one is secure from the threats of climate change are essential to bring the world leaders into a compromise global climate change regime.

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Moore, Richard Herbert. "Using measurements of CCN activity to characterize the mixing state, chemical composition, and droplet growth kinetics of atmospheric aerosols to constrain the aerosol indirect effect." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45945.

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Atmospheric aerosols are known to exert a significant influence on the Earth's climate system; however, the magnitude of this influence is highly uncertain because of the complex interaction between aerosols and water vapor to form clouds. Toward reducing this uncertainty, this dissertation outlines a series of laboratory and in-situ field measurements, instrument technique development, and model simulations designed to characterize the ability of aerosols to act as cloud condensation nuclei (CCN) and form cloud droplets. Specifically, we empirically quantify the mixing state and thermodynamic properties of organic aerosols (e.g., hygroscopicity and droplet condensational uptake coefficient) measured in polluted and non-polluted environments including Alaska, California, and Georgia. It is shown that organic aerosols comprise a substantial portion of the aerosol mass and are often water soluble. CCN measurements are compared to predictions from theory in order to determine the error associated with simplified composition and mixing state assumptions employed by current large-scale models, and these errors are used to constrain the uncertainty of global and regional cloud droplet number and albedo using a recently-developed cloud droplet parameterization adjoint coupled with the GMI chemical transport model. These sensitivities are important because they describe the main determinants of climate forcing. We also present two novel techniques for fast measurements of CCN concentrations with high size, supersaturation, and temporal resolution that substantially improve the state of the art by several orders of magnitude. Ultimately, this work represents a step toward better understanding how atmospheric aerosols influence cloud properties and Earth's climate.

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Swetnam, Tyson L., Paul D. Brooks, Holly R. Barnard, Adrian A. Harpold, and Erika L. Gallo. "Topographically driven differences in energy and water constrain climatic control on forest carbon sequestration." WILEY, 2017. http://hdl.handle.net/10150/624369.

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Mountains are vital to ecosystems and human society given their influence on global carbon and water cycles. Yet the extent to which topography regulates montane forest carbon uptake and storage remains poorly understood. To address this knowledge gap, we compared forest aboveground carbon loading to topographic metrics describing energy balance and water availability across three headwater catchments of the Boulder Creek Watershed, Colorado, USA. The catchments range from 1800 to 3500 m above mean sea level with 46-102 cm/yr mean annual precipitation and -1.2 degrees to 12.3 degrees C mean annual temperature. In all three catchments, we found mean forest carbon loading consistently increased from ridges (27 +/- 19 Mg C ha) to valley bottoms (60 +/- 28 Mg C ha). Low topographic positions held up to 185 +/- 76 Mg C ha, more than twice the peak value of upper positions. Toe slopes fostered disproportionately high net carbon uptake relative to other topographic positions. Carbon storage was on average 20-40 Mg C ha greater on north to northeast aspects than on south to southwest aspects, a pattern most pronounced in the highest elevation, coldest and wettest catchment. Both the peak and mean aboveground carbon storage of the three catchments, crossing an 11 degrees C range in temperature and doubling of local precipitation, defied the expectation of an optimal elevation-gradient climatic zone for net primary production. These results have important implications for models of forest sensitivity to climate change, as well as to predicted estimates of continental carbon reservoirs.

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Bonnefoy-Claudet, Clément. "Diversité et sensibilité à la température des matières organiques de sols forestiers du Morvan sous contrainte climatique : évolution de la respiration des sols et facteurs de contrôle." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. https://theses.hal.science/tel-04882870.

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L’évolution climatique actuelle et les changements d’occupation et de gestion des terres sont susceptibles de modifier la dynamique de décomposition des matières organiques des sols et les flux de carbone associés. Les écosystèmes forestiers représentent 40 % du stock de carbone organique des surfaces continentales et constituent ainsi un objet d’étude prioritaire. Localement, le Morvan, zone de moyenne montagne couverte à 45 % par de la forêt, apparaît plus sensible au changement climatique que les plaines qui l’entourent. Dans ce contexte, cette étude a porté sur la dynamique du carbone organique dans les sols forestiers tempérés face au changement climatique. Ces travaux ont été principalement menés sur le site du mont Beuvray, un massif forestier situé au sud du Parc Naturel Régional du Morvan. Un échantillonnage de sols représentant la diversité spatiale du massif pour chacune des essences (Hêtre, Douglas, Sapin pectiné, Epicéa) a été réalisé. La diversité moléculaire des matières organiques a été caractérisée par pyrolyse couplée à la chromatographie en phase gazeuse et spectrométrie de masse (Py-GC-MS). Les résultats suggèrent une matière organique plus facilement dégradable dans les sols sous sapin pectiné par rapport à la matière organique des sols sous Douglas. La sensibilité à la température de la respiration des sols a été évaluée par la mesure du paramètre Q10, dont les valeurs varient de 2,3 à 3,0. Une valeur plus élevée pour le hêtre (2,8 ± 0,1) a été observée en comparaison des essences de résineux (2,6 ± 0,1). Ceci indique que les sols sous feuillus pourraient émettre plus de CO2 que les sols sous résineux avec le changement climatique. La variabilité observée de ce paramètre Q10 est principalement expliquée par l’interaction entre la composition moléculaire de la matière organique et l’activité des microorganismes (activités enzymatiques extracellulaires). L’ensemble de ces résultats permettra de mieux évaluer et anticiper l’évolution de la dynamique de la matière organique des sols forestiers de moyenne montagne
Current climate change and shifts in land use and management are likely to alter the dynamics of soil organic matter decomposition and associated carbon fluxes. Forest ecosystems account for 40 % of the organic carbon stock on continental surfaces and are therefore a priority for research. Locally, the Morvan, a mid-mountain region covered by 45% forest, appears to be more sensitive to climate change than the surrounding plains. In this context, this study focused on the dynamics of organic carbon in temperate forest soils in the face of climate change. This work was mainly carried out on the Mont Beuvray site, a forested massif located in the southern part of the Morvan Regional Natural Park. Soil samples representing the spatial diversity of the massif were taken for each tree species (beech, Douglas fir, silver fir, spruce). The molecular diversity of organic matter was characterised by pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC-MS). The results suggest that organic matter in soils under silver fir is more readily degradable than that in soils under Douglas fir. The temperature sensitivity of soil respiration was assessed by measuring the Q10 parameter, with values ranging from 2.3 to 3.0. A higher value was observed for beech (2.8 ± 0.1) compared to conifers (2.6 ± 0.1). This suggests that with climate change, soils under deciduous species could emit more CO2 than soils under conifers. The observed variability in this Q10 parameter is mainly explained by the interaction between the molecular composition of organic matter and the activity of microorganisms (extracellular enzymatic activities). These results will help to better assess and anticipate changes in the dynamics of organic matter in mid-mountain forest soils

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20

Parker, Scott Landsborough. "Physiological and Ecological Constraints on the Evolution of Viviparity in Sceloporine Lizards." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/26050.

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The purpose of this study was to evaluate putative physiological and ecological constraints on the evolution of viviparity in sceloporine lizards. In Chapters one and two, I investigated the role of in utero oxygen availability as a constraint on the capacity to support embryonic development during extended egg retention. I incubated eggs of sceloporine lizards under conditions that simulated retention in the oviduct under a range of oxygen partial pressures. In Chapter one, I tested the hypothesis that embryos of the oviparous lizard Sceloporus undulatus from a high-latitude population are laid at more advanced developmental stages and have a higher developmental rate at low partial pressure oxygen (pO2) under simulated in utero conditions than embryos from a low-latitude population. This hypothesis was rejected; embryos from the two populations did not differ in embryonic stage at oviposition or developmental rate when incubated under simulated in utero conditions at low pO2. In Chapter two I tested the hypothesis that the degree of embryonic development attained by reptilian embryos in utero is directly related to in utero pO2. The species chosen for the study differed in their capacity to support embryonic development during egg retention and were characterized by developmental arrest (Urosaurus ornatus), retarded development (Sceloporus virgatus), and normal development (Sceloporus scalaris) when eggs are retained past the normal time of oviposition. The estimated in utero pO2's for the three species increased in the order of U. ornatus (5-6 kPa) < S. virgatus (9-11 kPa) < S. scalaris (> 11 kPa). These results indicate that in utero oxygen availability is associated with interspecifc differences in the capacity to support embryonic development during extended egg retention. In Chapter three I tested the hypothesis that embryo thermal requirements determine the northern distributional limit of Sceloporus undulatus. I incubated eggs of S. undulatus under temperature treatments that simulated the thermal environment that eggs would experience if located in nests within their geographic range at 37 °N and at latitudes north of the species present geographic range at 42 and 44 °N. Incubation temperatures simulating nests at 44 °N prolonged incubation and resulted in hatchlings with shorter tails, shorter hind limb span, slower growth and lower survival than hatchlings from eggs incubated at temperatures simulating nests at 37 and 42 °N. I also predicted that the northernmost distributional limit of S. undulatus would be associated with locations that provide the minimum heat sum (degree-days) required to complete embryonic development. Eighty-four percent of location between 37-40 °N had > 495 degree-days above a threshold of 17 °C accumulated during June-September compared to eleven percent of locations between 41-50 °N. These results are consistent with the hypothesis that incubation temperature is an important factor limiting the geographic distributions of oviparous reptile species at high latitudes and high elevations.
Ph. D.

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21

Semenzato, Paola. "Movement ecology of female alpine ibex (Capra ibex): influence of resources, climate, and reproductive constraints." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3422315.

