Tesis sobre el tema "Changements climatiques – Sahel"
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Barbier, Jessica. "Extrêmes climatiques - les vagues de chaleur au printemps sahélien". Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/19810/6/Barbier_Jessica_2_sur_3.pdf.
Texto completoCournoyer-Cyr, Vanessa. "Migrations environnementales et stratégies d'adaptation vers une intégration viable". Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/5724.
Texto completoGuilbert, Marcellin. "Réponse des moussons indienne et africaine au changement climatique d’origine anthropique". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS454.
Texto completoThe monsoons are defined by a seasonal reversal of winds that brings more than 80% of annual precipitation to India and the Sahel, which are largely dependent on them. Predicting their evolution under the influence of man - the so-called anthropogenic response - is therefore of the utmost importance, all the more so as these two regions will be home to two billion people by 2100. However, the monsoon projections we are currently able to provide are accompanied by major uncertainties concerning the amplitude and sometimes the very sign of these changes. Using recent simulations carried out for the 6th report of the Intergovernmental Panel on Climate Change (IPCC), we seek to understand the origin of these uncertainties in climate models. The performance of these models in reproducing historical trends (1850-2014) is a factor of confidence in their ability to predict the future. However, these historical trends are also marked by uncertainties. Consequently, the first question we want to answer is: can we explain the uncertainty of the models in simulating the evolution of the Indian and Sahelian monsoons over the historical period? Model errors in relation to an observed climatology calculated over a reference period of at least thirty years are called biases, and we wish to test the hypothesis that they may partly explain the different responses of the models. We first consider the case of India, and following this hypothesis, we show that the climatological temperature biases of models in the equatorial Pacific Ocean modulate the way they simulate the historical response of the Indian monsoon. Indeed, we show that by modulating the historical response of the Pacific Ocean, climatological biases in the latter affect the Indian monsoon via mechanisms similar to those linking ENSO (El Niño - Southern Oscillation) and monsoon interannual variability. We then reproduce the same study for the Sahelian monsoon, where we show that climatological temperature biases in all the Tropics are strongly linked to the way models simulate its historical evolution. We do not, however, identify the precise physical mechanism linking this bias to the Sahelian monsoon, but we do show that the latter is strongly dependent on the way models simulate the response of the inter-hemispheric temperature gradient, which is physically consistent with the known role of this gradient as a modulator of the position of the inter-tropical convergence zone (ITCZ). In the second part of our investigations, we switch to projections (2014-2100) based on a pessimistic scenario of high emissions, and address the following question: what are the sources of uncertainty in the forced response of the monsoons within the projections? This time, we tackle the Sahel case first and link the diversity of responses across models to two factors: the response of the inter-hemispheric temperature gradient and that of the equatorial Pacific. The underlying mechanisms involve ITCZ migration and enhanced surface circulation for the first factor, and modulation of the Walker circulation and tropical waves for the second. These two factors account for 62% of the uncertainty in Sahel projections. Finally, we look at the future of the Indian monsoon, and show that its uncertainties are strongly linked to the temperature response of deserts from the Sahara to Pakistan, which also influences the response of the Sahelian monsoon. Indeed, the stronger the temperature response, the more pronounced the thermal depression over the deserts, the stronger the monsoon surface circulation and hence the precipitation
Abdourhamane, Touré Amadou. "Erosion en milieu sableux cultivé au Niger : dynamique actuelle et passée en liaison avec la pression anthropique et les changements climatiques". Phd thesis, Université de Bourgogne, 2011. http://tel.archives-ouvertes.fr/tel-00833028.
Texto completoNacanabo, Amade. "Impact des chocs climatiques sur la sécurité alimentaire dans les pays sahéliens : approches macroéconomiques et microéconomiques". Electronic Thesis or Diss., Toulon, 2021. http://www.theses.fr/2021TOUL2007.
