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January 20, 2026

Entretien annuel : le danger du marketing de soi

Source: The Conversation – France (in French) – By George Kassar, Full-time Faculty, Research Associate, Ascencia Business School

L’effet Dunning-Kruger caractérise cette tendance : les moins compétents surestiment leurs capacités tandis que les plus compétents se montrent plus prudents dans leur jugement. StockHolm/Shutterstock

Nous sommes bel et bien en janvier. Le mois du blanc est surtout celui du grand théâtre des entretiens d’évaluation individuelle de performance dans bien des entreprises. Alors, comment les cadrer au mieux pour distinguer les salariés qui se mettent en scène de ceux qui créent réellement de la valeur, mais sous-estiment leur capacités ?

L’entretien annuel de performance est devenu un passage obligé dans la plupart des organisations. Il ne s’agit pas d’une simple discussion informelle, mais d’un moment qui pèse sur les primes, les promotions ou les opportunités de carrière. Très différent des entretiens de parcours professionnels qui sont une obligation légale, les salariés y voient un verdict sur leur année ; les managers doivent trancher, classer, justifier. La pression est forte des deux côtés de la table.

Dans ce contexte tendu, le collaborateur entre, armé de son powerpoint mental avec ses objectifs atteints, ses initiatives personnelles ou son leadership exemplaire. Le manager, lui, soucieux de préserver l’éthique dans ce processus, coche des cases, écoute poliment et note des mots-clés : confiance, dynamisme, vision, etc. Tout semble sérieux, objectif, quantifié. En réalité, la scène tient parfois plus du théâtre qu’une vraie application scientifique de la gestion de la performance.

De ce fait, ces entretiens, pourtant censés évaluer les résultats concrets, finissent souvent par mesurer autre chose, celle de la capacité à se vendre. Ce glissement ne serait qu’un détail s’il n’avait pas de conséquences bien réelles sur la motivation et la rétention des « talents ».

Quand la confiance se déguise en compétence

Durant le mois de janvier, un paradoxe managérial devient presque une tradition. Ceux qui maîtrisent tout juste leur sujet arrivent sûrs d’eux, brandissant leurs « grandes réussites » et occupent l’espace. Les vrais compétents, eux, minimisent leurs exploits, soulignent ce qui reste à améliorer… et passent sous le radar. Résultat : on récompense ceux qui parlent le plus fort, pas forcément ceux qui contribuent le plus. On s’étonne ensuite de voir les meilleurs partir.

Le phénomène a un nom : l’effet Dunning-Kruger. Décrit dès 1999 par les psychologues David Dunning et Justin Kruger, il désigne la tendance des moins compétents à surestimer leurs capacités tandis que les plus compétents se montrent plus prudents dans leur jugement.

Les études contemporaines confirment que ce biais ne s’arrête pas à la salle de classe, au laboratoire ou même sur le champ. Transposé au bureau, ce syndrome donne une situation paradoxale : plus on est limité, plus on risque de se croire excellent, plus on est bon, plus on doute et plus on voit ce qui pourrait être mieux.

Marketing de soi-même

Si le manager ne s’appuie que sur le discours tenu pendant l’entretien, sans preuves solides, il a toutes les chances de se laisser influencer par cette confiance parfois mal placée. L’aisance orale, la capacité à « vendre » un projet ou à reformuler ses tâches en succès stratégiques deviennent des critères implicites d’évaluation.

Cette surestimation omniprésente pourrait entraîner de graves atteintes au bon jugement professionnel. Elle déforme la perception des compétences réelles et favorisent une culture d’apparence plutôt qu’une culture de résultats.

Les vrais performants, souvent modestes, finissent par comprendre que la reconnaissance interne ne récompense pas les résultats et l’impact de leur travail, mais le récit qu’on en fait et la capacité à se mettre en scène.

Ces derniers peuvent ressentir un décalage entre ce qu’ils apportent réellement et ce que l’organisation valorise. Leur engagement s’érode, leur créativité aussi. Ce qui est un facteur bien documenté de démotivation et de départ.

Le plus ironique ? Ceux qui doutent d’eux-mêmes sont souvent ceux qu’on aimerait garder. Les études sur la métacognition montrent que la capacité à se remettre en question est un signe de compétence. À l’inverse, les plus sûrs n’évoluent pas. Persuadés d’avoir déjà tout compris, ils s’enferment dans leur propre suffisance durable.

L’entreprise perd, dans le silence, celles et ceux qui faisaient avancer les projets les plus exigeants et les plus sensibles. Elle garde ceux qui savent surtout parler de leurs succès.

Cadrer l’évaluation sur des faits

La bonne nouvelle est qu’il est possible de corriger cette dérive. Les pistes sont connues mais rarement appliquées.

Tout commence par un bon cadre pour la mise en place de l’évaluation de la performance. Une formation adaptée aux managers, évaluateurs et collaborateurs est encouragée, avec un système de revue fréquente de la performance, un dispositif de mesure clairement défini et un groupe d’évaluateurs multiples.

Il est important de fonder les évaluations sur des faits en revenant à des concepts fondamentaux tels que le management by objectives (MBO). L’enjeu : définir des objectifs clairs, mesurables, ambitieux mais réalistes, suivi à l’aide d’indicateurs alignés sur l’impact réel, avec une stratégie de mesure fondée sur les données pour évaluer des résultats concrets, et pas seulement le récit de la personne évaluée.

L’avis d’un seul manager ne devrait pas suffire à juger la performance d’une personne qui travaille en équipe. Il faut regarder sa contribution au collectif.

Les dispositifs de « feed-back à 360° » permettent de diversifier les retours
– collègues, clients, revues de projets, etc. Quand plusieurs personnes confirment la contribution d’un collaborateur discret, il devient plus difficile de l’ignorer. À l’inverse, un profil très visible mais peu fiable sera plus vite repéré.

Distinguer assurance et compétence

Il est important de garder à l’esprit que la gestion de la performance est un processus social. Les recherches montrent que le feed-back formel, donné lors de l’entretien annuel, est bien plus efficace lorsqu’il est soutenu par un feed-back informel et des échanges réguliers. Ces discussions spontanées renforcent la confiance et créent le contexte nécessaire pour que l’évaluation finale soit juste, non biaisée, acceptée et réellement utile.

Il est essentiel de former les managers à mieux reconnaître et anticiper les biais cognitifs, en particulier ceux du jugement, dont le fameux décalage entre confiance affichée et compétence réelle. Comprendre que l’assurance n’est pas une preuve en soi, et que la prudence peut être le signe d’une réelle expertise, change la manière de conduire un entretien.

Tant que les entreprises confondront assurance et compétence, elles continueront à promouvoir les plus confiants et à perdre, peu à peu, leurs meilleurs éléments.

Dans un marché où les talents ont le choix, ce biais n’est pas qu’un détail psychologique : mais un véritable risque stratégique. Après tout, ceux qui parlent le plus fort ne sont pas toujours ceux qu’il faudrait écouter !

George Kassar ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d’une organisation qui pourrait tirer profit de cet article, et n’a déclaré aucune autre affiliation que son organisme de recherche.

– ref. Entretien annuel : le danger du marketing de soi – https://theconversation.com/entretien-annuel-le-danger-du-marketing-de-soi-271897

January 20, 2026

Opera is not dying – but it needs a second act for the streaming era

Source: The Conversation – USA (2) – By Christos Makridis, Associate Research Professor of Information Systems, Arizona State University; Institute for Humane Studies

American soprano Renee Fleming performs at a dress rehearsal for a Metropolitan Opera production of ‘The Merry Widow’ in New York in 2014. Jack Vartoogian/Getty Images

Every few years, you’ll hear a familiar refrain: “Opera is dying.”