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There is now ample evidence of the ecological impacts of recent climate change on Alpine ecosystems. Animal populations, and in particular herbivores, can be affected directly, through modifications of the environmental temperature, and indirectly, through alteration of both distribution and phenology of plant communities. Understanding the behavioral strategies and tactics that populations and individuals use to buffer climatic variability and its impacts are particularly relevant in order to evaluate their vulnerability to climate change and develop incisive management and conservation actions. This dissertation investigates how females of Alpine ibex (Capra ibex) taken as a model for specialized Alpine large herbivore species, shape their behavior to deal with environmental and climatic variation and reproductive constraints during summer, a crucial period for the fitness of females of a capital breeder species. For this purpose, I used GPS locations and activity data of 22 females monitored in the Marmolada massif (northeastern Italian Alps) from 2010 to 2016. I tested for differences in space use and activity patterns of female ibex at different temporal scales (annual, intra-seasonal and hourly), in relation with changes in temperature, habitat type, and food resource availability -productivity (NDVI) and green up (?NDVI) of vegetation-. In addition, I evaluated anti-predator behavior contrasting the tactics of use of refuge areas and habitat types of females with different reproductive status. My findings showed how female ibex vary the use of space, habitat selection and rhythms of activity in a continuous trade off that allow them to fulfill different physiological needs in response to variation in environmental and climatic conditions, and under reproductive constraint. Ibex females responded to the altitudinal gradient in vegetation productivity with an altitudinal shift in spring and summer, to exploit the vegetation in earlier phenological stages. At the same time, females avoided thermal stress and maintained constant the daily foraging time through adjustments in circadian activity rhythms and altitudinal shifts. Moreover, during the reproductive period females with kids modified their movement patterns, feeding activity, and habitat use cope with increased energetic demands and the need of protecting kids with their limited locomotion capacity. My results have shown that the spatial behaviors that act at different scales were an effective strategy to optimize thermoregulation needs and forage acquisition while reducing predation risk. This thesis enriches knowledge on the influence of resources, climate, and reproductive constraints on behavioral strategies and tactics of female ibex. It represents the first attempt for this species, to my knowledge, to describe these behavioral responses as part of a complex trade-off mechanism, which occurs across different temporal scales, highlighting a presence of behavioral plasticity in ibex females. Such behavioral plasticity may allow them to buffer the environmental variations associated with current climate change.
Risulta ormai evidente come il cambiamento climatico in atto stia avendo un forte impatto sull’ecosistema alpino. Le popolazioni animali, ed in particolare su gli erbivori possono essere influenzati direttamente, delle variazioni delle temperature ambientali, e indirettamente, dalle alterazioni nella distribuzione e nelle fasi fenologiche della vegetazione. La comprensione delle strategie comportamentali, utilizzate dagli animali per rispondere al cambiamento climatico è particolarmente rilevante per valutare la loro vulnerabilità a tali modifiche, permettendo così di sviluppare azioni di gestione e conservazione efficaci. Questa tesi esamina come le femmine di stambecco Capra ibex (prese come specie modello specializzata all’ambiente alpino di alta quota) variano il loro comportamento spaziale e i ritmi di attività in risposta ai cambiamenti ambientali e climatici, nonché ai vincoli riproduttivi durante il periodo primaverile e estivo. Per raggiungere gli obiettivi della mia tesi, ho utilizzato le localizzazioni raccolte attraverso collari GPS e i dati di attività del sensore di movimento posizionato sui collari di 22 femmine monitorate dal 2010 al 2016 nel massiccio della Marmolada (Alpi nord-orientali). Ho analizzato le variazioni a diverse scale temporali (annuale, intra - stagionale e oraria) del comportamento spaziale e dei pattern di attività delle femmine di stambecco in relazione ai cambiamenti nella disponibilità delle risorse trofiche - produttività (NDVI) e green-up (?NDVI) della vegetazione -, della temperatura ambientale e all’uso dei diversi tipi di habitat. Inoltre, ho valutato il comportamento anti-predatorio confrontato l'uso delle aree di rifugio delle femmine a diverso stato riproduttivo. I risultati dimostrano come le femmine di stambecco abbiano variato l'uso dello spazio, della selezione degli habitat e dei ritmi di attività, in un meccanismo di trade-off, per soddisfare diverse esigenze fisiologiche in risposta alla variazione delle condizioni ambientali, climatiche e al loro stato riproduttivo. Durante la stagione primaverile e estiva le femmine di stambecco hanno risposto al gradiente altitudinale della produttività della vegetazione con uno spostamento verso le quote più alte, per sfruttare la vegetazione nei primi stadi fenologici. Allo stesso tempo, hanno evitato lo stress termico e hanno mantenuto costante l'attività di alimentazione regolando, a scala giornaliera, i ritmi di attività e gli spostamenti altitudinali. Lo studio ha premesso di descrivere come la variazione circadiana e stagionale dell’uso dei diversi tipi di habitat rappresenti una strategia ottimale di uso dello spazio, minimizzando lo stress termico e massimizzando l'acquisizione delle risorse trofiche. Inoltre è stato messo in luce come, durante il periodo riproduttivo le femmine con il piccolo modifichino il loro comportamento spaziale e l’attività di alimentazione, variando altresì l’uso dell’habitat in risposta all'aumento delle esigenze energetiche e delle necessità di protezione dei piccoli, nonché la loro minore capacità di locomozione. I risultati hanno dimostrato come strategie comportamentali che agiscono a diverse scale rappresentano un modo efficace per ottimizzare le esigenze di termoregolazione, l'acquisizione di risorse alimentari e per ridurre il rischio di predazione. Questa tesi arricchisce le conoscenze sull'influenza delle risorse trofiche, del clima e dei vincoli riproduttivi sulle strategie e tattiche comportamentali delle femmine di stambecco. Essa rappresenta il primo tentativo per questa specie, secondo le mie conoscenze, di descrivere queste risposte comportamentali come parte di un complesso trade-off che si verifica a diverse scale temporali, evidenziando una presenza di plasticità comportamentale nelle femmine di stambecco. Tale plasticità comportamentale potrebbe consentire a questa specie di tamponare le variazioni ambientali associate agli attuali cambiamenti climatici.

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Subt, Cristina. "Resolving chronological and temperature constraints on Antarctic deglacial evolution through improved dating methodology." Scholar Commons, 2017. https://scholarcommons.usf.edu/etd/7447.

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In order to determine the timing of Antarctic ice sheet retreat and advance during the Late Quaternary, various tools are used to measure the age of marginal marine sediments. Carbonate 14C dating is a well-established approach, but requires foraminiferal microfossils, shells or other carbonate materials that are rare in most Antarctic regions, and may also suffer from vital effects, which can result in variability of up to 500 years in living organisms. Bulk acid insoluble organic (AIO) 14C dates are frequently as an alternative, but this approach works best where high productivity and sedimentation rates reign, and not too well in condensed sequences where high proportions of detritus are present. Compound specific dating methods have also been employed, but these may still yield an average age from a mixture of components and require very large sample sizes. Alternate methods of applying a chronology have also been used, such as magnetic intensity dating, or regional correlation with well-dated cores, but these may not always provide accurate and precise dates. Here I present work, some published with co-authors, of progressive improvements of Ramped PyrOx 14C dating, which utilizes the thermochemical degradation of components within a bulk AIO sediment sample. This dissertation focuses on the study, improvement and application of advanced Ramped PyrOx techniques. These improvements include novel techniques, such as compositing and isotope dilution that I use to date sediments where the proportion of contemporaneously deposited carbon is very small relative to other detrital components, and maximize the accuracy of resulting dates while minimizing costs in precision from utilizing ultra-small fractions of the bulk sample. Ramped PyrOx 14C dating techniques allows us to generate chronologies for cores that would otherwise go undated. Furthermore, these techniques can be used to push the limits of radiocarbon dating not only to regions where accurate core chronologies have been difficult to come by, but also further back in time, into marine sediment horizons deposited at or before the last glacial maximum (LGM), where highly detrital material has precluded radiocarbon dating in the past. Wider use of these techniques can enable more coordinated a priori coring efforts to constrain regional glacial responses to rapid warming.

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Pattison, James Lee. "Orma livelihoods in Tana River district, Kenya : a study of constraints, adaptation and innovation." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5928.

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This study focuses on the constraints, adaptations and innovations in the livelihoods of Orma pastoralists. The fieldwork took place with families around Tiltila, Waldena and Kalalani over a period of 9 months in 2007/08. The position of pastoralist peoples in East Africa is characterised by social, political and economic marginalisation, weak land tenure, and declining per capita livestock holdings, while their shrinking grazing lands are widely regarded to be on the front line of climate change, both in terms of climate impacts and biofuel/agribusiness land pressure. The dearth of good quality data on pastoralist populations and livelihoods is widely cited as one of the fundamental barriers to improving the effectiveness of development support in the drylands. This study seeks to address these knowledge gaps for Orma pastoralists, while contributing to the body of theory on pastoralist livelihood dynamics. Data on the effects of wealth, education and food aid on household mobility were analysed using a theory of asset threshold dynamics. An adapted typology of livelihood strategies was developed to interpret and structure the data. Using child mortality as a proxy for respondent health, the impacts of wealth and mobility status on families’ health were explored. In the context of an almost total lack of data on community redistribution of food aid, both for the Orma and for East African pastoralists more generally, the study provides empirical data on de facto community food aid allocation patterns. The study also examines a controversial large-scale expropriation of land in Tana River (subsidised under the Kyoto Protocol’s Clean Development Mechanism) which will undermine the capacity of Orma pastoralists and other minority groups, to adapt to increased and more extreme environmental variability. In an environment in which enrolment in formal education is very low (particularly for girls), the study found that community nursery schools represent a relatively recent (and thus far undocumented) innovation organised and funded by groups of parents. The data demonstrates unprecedented levels of female enrolment despite cost constraints faced by least wealthy families. It is therefore suggested that incorporation of the community nursery model into the basic literacy element of the proposed national distance learning strategy, offers significant potential for addressing ‘Education For All’ in Kenya’s drylands.

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Dutta-Koehler, Madhu Chhanda. "Making climate adaptation work : strategies for resource constrained South Asian mega-cities." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81638.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 277-329).
This dissertation compares the responses of Dhaka, Bangladesh and Kolkata, India to the serious challenges posed by climate change, particularly in the water sector. Drawing on the theories of "adaptation as development" and cross-case analyses of ongoing planning initiatives in these two bellwether cities, this dissertation explores the factors that promote or hinder successful climate action. This work identifies practical, less resource-intensive adaptation strategies suited to the context of urban South Asia, where the findings suggest that, given the absence of dedicated adaptation planning at the city level, the most effective approaches are those that integrate both development and adaptation criteria. Resources allocated for local development can thus simultaneously address adaptation needs without substantial additional investments. Moreover, since such efforts are already part of ongoing planning initiatives, they obviate the need for more extensive "specialized adaptation" planning and technical expertise. These actions may thereby reduce the vulnerabilities of urban residents in these most threatened regions of the world. Drawing upon over ninety in-depth interviews, primary documents, firsthand observation, relevant scholarship, and three emblematic, developmentally oriented project case studies that address the cities' most urgent climate risks in water, flood and wetlands management, this research proposes a "contingent adaptation" approach as best-suited to such resource-constrained environments. Such an approach has the ability to overcome inherent local resource constraints, institutional limitations, while increasing the likelihood of adoption of adaptation-oriented projects. This work identifies several factors-among them, developing collaborative partnerships to bridge technical deficits, reforming local organizational structures to generate internal resources, and building political consensus for climate action-as essential for successful climate adaptation. This work seeks to provide a theoretical framework for effectively implementing adaptation-related local planning initiatives while building broader support for substantial climate action. Such contingent adaptation approaches may thereby provide a blueprint for immediate, proactive, and cost-effective practical applications in similar cities in South Asia and in comparable developing regions.
by Madhu Chhanda Dutta-Koehler
Ph.D.

