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In this PhD project, use will be made of the regional climate model CCLM, in which only very recently, the freshwater lake parameterisation scheme FLake has been implemented. The research will be build around three main axes: (i) improvement of the treatment of turbulent exchanges and lake dynamics in FLake, (ii) climate simulations -and evaluation- for Central and Eastern Africa using CCLM driven by Global Climate Model (GCM) output, and (iii) assessing the uncertainty range of these simulations by developing and implementing a new method, the so-called physically-based statistical downscaling. The second axis again falls into two parts, as runs will be performed to reconstruct both present (2001-2012) and future (2071-2100) climatic conditions. 1. Improving CCLM's FLake module The interaction of the atmosphere with an underlying lake surface strongly depends upon the lake's surface temperature and its time-rate-of-change. Moreover, lakes strongly modify the structure and transportproperties of the atmospheric surface layer and therefore the surface fluxes of heat, moisture and momentum. The two layer freshwater lake model FLake attempts to address both issues by solving a set of differentialequations while using a parameterised vertical temperature structure. However, although the model performs well for small and shallow lakes, ithas difficulties reproducing both the near-surface air temperature and the thermal structure of large lakes. Three major model deficiencies canbe identified in the current version: the representation of turbulent fluxes, the parameterisation of temperature profiles and the spin-up time, each of which will be investigated within the research proposed. First, the parameterisation of surface water roughness lengths with respect to wind and scalar quantities such as potential temperature and specific humidity will be investigated. For example, the effect of a limited wind fetch over inland water surfaces compared to sea surfaces on the momentum transfer equation needs to be assessed as it is still lacking in the present model version and biases the parameterisation of turbulent flux exchanges. Second, the temperature profile parameterisation will be improved and extended as to include the abyssal layer. This issue is especially important in the context of the African rift lakes, given that primary production highly depends on it, and hence a good representation of the lake's thermal structure is of primary importance for predicting future ecosystem productivity. One possible way of improvement would be to allow for horizontal heat and water transfers to influence the water'sthermal structure. For the evaluation of FLake's ability to represent lake Kivu's thermal structure, use will be made of lake temperature profiles collected during multiple past and near-future field campaigns in the Kivu region organised by the EAGLES consortium. Finally, the technicalissue of the lake temperature spin-up following a cold start of FLake will be addressed. Since lakes have a long memory, erroneous initial conditions lead to wrong lake surface temperatures until the memory is faded. A way out of this problem could be to determine a climatological mean state of the lake and to use this as initial conditions for the Flake module. These mean conditions can be derived from an offline Flake integration. 2.1. Simulating present conditions A present-day simulation will be performed with CCLM for the period 2001-2012, using the lateral boundaries from the European Centre for Medium-range Weather Forecasting (ECMWF) re-analyses. The domain will enclose the larger Central andEastern Africa, using 150 x 150 x 32 grid points with a resolution of ~0.0625° (7 kilometres). This spatial resolution is sufficient to take into account the effect of Lake Kivu on the local climate, as is shown ina modelling study over Lake Chad in West Africa. Before futureclimate predictions can be performed, it is important to evaluate the model performance for the present-day climate. The ability of CCLM to reproduce the present-day central and eastern African climate will be evaluated using in situ measurements available for the period 2002-2010 from local meteorological stations around the lake and gathered in the EAGLESproject's Kivu database. Satellite data from the Tropical Rainfall Measurement Mission (TRMM) are available since 2000 on a 0.25° resolution and will be used to spatially evaluate 3 hourly or monthly accumulated precipitation. Cloud cover will be evaluated using satellite observations from the Moderate-resolution Imaging Spectroradiometer on board the Terrasatellite (MODIS-Terra) or the Meteosat Second Generation (MSG) program, available every 15 minutes at a 1km spatial resolution, and atmospheric soundings available from the University of Wyoming. 2.2. Understanding and attributing climate change around Lake Kivu The climate change signal around Lake Kivu will be simulated using the CCLM model for the period 2071-2100. The Hamburg GCM (ECHAM5) will deliver initial and lateral boundary conditions. These fields are available from international intercomparison exercises contributing to the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment report, more specifically the Coordinated Regional Climate Downscaling Experiment (CORDEX). Their aim is to provide higher-resolution climate information than is available directly from contemporary global climate models (~ a few hundred kilometres). For Africa, the standard spatial resolution of the experiments of CORDEX is 0.44° (50 kilometres). Again, the simulation will be doneon a resolution of 0.0625° for the same domain as the present-day climate simulations. Based on these simulations, changes in atmospheric circulation and their effect on local climate around the African rift lakes will be investigated. For example, the potential effect ofchanges in large-scale climate oscillations (e.g. El Niño-Southern Oscillation) on the lake physics will be examined, by analogy with what has been reported in Lake Tanganyika. 