Texto completoOften used metaphorically to refer to the southern fringes of the Sahara, the Sahel's geographical position makes it a region vulnerable to climate change. Agriculture is highly rain-fed and largely dependent on climatic conditions. If food security is to be achieved in the Sahel, climate change must be taken into account. By combining empirical and theoretical work, this thesis aims to contribute to a better understanding of the impact of climate change on food security in the Sahel at the microeconomic and macroeconomic levels. The first chapter examines the food security situation in the Sahel at the macroeconomic level, after analysing its demographic dynamism. The results of this chapter show that the Sahel has not yet begun its demographic transition. The demographic growth rate is high compared with the average for sub-Saharan Africa. Undernourishment is on the decline, but remains prevalent in the region. Reducing undernourishment necessarily involves agricultural production, which is dependent on the vagaries of the climate. The second chapter therefore looks at the effects of climate change on the yields of certain crops (millet, sorghum and maize) in the Sahel. The results indicate that climate change is having an overall negative impact on agricultural yields in the Sahel. This analysis at the macroeconomic level is then supplemented by two chapters which, at the microeconomic level, focus on the behaviour of farmers in the Sahel. The third chapter seeks to analyse the impact of climatic shocks, as measured by farmers' perceptions, on the inefficiency of agricultural plots. This study shows that climatic shocks increase the inefficiency of agricultural plots. Through lower yields and plot inefficiency, climate change may affect the poverty and food vulnerability of Burkinabé farming households. To this end, the fourth chapter identifies the individual and contextual determinants of poverty and food vulnerability among farming households in Burkina Faso. The results show that, in addition to the individual characteristics of farm households, such as their size or the level of education of the head of household, the climatic context in which they live helps to explain their poverty and food vulnerability
Sy, Souleymane. "Impact du changement d'occupation des sols passé et à venir sur la dynamique de la circulation de la mousson ouest africaine". Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066208.pdf.
Texto completoBy climate models developed in the LUCID project and CMIP5 models used in the LUCID-CMIP5 projet, this thesis aims to identify and evaluate biogeophysical impacts of LULCC of the past 150 years and the end of XXIst century on surface climate in West Africa. Focusing analysis in two contrasted regions of West Africa: Sahel and Guinea where land cover change is above 5% since pre-industrial times, results reveal expansion of crops and pasture and deforestation in Guinea in all LUCID models. In this work, simulations of present-day rainfall and surface air temperature have been compared with observed datasets. Results show that the observed mean and inter-annual variability of rainfall are respectively underestimated and overestimated by most of the seven climate models. Overall surface air temperature is better simulated than precipitation.Two simulations of rainfall and surface air temperature, forced respectively with present-day and pre-industrial land cover distribution are also compared. Results show that there is no obvious/visible difference between the two simulations with respect to mean climatic values of both rainfall and temperature as if the changes in land cover did not really matter for the good representation of those variables. Finally, this thesis evaluates leaf area index (LAI) in the LUCID models and its relationships with surface climate. Observations reveal that precipitation is highly and positively correlated to foliage density with values larger or equal to 0.8 in both the Sahel and Guinea. Five out of seven models show positive correlations, but not as large as in the observations. However none of the models is able to capture a larger correlation between precipitation and LAI in Guinea than in the Sahel. Most of climate models show that correlation between LAI and surface air temperature is positive in the Sahel and negative in Guinea. It suggests that more LAI in Guinea will lead to more evapotranspiration and therefore cooler surface, while in the Sahel the albedo effect of increased LAI may dominate and increase surface temperature. Finally, analysis reveals that historical effects of land-use changes are not regionally significant among the seven climate models due to a small land-cover change prescribed in these regions compared to the changes induced by large scale forcing such as sea surface temperatures changes and CO2 concentration increase.Furthermore, biogeophysical impact of land-use change in the XXIst Century climate were evaluated using specific simulations similar to RCP8.5 scenarios but with a prescribed fixed land cover map on 2006. The analysis reveals, that in contrast of last 150 years, deforestation continues in the coming years in tropical region in scenarios resulting from the extension of the cultivated area reaching 15 million km2 in 2100 over tropical Africa. Regionally, the biogeophysical impacts of projected changes in land cover in RCP8.5 scenarios were generally small but statistically significant in the Sahel and Central Africa regions where deforestation is more than 10% with a wide dispersion of climate response due to differents parameterizations of land surface in climate models
Hubert, Nicolas. "Environnement, Ressources et Conflits au Burkina Faso". Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41871.
Texto completoWilcox, Catherine. "Evaluation de changements hydrologiques en Afrique de l'Ouest : Détection de tendances et cadre de modélisation pour projections futures". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAU016/document.