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Cabon, Antoine Pierre Clément. "Predicting forest responses to climate. Integrating water and temperature constraints from the cell to the region." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670136.

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El canvi climàtic en curs està afectant els boscos a tot el món, però ¿com i en quina mesura? Els recents esdeveniments severs de decaïment forestal mostren la potencial amplitud de les conseqüències d’un clima més càlid i sec, però encara segueixen existint grans incerteses pel que fa a la resposta dels boscos. Caracteritzar i pronosticar la resposta dels boscos a les variacions climàtiques és críticament necessari per dissenyar estratègies de mitigació i adaptació. Els models basats en processos són una eina essencial en aquesta tasca, però el seu ús es veu limitat per llacunes de coneixement sobre els mecanismes que impulsen les respostes dels boscos i la seva representació dins dels models. L’objectiu general d’aquesta tesi és avançar en la comprensió i el modelatge dels efectes de l’aigua i la temperatura sobre l’estructura i el funcionament dels boscos. Per a aconseguir-ho, la hidràulica de les plantes i els principis biofísics estan articulats dins d’una perspectiva de modelatge mecanicista, de manera que la resposta dels boscos és una propietat emergent de la integració de processos a través de diferents escales. Els resultats d’aquesta tesi llancen nova llum sobre el paper de la disponibilitat d’aigua i el seu transport a través de la planta en el control dels processos que sustenten la formació de fusta, el creixement dels arbres i l’estructura forestal . És a dir, es suggereix que durant la formació de la fusta, el potencial hídric modifica la pressió de turgència de les cèl·lules i d’aquesta manera impulsa l’expansió cel·lular, produint variacions en les dimensions dels conductes del xilema i en les taxes de divisió cel·lular en el càmbium. A més, es proposa que l’efecte de la temperatura sobre l’extensibilitat cel·lular modula l’expansió i divisió cel·lular. Segons aquest model biofísic, les fluctuacions estacionals de potencial hídric i temperatura influeixen directament en la variació estacional de la quantitat i estructura de la fusta formada, independentment de l’assimilació de carboni per fotosíntesi. La validació del model es porta a terme en dos localitats d’estudi que inclouen els límits àrids o freds de distribució de les espècies considerades. A escala interanual, els resultats suggereixen que el creixement dels arbres esta determinat per la interacció dels controls biofísics de la formació de la fusta amb els de l’assimilació de carboni. D’altra banda, es formula un model teòric en el qual se suposa que l’estructura aèria i subterrània de bosc tendeix a estar en equilibri amb les precipitacions i la demanda hídrica de l’atmosfera. Aquest model s’utilitza per predir la distribució radicular dels boscos a partir de caràcters hidràulics i fluxos d’aigua simulats, la qual cosa es valida mitjançant diversos llocs d’estudi, incloent condicions climàtiques contrastades a Catalunya. L’aplicació d’aquesta metodologia a les dades de l’inventari forestal a Catalunya permet obtenir estimacions de la distribució d’arrels a escala regional. En el seu conjunt, aquesta tesi destaca l’extensió de les respostes dels boscos al clima des de l’escala cel·lular a la regional, així com els mecanismes hidràulics i biofísics subjacents. Es proposen noves solucions de modelatge que integren els processos destacats a través de diferents escales. La seva implementació dins dels models de dinàmica de la vegetació i un major enfocament en les reserves i fluxos d’aigua podria ajudar a reduir les incerteses existents actualment pel que fa a la destinació dels boscos davant del canvi climàtic.
El cambio climático en curso está afectando a los bosques en todo el mundo, pero ¿cómo y en qué medida? Los recientes eventos severos de decaimiento forestal muestran la potencial amplitud de las consecuencias de un clima más cálido y seco, pero todavía siguen existiendo grandes incertidumbres en cuanto a las respuestas de los bosques. Caracterizar y pronosticar las respuestas de los bosques a las variaciones climáticas es críticamente necesario para permitir estrategias de mitigación y adaptación. Los modelos basados en procesos son una herramienta esencial en esta tarea, pero su uso se ve limitado por lagunas de conocimiento sobre los mecanismos clave que impulsan las respuestas de los bosques y su representación dentro de los modelos. El objetivo general de esta tesis es avanzar en la comprensión y el modelado de los efectos del agua y la temperatura sobre la estructura y el funcionamiento de los bosques. Para ello, la hidráulica de las plantas y los principios biofísicos están articulados dentro de una perspectiva de modelado mecanicista, de modo que la respuesta de los bosques es una propiedad emergente de la integración de procesos a través de distintas escalas. Los resultados de esta tesis arrojan nueva luz sobre el papel de la disponibilidad de agua y su transporte a través de la planta en el control de los procesos que sustentan la formación de madera, el crecimiento de los árboles y la estructura forestal. Es decir, se sugiere que durante la formación de la madera, el potencial hídrico modifica la presión de turgencia de las celdas y de este modo impulsa la expansión celular, produciendo variaciones en las dimensiones de los conductos del xilema y en las tasas de división celular en el cambium. Además, se propone que el efecto de la temperatura sobre la extensibilidad celular modula la expansión y división celular. Según este modelo biofísico, las fluctuaciones estacionales del potencial hídrico y la temperatura influyen directamente en la variación estacional de la cantidad y estructura de la madera formada, independientemente de la asimilación de carbono por la fotosíntesis. La validación del modelo se lleva a cabo en dos sitios de estudio que incluyen los límites áridos o fríos de distribución de las especies consideradas. A escala interanual, los resultados sugieren que el crecimiento de los árboles está determinado por la interacción de los controles biofísicos de la formación de la madera con la asimilación de carbono. Por otra parte, se formula un modelo teórico en el que se supone que la estructura aérea y subterránea del bosque tiende a estar en equilibrio con las precipitaciones y la demanda hídrica de la atmósfera. Dicho modelo se utiliza para predecir la distribución radicular de los bosques a partir de rasgos hídricos y flujos de agua simulados, lo cual se valida mediante varios sitios de estudio, incluyendo condiciones climáticas contrastadas en Cataluña. La aplicación de esta metodología a los datos del inventario forestal en Cataluña permite obtener estimaciones de la distribución de raíces a escala regional. En su conjunto, esta tesis destaca la extensión de las respuestas de los bosques al clima desde la escala celular a la regional, así como los mecanismos hidráulicos y biofísicos subyacentes. Se proponen nuevas soluciones de modelado que integran los procesos destacados a través de distintas escalas. Su implementación dentro de los modelos de dinámica de la vegetación y un mayor enfoque en las reservas y flujos de agua podría ayudar a reducir las incertidumbres existentes actualmente respecto al destino de los bosques ante el cambio climático.
Ongoing climate change affects forests worldwide, but how and how much so? Recent widespread forest die-off events highlight potentially dramatic outcomes brought by overall warmer and drier conditions, but large uncertainties remain regarding forest responses. Characterizing and forecasting forest responses to climate is critically needed in order to enable mitigation and adaptation strategies. Process-based models are an essential tool in this task, yet their use is hindered by knowledge gaps regarding the key mechanisms driving forest responses and their representation within models. The general objective of this thesis is to advance the understanding and modelling of the effects of water and temperature on forest structure and functioning. To do so, plant hydraulics and biophysical principles are leveraged within a mechanistic perspective, so that the integration of processes across scales yields emergent forest behavior. Results from this thesis cast new light on the role of water availability and transport in governing the processes underpinning wood formation, tree growth and forest structure. Namely, water potential is suggested to modify cell turgor pressure and subsequently drive cell expansion, yielding variations in conduit dimensions in the xylem and cell division in the cambium. The effect of temperature on cell extensibility is further proposed to modulate cell expansion and division. According to this biophysical model, seasonal fluctuations in water potential and temperature directly influence the amount and structure of wood formed within a year, independently of carbon assimilation. Model validation is carried out at two study sites, including xeric and cold species distribution margins. At the inter-annual scale, results suggest that biophysical drivers interact with carbon assimilation to determine tree growth. Besides, a theoretical model is formulated where forest below- and aboveground structure is assumed to tend towards an equilibrium with precipitations and atmospheric water demand. The model is used to predict root distribution from hydraulic traits and simulated water fluxes and is validated using several study sites, including contrasting climatic conditions in Catalonia (NE Spain). Application to forest inventory data in Catalonia yields estimates of root distribution at the regional scale. Overall, this thesis highlights the range of forest responses to climate from the cellular to regional scale and the hydraulic and biophysical mechanisms underlying them. New modelling solutions integrating evidenced processes and bridging scales are proposed. Their implementation within vegetation models and a greater focus on water pools and fluxes could help reducing uncertainties regarding the fate of forests in the face of climate change.

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Anderson, Benjamin Mark. "Feedback mechanisms and constraints on climate sensitivity from a perturbed physics ensemble of general circulation models." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670120.

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Gawith, David. "Estimating the adaptation deficit : an empirical analysis of the constraints on climate change adaptation in agriculture." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274921.

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Agricultural adaptation to climate change is often simulated by changes in land use over time. Land use is commonly optimised in economic models, which rests on the neoclassical economic assumption of rational choice among farmers. A wealth of experimental and empirical evidence demonstrates that rational choice can be a poor approximation of human decision making. Models simulating adaptation by optimising producers’ behaviour are in effect simulating adaptive potential. Much evidence demonstrates that adaptive potential does not necessarily translate into adaptation. This investigation focuses on the ways by which farmers’ real-world adaptive behaviours depart from those assumed by the dominant economic models of agricultural responses to climate change. These departures are characterised as adaptation constraints, and they are assessed through an empirical case study of adaptive behaviours in the Hikurangi catchment, New Zealand. Data are collected using a mixed methodology comprising an extensive survey of rural decision making, to which this study contributes, and a suite of semi-structured interviews. The interviews give an understanding of the origins and processes of adaptation constraints, while the surveys provide information about the extent to which they impact adaptive propensity. These adaptation constraints are then formalised as mathematical rules and written into an existing agent-based model of land use change, which is substantially modified for the purposes of this study. Different combinations of constraints are then tested in order to produce estimates of their economic impacts. The constraints on adaptation are found to significantly reduce profits relative to a specification that assumes rational choice among farmers. This is understood to be the first empirically derived estimate of the extent of the adaptation deficit. The size of the deficit identified in this study implies that current economic models are likely to significantly underestimate the costs of adaptation to climate change, the benefits of climate change mitigation, and the residual loss and damage climate change will cause.