3. Assessing the uncertainty range by means ofphysically-based downscaling It is important to emphasize that one RCM simulation for the future provides no information on the range of uncertainty. In order to deal with this critical issue, one can perform multiple dynamical downscaling experiments, i.e. conduct several integrations with the RCM, each time initiated and fed at the boundaries by output from a different GCM. However, although much is to say infavour of this approach, the multi-model ensemble method is computationally very expensive. Given the presence of abundant in-situ observations, one could also opt for statistical downscaling, wherein one searches for linear relationships between e.g. observed surface temperature and precipitation and a range of atmospheric predictor variables. However thisapproach is tenuous as good observational data are very sparse in the present Central African context. In the PhD project, it is proposed to develop a physically-based statistical downscaling method that uses linear relationships between output both from global and high-resolution regional climate model integrations. Hence, transfer functions will be derived that calculate the temperature and precipitation distributionas a function of, on the one hand, geophysical features (orography, vegetation type, soil characteristics, background albedo, etc.) and, on theother hand, large-scale meteorological conditions like circulation patterns, temperature, humidity, convective available potential energy and other variables derived from ECMWF re-analyses data. Also, the implementation of more advanced statistical techniques is envisaged, such as principal component analysis and maximum covariance analysis, as they allow to find patterns within and between large datasets, and the Mann-Kendall non-parametric trend test, as it is able to detect non-linear relationships. The ability of the physically-based statistical downscaling model to reproduce present climate will be evaluated in similar ways as explained in §2.1. This off-line model will subsequently be driven by the large-scale atmospheric conditions from different GCM climate scenarios available from CORDEX to obtain different possible realisations of future near-surface climate. Hence, variation in the sensitivity of African climate under different scenario's of future changes in large-scale atmospheric circulation will be taken into account. Moreover, this off-line model will even allow to assess the uncertainty related to the magnitude of the expected global warming -i.e. the choice of the radiative forcing pathway- as it will also be run for different 'Representative Concentration Pathways' (RCPs).

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Summary Tropical deforestation has strong impacts on many ecosystem services such as global climate regulation, preservation of biodiversity and regulation of sediment and water fluxes.The Greenland ice sheet (GrIS) is the second largest body of ice on Earth. Holding a potential of 7 m of global mean sea level rise, its rapidly increasing mass loss in response to global climate change will affect the entire planet. This mass loss is partly the result of a strongly decreasing surface mass balance (SMB), predominantly through increased meltwater runoff. Yet, the mechanisms involved in this decreasing SMB remain poorly understood. Recently, clouds have emerged as potential contributors to increased melt rates over the GrIS through their radiative warming of the surface, but Greenland-wide assessments of this effect are still largely lacking. Here we show that clouds have on average a radiative effect of 29.5 (±5.2) W m−2, using a unique combination of active satellite remote sensing, ground-based observations and a regional climate model. We develop an improved algorithm for cloud-base detection by ceilometer in polar regions, a smart sampling approach for estimating surface radiative fluxes based on CloudSat and CALIPSO satellite observations, and a hybrid satellite-climate model dataset with improved temporal resolution over the GrIS. Using snow model simulations, we show that the demonstrated radiative effect is responsible for a one-third increase in GrIS meltwater runoff compared to clear-sky conditions. Unexpectedly, this enhanced meltwater runoff is not caused by a direct increase in meltwater generation during the day, but rather by a reduction in refreezing rates of meltwater at night, when cloud warming is largest. Given the demonstrated high sensitivity of the GrIS to clouds in combination with the current inability of state-of-the-art climate models to reproduce the observed cloud properties, we conclude that only by incorporating new knowledge from observations in cloud parameterizations, we will be able to enhance the reliability of future projections of the GrIS and its contribution to global sea level rise.

