HAL-Ecole des Ponts ParisTech
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Heterogeneous peer effects and gender-based interventions for teenage obesity
No full textInternational audienceThis paper explores the role of gender heterogeneity in the social diffusion of obesity among adolescents and its policy implications. We propose a social interaction model which allows for gender-dependent heterogeneity in peer effects. Our empirical approach is consistent with the best response functions of a non-cooperative model where social interactions stem from the channel of pure spillover or pure conformity. We estimate the model using data on adolescent Body Mass Index and network-based interactions. Our approach allows us to account for network endogeneity. Our results show that peer effects are gender-dependent, and male students are particularly responsive to the weight of their female friends. According to simulations, reaching out to women results in an 8% increase in effectiveness in reducing overall BMI, based on the most conservative scenario. Thus, female-tailored interventions are likely to be more effective than a gender-neutral approach to fighting obesity in schools
La vulnérabilité des populations face aux changements climatiques dans les Pays de la Loire
No full textCe rapport spécial du GIEC des Pays de la Loire propose une analyse approfondie des vulnérabilités humaines et territoriales face aux changements climatiques. Il rappelle l’impératif d’une adaptation juste, pensée à l’échelle locale, construite avec les populations et fondée sur une solidarité active. Car anticiper les impacts ne suffira pas : il faut aussi agir sur leurs causes, pour limiter l’ampleur des perturbations à venir.
Rethinking traffic count methodologies to derive OD matrices from aggregated mobile phone data
No full textInternational audienceAmong the recently identified Big Data sources identified for mobility analysis, Mobile Phone Data (MPD) has been is considered as a promising passive source of information to complement traditional travel surveys thanks to large samples that are not limited to one mode of transport. Unlike individual MPD, aggregated MPD avoids privacy concerns and can be collected over long periods of time, but it only provides the number of people in a given area during a given time interval and requires further processing for mobility management. This paper therefore proposes a theoretical framework for generating OD matrices from AMPD, using methods derived from traffic counts. To ensure proper data transformation, several algorithms are tested, first in simulation and then using real data. The results demonstrate the potential of AMPD to generate high quality OD matrices on a continuous basis
The unique continuation problem for the wave equation discretized with a high-order space-time nonconforming method
No full textInternational audienceWe are interested in solving the unique continuation problem for the wave equation, i.e., we want to reconstruct the solution of the wave equation given its (noised) value in a subset of the computational domain. Homogeneous Dirichlet boundary conditions are imposed, whereasthe initial datum is unknown. We discretize this problem using a space-time discontinuous Galerkin method (including hybrid variables in space and in time) and look for the solution corresponding to the saddle-point of a discrete Lagrangian. We establish discrete inf-sup stability and bound the consistency error, leading to a priori estimates on the residual. Our main result proves the convergence of the discrete solution to the exact solution in a shifted energy norm involving weaker Sobolev norms than the standard energy norm for the wave equation. The proof combines the above a priori bound with a conditional stability estimate at the continuous level. Finally, we run numerical simulations to assess the performance of the method in practice. A static condensation procedure is used to eliminate the cell unknowns and reduce the size of the linear system
Effects of clay content distribution on soil hydrothermal responses in the Lake Chad region: Numerical investigation
No full textInternational audienceUnderstanding water dynamics under the effect of climatic conditions is important to improve water sustainability over the medium-and long-term. Clay content can affect soil hydrothermal properties, and hence modify water and heat exchange between soil and atmosphere, e.g. evapotranspiration and infiltration. This work aims to develop a numerical approach to explore the influence of clay content on soil hydrothermal response to the timely climatic conditions in the Lake Chad region, Sahel Region of west-central Africa. The meteorological information at the studied points, i.e. points A and B with a clay content of 8.3% and 25%, during the year 2008 is collected from ERA5-Land hourly data. The numerical results allow for understanding the effect of clay content on the hydrothermal response of the surface soil layer. Specifically, the soil surface temperature under point A is lower than that under point B during the dry season due to the dominant effect of heat conduction. However, the converse tendency is observed during the wet season because of the combined effect of heat conduction and latent heat. The variations of soil volumetric water content are closely related to the timely interaction between the soil and atmosphere, in addition to the hydrothermal properties of soil. Moreover, the outcomes of this work improve the understanding of the heat and water dynamics under the effect of climatic conditions and clay content, and provide further insights into the potential water protection in arid and semi-arid regions in the future
Improving analogues-based detection & attribution approaches for hurricanes
No full textInternational audienceThis paper presents a proof of concept for a new analogue-based framework for the detection and attribution of hurricane-related hazards. This framework addresses two important limitations of existing analogue-based methodologies: the lack of observed similar events, and the unsuitability of the distance metrics for hurricanes. To do so, we use a track-based metric, and we make use of synthetic tracks catalogues. We show that our method allows for selecting a sufficient number of suitable analogues, and we apply it to nine hurricane cases. Our analysis does not reveal any robust changes in wind hazards, translation speed, seasonality, or frequency over recent decades, consistent with current literature. This framework provides a reliable alternative to traditional analogue-based methods in the case of hurricanes, complementing and potentially enhancing efforts in addressing extreme weather event attribution
Demand-side strategies enable rapid and deep cuts in buildings and transport emissions to 2050
No full textInternational audienceDecarbonization of energy-using sectors is essential for tackling climate change. We use an ensemble of global integrated assessment models to assess CO2 emissions reduction potentials in buildings and transport, accounting for system interactions. We focus on three intervention strategies with distinct emphases: reducing or changing activity, improving technological efficiency and electrifying energy end use. We find that these strategies can reduce emissions by 51–85% in buildings and 37–91% in transport by 2050 relative to a current policies scenario (ranges indicate model variability). Electrification has the largest potential for direct emissions reductions in both sectors. Interactions between the policies and measures that comprise the three strategies have a modest overall effect on mitigation potentials. However, combining different strategies is strongly beneficial from an energy system perspective as lower electricity demand reduces the need for costly supply-side investments and infrastructure
Climate change and the global distribution of wealth
No full textInternational audienceWealth inequality dynamics influence economic and social outcomes and stability. While climate change and climate policies affect both physical capital and financial assets, their impacts on aggregate wealth and its distribution remain underexplored. Preliminary calculations suggest that climate change and climate investments could have substantial effects on wealth inequality, although the direction of these changes remains uncertain. This Perspective builds on numerical insights, outlines a conceptual framework and proposes a research agenda aimed at advancing the understanding of global wealth inequality under climate change, highlighting the need for interdisciplinary collaboration on the issue
