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Getting Around the Issue of the “Carbon Tax”
No full textInternational audienceWhen thinking about the genesis of the Citizens' Convention for Climate, one must inevitably think of its connection to the “Gilets jaunes” social movement, which was triggered in October 2018 by a rejection of the rise in fuel tax that the French government were intending to bring in. This chapter describes and analyzes the shift in the citizens' stance on taxing fuel. It shows how the members rapidly turned against the idea of a carbon tax and developed a range of different measures to limit vehicular carbon dioxide (CO 2 ) emissions. In parallel to their examination of the carbon tax, the citizens mused about the notion of social justice, which was part of the official mandate. After an initial rejection of the idea of carbon taxation, the citizens went in search of substitute measures, so the matter of taxation was not off the table
Contester les projets olympiques en Seine-Saint-Denis.Une coproduction des connaissances face à l’urbanisme événementiel ?
No full textInternational audienceSince 2017, in Seine-Saint-Denis (France), the Comité de Vigilance JO 2024 has been mobilizing residents, associations, and researchers to challenge the urban projects linked to the Paris 2024 Olympic and Paralympic Games. Faced with the transformations imposed by this event-driven urban planning, the collective has been developing forms of counter-expertise with residents and citizens, such as territorial analysis, pleas, and alternative projects. The aim was to document the social and environmental effects of these developments and to call for local needs to be better taken into account. This paper explores the processes of co-production of knowledge between residents, activists, professionals, and researchers, aimed at building an audible and credible alternative account of the Olympic projects, informing public opinion, and challenging public and private organizations. By exploring the epistemic dimension of this mobilization, the objective of this research is to understand how collective knowledge, rooted in local experience, can influence the urban fabric in the context of mega-events and strengthen people’s ability to cope with current socio-spatial and environmental challenges.Depuis 2017, le Comité de vigilance JO 2024 à Saint-Denis mobilise habitant·es, associations et chercheur·es pour contester les projets urbains liés aux Jeux olympiques et paralympiques de Paris 2024. Face aux transformations imposées par cet urbanisme événementiel, le collectif élabore des contre-expertises habitantes et citoyennes – diagnostics, plaidoyers et projets alternatifs – pour documenter les effets sociaux et environnementaux de ces aménagements et demander une meilleure prise en compte des besoins locaux. Cet article analyse le processus de coproduction des savoirs entre habitant·es, militant·es, professionnel·les et chercheur·es visant à construire un récit alternatif audible et crédible des projets olympiques, à informer l’opinion publique et à interpeller les institutions. En explorant la dimension épistémique de cette mobilisation, il s’agit de comprendre comment des savoirs collectifs, ancrés dans l’expérience locale, peuvent influencer la fabrique urbaine dans un contexte de méga-événements et renforcer la capacité des populations à faire face aux défis socio-spatiaux et environnementaux actuels
Attribution of the 2025 Mediterranean Marine Heatwave to Climate Change Using Analogues
No full textInternational audienceThe Mediterranean Sea experienced a record-breaking marine heatwave in 2025, raising questions about the influence of human-induced climate change. Using an analogue-based attribution approach, we compared historical sea surface temperature (SST) patterns from ERA5 reanalysis (1950-2024) to those observed during the event. By identifying the most similar SST anomaly patterns in a past period (1950-1986) and a more recent one (1987-2024), we assessed changes in SST and related atmospheric variables. We find that, under present day climate conditions, analogous patterns result in significantly higher SST anomalies and stronger atmospheric responses-such as warmer near-surface air temperatures and intensified radiative fluxes-compared to the past.Statistical tests confirm that long-term warming trend has amplified Mediterranean SST extremes by up to 1.5°C and associated heat exchange processes, though shifts in large-scale natural climate variability may also influence these outcomes, complicating attribution. Nonetheless, the dominant contribution to the 2025 marine heatwave severity is attributable to anthropogenic forcing. This study proves the effectiveness of the analogue method for assessing extreme events, also including marine heatwaves, in a warming Mediterranean context