National surveys point to slumping attendance at live performances. Audiences are aging, leaving fewer fans to fill seats at productions of “La Bohème,” “Carmen,” “The Magic Flute” and the like, while production costs grow.

I’m a labor economist who studies the economics of art and culture. To
assess the state of opera in the U.S., I analyzed financial data collected by Opera America, an association whose roughly 600 members are overwhelmingly nonprofit opera companies.

After crunching the numbers, as I explained in a 2026 paper published in the Journal of Arts Management, Law, and Society, I reached a surprising conclusion about the state of those nonprofits.

Funding model is faltering

Although opera companies are experiencing financial stress, opera isn’t a dying art form. Instead, I found that the public’s demand for meaningful, live cultural experiences – including opera – remains strong.

That said, opera’s traditional business model is faltering.

Opera is, for the most part, stuck in the past. Many companies still depend on a business model that relies on season ticket sales and a small circle of big donors. This approach worked better in the 20th century than it does now.

Few opera companies have embraced strategies the rest of the entertainment industry regularly uses: audience data analysis, experimentation with digital content and streaming, and engagement through online platforms rather than brochures.

In other words, opera management practices, metrics and audience development tactics didn’t change much even as the world transitioned into the digital age.

Change is needed because subscriptions and individual ticket sales have declined for many companies, especially those with budgets above US$1 million.

The number of opera tickets those companies sold fell 21% between 2019 and 2023. Ticket revenue fell 22% over the same period.

Meanwhile, opera companies received 19% of their budgets from donations and grants in 2023, down from roughly 25% in 2019, as earned revenue weakened and fundraising failed to fully recover.

Opera companies receive more than twice as much funding from philanthropy as from government sources. Government support was low and relatively stable prior to 2020 and rose sharply during the first two years of the COVID-19 pandemic before declining again to roughly 8% of operating revenue by 2023.

A couple reads program notes in a theater. — Many audience members at operas skew older.
Robert Nickelsberg/Getty Images

Managing institutions in trouble

I don’t dispute that opera’s economic woes are troubling. But I don’t see them as a sign that this art form is in cultural decline. Instead, I believe that opera institutions need to modernize how they operate.

Audiences continue to respond to the repertoire when companies find new ways to tell familiar stories.

Productions of canonical works such as La Traviata and Don Giovanni that place well-known narratives in contemporary settings or reframe them through modern staging have drawn strong attendance and critical attention. Crossover projects that bring operatic voices into dialogue with jazz, musical theater or popular musical performance have also sold out limited runs aimed at new audiences.

And smaller-scale formats, including chamber operas and performances staged in studios or alternative venues, have consistently filled seats – even as large main-stage productions struggle to sell tickets.

Those examples point to underlying demand for experiencing operas – even if fewer people are buying season tickets.

To be sure, there are some signs of progress. Some opera companies are taking their digital productions seriously.

Boston Baroque is primarily an orchestra and chorus, but it also produces staged operas. It offered livestreams of its performances during the pandemic to earn extra money.

New York City’s Metropolitan Opera has maintained a standalone direct-to-consumer subscription product, Met Opera on Demand, that anyone in the world can access. But it illustrates the strategic tension many companies face: Digital expansion can broaden reach, but it may also complicate efforts to fill empty seats.

This 1968 recording of Luciano Pavarotti conveys the power of the opera at its best.

Grappling with an economic problem

Opera’s biggest challenge is structural, not artistic.

Live performance is inherently labor intensive – and expensive. You cannot automate a string quartet or speed up an aria without destroying what makes it valuable.

Notably, opera companies have nearly doubled administrative costs as a share of their budgets since the mid-2000s, while spending on artistic programming has remained flat.

Some of the increase in administrative spending reflects the growing complexity of fundraising, compliance and labor management. But the magnitude of the shift strongly suggests declining organizational efficiency, with managerial and overhead functions expanding faster than opera’s capacity to stage productions or build its audience in the United States.

Meanwhile, ticket sales have declined and the number of major opera donors has declined.

Facing a similar turning point

Financial distress is not unique to opera.

Many U.S. orchestras have confronted serious financial stress, including bankruptcies and closures in places like Honolulu, Syracuse, N.Y. and Albuquerque, N.M..

The orchestras that survived tended to diversify revenue, analyze data and treat innovation as part of their mission – three strategies opera companies have failed to pursue consistently.

Reaching the public where it already is

The assumption that younger generations do not care about classical music is unfounded.

When opera companies put performances on streaming platforms during the pandemic, many younger listeners tuned in.

A 2022 survey of music consumption in the United Kingdom conducted by the Royal Philharmonic Orchestra; Deezer, one of several global services tracking the digital consumption of classical music; and the British Phonographic Industry found that 59% of people under 35 streamed orchestral music during the COVID-19 lockdown, compared with a 51% national average across all age groups.

Meanwhile, classical music streaming rose sharply across digital platforms during the first months of the pandemic. Deezer reported a 17% increase in classical streams in the 12 months beginning in April 2019.

These patterns suggest that younger audiences can become interested in opera and classical music when access to those genres is easy, and that digital formats can meaningfully expand the base of younger listeners.

But younger audiences usually encounter the music they listen to through algorithms or short-form video.

Treating performances as content

The lesson is not that opera should abandon live performance – if anything, everyone needs more, not less, in-person interaction in this hybrid-work era. Instead, I believe that opera companies should treat performances as content that can be accessed both in person and in digital spaces.

That way, they can spread those fixed artistic costs across multiple formats and markets, whether they’re recordings, livestreams, educational licenses or smaller-scale spinoff events.

Opera has survived wars, depressions, technological revolutions and cultural upheavals because it evolved. Today, the risk is not that people have stopped caring about music; it’s that opera companies have presumed that upholding tradition requires a rigidity at odds with their own success.

Christos Makridis is also a co-founder of Living Opera and the Living Opera Foundation and founder of CM Culture Management. He is also an affiliate and contributor to several think tank communities across the aisles.

– ref. Opera is not dying – but it needs a second act for the streaming era – https://theconversation.com/opera-is-not-dying-but-it-needs-a-second-act-for-the-streaming-era-271376

January 20, 2026

Comprender antes de juzgar: ¿qué enseñan los fallos ferroviarios del pasado sobre el accidente de Adamuz?

Source: The Conversation – (in Spanish) – By José Ygnacio Pastor Caño, Catedrático de Universidad en Ciencia e Ingeniería de los Materiales, Universidad Politécnica de Madrid (UPM)

Los bomberos trabajan en la cabecera del tren Iryo siniestrado en Adamuz. Guardia Civil.

La primera vez que entendí de verdad la palabra fatiga no fue en un laboratorio, sino en el salón de casa: una silla aparentemente nueva decidió, sin aviso previo, convertirse en cuatro patas y en un argumento filosófico sobre la gravedad. Nadie la había maltratado. Nadie la había sobrecargado. Simplemente, tras miles de ciclos de carga, una microscópica grieta creció hasta alcanzar su tamaño crítico y se propagó, fracturando el material. Y ahí estaba yo: indignado, tentado de buscar culpables… y, al mismo tiempo, obligado a admitir lo obvio: los fallos complejos rara vez se explican con un dedo acusador.

Con el siniestro de tren en Adamuz ocurre algo parecido, solo que la silla pesa cientos de toneladas, se movía a 200 km/h y transportaba vidas. En este caso, lo mínimo exigible es no convertir la tragedia en una tertulia especulativa de barra de bar.

