Avant de cartographier le ciel avec la plus grande caméra au monde : que révèlent vraiment les « premières » images du télescope Vera-C.-Rubin ?

Source: The Conversation – France in French (2) – By Pierre-Alain Duc, Directeur de recherche au CNRS, directeur de l’Observatoire astronomique de Strasbourg, Université de Strasbourg

Zoom dans l’amas de la Vierge. Cette image fait partie des « premières » images prises par le télescope Vera-C.-Rubin. NSF–DOE Vera-C.-Rubin Observatory, CC BY

L’observatoire Vera-C.-Rubin vient de débuter un grand sondage du ciel, le Legacy Survey of Space and Time (LSST) et a livré en juin 2025 de « premières » images au grand public : une grandiose visualisation d’une partie de l’amas de galaxies de la Vierge.

Mais de telles « premières » images ont une importance qu’il convient de relativiser, ou tout au moins recontextualiser car leur intérêt n’est pas forcément celui que l’on croit ou voit immédiatement.

Les images de Vera-C. Rubin se distinguent par la taille de leur champ exceptionnellement grande et la rapidité du nouvel observatoire, qui lui permet de cartographier des lumières même ténues sur une grande partie du ciel plusieurs fois par mois.


La « première lumière » d’un nouvel observatoire est un évènement symbolique et médiatique. Les images dévoilées ce jour-là au public ne sont en effet pas les vraies premières acquisitions – ces dernières servent des objectifs purement techniques et n’ont que peu d’intérêt pour le public. Elles ne témoignent pas forcément des buts scientifiques primaires qui ont motivé la construction du télescope. Elles existent essentiellement pour impressionner et susciter l’intérêt : pour cela, elles doivent posséder une valeur esthétique… qui ne doit pas occulter les performances techniques de l’instrument qui les a générées.

En quoi, alors, cette « première » image du sondage Legacy Survey of Space and Time (LSST), centrée sur l’amas de galaxies de la Vierge, est-elle originale et doit-elle nous interpeller ?

Parce qu’elle dévoile des astres encore inconnus ?

Pas tout à fait. Les structures les plus remarquables, visibles sur cette image, étaient familières, comme ce couple de spirales vues de face (au centre, à droite), cette galaxie naine mais étonnamment étendue et diffuse (en haut à droite) ou, enfin, ces spectaculaires traînées stellaires qui relient plusieurs galaxies d’un groupe situé à l’arrière-plan (en haut à droite), fruits de collisions en cours qui arrachent les étoiles à leurs galaxies.

Ces queues dites « de marée » avaient déjà été cartographiées par des caméras d’ancienne génération, comme Megacam sur le vénérable Canada-France-Hawaii Telescope (CFHT).

Parce que sa qualité optique est exceptionnelle ?

Obtenue depuis le sol, et subissant la turbulence de l’atmosphère qui floute toute lumière venue de l’espace, sa finesse est loin des standards des télescopes spatiaux Hubble, James-Webb ou Euclid, qui présentent une résolution spatiale de 5 à 10 fois meilleure.

Parce qu’elle présente d’éclatantes couleurs ?

Certes, mais depuis que le sondage du Sloan Digital Sky Survey (SDSS) a démarré en 2000, il a systématiquement observé une grande partie du ciel dans des bandes devenues standards (u,g,r,i,z) et a combiné ses images pour produire de « vraies couleurs ». Le public s’est habitué à une vision colorée des objets astronomiques.




À lire aussi :
Comment sont façonnées les images du ciel? Dans les pas du télescope pionnier Hubble


Désormais, chaque nouvelle mission utilise sa propre palette qui varie selon le jeu utilisé de filtres.

Parce qu’elle dispose de canaux de diffusion importants ?

Certainement ! Les États-Unis ont une culture de médiation scientifique bien plus développée qu’en Europe, et leurs agences, dont le département de l’énergie américain et la Fondation nationale pour la science qui portent le projet LSST, accordent des moyens financiers conséquents aux actions de communication, relayées par l’ensemble des partenaires, parmi lesquels, en France, le CNRS dont l’Institut nucléaire et particules est chargé, entre autres, d’une grande partie de la chaîne de traitement des données.

Mais faut-il pour autant faire la fine bouche face à cette belle, mais pas si originale image produite par le LSST ? Assurément, non ! Elle mérite vraiment de s’y intéresser – non donc par ce qu’elle montre, mais par ce qu’elle cache !

Ce que cachent les premières images du nouveau télescope Vera-C.-Rubin et de son sondage LSST : un potentiel énorme et une prouesse technique

Ce qui est réellement derrière cette image, c’est un potentiel scientifique énorme, lui-même résultat d’une prouesse technique remarquable.

L’image a été acquise avec la plus grande caméra au monde. Elle dispose d’un capteur de 3,2 milliards de pixels (en fait une mosaïque de 189 capteurs CCD), soit 100 fois plus qu’un appareil photo classique.

