HAL-Ecole des Ponts ParisTech
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Identifying and Quantifying the Impact of Climatic and Non‐Climatic Drivers on River Discharge in Europe
No full textInternational audienceOur water resources have changed over the last century through a combination of water management evolution and climate change. Understanding and decomposing the drivers of discharge changes is essential to preparing and planning adaptive strategies. To separate the response of catchment dynamics between climate change‐related and other factors in discharge observations, we propose a methodology to compare discharge observations to discharge from a physically based model. The novelty lies in the fact that, to keep the comparison pertinent despite systematic biases in physically based model outputs, we compare both systems using a common framework of interpretation, a parsimonious model, which allows us to isolate trends in catchment dynamics from trends due to average changes in annual climate variables. The modeled system stands as the reference to reproduce changes only due to evolving climate dynamics. Comparing it to the interpretation framework applied to the observation system highlights the effect of the non‐modeled factors on catchment dynamics and discharge, such as human intervention in rivers and water uptakes. We show that over Europe, especially in the South, the dominant explanations for discharge trends are non‐climatic factors. Still, in some catchments of Northern Europe, climate change seems to be the dominating driver of change. We hypothesize that the dominating non‐climatic factors are irrigation development, groundwater pumping and other human water usage. These results show the importance of including non‐climatic factors in physically based models to understand the main drivers of discharge better and accurately project future changes
Léon Lalanne: Un ingénieur entre la science, la politique et l'industrie au XIXe siècle [Léon Lalanne: An engineer between science, politics and industry in the nineteenth century] ed. by François Jarrige (review)
No full textInternational audienc
Pricing in markets without money: Theory and evidence from home exchanges
No full textA growing number of markets use token money instead of real money to allocate resources such as class seats, food donations or holiday homes. Agents earn token money by supplying and can only spend tokens by consuming within the system. A platform decides how to set goods’ token prices. Should it i) clear the market, as assumed in canonical competitive equilibrium frameworks, or ii) compress prices and ration excess demand? I characterize in a two-type, two-period model under which conditions compressing prices increases supply and utilitarian welfare. Intuitively, this is possible when income effects are strong—because agents are easily satiated with tokens—and participation effects are weak. I confirm the model’s predictions on a large home exchange platform, combining proprietary data on the universe of transactions with natural experiments. I find that income effects are large empirically and that a reform that reduced the price of attractive homes increased their supply and did not reduce participation. I show that many users have a strong preference against for-money platforms, allowing the exchange platform to set non-market-clearing prices. Broader insights are that lessons from traditional markets may not easily extend to token economies and that market designs without real money can have advantages even in settings where money is common
A fresh look at the pre-industrial air–sea carbon flux using the alkalinity budget
No full textInternational audienceAbstract. Disparities between observational and model-based estimates of the ocean carbon sink persist, highlighting the need for improved understanding and methodologies to reconcile differences in both magnitude and trends over recent decades. A potential key source of uncertainty lies in the pre-industrial air–sea carbon flux, which is essential for isolating the anthropogenic component from observations. This flux, thought to result globally from an imbalance between riverine discharge and sediment burial of carbon, remains highly uncertain, limiting the confidence in impactful applications such as the Global Carbon Budget (GCB). In this study, we present a new theoretical framework that enables direct estimation of the riverine/burial-driven pre-industrial carbon outgassing using both carbon and alkalinity budgets. This approach is validated with a series of ocean biogeochemical simulations, which also highlight the main factors influencing its regional distribution. We then demonstrate the utility of the framework through two proof-of-concept applications. The first revisits the pre-industrial riverine/burial-driven air–sea carbon flux using existing carbon and alkalinity budgets, offering a simple method for reassessment as these budgets are updated. The second application leverages sensitivity simulations to construct a composite simulated estimate that aligns with both carbon and alkalinity budgets to assess the regional distribution of the pre-industrial riverine/burial-driven air–sea carbon flux. This approach is well suited for model intercomparisons, enabling an efficient reassessment of regional flux patterns and helping to reduce biases related to ocean model physics or biogeochemical parameterizations
The causal impact of children? Rethinking the identification and estimation of child penalties
No full textA fast-growing literature estimates child penalties -the impact of parenthood on the labor market outcomes of mothers relative to fathers -using event study design. This paper clarifies the identification assumption underlying the most commonly used specification with event time, year, and age fixed effects, and shows that this approach is prone to bias in the presence of heterogeneity by age and calendar year, even under valid identification. I then propose an unbiased estimator, using the same identification framework. Applied to French administrative data, my estimates for mothers are 27% smaller than those using the standard approach. The paper also discusses identification under an alternative parallel trend assumption, that is, when controlling for individual unobserved heterogeneity, and highlights key trade-offs in defining counterfactuals, as one cannot simultaneously absorb individual heterogeneity, age, age at birth, and event time. I provide a framework to build an estimator step-by-step, which is easily adaptable depending on which comparisons researchers assess most appropriate. Finally, I document substantial heterogeneity by age at childbirth for both mothers and fathers. By eight years after the birth of their first child, mothers aged 20-25 at birth lose 50% compared to their counterfactual earnings, compared to 12-20% for older mothers. Fathers aged 20-25 at first birth earn on average 26% less eight years later, while effects for older fathers are close to zero. These findings have important implications for both policy and applied research using event study designs to estimate the causal impact of children