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More than seven thousand years ago, the arrival of the first sedentary groups of farmers in the loess regions of Central and Western Europe marked the onset of a millennia-long decrease of natural vegetation in favour of agricultural land. Concurrent with the growing pressure on forests, man’s impact on earth surface processes and atmospheric cycles increased as well. However, neither the quantity and nature of past human-induced land cover changes, nor their relation with other components of the environmental system, is fully understood. This thesis aims to improve our insight in the long-term evolution and spatial distribution of anthro-pogenic land cover and its environmental impact in a case study for the Belgian Loess Belt.In combination with a spatially distributed soil erosion and sediment transport model, land cover reconstructions may serve as an effective means to quantify the cumulative impact of agricultural land use on sediment redistribution since Neolithic times. However, the coarse spatial resolution and limited thematic detail of currently available historical land cover data sets raises doubts regarding their potential for application in geomorphic models. In order to assess the influence of the spatial and thematic resolution of land cover scenarios on simulated sediment fluxes, the Watem/Sedem geomorphic model was applied to the Scheldt basin (ca. 19,000 km2) with varying land cover input maps and subsequently confronted with a field-based reference sediment budget of the Dijle subcatchment (758 km2). The results indicate that low-resolution land cover information, expressed as proportions of cropland, grassland and forest within each grid cell, leads to largely overestimated soil erosion and sediment delivery rates due to the inaccurate representation of landscape connectivity. In contrast, spatial allocation of land cover patches to a high-resolution grid yields more accurate results. Furthermore, at both resolutions, modelled soil erosion and sediment delivery are non-linearly related to the area under cropland. This highlights not only the need for land cover reconstructions at a detailed spatial resolution, but also demonstrates that differentiation of anthropogenic land cover types is essential for an accurate quantification of human-induced sediment dynamics.Archaeological records provide a direct indication of anthropogenic activity in past cultural time periods, and are therefore a valuable source of information in land cover reconstruction studies. Moreover, they can reveal if and how the distribution of ancient settlements is related to the topographic, hydrological, lithological and soil characteristics of the landscape. As such, archaeological site locations may serve as a basis to determine settlement probability patterns for a broader area. Here, rare events multivariate logistic regression analyses were applied to a database of Early Roman to Merovingian rural habitation and burial sites for two contrasting Belgian regions, i.e., the Hesbaye (3630 km2) and Condroz (2720 km2), in order to evaluate the impact of the ancient road network and multiple environmental factors on site locations. The analyses point out that the regional site pattern is significantly affected by the proximity of loess and limestone in the Hesbaye and the Condroz, respectively. Nevertheless, the fragmentary nature of archaeological finds imposes a limitation to the models’ perfor-mance. Furthermore, comparison of observed site densities with the sensitivity for soil erosion and the presence of agricultural land use demonstrated that the archaeological record is biased by the spatially differential preservation and discovery potential of sites.Although both are closely linked with historical land use, the reconstruction of landscapes based on palynological and geomorphological archives is complicated by the equifinality of pollen-dispersal and sediment redistribution processes, meaning that a variety of vegetation patterns can produce identical end signals. In order to reduce the number of possible outcomes with reference to single-record approaches and yet capture the all too often ignored diversity of equifinal land cover compositions, this study presents a novel methodological framework to integrate multiple proxy variables in the spatial reconstruction of land cover. First, more than sixty thousand high-resolution hypothetical land cover scenarios were created for the Dijle catchment by allocating various quantities of cropland, grassland and forest while accounting for the land’s agricultural suitability. In a second stage, the scenarios were evaluated based on their correspondence with available palynological and geomorphological proxy data in order to identify realistic land cover patterns for six cultural time periods between ca. 5200 BC and present. For this purpose, regional forest proportions