Búsqueda de evidencias para la identificación de víctimas e investigación del accidente ferroviario el 19 de enero de 2026. Guardia Civil de España.

En busca de un culpable

Lo demás –la causa raíz– es, por definición, una investigación en curso. Aun así, el ser humano necesita cerrar historias rápido: “fue el maquinista”, “fue la vía”, “fue el tren”, “fue algo con nombre propio”.

La información disponible apunta, precisamente, a que no estamos ante el relato fácil del culpable único: fuentes oficiales señalan que se exploran fallos de infraestructura o mecanismos como indicios de una posible anomalía (¿grieta?) en el carril o en elementos del tren. En cualquier caso, no hay que pensar en un sabotaje, ya que, en ese caso, hubiera descarrilado todo el tren.

Esquema simplificado de cómo se investiga un accidente ferroviario.
José Ygnacio Pastor, Universidad Politécnica de Madrid, CC BY-NC

Investigar lleva tiempo

Las investigaciones serias tienen un defecto insoportable: tardan lo que tardan y no entienden de prisas. La normativa europea exige publicar el informe final antes de doce meses; si no se llega a ese plazo, debe emitirse un avance intermedio. Es decir, incluso con presión pública, el sistema está diseñado para que la prisa no sea la autora intelectual del informe.

Accidente ferroviario en Angrois cerca de Santiago de Compostela, el 24 de julio de 2023.
Wikimedia Commons., CC BY

Para hacernos una idea, el accidente de Santiago de Compostela (24 de julio de 2013) obtuvo el informe final en mayo de 2014. En Hatfield (Reino Unido, 2000), la combinación de análisis técnico, responsabilidades y reformas operativas duró años, porque un fallo material puede ser solo el primer dominó de una cadena organizativa.

La seguridad se aprende a partir de los errores del pasado: análisis de las enseñanzas de tres accidentes europeos recientes.
José Ygnacio Pastor, Universidad Politécnica de Madrid, CC BY-NC

Tres lecciones del pasado (sin necesidad de adivinar el futuro)

–A veces, el material es el tren, no la vía.

El accidente de Eschede (Alemania, 1998) es el recordatorio más cruel de que una fisura por fatiga en un componente puede desencadenar una catástrofe, aunque el resto del sistema “parezca” correcto. El detalle relevante es la idea de iniciación y propagación de grietas bajo cargas no críticas repetidas y la importancia de su detección antes del umbral crítico.

–A veces el material es la vía, y el problema es invisible… hasta que deja de serlo.

La fatiga por contacto rodante es una especialidad de la física con mala educación: trabaja en silencio, en la interfaz rueda–carril, con tensiones que pueden alcanzar magnitudes enormes en la zona superficial, y va sembrando grietas. Es lo que pasó en Hatfield, en 2000.

–A veces la causa dominante no es materiales, sino operación y barreras.

El siniestro de 2013 en Santiago de Compostela muestra otra familia: velocidad, factores humanos, transición entre sistemas de protección… y, sobre todo, el debate sobre cuántas capas debe tener un sistema para que un solo error no sea fatal. No es el mismo patrón que el de un descarrilamiento en recta tras una renovación reciente, pero sí enseña el mismo método: no buscar una bala de plata, sino una cadena de eventos.

Esquema simplificado. — Árbol de familias causales del accidente y diferentes tipos de pruebas de peritaje científico que pueden usarse para discriminar entre ellas.
José Ygnacio Pastor, Universiad Politécncia de Madrid, CC BY-NC-ND

¿Y Adamuz? Hipótesis razonables

Si el foco mediático insiste en que la vía era moderna y renovada y el tren era reciente, lo técnico debe responder con humildad: precisamente, por eso, el abanico plausible incluye fallos súbitos o defectos que escaparon a las inspecciones rutinarias. Algunas hipótesis, o todas ellas, podrías responder a nuestra curiosidad:

-Posible problema de unión-soldadura-fatiga de carril: las pruebas habría que buscarlas desde la fractografía (análisis de las superficies de fractura): marcas de avance por fatiga frente a rotura bruca. También, en el historial de ensayos no destructivos en el punto y soldaduras cercanas, en la geometría de vía y asentamientos (registros de auscultación) y en evidencias de campo (fragmentos, deformaciones, “marca de inicio” del descarrilamiento…).

-Si fuera material rodante (rueda-eje-rodamiento/bogie), lo que suele delatarlo son señales previas en los registradores (vibraciones, alarmas, temperatura de los rodamientos), daño característico en la rueda o el eje y en su superficie de fractura y correlación con el mantenimiento real.

-Si no se tratara de un problema de materiales, seguirían siendo hipótesis plausibles —hasta ahora no descartables— la colisión con un obstáculo en la vía, una anomalía local de geometría, el fallo de sujeciones o de un aparato de vía cercano, así como efectos del viento o tensiones térmicas locales, menos habituales en enero, pero relevantes porque la vía responde a la variación cíclica de la temperatura del carril.

En la interacción constante entre las ruedas del ferrocarril, pueden formarse grietas debido al desgaste continuo, al incremento cíclico de las temperaturas y a las cargas repetitivas que provocan la fatiga de los materiales implicados.
José Ygnacio Pastor, Universidad Politécnica de Madrid, CC BY-NC

La seguridad del futuro: más velocidad, más sensores, más humildad

China ha presentado prototipos como el CR450, que operarán hasta 450 km/h. La promesa de seguridad no está en la magia del récord, sino en el ecosistema: instrumentación, mantenimiento predictivo, inspección automatizada, gemelos digitales y una cultura donde un aviso pequeño no se archiva como molestia.

Al final, vuelvo a mi silla rota. Si me hubiera fiado de la intuición, habría culpado a la carpintería, al destino o a esa pata coja. Pero cuando uno analiza, aparece la cadena: un diseño con sus compromisos, una unión que concentra tensiones, un microdefecto, miles de cargas repetidas… y, por fin, un último ciclo que no fue el más fuerte, sino el primero que alcanzó al umbral de rotura.

Comprender antes de juzgar

El análisis forense obliga a leer las huellas del fallo como si fueran un texto, desde la fractografía submicrométrica hasta el macrocosmos del sistema, donde cada decisión humana y técnica deja también su firma.

Con Adamuz, la única postura seria es comprender antes de juzgar. Porque si algo nos enseñan las grandes catástrofes ferroviarias del pasado es que el progreso en seguridad no nace del análisis más rápido, sino de las evidencias más pacientes. Y esas evidencias, como las grietas, no se aprecian fácilmente… pero inevitablemente existen.

Se inspeccionan cabeza y alma del carril, juntas y soldaduras para detectar defectos internos subcríticos invisibles a simple vista. — Comprobación de raíles con un equipo de ultrasonidos manual (Túnel de Base del Gotardo, Suiza).
Wikimedia Commons., CC BY

José Ygnacio Pastor Caño recibe fondos del proyecto PID2022-137274NB-C33, financiado por el Plan Estatal 2021–2023 de la
Agencia Española de Investigación del Gobierno de España.