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Yang, Chengfan. "Li isotope study of Yangtze River sediments : new constraints on climate, weathering and carbon cycle relationships." Electronic Thesis or Diss., Sorbonne université, 2020. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2020SORUS433.pdf.

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Au cours de ce travail, j’ai réalisé une série d'études dans le bassin du Changjiang (Yangtze), afin de mieux comprendre l'influence de ces effets.Tout d'abord, l'exploitation du barrage des Trois Gorges (TGD) a modifié la composition géochimique des sédiments en aval. Depuis 2003, les sédiments venant des hauts bassins ont été en grande partie retenus en amont, tandis que les sédiments précédemment déposés dans le bassin moyen-inférieur ont été progressivement remis en suspension. Ces processus expliquent l’évolution géochimique des sédiments exportés vers la mer de Chine. En deuxième partie, une étude systématique démontre que les compositions isotopiques en lithium des phases dissoutes et particulaires se comportent de façon conservative dans la zone de mélange de l'estuaire du Changjiang. Cependant, les phases échangeables ne représentent qu'une faible quantité de Li, ce qui explique son impact négligeable dans cette zone. Troisièmement, Cette étude confirme que dans les grands bassins versants, l'altération chimique peut réagir rapidement à de grandes amplitudes climatiques. Ceci est particulièrement bien illustré, dans la carotte CM97, par la période du Younger Dryas. Depuis 2 000 ans, les δ7Li des argiles s’accentuent clairement par rapport à la période précédente, à cause de l'érosion des sols de plaines induite par l'homme. En résumé, ces résultats apportent de nouveaux éclairages sur l'interprétation des proxys et sur la réponse de l'altération chimique aux variations climatiques, ce qui est essentiel pour mieux quantifier l’impact du l’altération continentale sur les climats passés et futurs de notre planète
In order to better understand the weathering-climate feedback, a series of studies was carried out in the Changjiang (Yangtze) Basin. First, the operation of the Three Gorges Dam (TGD) changed downstream sediment geochemical compositions. Before 2003, large amounts of upstream-derived sediments deposited and experienced further weathering in the mid-lower basin. Since 2003, strong riverbed sediment resuspension changed the roles of the mid-lower reaches from important sinks to major sources of sediments delivered to the sea. As a consequence, an intensified weathering intensity of downstream sediment was observed.Second, dissolved δ7Li exhibit a conservative behavior in the Changjiang Estuary. During the process of SPM transported offshore, weathering product flocculated and deposited, while primary minerals resuspended. The combined effect resulted in the UCC-like SPM δ7Li values. There is a Li isotope fractionation between the dissolved load and exchangeable phase. However, this process shows negligible impact on δ7Li of dissolved load and particulates. Third, weathering response to climate is complex in large river basins. During the Younger Dryas, the positive excursion of clay δ7Li is consistent with enhanced incongruent weathering, in response to temperature cooling. The minor variation of clay δ7Li at 11 – 2 ka likely indicate stable weathering and mile climate variation. Over the last 2 kyr, the fluctuation of clay δ7Li is mostly caused by intensification of human activities. In summary, this thesis sheds new lights on the weathering-climate feedback over geologic past, and provides perspectives on how human activities affect natural processes

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Prendin, Angela Luisa. "Environmental effects and biophysical constraints on xylem physiology and tree growth in conifers in the Alps." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3423237.

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Trees are impressive long-living organisms that continuously increase in size by many orders of magnitude during ontogeny by accumulating xylem biomass in stem, branches and roots. While growing taller, trees continuously adjust the xylem structure to achieve an optimal balance of carbon costs for the competing biomechanical and hydraulic requirements. One of the main function of the xylem structure is the delivery of the water from the roots up to the leaves. This must be maintained during the ontogeny, when the hydrodynamic resistance increase due to the increase in the xylem path length. However, by widening the diameter of xylem conduit (from the stem apex downwards), trees are able to minimize the negative effect of height growth. Additionally, this widening is stable during ontogeny, thus determining the radial change in conduit dimension with cambial age (from the pith outwards), implying a dependency between the variation of conduit-lumen diameter with cambial age and the rates of stem elongation. These adjustments in the xylem structure remain permanently fixed and chronologically archived in the secondary xylem, and, given the tight link between structures and functions, these provide a ‘time component’ to functional responses induced by xylem plasticity, thus allowing to reconstruct growth dynamics under different environmental conditions. However, there is a lack of detailed information and standardized procedures to explore, at the intra-specific level, the long-term modifications of xylem traits over the full life-span of trees, together with their variability along axial and radial profiles. Additionally, little is known about the relationships between the structures and functions in a view of exploring the future challenges in how a plant’s hydraulic architecture may respond to the ongoing climate change. This thesis, represent a set of studies based on dendro-anatomical and physiological approaches aimed to: - identify priorities and trade-offs among xylem functions; - determine the anatomical traits responsible for them; - retrospectively analyze how these relationships vary during ontogeny under different environmental condition; - analyze the functional response to xylem modifications occurring during ontogeny; - investigate the possibility of retrospectively analyzed height growth based on hydraulic radial profiles. Furthermore, a guidance from sample collection to xylem anatomical data and a new approach to customize cell wall thickness measurements according to the specific aims of the study, were developed. This thesis has highlighted that the xylem anatomical structure of conifer trees (Larix decidua, Picea abies, Pinus cembra) showed a high priority and biophysical determination of traits linked to hydraulic efficiency, such as conduit size, to efficiently support assimilation necessary for tree growth. Besides, other functional traits linked to mechanical support and metabolic xylem functions showed more plastic responses to intrinsic and extrinsic factors. Due to the ontogenetic stability of axial patterns of conduit size, it was possible, based on radial profiles of xylem conduit diameter of tree rings, to estimate tree growth rate, even if species-site specific, and make comparison between trees living in different epochs. In addition, despite the risk of becoming more vulnerable to air seeding cavitation, trees showed to prioritize of hydraulic efficiency vs. safety during the ontogenetic development, as the increase in xylem conductance with tree height determined a contextual decrease in the hydraulic safety margin. This study showed the importance of taking into account the three dimensional anatomical trends to better understand of the trade-offs of hydraulic safety vs. efficiency shape up the tree architecture and affect its adjustments occurring during ontogeny to cope with the arising intrinsic (i.e., size-related) and extrinsic (i.e., environmental) constraints to growth.
Gli alberi sono organismi viventi che aumentano continuamente di dimensione (anche diversi ordini di grandezza) durante l'ontogenesi, accumulando biomassa nel fusto, nei rami e nelle radici. Durante la crescita, la struttura xilematica degli alberi continua ad adattarsi mantenendo un equilibrio nell’ottimizzazione del carbonio, garantendo contemporaneamente un’adeguata stabilità meccanica ed efficienza idrica della pianta. Il trasporto dell'acqua dalle radici fino alle foglie è una funzione fondamentale dello xilema e deve essere mantenuto efficiente durante tutte le fasi ontogenetiche. La resistenza idraulica del sistema infatti è fortemente influenzata dall’incremento della lunghezza del percorso idrico. Tuttavia, allargando la dimensione degli elementi di conduzione dello xilema (dall'apice alla la base del fusto), le piante sono in grado di minimizzare l'effetto negativo della crescita in altezza. Inoltre, data la stabilità di questo trend assiale durante l’ontogenesi, le dimensioni dei condotti xilematici aumentano anche in direzione radiale con l'età cambiale (dal midollo verso l'esterno), determinando una forte relazione tra la variazione del diametro dell’elemento conduttivo con l'età cambiale ed il tasso di allungamento del fusto. Le modifiche nella struttura xilematica, rimanendo impresse e cronologicamente archiviate nel legno, rappresentano un’importante fonte di informazioni che permette di aggiungere una componente temporale legata a meccanismi funzionali e di plasticità xilematica e, quindi, permetterebbe di ricostruire le dinamiche di crescita in diverse condizioni ambientali. Esiste tuttavia, una carenza di conoscenza e di procedure standard atte ad esplorare, a livello intra-specifico, le modificazioni a lungo termine dello xilema e la variabilità della sua struttura lungo profili assiali e radiali. Rimangono inoltre poco chiari i rapporti tra la struttura e la funzionalità, utili a prevedere in futuro eventuali adattamenti del sistema idraulico e metabolico al cambiamento climatico. Questa tesi riporta una serie di studi che si basano su un approccio dendro-anatomico e fisiologico, allo scopo di: - individuare priorità e compromessi tra le varie funzioni xilematiche; - determinarne i tratti anatomici responsabili; - analizzare in maniera retroattiva la loro variazione durante l'ontogenesi e in diverse condizioni ambientali; - analizzare risposte funzionali alle modifiche anatomiche che occorrono durante l’ontogenesi; - esaminare la possibilità di ricostruire i trend di accrescimento in altezza basandosi su profili idraulici radiali. E’ stata definita una guida alla standardizzazione della procedura, dalla raccolta del campione al dato anatomico dei tratti xilematici. Inoltre è stato sviluppato un nuovo approccio di quantificazione dello spessore della parete cellulare al fine di soddisfare gli obiettivi specifici dello studio. La struttura xilematica delle conifere (Larix decidua, Picea abies, Pinus cembra) evidenzia priorità e determinazione biofisica di tratti legati all’efficienza idraulica, come le dimensioni delle tracheidi, al fine di sostenere l'assimilazione necessaria per la crescita degli alberi. Altri caratteri funzionali invece, legati al supporto meccanico ed all’attività metabolica, mostrano più plasticità a fattori intrinseci ed estrinseci. Grazie alla stabilità del trend assiale dei condotti idraulici durante l’ontogenesi è stato possibile, basandosi sul conseguente pattern radiale, stimare il tasso di accrescimento delle piante, anche se specie-sito specifico, e confrontare quindi i trend con le piante che sono vissute in epoche diverse. Nonostante il rischio di aumentare la vulnerabilità alla cavitazione, gli alberi tendono a priorizzare l’efficienza a discapito della sicurezza idraulica durante lo sviluppo ontogenetico, a causa dell’aumento della conduttanza e conseguente riduzione del margine di sicurezza idraulica. Questo studio dimostra l'importanza di considerare la tridimensionalità dei trend anatomici al fine di comprendere meglio i rapporti tra la sicurezza idraulica e l’efficienza che modella l’architettura della pianta, influenzandone le modifiche ontogenetiche e compensandone i vincoli di crescita intrinsechi (dimensione-dipendenti) ed estrinseci (ambiente-dipendenti).

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Stumpp, Inga. "Combining mobility demand and climate protection in urban transport systems. Obstacles and constraints in the case of Berlin." Thesis, Malmö universitet, Fakulteten för kultur och samhälle (KS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-21626.