were inferred from fossil pollen records using the Reveals quantitative regional vegetation reconstruction model. The Watem/Sedem geomorphic model served to simulate sediment delivery rates for each hypothetical land cover scenario.Depending on the cultural period, the joint evaluation of scenarios based on palynological and geomorphological proxy data effectively reduced the number of equifinal land cover patterns to several thousands or even hundreds. Furthermore, detailed analyses of the selected scenarios revealed various aspects about the quantity and spatial characteristics of past anthropogenic land cover in the Dijle catchment, including a temporal shift in the relative importance of cropland and grassland. Yet, the multiplicity of the remaining scenarios also points to the limitations of proxy records and the applied models as a tool to reconstruct historical land cover distributions with high spatial accuracy. The inclusion of archaeological site patterns as an additional reference for scenario evaluation, if available, is promising to achieve more insight in the spatial differentiation of land use at the subcatchment scale.Finally, two widely used global historical land cover data sets that are based on population and agricultural land per capita estimates were evaluated for various cultural periods in the central Belgian Loess Belt as well. Palynological and geomorphological records indicated both independently that the HYDE 3.1 data set strongly underestimates cropland and grassland areas over the entire considered time span. KK10 land cover scenarios present a more realistic evolution of human impact in the Dijle catchment, although they overestimate anthropogenic vegetation proportions prior to the Roman Age and underestimate deforestation rates during the last millennium.

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How to frame the (re)emergence of contentious initiatives in the housing sector in relation to the current debt and financial crisis and the consequent adoption of austerity policies? Centred on the cases of squatting initiatives in Rome and the main social movement around housing (Plataforma de los Afectados por la Hipoteca PAH) in Barcelona/Sabadell, the dissertation connects a series of debates and issues rooted at the intersection of critical political economy, geography, urban studies, social movements’ studies and sociology. Indeed the emergence of these initiatives is related to some of the main processes at work in contemporary political economy, notably indebtedness, financialization, precarity, neoliberal/austerity urbanism and the re-configuration of the welfare state through the process conceptualized by Sassen (2014) as “expulsions”.Political economists have paid a great attention to the emergence of social movements opposing austerity politics, in some cases acknowledging the potentially contentious character of housing and real estate to favor mobilization. Indeed the massive increase of foreclosures and evictions that followed the burst of the bubble highlights one of the main basic contradictions of capitalism (use-value vs exchange-value): a basic need is opposed to the research for profits by financial institutions. However, when stressing the potentially contentious character of housing and real estate, these contributions analyze social movements’ initiatives as a response to the “violence of financial capitalism” in a dynamics of hegemonic power/resistance. So they fail to recognize how contentious practices in the housing sector can be brought by the same subjects that were previously involved in making the hegemonic process at work.Against such a dualistic perspective, the dissertation develops a theoretical framework mostly relying on the Foucauldian analysis of the economy. Neoliberalism and its dispositifs (such as indebtedness or financialization, among others) are thus seen as immediately subjective, i.e. they produce specific subjects following specific moral imperative reproducing hegemonic power relations through their everyday actions and beliefs (Foucault, 2008). So neoliberalism (as well as indebtedness or financialization) involves always a “work on the self” interlocking economy and ethics- the latter meant as a relation of self to itself in terms of moral agency, thus figuring the intentional work of individuals on themselves to subject themselves to specific sets of moral imperatives and norms of conduct. Building on this main Foucauldian assumption, the main argument I develop through the five papers is that the emergence of these initiatives can be framed as resulting from a rupture within the processes of subjectification involved by neoliberalism and its dipsositifs. This argument relies on the Foucauldian conceptualization of power as a circular force (1982): likewise any other power relation, neoliberalism and its dispositifs contain within themselves the possibilities of rupture.