– ref. Comprender antes de juzgar: ¿qué enseñan los fallos ferroviarios del pasado sobre el accidente de Adamuz? – https://theconversation.com/comprender-antes-de-juzgar-que-ensenan-los-fallos-ferroviarios-del-pasado-sobre-el-accidente-de-adamuz-273879

January 20, 2026

Manger sans viande est-il bon pour la santé ? Un débat récurrent dans l’histoire de la diététique

Source: The Conversation – in French – By Bruno Laurioux, Professeur émerite, Université de Tours

Image extraite de _Mœurs, usages et costumes au Moyen Âge et à l’époque de la Renaissance_ (1871), de Paul Lacroix, illustré par F. Kellerhoven., CC BY

De l’intérêt de limiter sa consommation de viande, voire de s’en priver, au bénéfice de sa santé. C’est un des arguments avancés par celles et ceux qui promeuvent le végétarisme. Mais savez-vous que cette question, ô combien d’actualité, divise les spécialistes depuis… le Moyen Âge ? C’est ce que nous raconte Bruno Laurioux, professeur émérite à l’université de Tours et président de l’Institut européen d’histoire et des cultures de l’alimentation dans Une histoire de la diététique. D’Hippocrate au Nutri-Score (éditions du CNRS, 2025).

Dans la longue histoire du végétarisme, trois arguments principaux ont été avancés pour justifier le refus – ou le rejet – de la viande. Le plus ancien est d’ordre éthique ; on le retrouve chez certains néo-pythagoriciens de l’Antiquité tardive, qui stigmatisent la violence faite à l’animal lorsqu’on le met à mort pour le consommer. L’argument le plus récent – il date du XX^e siècle – est de nature environnementale et pointe les impacts très négatifs de l’élevage intensif, en termes de rejet de gaz à effet de serre ou de prélèvement des eaux.

Mais, on l’oublie souvent, l’une des motivations de ceux qui se privent totalement de viande peut être le souci de leur santé. Entretenue par les crises sanitaires à répétition qui touchent le secteur de la production animale depuis le déclenchement de l’encéphalopathie spongiforme bovine (ESB, surnommée communément « maladie de la vache folle ») à la fin des années 1990, puis ravivée par la mise en évidence des effets cancérogènes d’une consommation soutenue de viande rouge, une méfiance certaine envers la viande s’est installée dans notre paysage.

Or, cette ligne de contestation de la consommation carnée a été également utilisée dans un passé parfois lointain, qui va du Moyen Âge au XX^e siècle. C’est ce que nous décrivons dans Une histoire de la diététique. D’Hippocrate au Nutri-Score.

La défense du régime chartreux « sans viande » : Arnaud de Villeneuve

Le traité De esu carnium (en français, Sur la consommation des viandes) a été composé entre 1302 et 1305 par l’un des plus grands médecins du temps, le Catalan Arnaud de Villeneuve ; la version originale intégrale de cet ouvrage intégrale étant De esu carnium d’Arnaldus de Villanova, éd. Dianne M. Bazell, Barcelone (Arnaldi de Villanova Opera medica Omnia, XI), 1999).

Professeur renommé à l’université de Montpellier, très bon connaisseur des textes médicaux traduits récemment de l’arabe, Arnaud de Villeneuve met ses talents de praticien au service du roi d’Aragon comme du pape. Il prend ici la défense des Chartreux ; cet ordre monastique rigoriste, fondé par saint Bruno, est accusé de laisser mourir ses membres malades, en leur refusant absolument l’usage de la viande. Or, la possibilité d’en manger avait été ouverte, précisément pour les malades, par la règle bénédictine, la plus répandue en Occident.

De manière générale, l’interdiction de la viande des animaux terrestres et aériens, qui constituait le cœur du carême pour les fidèles et s’imposait aux moines à perpétuité, s’était notablement assouplie. Et ceci sous l’effet du système de représentation dominant dans la société laïque qui valorisait la consommation carnée ; un système face auquel les petites communautés de Chartreux apparaissaient comme des pôles de résistance.

Contre les détracteurs des Chartreux qui les présentent comme cruels ou dénués de toute humanité en ne permettant pas la viande aux malades en grand danger de mort, Arnaud de Villeneuve veut prouver qu’on agit plus efficacement en leur administrant des médicaments et que les mets végétaux ne présentent aucun danger supplémentaire par rapport aux mets carnés – bien au contraire. Il pose ainsi une série d’arguments médicaux tirés des auteurs de référence qu’il maîtrise à merveille.

D’abord, démontre-t-il, prescrire de la viande ne sert à rien quand le malade a juste besoin de médicaments. Ensuite, la chaleur supplémentaire que procure la graisse contenue dans la viande, invoquée par certains détracteurs des Chartreux, n’apporte rien aux malades et peut même être très nuisible à leur guérison.

Troisième argument : la viande restaure certes les muscles mais non la force vitale tout entière ; si le sang « épais et glutineux » qu’elle engendre peut certes aider le corps au quotidien, le vin et les jaunes d’œuf (qui font partie du régime monastique ordinaire), parce qu’ils sont « légers et subtils », se révèlent, juge-t-il, bien plus utiles pour restaurer l’ensemble de ses fonctions physiques et cognitives. (La « prescription » de vin à des malades peut surprendre aujourd’hui, à raison. Mais à l’époque, leur donner du vin, donc de l’alcool, ne fait pas débat, ndlr).

Le médecin catalan, qui se pique aussi de théologie, rappelle au passage que la Bible ne présente jamais la viande comme une nourriture saine ni nécessaire. Et il constate que les Chartreux, même s’ils se privent totalement de viande, vivent fort vieux, atteignant couramment 80 ans, à l’instar des patriarches des premiers âges du monde, où la viande n’était pas encore d’usage.

La conclusion s’impose : la consommation de viande n’est nullement une nécessité en cas de maladie et, par conséquent, s’en priver ne constitue pas un danger ; ceux qui prétendent nécessaire l’usage de la viande ont en réalité mal compris ses effets sur l’alimentation. Conclusion forte, qui intéressa les lecteurs mais n’eut guère d’impact sur les pratiques. Le De esu carnium fut souvent copié et parfois cité mais n’empêcha pas le vaste courant favorable à la viande de se développer et d’emporter tout sur son passage.

Les bienfaits du carême : Andry contre Hecquet

Pourtant le plaidoyer anti-viande ressurgit au début du XVIII^e siècle, sous la plume du bouillant Philippe Hecquet. Ce « self-made-man », devenu médecin du prince de Condé et doyen de la faculté parisienne, manifeste ses talents de polémiste en s’attaquant aux libertés que des fidèles toujours plus nombreux ont pris avec les obligations du carême. Et, scandale majeur pour le rigoureux janséniste qu’il est, sur les conseils mêmes de leur médecin traitant !

Car le contexte a bien changé depuis Arnaud de Villeneuve. Le carême s’est retrouvé au cœur de la contestation que la Réforme protestante a menée contre bien des dogmes et des pratiques catholiques non attestés dans l’Écriture. Avec le siècle des Lumières s’amorce un mouvement encore plus profond dans la société d’Ancien Régime, celui d’une déchristianisation progressive. S’ensuit une forte augmentation de la vente de viande, qui, durant le carême, est traditionnellement détenue par l’Hôtel-Dieu, en vertu des dispenses accordées aux malades.

C’est contre cette évolution que s’élève Hecquet, lorsqu’il publie en 1709 son Traité des dispenses du carême.

Il entend notamment y établir « par l’histoire, par l’analyse et par l’observation », la « convenance » que les aliments maigres entretiennent « avec la santé ». Au bout de quelque 73 chapitres, Hecquet a réussi l’exploit de démontrer à la fois

« que le Carême n’a rien de si extraordinaire » ni de « trop austère » et « que les fruits, les grains et les légumes sont », contrairement à la viande, « les aliments les plus à naturels à l’homme ».

Pour cela, il dresse le profil diététique d’un grand nombre de produits végétaux.