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Transportation is an essential part of city life. However the extensive use of private cars in urban transport systems leads not only to a decrease in public health and quality of life but also drives global warming through the emission of GHG. The growth rate of CO 2 emissions caused by transportation is among the highest across all energy sectors. In order to mitigate climate change, it is therefore crucial to reverse this trend and change urban transport systems towards more climate compatibility. Thus, this thesis investigates if and how mobility demand and climate protection can be combined in urban transport systems.To answer these questions, the thesis discusses characteristics of climate-friendly transportation based on findings from academic literature. Moreover, policy instruments to transform urban transportation towards climate compatibility as well as possible obstacles and constraints in this regard are investigated. More precisely, socio-technical/infrastructural, technological, financial, legal, institutional/organisational, political, habitual, and cultural constraints are described and the significance of pragmatic, moral, and cognitive legitimacy is ascertained with regard to public and political acceptance of policies.Drawing on these theoretical assumptions, the case of Berlin is analysed in more detail. Based on policy documents, statistical data, expert interviews, and a public hearing in the Senate of Berlin, it is investigated how the city plans to make its transport system more climate-friendly and what the actual state of climate compatibility within the transport sector is at the moment. As a result, it could be observed that policies for climate-friendly transport are in place and mostly implemented but that the amount of CO 2 emissions caused by the transport system and especially by road traffic has more or less stagnated since the 1990s. Several reasons for this development could be ascertained: The transformation towards climate compatibility is, on the one hand, constrained bylegal, infrastructural, institutional, political, habitual, and cultural factors as well as by the lack of personnel within the city administration, and, on the other hand, hampered by the perceived inacceptability of car-restrictive policies.The conclusion from this thesis is therefore that it is thereotically possible to combine mobility demand and climate protection in urban transport systems and it is furthermore imperative in order to mitigate climate change and its dreaded impacts. In practical terms, however, cities face several intertwined and often very distinct obstacles and constraints that can only be overcome by long-term, dedicated, and citizen-oriented policy planning and implementation.

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Hamdi-Cherif, Meriem. "Aligning development and energy policies under climate constraints in China : lessons from a second-best general equilibrium framework." Paris, EHESS, 2016. http://www.theses.fr/2016EHES0105.

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Comprendre les impacts des politiques climatiques en Chine ainsi que leurs dynamiques sous-jacentes est crucial dans le cadre de la gouvernance climatique internationale. Cette thèse contribue à ce débat en tentant d'analyser les coûts et opportunités d'une transition vers une économie bas-carbone en Chine, dans un contexte où l'on prend en compte les frictions et les limites à la flexibilité des ajustements économiques, dimensions souvent négligées dans les études existantes. Elle fournit des évaluations des coûts macro-économiques de la mise en place de politiques de réduction des émissions de gaz à effet de serre en Chine. Ces évaluations sont faites à partir d'un modèle d'équilibre général calculable prenant en compte des mécanismes de « second-rang » et fournissant des analyses des interactions économie-énergie-environnement. Cette architecture de modélisation permet d'exhiber certains importants mécanismes enjeu lorsque des politiques d'atténuation contraignantes sont mises en place et de révéler des leviers qui pourraient être activés afin d'amoindrir les coûts de l'atténuation. Les analyses effectuées permettent de démontrer qu'au-delà du prix du carbone, les coûts des politiques climatiques dépendent fondamentalement du séquençage de politiques complémentaires, avec un rôle crucial des mesures « bottom-up » susceptibles de compléter le prix du carbone. La thèse défend l'idée qu'un futur durable nécessite la mise en place de mesures locales aptes à (i) fournir les bons signaux, autres que les prix courants du marché, pour les investissements de long-terme ainsi qu'à (ii) intégrer des mesures sectorielles qui agissent de façon complémentaire aux signaux prix
Understanding the impacts of climate policies in China and their dynamics is essential for the international climate policy. This thesis contributes to this debate by analyzing the costs and opportunities for China to transition to a low-carbon economy in an adverse overall economic context. It provides macroeconomic evaluation of the costs of mitigation in China using a Computable General Equilibrium model in a second-best framework. The tool used captures important element that are not systematically covered by exiting analyses, like inertia constraints, imperfect expectations and non optimal exploitations of production factors (labor, capital). Beyond the comprehensive assessment of climate mitigation costs, the thesis allows (i) exhibiting the mechanisms underlying these costs in the short-term and in the long-term, and thus (ii) revealing levers that might be used to reduce them. Furthermore, the conducted analyses demonstrate that beyond the carbon price, the costs of climate policy essentially depend on the sequencing of complementary policies, with a crucial role of bottom-up measures likely to complement the carbon price. It proclaims that an innovative development pathway with a sustainable future will require implementing local measures able to (i) provide appropriate incentives for long-term investments by resorting to other signals than current market prices and (ii) incorporate sectoral measures that act complementarity

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Lee, Kyuha. "Sustainable Process and Supply Chain Design with Consideration of Economic Constraints, Climate Change, and Food-Energy-Water Nexus." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1598205952374569.

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Cherian, Ribu, Johannes Quaas, Marc Salzmann, and Martin Wild. "Pollution trends over Europe constrain global aerosol forcing as simulated by climate models." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-176389.

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An increasing trend in surface solar radiation (solar brightening) has been observed over Europe since the 1990s, linked to economic developments and air pollution regulations and their direct as well as cloud-mediated effects on radiation. Here, we find that the all-sky solar brightening trend (1990–2005) over Europe from seven out of eight models (historical simulations in the Fifth Coupled Model Intercomparison Project) scales well with the regional and global mean effective forcing by anthropogenic aerosols (idealized “present-day” minus “preindustrial” runs). The reason for this relationship is that models that simulate stronger forcing efficiencies and stronger radiative effects by aerosol-cloud interactions show both a stronger aerosol forcing and a stronger solar brightening. The all-sky solar brightening is the observable from measurements (4.06 ± 0.60Wm−2 decade−1), which then allows to infer a global mean total aerosol effective forcing at about −1.30Wm−2 with standard deviation ±0.40Wm−2.

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Cherian, Ribu, Johannes Quaas, Marc Salzmann, and Martin Wild. "Pollution trends over Europe constrain global aerosol forcing as simulated by climate models." Wiley, 2014. https://ul.qucosa.de/id/qucosa%3A13436.

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An increasing trend in surface solar radiation (solar brightening) has been observed over Europe since the 1990s, linked to economic developments and air pollution regulations and their direct as well as cloud-mediated effects on radiation. Here, we find that the all-sky solar brightening trend (1990–2005) over Europe from seven out of eight models (historical simulations in the Fifth Coupled Model Intercomparison Project) scales well with the regional and global mean effective forcing by anthropogenic aerosols (idealized “present-day” minus “preindustrial” runs). The reason for this relationship is that models that simulate stronger forcing efficiencies and stronger radiative effects by aerosol-cloud interactions show both a stronger aerosol forcing and a stronger solar brightening. The all-sky solar brightening is the observable from measurements (4.06 ± 0.60Wm−2 decade−1), which then allows to infer a global mean total aerosol effective forcing at about −1.30Wm−2 with standard deviation ±0.40Wm−2.

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Tunon, Meagan. "Time Constraint and Genetic (Phenotypic) Variation in Wing Shape in a Damselfly Along a Latitudinal Gradient." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-410764.

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This degree project examined the effect of time constraint on wing shape and phenotypic variation in wing shape along a latitudinal gradient in the damselfly species Lestes sponsa. Fore and hind wings from individuals originating from three different latitudes: North (66°N), Central (59°N) and South (54°N) Europe were treated with their native temperature and photoperiod. In addition, the north and south populations were treated with south and north conditions respectively, resulting in five groups in total. Morphometric analyses of the wings revealed a positive correlation between body mass and wing centroid size, along with a difference in wing shape between the groups. Forewings and hindwings from the northern group were broader and rounder than wings from the central and southern groups. Additionally, the wings from the transplant groups resembled those of the native group of their treatment, indicating a phenotypic plasticity in wing shape. Lastly, statistical tests of phenotypic variation revealed that variation was highest in relative warp 2 in the forewings and hindwings, and this warp represents the curvature of the wing both upwards/downwards or towards the inside/outside of the wing. These results on phenotypic variation indicate that even in a new or changing environment, L. sponsa could be capable of adapting to varying temperatures and environmental conditions. This study builds our understanding of how this damselfly species, and potentially insects, will be affected by current and future potential climate change.

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Mbzibain, Aurelian. "An empirical investigation into the uptake, motivations and constraints and the factors affecting farmers' renewable energy investment intentions." Thesis, University of Wolverhampton, 2012. http://hdl.handle.net/2436/298090.

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The rate of adoption of renewable energy (RE) production and associated enterprises onfarms in the UK has been lower than expected suggesting that the UK government’s energy, agricultural and climate change objectives may not be achieved. The aim of this research is to investigate why this is the case by assessing the uptake, motivations, constraints and the factors affecting farmers’ RE investment intentions. Building on extant research literature (institutional theory, social cognition theory, theory of planned behaviour and the resource based view) a novel comprehensive and multidimensional model of entrepreneurial intentions was developed and tested using principal component, path and multivariate regression analysis techniques. Data were collected to test the model through a sample of 2000 farmers in the West Midlands Region of the UK. Of the 393 farmers who responded, 14% adopted RE enterprises, with half of adopters reporting slight to significant improvements in farm business performance in 2009. Solar panels were the most popular of the RE technologies available to farmers, compared to biomass related technologies. The study found that the most influential personal level factors contributing to the adoption of RE and associated technologies were cognitive such as the level of education. Of current 338 non-adopters, 66% might decide to invest in RE technologies over the next five years. For these potential adopters, the study shows that the type of tenure, educational attainment and the type of farm business diversification activity in which a farmer is engaged are the most significant personal and farm business situational factors which influence farmers’ RE investment intentions though contrary to expectation current non-adopters assessed the policy support framework more favourably than current adopters. The explanation of this seems to be connected with timing, in that two very positive and encouraging signals in relation to ii Feed in Tariffs (2010) and the Renewable Heat Incentive (2011) were underway or near introduction before this research took place. The study provides the first empirical evidence of the effects of the multidimensional measures of the country’s institutional profile on farmers’ RE investment intentions. Secondly, it clarifies the distinct role played by national formal and informal institutions on farmers’ investment intentions showing that informal institutions and not formal regulatory factors have a direct effect on farmers’ intentions to invest in RE enterprises. Thirdly, the investigation reveals that social acceptability of entrepreneurship in the RE sector is negatively related to investment intentions and moderates the efficacy of formal government policies in influencing entrepreneurial behaviour in the RE sector. The study concludes that any study that relies only on one type of institution will be making significant prediction mistakes. This study provides further support for cognitive based process models of intentions by showing strong significant positive effects of perceived self-efficacy and perceived desirability of RE enterprises on investment intentions. In fact, the study shows that farmers’ attitudes towards RE explain the highest amount of variance in investment intentions over and above the combined effect of external resource and institutional factors. The study illustrates that perceived self-efficacy and perceived desirability of RE enterprises mediate the effect of the rich set of exogenous variables investigated in this study on investment intentions and argues that policy makers need to focus on improving the regulatory, cognitive and normative institutional environments as a way to improve attitudes towards RE and consequently their intentions to invest in these enterprises.

