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Ground-breaking exoplanet science with the ANDES spectrograph at the ELT
No full textInternational audienceIn the past decade the study of exoplanet atmospheres at high-spectral resolution, via transmission/emission spectroscopy and cross-correlation techniques for atomic/molecular mapping, has become a powerful and consolidated methodology. The current limitation is the signal-to-noise ratio that one can obtain during a planetary transit, which is in turn ultimately limited by telescope size. This limitation will be overcome by ANDES, an optical and near-infrared high-resolution spectrograph for the Extremely Large Telescope, which is currently in Phase B development. ANDES will be a powerful transformational instrument for exoplanet science. It will enable the study of giant planet atmospheres, allowing not only an exquisite determination of atmospheric composition, but also the study of isotopic compositions, dynamics and weather patterns, mapping the planetary atmospheres and probing atmospheric formation and evolution models. The unprecedented angular resolution of ANDES, will also allow us to explore the initial conditions in which planets form in proto-planetary disks. The main science case of ANDES, however, is the study of small, rocky exoplanet atmospheres, including the potential for biomarker detections, and the ability to reach this science case is driving its instrumental design. Here we discuss our simulations and the observing strategies to achieve this specific science goal. Since ANDES will be operational at the same time as NASA's JWST and ESA's ARIEL missions, it will provide enormous synergies in the characterization of planetary atmospheres at high and low spectral resolution. Moreover, ANDES will be able to probe for the first time the atmospheres of several giant and small planets in reflected light. In particular, we show how ANDES will be able to unlock the reflected light atmospheric signal of a golden sample of nearby non-transiting habitable zone earth-sized planets within a few tenths of nights, a scientific objective that no other currently approved astronomical facility will be able to reach
Écoulements de suspensions fluide-particules dominés par la sédimentation
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“Bad” Oil, “Worse” Oil, and Carbon Misallocation
No full textInternational audienceNot all barrels of oil are created equal: their extraction varies in both private cost and carbon intensity. Leveraging a comprehensive micro-dataset on world oil fields, alongside detailed estimates of carbon intensities and private extraction costs, this study quantifies the additional emissions and costs from having extracted the “wrong” deposits. We do so by comparing historical deposit-level supplies to counterfactuals that factor in pollution costs, while keeping annual global consumption unchanged. Between 1992 and 2018, carbon misallocation amounted to at least 11.00 gigatons of CO2-equivalent (GtCO2eq), incurring an environmental cost evaluated at 2018). This translates into a significant supply-side ecological debt for major producers of high-carbon oil. Looking forward, we estimate the gains from making deposit-level extraction socially optimal at about 9.30 GtCO2eq, valued at $1.9 trillion, along a future aggregate demand pathway coherent with the objective of net-zero emissions in 2050, and document unequal reserve stranding across oil nations
Bilan des émissions de gaz à effet de serre (BEGES) d'un projet d'entrepôt urbain : Green Dock à Gennevilliers
No full textArticle to be published in the June 2025 issue of Transports-Infrastructures et Mobilité (TI&M) magazine and that will be subsequently submitted, in an updated English version, to a scientific journal. The study presented here examines an interesting but little-known aspect of the environmental impact of economic activities on territories: logistics, which consists of both the flow of goods and the buildings (warehouses) that organize these flows. With nearly 4,000 warehouses larger than 10,000 m² in France (Bayardin, 2024) and significant growth in their number over the past two decades, logistics real estate has become an important part of the economic and physical landscape of regions. The location of warehouses plays a very important role in the spatial organization of truck and van movements and the distances traveled. It has a significant impact on the modal choices of logistics operators, between a dominant road mode and rail, river, and intermodal modes, which are often cited as an obvious solution to the environmental crisis in freight transport. These various issues are discussed here through a case study of a logistics building project in the port of Gennevilliers in the Hauts-de-Seine department near Paris, a project that has several unique features (including its urban centrality and multi-story design), which are detailed below. The study focused on the project's greenhouse gas emissions (or carbon footprint), but we remind readers in the introduction and in the final discussion and conclusion section that there are other very important aspects of environmental impact when it comes to freight transport and logistics warehouses.Article à paraître dans le magazine Transports-Infrastructures et Mobilité (TI&M) de juin 2025 et qui sera soumis ultérieurement, dans une version anglaise et actualisée, dans une revue scientifique. L'étude présentée ici se penche sur un aspect intéressant mais peu connu de l'impact environnemental des activités économiques sur les territoires : celui de la logistique, constituée à la fois de flux de transport de marchandises et de bâtiments (les entrepôts) qui organisent ces flux. Avec près de 4 000 entrepôts de plus de 10 000 m 2 en France (Bayardin, 2024) et une croissance importante de leur nombre depuis une vingtaine d'années, l'immobilier logistique est devenu une dimension importante du paysage économique et physique des