Texto completoThe semi-arid regions of West Africa are known for their dry conditions which have predominated since the 1970s. In recent years, however, West Africa has witnessed a series of severe flooding events which caused widespread fatalities and socioeconomic damages. The emergence of this new problem demonstrates the sensitivity of the region to changes in the hydroclimatic system and calls for an improved characterization of flood hazard and the mechanisms that generate it. It also signals the need to develop projections for how flood hazard may evolve in the future in order to inform appropriate adaptation measures.In this context, the following PhD thesis seeks to answer three main questions:1) Is there a significant trend in extreme streamflow in West Africa, or are the documented flooding events isolated incidences?2) How can one model mesoscale convective systems, the primary driver of runoff in the region, in order to explore the properties of precipitation that drive streamflow?3) Based on potential climate change in the region, what trends might be observed in streamflow in the future?First, changes in extreme hydrological events West Africa over the past 60 years are evaluated by applying non-stationary methods based on extreme value theory. Results show a strong increasing trend in extreme hydrological events since the 1970s in the Sahelian Niger River basin and since the 1980s in the Sudano-Guinean catchments in the Senegal River basin. Return levels calculated from non-stationary models are determined to exceed those calculated from a stationary model with over 95% certainty for shorter return periods (<10 years).Next, recent developments are presented for a stochastic precipitation simulator (Stochastorm) designed for modeling mesoscale convective storms, the main rainfall source in the Sahel. Developments include a model for storm occurrence, the explicit representation of extreme rainfall values, and an improvement in the modeling of sub-event intensities. Using high-resolution data from the AMMA-CATCH observatory, simulation outputs were confirmed to realistically represent key characteristics of MCSs, showing the simulator’s potential for use in impact studies.Finally, a modeling chain for producing future hydrological projections is developed and implemented in a Sahelian river basin (Dargol, 7000km2). The chain is original as it is the first attempt in West Africa to encompass the continuum of scales from global climate to convective storms, whose properties have major impacts on hydrological response and as a result local flood risk. The modeling chain components include the convection-permitting regional climate model (RCM) CP4-Africa, the only RCM (to date) explicitly resolving convection and providing long-term simulations in Africa; a bias correction approach; the stochastic precipitation generator Stochastorm; and a rainfall-runoff model specifically developed for Sahelian hydrological processes. The modeling chain is evaluated for a control period (1997-2006) then for future projections (ten years at the end of the 21st century). Hydrological projections show that peak annual flow may become 1.5-2 times greater and streamflow volumes may double or triple on average near the end of the 21st century compared to 1997-2006 in response to projected changes in precipitation.The results raise critical issues notably for hydrological engineering. Current methods used to evaluate flood risk in the region do not take non-stationarity into account, leading to a major risk of underestimating potential floods and undersizing the hydraulic infrastructure designed for protecting against them. It is also suggested to not only consider rainfall changes but also societal and environmental changes, interactions, and feedbacks in order to better attribute past hydrological hazards and their future trajectories to related causes
Diallo, Alassane. "Changement climatique et migrations humaines au Sénégal : une approche en termes de vulnérabilité du système socio-écologique". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAE004/document.
Texto completoClimate change and human migration are two major issues of our time. Starting from the observation of a dichotomous knowledge between maximalists and minimalists, which results in a limited capacity of scientific research to take into account the dynamic and complex interactions between climate and human migrations, this thesis proposes a better understanding and explanation of the climate-migration relations through a renewed and integrative approach (the vulnerability of the socio-ecological system). It aims to fulfill two objectives. On the one hand, to produce new knowledges those take into accounts socio-ecological interactions and feedbacks at different spatial and temporal scales and, on the other hand, to propose a quantified instrumentation of these social-ecological interactions and feedback. This contribution could serve as a starting point for a decision-making tool to evolve towards more targeted and effective policies.This thesis emphasizes a certain difficulty in highlighting a robust relationship between climate change and migration in the Sahel region. This latter, often seen as a relatively homogeneous entity, presents complex socio-economic and physical-climatic spatial heterogeneities that do not allow a stronger understanding of migratory movements which are in change since the 1970s. For this purpose, a reduced complexity model, based both on a partitioning of the study area (Senegal) and a partitioning of data (agro-ecological zones and regions of Senegal), is mobilized as a framework for the analysis of social-ecological migrations in terms of vulnerability induced by climate change. Thus, the innovative heuristic framework built (knowledge model with a sequencing of variables) has made it possible to instrument the climate-migration relationships within Senegal.Our results show an accelerating/amplifying climatic effect of interregional migrations underlying the living conditions of populations. In general, climate alone is not sufficient to "produce" migration. The climatic effects channel through the socio-economic variables (initial vulnerability). Under these results, we retained in fine the name of "eco-climatic migrants". Thus, policies relating to eco-climatic migration in this western part of the Sahel should move towards both: (i) development issues by reducing socio-economic vulnerabilities (poverty and inequality) by acting on the environment and the populations consistently and extensively respectively; and (ii) climate economics issues by reducing the physical-climatic vulnerability through appropriate mitigating and adapting policies to face climate change
Boulain, Nicolas. "Effet des facteurs climatiques et anthropiques dans l'évolution récente des écosystèmes tropicaux : modélisation spatialisée du bilan hydrique d'un petit bassin versant sahélien". Paris 6, 2004. http://www.theses.fr/2004PA066016.