La conclusion qu’il en tire est sans appel :

« Il est vrai de dire que le maigre est plus naturel à l’homme que le gras, qu’il fait moins de maux, et guérit plus de maladies. »

C’est un renversement complet du système de valeur diététique qui est ici proposé, avec l’affirmation d’une absolue supériorité médicale des céréales, fruits et légumes.

Le traité de Philippe Hecquet connait un retentissement immédiat. Mais il indispose fort la plupart des collègues. Dans l’ombre, l’un d’entre eux fourbit ses armes en vue d’un ouvrage qui va en prendre le contrepied. Pour ce Nicolas Andry, l’abstinence de viande n’est ni plus ni moins que « l’écueil de la santé ». Or, Hecquet affirme exactement le contraire, en voyant dans l’antériorité du régime végétal mentionnée dans la Bible la preuve de sa supériorité sur le régime carné : Dieu n’a-t-il pas ainsi manifesté sa préférence ?

D’autre part, tout à sa volonté de combattre les dispenses abusives de carême, Hecquet a déniché, dans les statistiques sur les consommations carnées de Paris, les preuves d’un fâcheux relâchement des pratiques d’abstinence. Ce faisant, il touche les puissants intérêts professionnels des bouchers comme ceux des médecins. Il semble aussi franchir une ligne rouge aux yeux de l’Église, en faisant de la privation de viande non plus une pénitence mais un choix, semblant revenir à d’anciennes hérésies.

Défaite du végétarisme médical en France, au XVIIIᵉ siècle

C’en est trop. Andry réfute point par point les arguments de Hecquet dans les deux volumes de son Traité des dispenses de Carême parus en 1713. L’une de ses affirmations les plus fortes se fonde sur un retournement de son raisonnement : c’est précisément parce que les aliments de carême nourrissent mal que l’Église en a prescrit l’usage, afin de ne pas satisfaire complètement les besoins du corps. En 1714, l’intervention du plus grand médecin du temps, Jean Astruc, qui affirme clairement la supériorité nutritive du gras sur le maigre, marque la défaite du végétarisme médical. Tout au moins en France.

Car, outre-Manche, le courant végétarien qui se développe à partir du XIX^e siècle s’appuie sur des arguments médicaux, auxquels une figure comme Anna Klingsford donnera la forme d’un axiome :

« Non seulement les substances végétales renferment tous les éléments nécessaires à la nutrition et à la production de force et de chaleur, mais […] même elles en contiennent plus que les substances animales. »

Paradoxalement, c’est dans la citadelle du carnisme qu’était devenue la faculté de Paris qu’elle soutiendra sa thèse en 1880.

Bruno Laurioux ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d’une organisation qui pourrait tirer profit de cet article, et n’a déclaré aucune autre affiliation que son organisme de recherche.

– ref. Manger sans viande est-il bon pour la santé ? Un débat récurrent dans l’histoire de la diététique – https://theconversation.com/manger-sans-viande-est-il-bon-pour-la-sante-un-debat-recurrent-dans-lhistoire-de-la-dietetique-272844

January 20, 2026

Juice cleanses, charcoal supplements and foot patches – is detoxing worth the hype?

Source: The Conversation – UK – By Katie Edwards, Commissioning Editor, Health + Medicine and Host of Strange Health podcast, The Conversation

If you’re healthy, do you need to do a charcoal detox? AtlasStudio/Shutterstock

January arrives with a familiar hangover. Too much food. Too much drink. Too much screen time. And suddenly social media is full of green juices, charcoal supplements, foot patches and seven-day “liver resets”, all promising to purge the body of mysterious toxins and return it to a purer state.

In the first episode of Strange Health, a new visualised podcast from The Conversation, hosts Katie Edwards and Dan Baumgardt put detox culture under the microscope and ask a simple question: do we actually need to detox at all?

Strange Health explores the weird, surprising and sometimes alarming things our bodies do. Each episode takes a popular health or wellness trend, viral claim or bodily mystery and examines what the evidence really says, with help from researchers who study this stuff for a living.

Katie Edwards, a health and medicine editor at The Conversation and Dan Baumgardt, a GP and lecturer in health and life sciences at the University of Bristol share a longstanding fascination with the body’s improbabilities and limits, plus a healthy scepticism for claims that sound too good to be true.

This opening episode dives straight into detoxing. From juice cleanses and detox teas to charcoal pills, foot pads and coffee enemas, Katie and Dan watch, wince and occasionally laugh their way through some of the internet’s most popular detox trends. Along the way, they ask what these products claim to remove, how they supposedly work, and why feeling worse is often reframed online as a sign that a detox is “working”.

The episode also features an interview with Trish Lalor, a liver expert from the University of Birmingham, whose message is refreshingly blunt. “Your body is really set up to do it by itself,” she explains. The liver, working alongside the kidneys and gut, already detoxifies the body around the clock. For most healthy people, Lalor says, there is no need for extreme interventions or pricey supplements.

That does not mean everything labelled “detox” is harmless. Lalor explains where certain ingredients can help, where they make little difference and where they can cause real damage if misused.

Real detoxing looks less like a sachet or a foot patch and more like hydration, fibre, rest, moderation and giving your liver time to do the job it already does remarkably well. If you’re buying detox patches and supplements then it’s probably your wallet that is about to be cleansed, not your liver.

Strange Health is hosted by Katie Edwards and Dan Baumgardt. The executive producer is Gemma Ware, with video and sound editing by Sikander Khan. Artwork by Alice Mason.

Dan and Katie talk about two social media clips in this episode, one from 30.forever on TikTok and one from velvelle_store on Instagram.

Listen to Strange Health via any of the apps listed above, download it directly via our RSS feed or find out how else to listen here. A transcript is available via the Apple Podcasts or Spotify apps.

Katie Edwards works for The Conversation and co-hosts the Strange Health podcast.

Dan Baumgardt and Trish Lalor do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

– ref. Juice cleanses, charcoal supplements and foot patches – is detoxing worth the hype? – https://theconversation.com/juice-cleanses-charcoal-supplements-and-foot-patches-is-detoxing-worth-the-hype-273394

January 20, 2026

Trump has threatened European countries with higher tariffs if he doesn’t get Greenland. Will it work?

Source: The Conversation – Global Perspectives – By Shannon Brincat, Senior Lecturer in Politics and International Relations, University of the Sunshine Coast

In an extraordinary escalation of his bid to claim Greenland, US President Donald Trump has threatened eight European countries – Denmark, Sweden, Norway, Finland, Great Britain, France and Germany and the Netherlands – with a 10% tariff on all goods coming into the United States from February 1 until he is able to buy the semi-autonomous Danish territory. That tariff will then increase to 25% on June 1.

On the one hand, Greenland is potentially rich in raw materials and rare earth minerals, highly desirable for US tech giants who control key levers of power in Washington. On the other, Trump claims it is necessary for national security.

Greenland is part of a sovereign country, Denmark, and any offensive action against it would constitute an act of aggression.

In the past few days, a small number of European troops have arrived in Greenland to bolster its defences. Trump’s recalcitrant stance has sent shockwaves across Europe, which is now questioning the future of NATO.

So what might happen now?

The US needs a pretext of self-defence

Aggressive wars are illegal under international law. Under the UN Charter, the use of force is lawful only when

1. authorised by the UN Security Council under Chapter VII

2. as self-defence under Article 51 in response to an armed attack.

In this case, as the US’ claims have no backing from the UNSC, its use of force would require a pretext or provocation that would allow self-defence – in other words, an attack or imminent attack.

As I always tell my students in international law, these must be scrutinised carefully as there is long, chequered history behind such claims. The key problem are “false flags” by which states fabricate or manufacture a threat or attack to justify their own offensive operations.