The implied volatility surface (also) is path-dependent
No full textWe propose a new model for the forecasting of both the implied volatility surfaces and the underlying asset price. In the spirit of Guyon and Lekeufack (2023) who are interested in the dependence of volatility indices (e.g. the VIX) on the paths of the associated equity indices (e.g. the S&P 500), we first study how vanilla options implied volatility can be predicted using the past trajectory of the underlying asset price. Our empirical study reveals that a large part of the movements of the at-the-money-forward implied volatility for up to two years time-to-maturities can be explained using the past returns and their squares. Moreover, we show that this feedback effect gets weaker when the time-to-maturity increases. Building on this new stylized fact, we fit to historical data a parsimonious version of the SSVI parameterization (Gatheral and Jacquier, 2014) of the implied volatility surface relying on only four parameters and show that the two parameters ruling the at-the-money-forward implied volatility as a function of the time-to-maturity exhibit a path-dependent behavior with respect to the underlying asset price. Finally, we propose a model for the joint dynamics of the implied volatility surface and the underlying asset price. The latter is modelled using a variant of the path-dependent volatility model of Guyon and Lekeufack and the former is obtained by adding a feedback effect of the underlying asset price onto the two parameters ruling the at-the-money-forward implied volatility in the parsimonious SSVI parameterization and by specifying Ornstein-Uhlenbeck processes for the residuals of these two parameters and Jacobi processes for the two other parameters. Thanks to this model, we are able to simulate highly realistic paths of implied volatility surfaces that are free from static arbitrage
A Room of One's Own. Work from Home and the Gendered Allocation of Time
No full textThe traditional specialization of men in paid work and women in unpaid work is rooted in the spatial separation of these activities. We examine the possible consequences of the recent expansion of Work from Home (WfH) for the gendered allocation of time. We focus on the time devoted to housework by men and women who work from home versus on site, before and after the Covid pandemic. Using data on several thousand workers drawn from the American Time Use Survey, we find that the gender gap in unpaid work has declined by about 27 minutes per day, i.e. by about 40%, for remote workers. Among remote workers, women now spend more time on paid work and less on unpaid work, whereas men spend a little more time on household chores. These results are driven by partnered respondents, with children under 10 years of age
From social to ‘affordable’. The financialization of publicly subsidised housing in France
No full textInternational audienc
A Statistical Study of Local Dust Storm Occurrences on Mars Using the 2.77 μm CO 2 Band Observed by OMEGA/Mars Express
No full textInternational audienceLocal Dust Storms (LDS) are defined as dust storm phenomena that cover an area smaller than 1.6 × 10 6 km 2 or persist for less than three sols. The study of LDS is critical for understanding dust transport processes in both horizontal and vertical directions and the evolution of large‐scale dust storms on Mars. However, the relatively small scale and short lifetime make it difficult to detect with previous studies. OMEGA onboard Mars Express (MEx) has conducted spectroscopic measurements with high spatial resolution (up to ∼400 m/pixel). Here, we present a method to retrieve dust optical depth and detect LDS using the 2.77 μm CO 2 absorption band. At this wavelength, photons are absorbed before reaching the surface, and the photons collected by OMEGA have been scattered around 20–30 km altitude by dust. We have detected 146 LDS events from the retrieved dust optical depth in MY27‐29. The LDS were generally observed in the southern summer season, while frequent occurrences of LDS were observed during the northern summer (Ls = 130°–150°) in MY27. The remarkable increase in LDS is also identified just before the global dust storm in MY28. We found a peak in the probability of LDS around noon in both seasons, Ls = 0°–180° and Ls = 180°–360°. In Ls = 0°–180°, high probability areas are found only in specific regions, such as Chryse Planitia. The probability areas expands over a wide range, except high‐latitude north of 40°N in Ls = 180°–360°. These findings highlight the spatiotemporal roles LDS play in dust transport, providing insights into the dust cycle (245/250 words)
Investigating Martian Meteoric Metal Variability Through the Intercomparison of MAVEN/NGIMS Deep Dip Data and PCM-Mars Simulations.