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Klein, David [Verfasser], Ottmar [Akademischer Betreuer] Edenhofer, and Keywan [Akademischer Betreuer] Riahi. "Bioenergy markets in a climate-constrained world / David Klein. Gutachter: Keywan Riahi ; Ottmar Edenhofer. Betreuer: Ottmar Edenhofer." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1067915443/34.

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Costa, Luis Filipe Carvalho [Verfasser]. "Assessing adaptation to climate change and its costs in a carbon-constrained world / Luis Filipe Carvalho Costa." Greifswald : Universitätsbibliothek Greifswald, 2013. http://d-nb.info/1043943773/34.

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Reusch, Christine [Verfasser], Gerald [Akademischer Betreuer] Kerth, Gerald [Gutachter] Kerth, and Oliver [Gutachter] Krüger. "Potential costs, benefits and constraints of responses to recent climate change in bats / Christine Reusch ; Gutachter: Gerald Kerth, Oliver Krüger ; Betreuer: Gerald Kerth." Greifswald : Ernst-Moritz-Arndt-Universität, 2019. http://d-nb.info/1177241536/34.

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Reusch, Christine Verfasser], Gerald [Akademischer Betreuer] [Kerth, Gerald [Gutachter] Kerth, and Oliver [Gutachter] Krüger. "Potential costs, benefits and constraints of responses to recent climate change in bats / Christine Reusch ; Gutachter: Gerald Kerth, Oliver Krüger ; Betreuer: Gerald Kerth." Greifswald : Ernst-Moritz-Arndt-Universität, 2019. http://d-nb.info/1177241536/34.

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Pittendrigh, Alistair. "The potential impact of greenhouse gas emissions constraints on the Southern African primary aluminium business." Thesis, Stellenbosch : Stellenbosch University, 2006. http://hdl.handle.net/10019.1/50666.

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Thesis (MBA)--Stellenbosch University, 2006.
ENGLISH ABSTRACT: The Kyoto protocol was signed early in 2005 whereby Annexure 1 industrialised countries committed to reducing their greenhouse gas (GHG) emissions. South Africa signed the Protocol. however being a developing country it has no GHG emissions reduction target for the first commitment period until 2012. Primary aluminium is a GHG intensive global commodity to which Southem Africa contributes significantly. This dissertation aims to investigate how the profitability of the Southern African primary aluminium sector may be affected by Kyoto Protocol GHG restrictions even though the smelters are situated in non-Annexure 1 countries. A Delphi-type survey is conducted to gather opinions on identified pressures and drivers that could affect the industry. The survey respondents indicate that the greatest impact will occur from internal pressures from holding companies. Further pressure will originate from external sources namely government, Non Governmental Organisations, shareholders and investors. Direct manufacturing costs are not expected to increase as a result of the Protocol. Rather. industry changes are expected to be the result of internal and external pressures. Opportunities for Clean Development Mechanism (COM) projects are rated as highly importance and are strongly recommended. Various strategies are identified and presented in a matrix to compare the effect of each on the various identified pressures and drivers. From the matrix it is observed that the majority of the selected strategies have a profound impact on the internal and external pressures. From this research report it is recommended that a cooperative proactive strategy be followed . focusing initially on low cost GHG emissions reduction projects and rigorously pursuing COM projects.
AFRIKAANSE OPSOMMING: Die Kyoto Protokol, waardeur Anneks 1 geindustraliseerde lande hul daartoe verbind het om hul kweekhuis gas (GHG) emissies te verminder, is vroeg in 2005 onderteken. Suidelike Afrika het die Protokol onderteken, maar weens sy status as ontwikkelende land, het dit geen GHG emissieverminderingsdoelwit vir die eerste verpligtingsfase tot en met 2012 nie. Primere aluminium is 'n GHG intensiewe globale kommoditeit waartoe Suidelike Afrika 'n groot bydrae lewer. Hierdie tesis poog om ondersoek in te stel na die impak van Protokol GHG beperkings op die winsgewendheid van die Suidelike Afrika primere aluminium sektor, ten spyle daarvan dat die smelters in nie-Annex 1 lande gelee is. 'n Delphi-tipe opname was geloods om opinies in te win oor geidentifiseerde drukpunte en drywers wat 'n impak kon he op die industrie. Die respondente het aangedui dat die grootste impak sal kom van interne druk van beheermaatskappye. Addisionele druk sal afkomstig wees van eksteme bronne soos die regering, Nie-regerings organisasies (NGO's), aandeelhouers en beleggers. Daar word nie verwag dat die direkte vervaardigingskoste sal eskaleer as gevolg van die Protokol nie. Daar word eerder verwag dat veranderinge in die industrie die gevolg sal wees van interne en eksterne druk. Geleenthede vir skoon-ontwikkelings meganisme (COM) projekte is geweldig belangrik en word sterk aanbeveel. Verskeie strategiee word geidentifiseer en voorgele in 'n matriks om sodoende 'n vergelyking te tref tussen die effek wat elk het op die onderskeie drukpunte en drywers. Uit die matriks kan afgelei word dat die meerderheid strategiee 'n diepgaande invloed het op die inteme en eksterne drukpunte. Hierdie navorsingsverslag beveel aan dat 'n samewerkende proaktiewe strategie gevolg word, wat aanvanklik sal fokus op lae-koste GHG emissieverminderingsprojekte, asook die nougesette najaag van CDM projekte.

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Wenzel, Sabrina [Verfasser], and Veronika [Akademischer Betreuer] Eyring. "Observationally-based constraints of future climate projections of carbon cycle feedbacks and the shift in the Austral Jet Stream / Sabrina Wenzel. Betreuer: Veronika Eyring." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1093125152/34.

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Pougy, Roberto. "Unconventional oil and natural gas supplies and the mitigation of climate change." Thesis, Paris, EHESS, 2017. http://www.theses.fr/2017EHES0075.

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Cette thèse en économie de l'énergie et de l'environnement étend le modèle de Hotelling du type exploration-extraction avec contraintes géologiques d’Okullo, Reynes et Hofkes (2015), afin de prendre en compte des trajectoires en forme de cloche pour l’ajout de réserves empiriquement observées par Laherrère (2003). Le modèle LOGIMA proposé (Images à Long terme sur le Pétrole et le Gaz) explique qu’elles sont la conséquence de « sweet spots » géologiques : des zones privilégiées où la concentration d’hydrocarbures est la plus élevée. Le modèle LOGIMA a été calibré sur une base de données issues couvrant les sept principaux bassins de pétrole et de gaz non-conventionnels du pays. Les résultats indiquent que la nécessité d’apprentissage par la pratique pour découvrir l’emplacement des sweet spots conduit à une mise en œuvre d’un effort d’exploration également en forme de cloche, ce qui permet de réduire le risque des activités d’exploration. Par conséquent, la réponse en termes des volumes offerts par les producteurs à des chocs sur les prix dévient fonction de l’ensemble des ressources mondiales antérieurement découvertes. Ensuite, nous appliquons le modèle LOGIMA pour étudier l’impact causé par l’offre de pétrole et de gaz naturel « non-conventionnels » aux États-Unis, sur les efforts mondiaux d’atténuation du changement climatique. Nous y parvenons en associant les scénarios à long-terme générés par LOGIMA avec le modèle d’évaluation intégrée, IMACLIM-R. Cette étude analyse comment des différentes cibles de prix de pétrole affecteraient son offre aux États-Unis. Nous estimons cette interaction au moyen de trois cadres de politiques en matière de climat : le cadre « business as usual » (BAU), les contributions décidées à l’échelle nationale (NDC) et les scénarios de 2°C (2DS). Les résultats de l’exercice indiquent que les approvisionnements non-conventionnels sont fortement susceptibles d’affecter les marchés énergétiques mondiaux, mais leur impact sur les émissions mondiales de gaz à effet de serre serait limité, car les différents effets déclenchés dans des différents secteurs viendraient les équilibrer approximativement
This thesis in energy and environmental economics extends the geological Hotelling-type extraction-exploration model from Okullo, Reynes and Hofkes (2015) in order to account for the bell-shaped reserve additions that were empirically observed by Laherrère (2003). The proposed model explains them as the result of geological “sweet spots”: premium areas within geological formations where the concentration of hydrocarbons is highest. The proposed theoretical formulation was programmed into the mathematical model LOGIMA – “Long-term Oil and Gas Images” – and calibrated on data covering the seven main unconventional oil and gas plays in the United States. Results indicate the need to learn the location of sweet spots through trial and error drillings leads to schedules of exploratory effort that allow the optimal “de-risking” of exploratory activities. As a result, the optimal response of producers to price shocks becomes contingent on the prevailing level of cumulative discoveries.We apply LOGIMA to investigate the impact, caused by the recent advent of large-scale supplies of unconventional oil and gas, in the United States, on the ongoing efforts to mitigate climate change. We do so by soft coupling long-term scenarios from LOGIMA with the integrated assessment model, IMACLIM-R, a recursive, computable general equilibrium model of integrated global energy, economy and environment systems. We analyze how different price targets, potentially pursued by the Organization of Petroleum Exporting Countries (OPEC), would affect supplies of unconventional oil and gas from the United States. We control this interplay under three climate policy frameworks: business as usual (BAU), nationally determined contributions (NDCs) and 2°C scenario (2DS). The results of the exercise show that, despite having a significant potential to affect global energy markets, unconventional oil and gas supplies would have a limited potential to affect global cumulative greenhouse gas emissions to 2040, as the different effects triggered in different sectors approximately balanced each other out

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Ishak, Muhammad Izzuddin Syakir. "A Reconnaissance Study of Water and Carbon Fluxes in Tropical Watersheds of Peninsular Malaysia: Stable Isotope Constraints." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30564.