A recent example of this is the illegal use of force in the US-led 2003 Iraq War. This was publicly sold on two claims that had no factual basis: that Saddam Hussein possessed weapons of mass destruction and/or had close ties to al-Qaeda (and, by implication, the September 11 attacks). Even though these have been disproven, many continue to believe it.

The US wants to take over Greenland as a forward base, so we should be wary of false flags that may arise in this context. The US has justified its claim as preventing aggression from China and Russia, even though there is no evidence of their presence.

However, the potential of rivals in a region does not authorise the use of force against a third-party state. Any attack on Greenland would remain naked aggression.

What could Europe do?

There are several things Europe could do in response.

It could deploy forces, as already requested by Greenland. The Danish government has already expanded its military in Greenland and launched “Operation Arctic Endurance” in cooperation with allies including France, Germany, Norway and Sweden.

But sending 50-100 troops to Greenland is hardly a show of strength, with a handful of soldiers to cover areas the size of Switzerland.

Countries in NATO have an agreement for collective defence.
In the unlikely event of a US attack, the alliance would be sorely tested, especially given the US is a long-standing member. NATO has weathered inter-alliance disputes before, such as the 1956 Suez Crisis.

Many question whether NATO would dissolve, or if many members would leave. Certainly, it would weaken its reputation and paralyse it for some time.

Europe could threaten to close access to all military bases in Europe as this would dramatically hamper US capabilities not only in Europe but Russia, the Middle-East, and North Africa.

However, the biggest retaliatory threat Europe could muster is the Anti-Coercion Instrument (ACI) and selling off of US bonds, of which Europe holds substantial leverage (around 28% of foreign holdings). If other states, such as China, followed suit, the US economy would likely collapse because of the rapid devaluing of the dollar. However, this is the “nuclear option”, and risks self-harm to European financial power at the same time.

Overall, Europe is in a much weaker position – hampered not only by lack of military parity but energy dependency on the US. After the mysterious destruction of the Nord Stream Pipeline, Europe is energy dependent on the US – and everyone knows it.

Moreover, if Europe took action against the US in Greenland, it would then also have to shoulder the commitment to Ukraine in the war with Russia. It would be hard-pressed on two fronts.

What would Australia and other allies do?

It is doubtful many states would actively defend Greenland against the US. But not many states would actively support it either, and with that turning away from the US as “saviour”, world order would have profoundly shifted. It would likely signal the end of the liberal international order, taking any semblance of international law with it.

All other allies would be put on notice of a rogue ally. Emboldening Trump would be highly dangerous: Cuba and Iran have already been listed. More operations in Venezuela would be possible. But he has also made statements about sending troops to Mexico and threatening Colombia. Canada is already extremely worried, given Trump’s claims of making it “the 51st state” in early 2025. Where would it end?

Australia would be in the extremely difficult position of having to side with either the US, Europe, or take an independent stance.

It would also be worried about risking the AUKUS agreement – a treaty essential for Australian defence. Taiwan would be questioning the credibility of US protection. World public opinion, already dangerously low regarding Trump, would plummet further.

For these reasons, it highly like this is all just bluster from the US to coerce Greenland from Denmark. Some have explored how US security concerns could be met without annexing Greenland but this is not the point for Trump, who is seeking to appear as the “strong man” to his MAGA supporters.

What appears likely is that European powers will offer concessions so that Trump appears to “win” for his domestic base. It has been reported that EU officials will propose to use NATO to bolster Arctic security and give the US concessions on mineral extraction. This is classic appeasement. Emboldened, we could expect further aggressive US action elsewhere.

The long-term damage would be to US credibility, with all allies on notice of aberrant and erratic behaviour. Trump’s attempts to grasp at resources and forward defences highlights US decline more than anything else.

Europe seems likely to fare little better, revealed to be utterly dependent on the US and a distinct lack of principles for its members. The real loser is the West: fractured and eating itself.

Shannon Brincat does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Trump has threatened European countries with higher tariffs if he doesn’t get Greenland. Will it work? – https://theconversation.com/trump-has-threatened-european-countries-with-higher-tariffs-if-he-doesnt-get-greenland-will-it-work-273698

January 20, 2026

Would you use AI to break writer’s block? We asked 5 experts

Source: The Conversation – Global Perspectives – By Nicola Redhouse, Lecturer, Publishing and Editing, The University of Melbourne

The founder and chief executive of Bloomsbury Publishing, responsible for blockbuster romantasy author Sarah J. Maas and literary heavyweights like George Saunders, has suggested AI “will probably help creativity” – including by helping authors defeat writer’s block.

“AI gets them going and writes the first paragraph, or first chapter, and gets them back in the zone,” he said.

We asked five creative writing experts, including authors who’ve published memoirs, novels and short stories, what they think. Would they use AI to break writer’s block?

Their answers – which ranged from “a hard no” to innovative reasons for “yes” – were illuminating, complicated and often surprising.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

– ref. Would you use AI to break writer’s block? We asked 5 experts – https://theconversation.com/would-you-use-ai-to-break-writers-block-we-asked-5-experts-271627

January 20, 2026

A year on from his second inauguration, Trump 2.0 has one defining word: power

Source: The Conversation – Global Perspectives – By Bruce Wolpe, Non-resident Senior Fellow, United States Study Centre, University of Sydney

As Donald Trump celebrates the anniversary of his second inauguration as president of the United States and begins his sixth year in office, his greatest asset is power. He covets absolute power.

The greatest threat to how Trump completes his term is how he wields his power.

Indeed, in the most foolish act in foreign policy in Trump’s presidency, he has threatened punitive tariffs on Denmark and seven other NATO allies in Europe to force the sale of Greenland to the United States. They are outraged. This is a ridiculous ploy that will not deliver Greenland to Trump.

Trump’s escalation in Denmark has already strengthened Putin’s iron resolve to get as much of Ukraine as he can. Prospects for ending the war in Ukraine are now near zero.

On top of Trump’s pending tariffs on Europe, if Trump seizes Greenland, the consequences will shake the world – including Australia. NATO will be terminated. Australia will face an existential question of whether, under those circumstances, it must terminate its alliance with the US.

We can see in a raft of polls at this one-year mark of Trump’s second term that voters across the country are expressing growing disquiet about his management of the economy and the affordability of housing and groceries, the raids by ICE agents as they seize and deport migrants as we saw last week in Minneapolis, and uncertainty about Trump’s foreign adventurism in the Americas and with Iran.

Trump is exercising this power because he can. This will jolt Republicans in Congress to break with Trump on this issue – the first such rift between Trump and his party since his re-election.

Welcome to Trump’s year six.

Trumpism in his second term

Following his election victory in 2024, Trump has been faithful to three of four pillars of Trumpism that made his base a movement that has changed America:

nativism (favouring US-born citizens over immigrants)
protectionism and tariffs
America First nationalism (“Make America Great Again”).

To those ends, Trump is acting aggressively, with immigration agents arresting and deporting tens of thousands, and threats to deploy US troops in American cities to enforce these policies. Trump has imposed punitive tariffs against every trading partner – including Australia, which has a significant trade deficit with the United States. Trump demands foreign companies invest in the United States and build new factories.

But on the fourth Trumpism pillar – America-First isolationism as a driver of America’s foreign policy – Trump has redefined his foreign policy settings with grander ambitions.

Trump has rejected the history of the US waging wars to project American values: protecting Asia from communism in Korea and Vietnam; turning back brutal aggression in Kuwait; punishing the export of radical Islamic terrorism in Afghanistan and Iraq.