Texto completoYobom, Oudah. "Climate Change, Agriculture and Food Security in Sahel". Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCG001.
Texto completoThis thesis deals with the impact of climate change on agriculture and food security in the Sahel zone that we define as a region comprising 12 countries and 52 agroecological zones within these countries. The study area covers Burkina Faso, Djibouti, Eritrea, Ethiopia, Mali, Mauritania, Niger, Nigeria, Senegal, Somalia, Sudan and Chad. The situation in this part of the world is strongly impacted by climate change because agriculture, largely rainfed, plays an important economic role there. Climate change is then expected to have an impact on food production, which will make food availability and access even more difficult.From a theoretical point of view, this thesis aims to feed the literature on climate change and its effects on agricultural sectors in the world, particularly in the Sahel, by focusing on agroecological zones. From an empirical point of view and by using a range of statistical and econometric techniques, this thesis takes into account the agricultural and climatic characteristics of each country and agroecological zones of the Sahel.In the first chapter, we deal with the issue of climate change and variability based on precipitation and temperature during the different seasons of the countries and agroecological zones of the Sahel. Using a linear regression model and an endogenous structural change model, we show that countries and agroecological zones are indeed affected by climate change and that the year 1980 is an essential point in explaining this phenomenon for both scales. We also show that desert and arid areas suffered a large number of shocks from 1901 to 2016, with the exception of Nigeria, where wetlands and non-desert areas suffered several shocks.In the second chapter, we study the relationship between climate change and variability, measured by temperature and precipitation conditions in the rainy seasons, and agricultural production at country level and at the level of agroecological zones in the Sahel. Focusing on an agricultural production index and five cereals (corn, millet, sorghum, wheat and rice), we study this relationship using an original database with socio-economic and climate variables. On the basis of an estimated agricultural production function for the 1961-2016 period, we show that precipitation and average temperatures during the growing season have very heterogeneous effects on agricultural production according to the cereal and agricultural zone, depending specific needs and stress linked to the cereal and agronomic and climatic conditions of each zone.In the third chapter, we analyze the link between climate change and food security in the Sahel countries. Based on a multidimensional analysis of food security and a panel data model with delayed climate variables of interest, we show that drought and floods negatively affect food security. In the presence of these climatic disasters, floods cause more damage to food security. Socioeconomic factors also play an important role in food security. Our results show that the low level of economic development, population growth and inflation of food prices do not guarantee food security. In addition, the absence of conflicts and political stability are important levers for improving the food security situation of the populations
Monerie, Paul-Arthur. "Le changement climatique en région de mousson africaine : évolution des champs pluviométriques et atmosphériques dans les simulations CMIP3 et CMIP5 sous scénario A1B et rcp45 (1960-1999, 2031-2070)". Phd thesis, Université de Bourgogne, 2013. http://tel.archives-ouvertes.fr/tel-00955371.
Texto completoIbrahim, Boubacar. "Caractérisation des saisons de pluies au Burkina Faso dans un contexte de changement climatique et évaluation des impacts hydrologiques sur le bassin du Nakanbé". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00827764.
Texto completoDiawara, Mamadou Oumar. "Impact de la variabilité climatique au nord Sahel (Gourma, Mali) sur la dynamique des ressources pastorales, conséquences sur les productions animales". Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30029.