territoires. La localisation des entrepôts joue un rôle très important dans l'organisation spatiale des mouvements de camions et camionnettes et des distances parcourues. Elle joue un rôle non négligeable sur les choix modaux des logisticiens, entre un mode routier dominant et des modes ferroviaires, fluviaux et intermodaux invoqués très souvent comme une solution évidente à la crise environnementale des transports de fret. Ces différents sujets sont évoqués ici au travers d'un cas d'étude, celui d'un projet de bâtiment logistique sur le port de Gennevilliers dans le département des Hauts-de-Seine à proximité de Paris, projet qui présente plusieurs originalités (dont la centralité urbaine et le caractère multi-étages) qui sont détaillées ci-dessous. L'étude s'est concentrée sur le bilan des émissions de gaz à effet de serre (ou bilan carbone) du projet mais nous rappelons en introduction et dans la section finale de discussion et de conclusion que d'autres dimensions très importantes de l'impact environnemental existent lorsque sont concernés les transports de marchandises et les entrepôts logistiques
Spatial and Temporal Distribution of Tire & Road Wear Particles and Microplastics in an Urban Stream
No full textInternational audienceGreen stormwater systems play an important role in urban environments by providing ecosystem services, such as stormwater management, pollutant filtration, and habitat preservation (Sokolova et al., 2024). Among them, urban streams receiving stormwater runoff act as both pathways and sinks for contaminants. This study focuses on a green stormwater system fed by stormwater runoff and consisting of a settling pond connected to an urban stream located in Nantes, France. The objective of this work is to characterize the spatial and temporal distribution and retention characteristics of tire & road wear particles (TRWP) and microplastics. For the study, we collected bottom sediment samples along the green stormwater system that approximately measures 426 meters. We collected samples from the settling pond connected to the stream that receives stormwater from a singular stormwater runoff inlet. We then collected samples at approximately 72 meters, 170 meters, and, 349 meters respectively downstream from the inlet. TRWP concentration and specific microplastic polymers were quantified and identified by Pyrolysis-GC/MS. In addition to TRWP, the microplastics analyzed included polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), and polyethylene (PE). The results were interpreted by taking into account factors such as sediment composition (e.g., grain size, organic content), hydrodynamics and proximity to urban infrastructure influencing the transport and retention of these contaminants. Our findings demonstrate that although efficient, the urban stream’s capacity to retain TRWP and microplastics was variable. This study highlights the importance of urban streams as green stormwater systems that can mitigate particulate contaminant mobility while simultaneously underscoring their vulnerability to pollution from urban activities. Understanding the spatial and temporal distribution of TRWP and microplastics in urban streams is also highlighted as an important factor for informing targeted management strategies to enhance their ecological functions
Inadequacies in the representation of sub-seasonal phytoplankton dynamics in Earth system models
No full textInternational audienceSub-seasonal phytoplankton dynamics on timescales between 8 d and 3 months significantly contribute to annual fluctuations, making it essential to accurately represent this variability in ocean models to avoid distorting long-term trends. This study assesses the capability of Earth system models (ESMs) participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) to reproduce subseasonal surface ocean phytoplankton variations observed in ocean colour satellite data. Our findings reveal that, unlike sea surface temperature, all models struggle to accurately reproduce the total surface ocean phytoplankton variance and its decomposition across sub-seasonal, seasonal and multi-annual timescales. Over the historical period, some models strongly overestimate sub-seasonal variance and exaggerate its role in annual fluctuations, while others underestimate it. Our analysis suggests that underestimation of sub-seasonal variance is likely a consequence of the coarse horizontal resolution of CMIP6 models, which is insufficient to resolve mesoscale processes -a limitation potentially alleviated with higher-resolution models. Conversely, we suggest that the overestimation of sub-seasonal variance is potentially the consequence of intrinsic oscillations such as predator-prey oscillations in certain biogeochemical models. ESMs consistently show a reduction in variance at sub-seasonal and seasonal timescales during the 21st century under high-emission scenarios. The poor capability of CMIP6 models at simulating sub-seasonal chlorophyll dynamics casts doubt on their projections at these temporal scales and multi-annual timescales. This study underscores the need to enhance spatial resolution and constrain intrinsic biogeochemical oscillations to improve projections of ocean phytoplankton dynamics
A History of Ecological Economic Thought - Poster