Eliciting preferences for well-being measurement: A comparison of methods
No full textThe elicitation of willingness to pay remains a serious empirical challenge. Such elicitation is important for cost-benet analysis. It is also central to the estimation of equivalent income, a multidimensional measure of well-being that respects individual preferences by adjusting income to incorporate an individual's willingness to pay to achieve a reference level in non-income dimensions. In this paper, we test four different preference elicitation methods with an online survey of almost 2,000 French respondents. Our experimental design allows us to compare both between-and within-respondent variations in willingness to pay and equivalent income. In addition, we consider two non-income dimensions: health and social interactions, the latter of which has been relatively neglected in welfare economics literature. We find large dierences between the elicited values across methods and dimensions
Hybrid Si/III-V quantum cascade lasers integrated on a phase-matched mid-infrared silicon photonic platform
No full textInternational audienceThe increasing demand for mid-infrared (MIR) photonic integrated devices in spectroscopic applications has driven the development of essential building blocks for chemical sensing, including quantum cascade lasers (QCLs), MIR silicon photonic platforms and integrated detectors. A fully integrated MIR silicon photonic chip would enable cost-effective mass production using CMOS-compatible fabrication, paving the way for consumer-grade MIR devices and large-scale onsite sensing applications. However, the integration of QCLs with MIR silicon platforms remains a major challenge due to inefficient optical coupling between the III-V active region and silicon waveguides, leading to high insertion losses and reduced device performance. In this work, we demonstrate the heterogeneous integration of a QCL onto a believed to be novel high-index-contrast, phase-matched silicon on nitride on insulator (SONOI) photonic platform using molecular bonding. By leveraging a phase-matching condition, we implement an adiabatic coupling scheme that ensures efficient optical power transfer from the III-V active region to the silicon waveguides, overcoming a key limitation of previous approaches. The resulting hybrid distributed-feedback (DFB) QCL exhibits single-mode emission at 4.315 µm and operates in pulsed mode up to 72 °C. This advancement opens new possibilities for fully integrated MIR photonic circuits, with potential applications in environmental monitoring, biomedical diagnostics, and industrial sensing
A methodology for stock assessment and traceability at the component level: the case of structural steel reuse
No full textInternational audienceTo reduce the environmental burden of the construction industry, reusing reclaimed steel instead of recycling it is seen as a promising option to move the structural steel industry towards a more circular economy. Assessing the material composition of the built environement is key to develop efficient circular stategies. Reliable sectorial data is required, per material type. This paper unvails the potentials of using first-hand construction documents to assess material stocks of structural steel within existing industrial buildings. It integrates into a bottom-up Material Flow Analysis (MFA) framework. A component-based archetype of an industrial steel structure is defined and its material composition is calibrated thanks to construction documents of built structures. The accuracy of stock evaluation will depend on the number and the variety of buildings available in the dataset. Data extraction from the available construction documents is still ongoing. Yet, the proposed method provides valuable insights on the potentials of construction document-based archetypes. As for future reuse strategies, leveraging such documentation is also interesting to ensure the traceability of today’s buildings. This paper explores the opportunities offered by construction documents in relation with state-of-the-art methods that aims at designing structures from reclaimed elements. Shipping lists are identified as highly relevant to inform decision-making on future reuse alternatives
Dynamique des microplastiques à l’exutoire d’un bassin versant périurbain : Effet des conditions hydrologiques et des événements extrêmes de crue
No full textInternational audienceÉtant donné l'intensification des crues liée au changement climatique, une compréhension fine de la dynamique temporelle des MPs dans les rivières est nécessaire afin d'estimer plus précisément les flux et leur contribution à la contamination plastique. La compréhension de l'influence des variations hydrologiques sur cette pollution reste encore limitée, en particulier en temps de crue. L’une des causes est liée au fait que l'échantillonnage est généralement réalisé avant et après l'événement pour des raisons pratiques, négligeant ainsi la montée de la crue et la décrue. Pour combler cette lacune, une vaste campagne d'échantillonnage a été menée le long d’une année hydrologique dans un petit bassin versant périurbain (Avenelles, 45 km², site de l’observatoire ORACLE). La campagne couvre à la fois les périodes de hautes et basses eaux et plusieurs crues dont un événement extrême (65 mm de pluie en 48 heures) suivi dans sa totalité (18 échantillons). L'échantillonnage des microplastiques (MPs) a été réalisé à l'aide d'un système de pompage couplé à une filtration in-situ (10 µm). Les analyses ont été effectuées par microspectroscopie infrarouge à transformée de Fourier (µ-IRTF). En parallèle les matières en suspension (MES) ont été mesurées. Au cours de la période de suivi, les concentrations et les flux de MPs ont montré une variabilité significative en réponse aux conditions hydrologiques. À l'échelle saisonnière, la concentration médiane de MPs pendant les périodes de basses eaux est environ dix fois plus faible (valeur médiane = 666 MPs m⁻³, n = 11) que celle observée lors des périodes de hautes eaux (valeur médiane = 6136 MPs m⁻³, n = 19). Lors d'un événement de crue, les concentrations ont atteint un pic à 32 941 MPs m⁻³ (21 576 MPs s⁻¹), soulignant la forte l'influence des conditions hydrodynamiques sur le transport des MPs. Ces résultats ont été confirmés par l'événement de crue extrême avec des concentrations et des flux de MPs qui ont considérablement augmenté entre les niveaux pré-crue (669 MPs m⁻³ et 398 MPs s⁻¹) et le pic de crue (10 804 MPs m⁻³ et 56 181 MPs s⁻¹). Quatre jours après le pic, les concentrations sont revenues aux niveaux pré-crue (977 MPs m⁻³ et 479 MPs s⁻¹). De plus, les concentrations de MPs et les MES ont suivi une tendance similaire indiquant que le comportement de ces paramètres sont liés. Ces résultats soulignent l'importance de considérer l'ensemble des conditions hydrologiques lors de l'évaluation du transport et de la dynamique des MPs. En effet, ce suivi fin a permis de démontrer un rôle majeur des événements de crue dans le transfert des microplastiques dans les cours d’eau