Trump has applied these lessons to Iran – so far. It is one thing to take out Iran’s nuclear capability. It is another to do regime change – a bridge too far back to the “forever wars” Trump despises.

Trump has buried America’s posture of globalism. He has withdrawn the US from virtually all the architecture, save the United Nations itself, erected after the second world war to ensure global security, stability and prosperity. He has ordered the US out of global organisations, and has cut billions in foreign aid.

The US attack on Venezuela was about much larger goals than arresting its leader. It was about power – controlling power over critical resources in the Americas, from Venezuela to Greenland and everything in between, from Mexico to Cuba to Canada.

Politics at home

Trump is paying a high price at home for his activism in wielding power abroad. Every day Trump spends projecting power outside the United States means he is not paying attention to the American people.

A recent poll shows 56% of US adults believe Trump has gone too far on Venezuela. 57% do not want the US to strike Iran. Even before Trump’s tariff announcement on Greenland, only 17% approved of Trump’s desire to acquire Greenland, and 71% rejected using military force to do it.

Trump’s overall polls are bad. His approval rating is 40% – nearly 10 points down since his inauguration – and disapproval is at 60%. AP-NORC also finds that “Trump hasn’t convinced the Americans that the economy is in good shape.”

CNN polling reports that 55% of those surveyed believe Trump’s policies “have hurt the economy” and that Trump is not doing enough to lower prices. Grocery prices are up sharply. The latest Wall Street Journal poll shows Trump is underwater by double digits on handling inflation, and that he is not focusing enough on the economy.

On immigration, the unrest in Minneapolis and other cities from the harsh methods employed by ICE agents is also taking a toll, with Trump’s approval on that issue lagging below 40%.

But even with all these red flags and warnings from the field, Trump is undeterred. He believes that as president, he can do anything he wants to do. Guardrails that have for decades protected America’s democracy have been cast aside.

Trump has not been blocked – yet – by an ultra-conservative Supreme Court or the pliant Republican Congress for the tariffs he is imposing, the government agencies he has shut down, the monies appropriated by Congress he has terminated, the hundreds of thousands of government employees he has fired, the military strikes he has ordered without advising, much less getting approval from, Congress.

Trump is seeking more control over the economy by seeking to prosecute the chair of the Federal Reserve Bank, an independent agency that sets monetary policy, and to pack its board with loyalists to Trump’s demands that interest rates be lowered.

Since his inauguration, Trump has instructed the Justice Department to prosecute those who attempted to bring him to justice in courtrooms and impeachment proceedings in Congress.

Trump’s musings on power

As Trump consolidates his power, Trump’s musings become imperatives. After months of expressing a desire to own it, Trump is now acting aggressively to conquer Greenland.

At home, Trump is now also musing – twice so far this month – over whether the US midterm elections will be cancelled. Trump knows the likelihood of the Democrats taking back control of the House of Representatives is high. That is precisely what he suffered in the 2018 congressional elections in his first term.

Trump told Reuters last week, “We shouldn’t even have an election,” because of all his great successes.

In January, Trump told Republicans in the House, “I won’t say cancel the election, they should cancel the election, because the fake news would say, ‘He wants the elections cancelled. He’s a dictator.’ They always call me a dictator.” He told them that if the Democrats take the House back they will “find a reason to impeach” him.

Any steps taken – such as declaring martial law to suspend the midterm elections – will be catastrophic. And that is an understatement.

Based on Trump’s restless mind and command of what he believes is absolute power, at stake this year are the future of democracy at home and alliances abroad.

Bruce Wolpe receives funding from the United States Studies Centre. He has worked with the Democrats in the US Congress and for Prime Minister Julia Gillard.

– ref. A year on from his second inauguration, Trump 2.0 has one defining word: power – https://theconversation.com/a-year-on-from-his-second-inauguration-trump-2-0-has-one-defining-word-power-273697

January 20, 2026

The way Earth’s surface moves has a bigger impact on shifting the climate than we knew

Source: The Conversation – Global Perspectives – By Ben Mather, ARC Early Career Industry Fellow, School of Geography, Earth and Atmospheric Sciences, The University of Melbourne

Our planet has experienced dramatic climate shifts throughout its history, oscillating between freezing “icehouse” periods and warm “greenhouse” states.

Scientists have long linked these climate changes to fluctuations in atmospheric carbon dioxide. However, new research reveals the source of this carbon – and the driving forces behind it – are far more complex than previously thought.

In fact, the way tectonic plates move about Earth’s surface plays a major, previously underappreciated role in climate. Carbon doesn’t just emerge where tectonic plates meet. The places where tectonic plates pull away from each other are significant too.

Our new study, published today in the journal Communications, Earth and Environment sheds light on how exactly Earth’s plate tectonics have helped to shape global climate over the past 540 million years.

Peering deep within the carbon cycle

At the boundaries where Earth’s tectonic plates converge, we get chains of volcanoes known as volcanic arcs. Melting associated with these volcanoes unlocks carbon that’s been trapped inside rocks for thousands of years, bringing it to Earth’s surface.

Historically, it’s been thought these volcanic arcs were the primary culprits of injecting carbon dioxide into the atmosphere.

Our findings challenge that view. Instead, we suggest that mid-ocean ridges and continental rifts – locations where the tectonic plates spread apart – have played a much more significant role in driving Earth’s carbon cycles throughout geological time.

This is because the world’s oceans sequester vast quantities of carbon dioxide from the atmosphere. They store most of it within carbon-rich rocks on the seafloor. Over thousands of years, this process can produce hundreds of metres of carbon-rich sediment at the bottom of the ocean.

As these rocks then move about the Earth driven by tectonic plates, they may eventually intersect subduction zones – places where tectonic plates converge. This releases their carbon dioxide cargo back into the atmosphere.

This is known as the “deep carbon cycle”. To track the flow of carbon between Earth’s molten interior, oceanic plates and the atmosphere, we can use computer models of how the tectonic plates have migrated through geological time.

What we discovered

Using computer models to reconstruct how Earth moves carbon stored on tectonic plates, we were able to predict major greenhouse and icehouse climates over the last 540 million years.

During greenhouse periods – when Earth was warmer – more carbon was released than trapped within carbon-carrying rocks. In contrast, during icehouse climates, the carbon sequestration into Earth’s oceans dominated, lowering atmospheric carbon dioxide levels and triggering cooling.

One of the key takeaways from our study is the critical role of the deep-sea sediments in regulating atmospheric carbon dioxide. As Earth’s tectonic plates slowly move, they carry carbon-rich sediments, which are eventually returned into Earth’s interior through a process known as subduction.

We show that this process is a major factor in determining whether Earth is in a greenhouse or icehouse state.

How much carbon is recycled into Earth’s mantle at subduction zones (blues) compared to how much is released through volcanic arcs and mid-ocean ridges (oranges) over the past 540 million years. Carbonate platforms – large accumulations of carbonate rocks – are indicated by green polygons, where light green indicates active platforms, and dark green indicates older, inactive platforms.

A shift in understanding the role of volcanic arcs

Historically, the carbon emitted from volcanic arcs has been considered one of the largest sources of atmospheric carbon dioxide.

However, this process only became dominant in the last 120 million years thanks to planktic calcifiers. These little ocean critters belong to a family of phytoplankton whose main talent lies in converting dissolved carbon into calcite. They are responsible for sequestering vast amounts of atmospheric carbon into carbon-rich sediment deposited on the seafloor.