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Evapotranspiration is a nexus for planetary energy and carbon cycles, as yet poorly constrained. Here I use stable isotopes of oxygen and hydrogen to partition flux of water due to plant transpiration from the direct evaporative flux from soils, water bodies and plant. The study areas, Langat and Kelantan watersheds represent examples of domains dominated by the respective Southwest and Northeast monsoons on the two sides of the main orographic barrier (Titiwangsa mountain range). Mean annual rainfall for the Langat watershed, obtained from 30 years of hydrological data, is 2145 ± 237 mm. Tentatively, 48% of this precipitation returns to the atmosphere via transpiration (T), with 33% partitioned into discharge (Q), 8% into interception (In), and 11% into evaporation (Ed). In the Kelantan watershed, the mean annual rainfall, also based on the 30 year hydrological data, is 2383 ± 120 mm. Similar to Langat, the T accounts for 43% of precipitation (P), 45% is discharged into South China Sea (Q), 12% partitioned into interception (In) and tentatively 0% for evaporation (Ed). Ed for the Langat watershed represents only a small proportion in terms of volumetric significance, up to almost ~11% with strong effect on the isotopic fingerprints of waters associated with the summer Southwest Monsoon (SWM). Note, however, that insignificant Ed for the Kelantan watershed may be an artefact of rain and river water sampling at only coastal downstream portion of the watershed. High humidity (80%) also was recorded for the Malaysian Peninsula watershed. T appropriates about half of all solar energy absorbed by the continents, here ~1000*103 g H2O m-2 yr-1 similar to other tropical regions at 900-1200*103 g H2O m-2 yr-1. The associated carbon fluxes are ~ 1300 g C m-2yr-1, independent of P. Vegetation responses to solar irradiance, via T and photosynthesis reflects the importance of stomatal regulation of the water and carbon fluxes. In order to maintain high transpiration in the tropical region, “constant” water supply is required for continuous pumping of water that delivers nutrients to the plant, suggesting that water and carbon cycle are co-driven by the energy of the sun. The existence of the water conveyor belt may be precondition for nutrient delivery, hence operation of the carbon cycle. Potentially, this may change our perspective on the role that biology plays in the water cycle. In such perspective, the global water cycle is the medium that redistributes the incoming solar energy across the planet, and the anatomical structures of plants then help to optimize the loop of energy transfer via evaporation and precipitation in the hydrologic cycle. The main features of aquatic geochemistry of the Langat and Kelantan rivers inferred from the Principal Component Analysis are controlled by three components that explain 80% and 82% of total variances. These components are reflecting of the geogenic factor with superimposed pollution, the latter particularly pronounced in urbanized sections of the Langat river and dominant in downstream of the Kelantan river. There is no correlation between seasonal variations in major ion chemistry and environmental variables such as precipitation, discharge, temperature or solar activity.

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Kongoletos, Johnathan J. (Johnathan James). "Implementation and evaluation of thermal avoidance strategies in arid, cost-constrained climates aimed at improving indoor thermal comfort : a case study in Bhuj, India." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118488.

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Thesis: S.M. in Building Technology, Massachusetts Institute of Technology, Department of Architecture, 2018.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 150-155).
The use of air conditioning in the buildings sector has been rapidly increasing. The International Energy Agency projects that rising income and greater access to air conditioning equipment in many developing countries will increase CO₂-equivalent emissions, energy consumption, and urban heat island effects. India is a prime example of a region where new building trends, hot climatic conditions, increasing social aspirations, and rapid population growth is likely to spread the adoption of air conditioning. To reduce the need for air conditioning, the research team has worked to develop, implement, and evaluate methods to reduce temperatures within the built environment using largely passive means. Building on the past work of Nelson and Gradillas, the thesis presents the results of long-term temperature monitoring within four homes in Bhuj, India. Results from the collective work have helped to inform future designs for the region, and resulted in an innovative roof concept. Using scale models, thermal simulations, and full-scale housing, results from the thesis explore new methods of implementing solutions for reduced solar heat gain, reduced heat absorption, and increased heat rejection. The research concludes by presenting early work on additional techniques and implications of using indigenous products to better thermal comfort conditions. Applicable outside of India, the techniques can be utilized in other regions and climates, as well as concurrently with active cooling systems to reduce energy consumption or extend existing capacity. Further work will seek to improve the design and adaptability of the system to different regions.
by Johnathan J. Kongoletos.
S.M. in Building Technology

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Agra, de Lemos Martins Tathiane. "Des contraintes solaires à des opportunités de projet urbain : optimisation de typomorphologies urbaines en climat tropical au Brésil." Thesis, Toulouse, INSA, 2014. http://www.theses.fr/2014ISAT0011/document.

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Environ trois quarts des ressources globales sont aujourd'hui consommés dans les aires urbaines. Le processus d'urbanisation induit des changements sévères du climat local, de la qualité environnementale des espaces, ainsi qu'une augmentation significative de la demande énergétique des bâtiments. Les projections statistiques sur la croissance de la population urbaine indiquent que cette situation tendra à s'aggraver dans les années à venir. Il devient donc impératif de chercher d'autres stratégies pour mieux adapter les environnements urbains aux nouvelles demandes énergétiques, afin de réduire l'empreinte environnementale des villes. Dans ce contexte, ce travail est une contribution à la recherche énergétique urbaine, plus particulièrement en ce qui concerne l'énergie consommée et potentiellement produite parles bâtiments à l'échelle urbaine locale. La morphologie urbaine est ici considérée comme un paramètre crucial dans le processus d'amélioration de l'efficacité énergétique du cadre bâti. Dans les zones de basses latitudes, sous climat tropical, l'énergie solaire incidente est extrêmement abondante. Toutefois, la bonne utilisation de cette ressource dans les bâtiments peut suggérer l'adoption de formes urbaines très peu denses et étales, en vue de réduire les obstructions produites par l'environnement proche. A rebours, ces formes urbaines très peu denses peuvent entrainer une augmentation des apports solaires sur les façades,élevant la demande énergétique. Le contrôle des gains solaires sur les façades pour la réduction de la demande énergétique peut ainsi représenter une perte potentielle en terme d'éclairement naturel des espaces, et une réduction du potentiel de production d'énergie solaire. Afin de quantifier le potentiel de ces stratégies conflictuelles, il devient indispensable de convoquer des modèles d'analyse pluridisciplinaires, permettant de mettre en oeuvre des approches multicritères dans le processus de conception de la forme urbaine. Cette thèse s'appuie sur une réflexion prospective sur les quartiers de la ville de Maceió, Alagoas, au Brésil. Dans un premier temps, un ensemble de paramètres morphologiques caractéristiques sont employés pour identifier et caractériser le potentiel solaire de typologies de référence de la ville. Ensuite, ces paramètres sont soumis à une analyse de sensibilité via un plan d'expérience. Les paramètres statistiquement significatifs sont alors intégrés à une méthode paramétrique d'optimisation dans laquelle l'algorithme génétique NSGA-II est couplé à un algorithme simplifiée de radiosité, visant à maximiser le potentiel de production d'énergie sur les toitures des bâtiments, tout en minimisant les apports solaires sur ses façades. Nous considérons des seuils d'éclairement naturel et intégrons des règles locales d'urbanisme comme contraintes aux projets. Cinq typologies représentatives du tissu urbain de Maceió ont ainsi été identifiées. L'ensemble des indicateurs les plus influents sur le potentiel solaire des formes urbaines a été hiérarchisé, en mettant l'accent notamment sur le rôle du prospect moyen ou de l'albédo des surfaces. La méthode d'optimisation a permis de tester plus de 80 000configurations d'ilots urbains et les résultats obtenus font apparaître une grande diversité de morphologies «optimum». Ces projets ont des performances solaires supérieures à celles des typologies existantes dans la ville. Cette intégration de stratégies énergétiques contradictoires montre qu'au-delà de l'intégration de contraintes variées et d'une meilleure adaptation à la complexité du processus de design urbain, l'approche utilisée ici apparaît très utile pour la recherche de solutions urbaines performantes à l'échelle des quartiers. Cette approche peut ainsi participer au renouvellement de l'Architecture de la Ville
At the beginning of 21th century, the world was faced with unprecedented environmental transformations. The urbanization process reached record levels and it keeps increasing, especiallyin developing countries. Around 3/4 of global resources are currently consumed in urban settlements, with corresponding adverse environmental consequences which leads to severe local climate changes, affecting environmental quality of spaces and leading to a significant increase of energy demand in buildings. A projection of the world urban population indicates that this situation will worsen in the coming years. It is therefore imperative that we understand how to design less resource intensive urban settlements. This research consists of a contribution to the energy debate in cities, focusing on the energy potentially consumed and produced by the built environment in the neighborhood scale. Urban morphology has been pointed out as a pivotal issue on shifting to climate adapted urban environments towards energy efficiency of buildings. In tropical climate regions, solar energy represents a high potential for renewable electric production in buildings, recording high levels of irradiation throughout the year. Though, engaging such a strategy may suggest applying sparsely low-density urban forms, aiming at reducing obstructions caused by the urban built surroundings. On one hand, scattered and less dense urban forms may result in significant increase of solar thermal load in buildings vertical facades, but on the other hand, the control of the solar heat gains in urban facades may represent significant losses on indoors daylight levels andalso reducing solar energy harness. Estimating the relative potential of these conflicting design strategies, taking into account the constrained parameters related to local building regulation, requires coupling multidisciplinary and multiobjective models of analysis in order to integrate multi-criteria approach in the urban design process. This thesis aims to contribute to a prospective energy debate toward sustainable urban districts for the city of Maceió in Brazil. Firstly, a set of energy-related morphological parameters are applied to identify, classify and characterize the solarpotential of local urban typologies. Then, these parameters are analyzed by means of a sensitivity analysis using a design of experiments reduced factorial method. The statistically most significant parameters are then submitted to a parametric design methodology via optimization, in which thenon-dominated sorting genetic algorithm (NSGA-II) is coupled with a simplified radiosity algorithm.The solar constraints are integrated as design criteria aiming at maximizing the solar energy potential on building roofs and minimizing solar gains on the their vertical facades. Daylight threshold levels as well as local building regulation parameters are taken into account as design constraints. Five representative types of urban fabric of Maceió were identified which allowed examining and adapting them from the use of energy-related indicators of the urban form. A set of most influential indicators of solar potential of urban forms was hierarchized, highlighting the role of the aspect ratio and albedo of urban surfaces. The application of optimization algorithm allowed testing more than 80,000 urban settings, pointing out a great diversity of "optimum" morphologies of urban blocks. The urban block designs obtained behaved better compared to the existing local typologies. Dealing with conflicting energy strategies by means of a constrained evolutionary optimization design process offered a great opportunity in searching for new solutions to the urban design in the neighborhood scale, helping to guide urban designers' decisions and allowing arenewal of the Architecture of the city

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Hoffmann, Munir [Verfasser], Anthony M. [Akademischer Betreuer] Whitbread, Jörg M. [Akademischer Betreuer] Greef, and Johannes [Akademischer Betreuer] Isselstein. "Understanding potential yield in the context of the climate and resource constraint to sustainably intensify cropping systems in tropical and temperate regions / Munir Hoffmann. Gutachter: Jörg M. Greef ; Johannes Isselstein. Betreuer: Anthony Whitbread." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1070423610/34.