No full textInternational audienceThis poster creatively showcases the results of a 3-year research into the history of ecological economics in the very long run, which has borne fruit with the publication of a monograph, 'A History of Ecological Economic Thought', in 2023 (Routledge). Prior to this publication, the literature had well examined the modern roots of ecological economics (e.g. Røpke 2004; Spash 2021) but except Joan Martinez Alier’s 1987 seminal book focusing on the history of energetics, very few contributions had explored the centuries-old roots of the field, i.e. the history of the substantial links between economic and natural-science knowledge, at times when sustainability, sometimes defined differently than today, was already under discussion. Alongside the well-known but hardly iconoclastic contributions of the Physiocrats, of the Classics and of early thinkers of resource scarcity and externalities (e.g. Jevons, Pigou, Hotelling), many authors – economists, naturalists and social theorists – actually did examine the relations between economic and natural dynamics in a inspiring way, by formulating proposals that have largely been forgotten. Those ideas, including Linnaeus’s economy of nature, Goethe’s natural philosophy, French and British sanitary reformism, Russian and Soviet ecology, Viennese late enlightenment, and American land economics, deserved to be rehabilitated to establish new landmarks in the history of ecological economics, and to find new sources of inspiration for 21st-century research agendas. The poster is composed of three parts: the upper part shows what “ecological economic thought” is; the central part provides a graphic and creative presentation of the various episodes covered by the book with portraits of (male and female) economists and ecologists who contributed to this history; the lower part highlights cross-cutting lessons for today’s research in ecological economics, post-growth, and degrowth studies, and future lines of research. The poster, and the book (https://www.routledge.com/9781032310749), are particularly suited for use in classrooms
Waterfall-Borůvka based algorithm for binary partition tree
No full textInternational audienceThis article presents an algorithm to construct the binary partition tree by altitude ordering based on Borůvka's minimum spanning tree strategy. The binary partition tree by altitude ordering is a data structure to represent an image in the form of a hierarchy of segmentations that is widely used in mathematical morphology processing. Recently, the authors of PANDORA \cite{Sao2024} have proposed a novel parallel algorithm for computing single linkage clustering from the minimum spanning tree of a point cloud on a GPU. In this article, we show that their method can indeed be nicely cast in the framework of watershed cuts and waterfalls for computing the binary partition tree by altitude ordering. More precisely, the method consists of performing a sequence of watershed cuts-basins contractions, seen as a variant of Borůvka's algorithm with a complexity of , followed by a dedicated post-processing. Furthermore, we show that this algorithm can be extended to process any edge weighted graphs and not only minimum-spanning trees. These results open a new path towards massively parallel algorithms for hierarchical watershed algorithms
Aligning Competitiveness and Sustainability: How Border Adjustments Can Strengthen the EU’s Agricultural Policy
No full textPublication parue dans la note EUTAX observatory Mars 2025EU policies promoting higher environmental standards in agriculture are often perceived as a challenge to the sector’s economic competitiveness. However, well-designed policies can align the EU’s environmental and economic goals, fostering sustainable and inclusive growth. This policy note examines the case of pesticide-reduction targets and finds that competitiveness trade-offs can be mitigated through complementary trade measures. Our analysis highlights that 44% of pesticide use embedded in EU agricultural consumption comes from imports, despite them representing only 16% of the consumption. Particularly striking, a substantial amount of the pesticide use embedded in imports is represented by banned pesticides, exposing a blind spot in current trade policies. Without appropriate safeguards, stricter EU pesticide regulations can shift production to less-regulated markets, undermining global pesticide reduction efforts while disadvantaging EU agriculture. Analysing the potential for policy solutions, we consider different border-adjustment mechanisms, drawing parallels with the Carbon Border Adjustment Mechanism (CBAM). Our findings indicate that such measures preserve EU agricultural competitiveness without compromising on environmental ambition. Aligning trade and environmental policies is therefore not only feasible but essential for effectively reducing global pesticide use while safeguarding EU agriculture
Sequential combination of micro-FTIR imaging spectroscopy and pyrolysis-GC/MS for microplastic quantification. Application to river sediments
No full textInternational audienceSeveral studies have focused on quantifying microplastics (MP) in the environment using μ-FTIR and Py-GC/MS, the most common analytical methods. However, their application to complex matrices like sediments is affected by interferences specific to each method. In this study, we developed a protocol combining μ-FTIR and Py-GC/MS for sequential analysis of MP (10–500 μm) in 16 river sediment samples, targeting PE, PP, and PS polymers. Mass concentrations were estimated from the particle volume in μ-FTIR and measured directly by Py-GC/MS using internal calibration. Results show consistency between the two methods across different sites, with variability of two orders of magnitude in concentration ranges from 0.3 to 50 items g−1 and 0.2 to 17 μg g−1 for μ-FTIR, and 0.8 to 21 μg g−1 for Py-GC/MS. Replicate analyses (2 to 6 per site) revealed that intra-site variability was mainly influenced by sample preparation and, to a lesser extent, by the measurement technique. While estimated and measured concentrations were similar, discrepancies were observed in polymer proportions: PP predominated in μ-FTIR, while PS was more prevalent in Py-GC/MS. These differences are explained by the specific limitations of each method, especially the limited detection of synthetic fibres and tyre or road abrasion particles by μ-FTIR, which are detected as MP by Py-GC/MS. This comparative study provides recommendations for evaluating compatibility between studies using either technique and offers guidelines for selecting the most appropriate method based on research interests