No full textInternational audienceIn 2014, NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) satellite made the first direct atmospheric measurements of planetary meteoric metals beyond Earth. A persistent layer of Mg+ was observed at ~90 km via the remote sensing of the Mg+ dayglow emission at 280 nm using MAVEN’s Imaging Ultraviolet Spectrograph (IUVS). This was first reported by Crismani et al. (2017) and the observed variability of the Mg+ layer was investigated by Crismani et al. (2023). Metallic species are injected into the Martian upper atmosphere via meteoric ablation, where the constituents of interplanetary dust particles (IDPs) are heated by thermal collisions and injected as metallic vapours. Ablation starts to occur at altitudes where the pressure is ~1 μbar and so the altitude of the Mg+ layer exhibits seasonal variability due to changes in the aerobraking altitude. On Mars the atmospheric density varies significantly over the Martian year due to the sublimation and deposition of CO2 at the polar caps.The MAVEN mission has included nine ‘Deep Dip’ campaigns in which the altitude of the spacecraft was lowered from its nominal altitude range of 150-500 km to include altitudes as low as 125 km. The timing and locations of these week-long campaigns were designed such that measurements could be made over a variety of local times, longitudes, latitudes, and solar longitudes. These Deep Dip campaigns offer the unique opportunity to make in situ measurements of meteoric metal species using the Neutral Gas and Ion Mass Spectrometer (NGIMS) instrument. NGIMS has measured a variety of meteoric metal ions including Mg+, Fe+, and Na+. This study investigates the diurnal, seasonal, and latitudinal variability of these metallic species through an intercomparison of NGIMS Deep Dip data and Laboratoire de Météorologie Dynamique (LMD) Mars Planetary Climate Model (PCM) simulations. The PCM-Mars is a 3D numerical model which simulates the Martian atmosphere from the surface to the exobase modelling temperatures, dust, winds, and photochemistry, as well as neutral and ion-molecule chemical reactions. The Leeds Chemical Ablation Model (CABMOD) of Vondrak et al. (2008) and the Meteoric Input Function (MIF) of Carrillo-Sanchez et al. (2022) have been used to simulate the injection of these metallic vapours and a full chemistry scheme of Mg, Fe, and Na reactions has been incorporated into the PCM-Mars.Examination of the NGIMS data has shown anomalous metallic isotopic ratio values, highlighting how it is important to be cautious when analysing this data. To ensure reliable profiles are extracted from the Deep Dip dataset, this work implements a data filter which identifies orbits in which the expected isotopic ratios are observed. Generally, metals with higher atomic masses and orbits during night-time hours provide more reliable data. This intercomparison of NGIMS Deep Dip data and PCM-Mars simulations with metal chemistry is integral to constraining global models and understanding the forces driving variability in the metal layers of the Martian upper atmosphere
Enfanter. Natalité, démographie et politiques publiques
No full textInternational audienceLa question de l’enfantement connaît actuellement de profondes transformations. Alors que la tendance est au déclin de la natalité dans une grande partie du monde, le désir d’enfant de certains couples hétérosexuels et de même sexe fait appel, en Europe comme en Chine ou en Inde, à des procédures multiples allant de l’adoption aux innovations technologiques d’aide médicale à la procréation et même de gestation pour autrui. Dans quelles conditions ces projets d’enfantement se réalisent-ils ?Puis, lorsque l’enfant paraît, que sait-on des transformations de la parentalité ? La conciliation avec le travail et ses nouvelles modalités se pose-t-elle encore différemment pour les pères et les mères ? L’autorité parentale est-elle remise en cause ? Et pourquoi la République populaire de Chine essaie-t-elle actuellement de réglementer la parentalité sur un mode ” scientifique ” ?Les dix contributions originales réunies dans cet ouvrage éclairent ces questions actuelles, à l’aide des outils des sciences sociales.Avec des contributions de : Marie-Caroline Compans, Romain Delès, Lynda Gaudemard, Estelle Herbaut, Renyou Hou, Anne Lambert, Manon Laurent, Mickael Melki, Jean-François Mignot et Marie Trespeuch