Planktic calcifiers only evolved about 200 million years ago, and spread through the world’s oceans about 150 million years ago. So, the high proportion of carbon spewed into the atmosphere along volcanic arcs in the past 120 million years is mostly due to the carbon-rich sediments these creatures created.

Before this, we found that carbon emissions from mid-ocean ridges and continental rifts – regions where tectonic plates diverge – actually contributed more significantly to atmospheric carbon dioxide.

A new perspective for the future

Our findings offer a new perspective on how Earth’s tectonic processes have shaped, and will continue to shape, our climate.

These results suggest Earth’s climate is not just driven by atmospheric carbon. Instead, the climate is influenced by the intricate balance between carbon emissions from Earth’s surface and how they get trapped in sediments on the seafloor.

This study also provides crucial insights for future climate models, especially in the context of current concerns over rising carbon dioxide levels.

We now know that Earth’s natural carbon cycle, influenced by the shifting tectonic plates beneath our feet, plays a vital role in regulating the planet’s climate.

Understanding this deep time perspective can help us better predict future climate scenarios and the ongoing effects of human activity.

Ben Mather receives funding from the Australian Research Council.

Adriana Dutkiewicz receives funding from the Australian Research Council.

Dietmar Müller receives funding from the Australian Research Council.

Sabin Zahirovic has received funding from the Alfred Sloan Foundation’s Deep Carbon Observatory, the Australian Research Council, and BHP via the STELLAR industry collaborative project.

– ref. The way Earth’s surface moves has a bigger impact on shifting the climate than we knew – https://theconversation.com/the-way-earths-surface-moves-has-a-bigger-impact-on-shifting-the-climate-than-we-knew-272352

January 20, 2026

Congress’ power has been diminishing for years, leaving Trump to act with impunity

Source: The Conversation – Global Perspectives – By Samuel Garrett, Research Associate, United States Studies Centre, University of Sydney

A year into US President Donald Trump’s second term, his record use of executive orders, impoundment of government spending, and military interventions in Venezuela and Iran have sparked criticisms from Democrats and even some Republicans. They say he is unconstitutionally sidelining Congress.

As Trump increasingly wields his power unilaterally, some have wondered what the point of Congress is now. Isn’t it supposed to act as a check on the president?

But the power of the modern presidency had already been growing for decades. Successive presidents from both parties have taken advantage of constitutional vagaries to increase the power of the executive branch. It’s a long-running institutional battle that has underwritten US political history.

The years-long erosion of Congress’ influence leaves the president with largely unchecked power. We’re now seeing the consequences.

A fraught relationship

Congress is made up of the House of Representatives and the Senate. Under the US Constitution, it’s the branch of the government tasked with making laws. It’s supposed to act as a check on the president and the courts.

It can pass legislation, raise taxes, control government spending, review and approve presidential nominees, advise and consent on treaties, conduct investigations, declare war, impeach officials, and even choose the president in a disputed election.

But the Constitution leaves open many questions about where the powers of Congress end and the powers of the president begin.

In a 2019 ruling on Trump’s tax returns, the judge commented:

disputes between Congress and the President are a recurring plot in our national story. And that is precisely what the Framers intended.

Relative power between the different branches of the US government has changed since independence as constitutional interpretations shifted. This includes whether the president or Congress takes the lead on making laws.

Although Congress holds legislative power, intense negotiations between Congress and the executive branch (led by the president) are now a common feature of US lawmaking. Modern political parties work closely with the president to design and pass new laws.

Redefining the presidency

By contrast, presidents in the 19th and early 20th centuries generally left Congress to lead policymaking. Party “czars” in Congress dominated the national legislative agenda.

Future president Woodrow Wilson noted in 1885 that Congress:

has entered more and more into the details of administration, until it has virtually taken into its own hands all the substantial powers of government.

Wilson and Franklin Roosevelt after him would later help to redefine the president not only as the head of the executive branch, but as head of their party and of the government.

In the 1970s, in the wake of the Watergate scandal and secret bombing of Cambodia, Congress sought to expand its oversight over what commentators suggested was becoming an “imperial presidency”.

This included the passage of the 1973 War Powers Resolution, designed to wrest back Congressional control of unauthorised military deployments.

Nevertheless, the Clinton, George W. Bush and Obama administrations all argued that Congressional authorisation was not required for operations in Kosovo, Iraq and Libya (though Bush still sought authorisation to secure public support).

In turn, the Trump administration argued its actions in Venezuela were a law-enforcement operation, to which the resolution does not apply.

Why presidents bypass Congress

Historically, presidents have sought to bypass Congress for reasons of personality or politics. Controversial decisions that would struggle to pass through Congress are often made using executive orders.

Obama’s 2011 “We Can’t Wait” initiative used executive orders to enact policy priorities without needing to go through a gridlocked Congress. One such policy was the 2012 creation of the DACA program for undocumented immigrants.

Franklin Roosevelt’s use of executive orders dwarfed that of his predecessors. He issued eight times as many orders in his 12-year tenure than were signed in the first 100 years of the United States’ existence.

The question of what constitutes a genuine threat to the preservation of the nation is especially pertinent now. More than 50 “national emergencies” are currently in effect in the United States.

This was the controversial basis of Trump’s tariff policy under the International Emergency Economic Powers Act. It bypassed Congressional approval and is now being considered by the Supreme Court.

Recent presidents have also increasingly claimed executive privilege to block Congress’ subpoena power.

Institutional wrestling

Institutional wrestling is a feature of Congressional relations with the president, even when the same party controls the White House and both chambers of the legislature, as the Republican party does now.

While Roosevelt dominated Congress, his “court-packing plan” to take control of the US Supreme Court in 1937 proved a bridge too far, even for his own sweeping Democratic majorities. The Democrats controlled three quarters of both the House and Senate and yet refused to back his plan.

More recently, former Democrat Speaker Nancy Pelosi delivered many of Barack Obama’s early legislative achievements, but still clashed with the president in 2010 over congressional oversight.

As House minority leader, she rallied many Democrats against Obama’s US$1.1 trillion (A$1.6 trillion) budget proposal in 2014. Obama was forced to rely on Republican votes in 2015 to secure approval for the Trans-Pacific Partnership, despite his heavy lobbying of congressional Democrats.

Even today’s Congress, which has taken Trump’s direction at almost every turn, demonstrated its influence perhaps most notably by forcing the president into a backflip on the release of the Epstein files after a revolt within Trump’s supporters in the Republican party.

Given the extremely slim Republican majority in Congress, the general unity of the Republican party behind Trump has been a key source of his political strength. That may be lost if public opinion continues to turn against him.

Is Trump breaking the rules?

Trump and his administration have taken an expansive view of presidential power by regularly bypassing Congress.

But he’s not the first president to have pushed the already blurry limits of executive power to redefine what is or is not within the president’s remit. The extent to which presidents are even bound by law at all is a matter of long running academic debate.

Deliberate vagaries in US law and the Constitution mean the Supreme Court is ultimately the arbiter of what is legal.

The court is currently the most conservative in modern history and has taken a sweeping view of presidential power. The 2024 Supreme Court ruling that presidents enjoy extensive immunity suggests the president is, in fact, legally able to do almost anything.

Regardless, public opinion and perceptions of illegality continue to be one of the most important constraints on presidential action. Constituents can take a dim view of presidential behaviour, even if it’s not technically illegal.

Even if Trump can legally act with complete authority, it’s public opinion — not the letter of the law — that may continue to shape when, and if, he does so.

Samuel Garrett does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Congress’ power has been diminishing for years, leaving Trump to act with impunity – https://theconversation.com/congress-power-has-been-diminishing-for-years-leaving-trump-to-act-with-impunity-273099