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Riano, Sanchez Jaime Andres. "Evolution of the global productivity of terrestrial ecosystems under constraint linked to nitrogen availability : analysis over the recent historical period and future projections." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASJ012.

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Les écosystèmes terrestres absorbent actuellement plus d'un quart des émissions de CO₂ d'origine anthropique, grâce à l'effet de fertilisation associé à l'augmentation du CO₂ atmosphérique. La plupart des modèles de systèmes terrestres utilisés dans les récents travaux du GIEC estiment que les écosystèmes terrestres continueront à se comporter comme un puits de carbone de plus ou moins grande ampleur au XXIe siècle, en fonction des trajectoires futures du CO₂ atmosphérique et du climat. Quelle que soit l'évolution de la concentration de CO₂ atmosphérique, il reste essentiel de déterminer si suffisamment de nutriments (en particulier l'azote) seront disponibles pour soutenir pleinement l'augmentation de la production primaire résultant de l'effet de fertilisation d'un CO₂ élevé. La plupart des modèles globaux des écosystèmes terrestres ne tiennent pas compte du cycle de l'azote et des interactions entre les cycles de l'azote et du carbone. La dernière version du modèle ORCHIDEE développé en France intègre ces nouvelles fonctionnalités. En utilisant ce modèle, l'objectif de la thèse sera d'analyser l'évolution de la productivité terrestre sur la période historique récente et de quantifier l'évolution future de la productivité des écosystèmes terrestres sous l'effet combiné de ces changements globaux : climat, concentration en CO₂, et évolution de la production d'azote réactif, selon différents scénarios socio-économiques. L'inclusion du cycle couplé de l'azote et du carbone dans ORCHIDEE nécessite également une meilleure approximation d'un apport clé d'azote résultant de la fixation biologique de l'azote qui est actuellement déterminé par l'évapotranspiration. Ceci a été récemment invalidé par une étude de méta-analyse. Le second objectif de cette thèse consiste donc à implémenter un modèle dynamique basé sur les processus pour reproduire la BNF dans ORCHIDEE afin d'améliorer l'estimation des flux de carbone
Terrestrial ecosystems currently absorb more than a quarter of CO₂ emissions of anthropogenic origin, thanks to the fertilization effect associated with the increase in atmospheric CO₂. Most of the terrestrial system models used in recent IPCC work estimate that terrestrial ecosystems will continue to behave like a carbon sink of greater or lesser magnitude in the 21st century, depending on the future trajectories of atmospheric CO₂ and climate. Whatever the evolution of atmospheric CO₂ concentration, it remains critical to determining whether enough nutrients (particularly nitrogen) will be available to fully support the increase in primary production resulting from the fertilization effect of elevated CO₂. Most global models of terrestrial ecosystems do not account for the nitrogen cycle and the interactions between the nitrogen and carbon cycles. The latest version of the ORCHIDEE model developed in France incorporates these new features.Using this model, the objective of the thesis will be to analyze the evolution of terrestrial productivity over the recent historical period and to quantify the future development of the productivity of terrestrial ecosystems under the combined effect of these global changes: climate, CO₂ concentration, and reactive nitrogen production evolution, according to different socio-economic scenarios. Including the coupled nitrogen and carbon cycle in ORCHIDEE also requires a better approximation to one key Nitrogen input resulting from Biological Nitrogen Fixation that is currently determined by evapotranspiration. This has been recently invalidated by a meta analysis study. The second objective of this thesis consists then of implementing a process-based dynamic model for reproducing BNF in ORCHIDEE to improve the estimation of the carbon fluxes

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Liu, Xiting [Verfasser], Rüdiger [Akademischer Betreuer] Henrich, and Gerhard [Akademischer Betreuer] Bohrmann. "Sediment Dynamics off the East African Continental Margin during the Last Deglaciation and the Holocene: Constrained by Changes in Climate and Sea Level / Xiting Liu. Gutachter: Rüdiger Henrich ; Gerhard Bohrmann. Betreuer: Rüdiger Henrich." Bremen : Staats- und Universitätsbibliothek Bremen, 2014. http://d-nb.info/1072226693/34.

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Merlier, Elodie. "Télédétection optique des réponses des forêts aux stress abiotiques." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS022/document.

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Anticiper les impacts des changements climatiques sur les écosystèmes terrestres, notamment sur le cycle du carbone, nécessite la compréhension et la quantification du fonctionnement photosynthétique des végétaux et leurs réponses aux contraintes abiotiques. Suivre l’évolution des propriétés spectrales des couverts végétaux par la télédétection permet d’avoir accès à leur fonctionnement à des échelles spatiales et temporelles variées. Plusieurs indicateurs optiques ont été développés afin d’accéder à la structure, la biochimie et le fonctionnement écophysiologique des végétaux. Le PRI (photochemical reflectance index), déterminé à partir de la réflectance mesurée dans des bandes étroites à 531 nm et 570 nm, est un proxy de l’efficacité de la plante à utiliser la lumière (LUE, light use efficiency) et plus particulièrement du cycle des xanthophylles, utilisé par la plante pour dissiper l’énergie lumineuse excédentaire sous forme de chaleur. Cependant son usage à l’échelle du couvert végétal, ou à plus larges échelles temporelles et spatiales, entraine l’implication de nombreuses sources de variabilités qui masquent la sensibilité du PRI au fonctionnement photosynthétique, particulièrement les variations biochimiques et phénologiques. L’objectif de ce travail est de mieux comprendre les facteurs qui jouent sur la variabilité du PRI à l’échelle de la feuille et du couvert, afin de caractériser ses réponses aux variations abiotiques de l’environnement et de démêler la composante phénologique de la composante physiologique du PRI. Des études ont été menées en conditions contrôlées, semi-naturelles et naturelles, sur des jeunes arbres et en forêt adulte, soumis à différentes contraintes abiotiques. L’analyse des courbes de réponse du PRI aux variations de lumière incidente utilisée pour la photosynthèse (PAR, photosynthetically active radiation) permet d’isoler 3 paramètres. Le PARsat, la valeur de PAR pour laquelle le PRI sature, le PRI₀, la valeur du PRI à une intensité lumineuse faible (mesurée) ou nulle (estimée) et le ∆PRI, l’amplitude de variation entre le PRI₀ et la valeur de PRI maximum. En période de végétation, la variabilité du PARsat est principalement contrôlée par la disponibilité en eau pour la plante. La variabilité du PARsat est aussi impactée par la concentration d’ozone atmosphérique. En période de débourrement et de sénescence, la variabilité du contenu en chlorophylle régit la valeur du PARsat. Ce paramètre explique la variabilité physiologique du PRI et varie en fonction du facteur limitant la photosynthèse. La variabilité du PRI₀ a été expliquée par la variabilité du contenu biochimique des feuilles en réponse au cycle saisonnier de la chlorophylle et à sa variabilité en conditions de stress. A l’échelle de la canopée, la variabilité de la structure du couvert s’ajoute à la variabilité biochimique du PRI₀. Le PRI₀, en temps que composante phénologique de la variabilité du PRI, peut être utilisé pour corriger le PRI afin de lui soustraire la variabilité structurale et obtenir un PRIc fortement corrélé à la LUE. A l’échelle de la canopée, il a été montré que le PRI est principalement représentatif de la strate supérieure du couvert. Le ∆PRI n’a montré aucune variation intra et inter-journalière, suggérant que le PRI répond non pas au contenu en xanthophylle des plantes, mais à un ratio maintenu constant. Ces résultats mettent en évidence l’importance d’isoler les différentes sources de variabilité du PRI avant de l’utiliser comme proxy du fonctionnement photosynthétique des écosystèmes terrestres
Anticipating impacts of climate change on terrestrial ecosystems, particularly on the carbon cycle, requires the understanding and the quantification of the plant photosynthetic functioning and of their responses to abiotic factors. Tracking variations of spectral properties of plants using remote sensing allows the access of plant functioning at various spatial and temporal scales. Several optical indices have been developed to assess plant canopy structure, biochemistry and ecophysiological functioning. The PRI (photochemical reflectance index), determined from reflectances measured in narrow bands at 531 nm and 570 nm, may be used as a proxy of light use efficiency (LUE) at leaf and canopy scales, and more particularly of the xanthophyll cycle used by plants to dissipate the excess light energy as heat. However the use of PRI at the canopy scale and at large temporal and spatial scales faces several difficulties related to the involvement of different sources of variability that blur PRI sensitivity to photosynthetic functioning. These sources of PRI variability are particularly linked to spatial and temporal variations of biochemical and phenological canopy properties. The aim of these studies is to better understand the factors affecting PRI variability at leaf and canopy scales, to assess the strength of the relationships between PRI and vegetation responses to environmental abiotic constraints and disentangling the phenological component from the physiological component of PRI. Studies were conducted under controlled, semi-natural and natural conditions, on young trees and a mature deciduous forest subjected to various abiotic constraints. The analysis of PRI responses to the variations of photosynthetically active radiation (PAR) allowed isolating three parameters. The PARsat, the PAR value at the PRI saturation; the PRI₀, the value of PRI at dim light (measured) or in darkness (estimated) and the ΔPRI, the range of PRI variations between the PRI₀ and the maximum value of PRI. During the leaf growing season, PARsat variability is mainly controlled by the availability of water content for the plant. The PARsat variability is also impacted by the atmospheric ozone concentration. During the phenological phases of budburst and the senescence, the variability of the leaf chlorophyll content governs PARsat values. This parameter describes the physiological variability of PRI and varies depending on the limiting factor for photosynthesis. The PRI₀ variability has been explained by the dynamic of the biochemical content of the leaves linked to the seasonal variations of chlorophyll content and to abiotic stress conditions. At canopy scale, the structural variability is added to the biochemical variability of PRI₀. The PRI₀, as the phenological component of PRI variability, can be used to correct PRI, removing its structural variability to obtain a PRIc strongly correlated to LUE. At canopy scale, it was shown that the PRI is mostly representative of the upper layer of the canopy. The ΔPRI showed no variation within and between days, suggesting that the PRI does not respond to the plant xanthophyll content but rather to a ratio maintained constant. These results highlight the importance of isolating the different sources of PRI variability before its use as a proxy of the photosynthetic functioning of terrestrial ecosystems

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Dissertations / Theses on the topic 'Climatic constraints'

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