Texto completoSeveral studies on the primary production of Sahelian rangelands that are dominated by annual herbaceous indicate large spatial heterogeneity and high inter-annual variations in production associated with changes in rainfall distribution mediated by run-off redistribution itself mostly bound to soil type. In Sahel, most of the forage production occurs during the rainy season, which lasts three to four months. The management of the stock of fodder which is the main nutrition resource for livestock during the long dry season requires a good knowledge of its seasonal dynamics under the combined effects of climate and grazing pressure. This thesis aims to study the impact of climate variability on the dynamics of the pastoral resources of the Gourma in the North-East of Malian Sahel and to assess the impact of resources variations on animal production. The approach used is based on a joint seasonal monitoring of vegetation and stocking rate. It combines an analytical study and the modeling of the dynamics of forage resources in response to rainfall distribution and stocking rate. The thesis is composed of four studies. The first is a sensitivity analysis of forage production to the intra-seasonal distribution of rainfall. The second study evaluates the impact of domestic ruminants grazing on standing straw and litter disappearance rates during the dry season. The third study addresses the same question by modeling the dynamics of fodder resources during the season depending on the livestock grazing pressure. The fourth and last study evaluates the breeding productivity of the herds and the sustainability of Gourma pastoralism. The results highlight the low productivity of pastoral breeding despite an overall under-utilization of the forage stock in the dry-season. They indicate that in the Sahelian pastoral systems with rangelands producing less than 2000 kg DM ha-1 on average, and very limited use of supplementary feeds in the late dry season, livestock suffer of nutritional stress in the late dry and early wet season, as revealed by residual masses of straws and litter tilling less than 10 % of rangeland yield at the end of the rainy season
Fane, Moussa. "Impact du climat sur l'écologie et la transmission du paludisme : analyse du risque palustre dans le septentrion malien". Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENS042/document.
Texto completoNous pensons que ces résultats aideront les acteurs de santé publique à mieux comprendre l’épidémiologie du paludisme au Sahel, en vue d’orienter d’avantage la recherche sur des outils additionnels de lutte pour freiner la propagation du paludisme grâce à la gestion environnementale. Ils fournissent une piste prédictive du comment le changement climatique impactera la transmission du paludisme en Afrique
Traoré, Abdoul Khadre. "Etude et modélisation de l'influence des processus couplés surface-atmosphère sur la variabilité des pluies et du climat Ouest Africain". Paris 6, 2011. http://www.theses.fr/2011PA066112.
Texto completoAg, Atteynine Solimane. "Changement climatique et rongeurs ravageurs des cultures : effet attractif des cultures de saison sèche sur les espèces du genre Arvicanthis au Mali". Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0130.
Texto completoIn Mali, during the dry season, there is the issue of the attractive effect of dry season crops on rodent pests, which would be all the more marked in the latitudinal gradient of Sudan-Sahel aridity GECS (1100 mm to 200 mm). These hypotheses are tested in the genus Arvicanthis (A.ansorgei, A. niloticus). The results of the previous cytogenetic survey 1994-1999 and an expanded survey 2009-2014 reveal recent changes in the distribution areas of both species; suggesting a strong role of their chronobiological adaptation in the determinism of their distribution. This horizontal approach followed by a vertical approach (2009-2016) compares four indicators of the attractiveness of the CSS vs. the MNC in the five climatic regions of GECS (Sikasso, Koulikoro, Ségou, Mopti, Gao). The population densities of both species are higher in the CSS vs. the MNC; and this attractiveness of the CSS increases with aridity in the area of A. niloticus. The ratio of "migratory strategists" within populations demonstrates the buffering effect of the CSS and confirms the frequency of these episodes. The diet study confirms their phytophagous diet. In a natural environment, aridity induces a decrease in the consumption of plants compensated by that of non-orthopterous Arthropods; and the diversity of plants consumed decreases with aridity in A.ansorgei vs increases with aridity in A. niloticus. The buffering effect of CSS "neutralizes" inter-specific differences, and in both species, in the CSS, the diversity of weeds consumed decreases to the detriment of crops, especially rice and the consumption in the Orthoptera increases
Dieppois, Bastien. "Etude par analyses spectrales de l'instabilité spatio-temporelle des téléconnexions basse-fréquences entre les fluctuations globales du secteur Atlantique et les climats de l'Europe du NW (1700-2010) et du Sahel ouest-africain (1900-2010)". Phd thesis, Université de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00843683.
Texto completoMohamed, Maher. "Le climat agricole au Sahel tunisien et les changements climatiques". Mémoire, 2009. http://www.archipel.uqam.ca/2466/1/M10930.pdf.
Texto completoParishkura, Dimitri. "Évaluation de méthodes de mise à l'échelle statistique : reconstruction des extrêmes et de la variabilité du régime de mousson au Sahel". Mémoire, 2009. http://www.archipel.uqam.ca/2472/1/M11075.pdf.
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