Cette débauche de pixels permet de couvrir un champ de vue sans précédent de 9,6 degrés carrés, soit 45 fois la taille apparente de la pleine Lune ou 35 000 fois celui de la caméra du télescope spatial Hubble.

Avec cette vision large, le LSST pourra cartographier la surface totale de l’amas de la Vierge en seulement 10 clichés (l’image présentée ici ne couvre qu’une partie de l’amas), et quelques dizaines d’heures d’observations, contre quelques centaines d’heures pour le télescope Canada-France-Hawaii, avec lequel nous osions une comparaison plus haut.

La taille de la caméra du LSST est digne de celle de son télescope, pourvu d’un miroir de 8,4 mètres, le plus grand au monde entièrement consacré à l’imagerie. Avec une telle machinerie, l’ensemble du ciel austral peut être observé en seulement trois jours, des performances idéales pour repérer les phénomènes transitoires du ciel, comme les supernovae ou pour découvrir des astéroïdes dont la position varie d’une image sur l’autre.

Chaque nuit d’observation, les terabytes de données s’accumulent et, pendant les dix ans du sondage, les images vont être empilées pour in fine atteindre une sensibilité inégalée, mettant en jeu une chaîne de traitement complexe sans commune mesure avec celles mises en œuvre pour les sondages anciens.

Cette base de données qui, comme le grand vin, se bonifie avec le temps, permettra d’effectuer des avancées dans de multiples domaines de l’astrophysique, de la physique stellaire à la cosmologie.

Alors, oui, il est tout à fait légitime d’être impressionné par cette première image du LSST et par le potentiel de découvertes qu’elle dévoile.

Et pour finir, il convient de rappeler que l’observatoire qui l’a acquise, installé dans le désert chilien de l’Atacama, honore par son nom l’astrophysicienne Vera Rubin, à l’origine de la découverte de la matière noire dans les galaxies. Donner un nom de femme à un projet astronomique d’envergure est aussi une première !

The Conversation

Pierre-Alain Duc 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. Avant de cartographier le ciel avec la plus grande caméra au monde : que révèlent vraiment les « premières » images du télescope Vera-C.-Rubin ? – https://theconversation.com/avant-de-cartographier-le-ciel-avec-la-plus-grande-camera-au-monde-que-revelent-vraiment-les-premieres-images-du-telescope-vera-c-rubin-262066

Kenya’s 1950 Kolloa massacre: Britain won’t own up to its colonial violence but communities need closure

Source: The Conversation – Africa (2) – By Chloé Josse-Durand, Senior Research Associate in African Politics, Newcastle University

In 1950, British forces killed at least 29 civilians in one of the deadliest, but least chronicled, episodes of colonial violence in Kenya.

Armed soldiers killed at least 29 civilian members of Dini ya Msambwa, a spiritual and anti-colonial movement in Kenya active around what is now West Pokot county in the north-western region. Survivors describe the group’s gathering on 24 April 1950 as a peaceful one. However, British colonial forces, fearing a potential uprising, violently confronted the group at the Kolloa trading centre.

It led to one of the highest number of deaths in a single day in a single place in Kenya’s colonial period.

For the surviving families and followers of Dini ya Msambwa (the “religion of the spirits” in Kiswahili), it was a massacre. However, the British government has never publicly apologised for this atrocity.

The movement’s adherents continue to seek justice and recognition, but they face legal, political and historical roadblocks.

I am part of a team at Newcastle University working on Afterlives of Colonial Incarceration, a project focused on former British colonies. I’ve been working closely with communities affected by colonial violence in Kenya, including Dini ya Msambwa adherents.

In my view, Britain’s recognition of the Kolloa massacre isn’t just a matter of historical record. It is about acknowledging that the group’s pain is real, their loss unjust and their struggle worth remembering.

To acknowledge Kolloa as a massacre would open the door to legal and moral accountability from the British government. This would help Dini Ya Msambwa followers affirm the legitimacy of their historical grievances and their place in Kenya’s national story.

Crucially, it could also lay the groundwork for reparations, which could include financial compensation for surviving families, and the restitution of confiscated land and livestock.

The British government remains silent on the massacre. But this doesn’t erase memory. Dini ya Msambwa followers and representatives and historians are working to ensure that Kolloa – like so many forgotten chapters of colonial violence in Africa and beyond – is not buried with the last of its survivors.

The group’s origins

Dini ya Msambwa was founded in the 1940s by Elijah Masinde among the Bukusu people of western Kenya. The movement rejected colonial authority, resisted Christian missionary dominance and called for a return to African spirituality and traditions.

This combination of cultural pride and political defiance made it a target for suppression by British authorities.

Lukas Pkech, a prominent Pokot leader, brought Masinde’s preachings to West Suk and Baringo in the British-administered north-west region in 1950. His teachings were increasingly influential among Pokot communities and were seen as a direct challenge to colonial order.

British district commissioner Arthur Simpsons, along with a contingent of tribal police and British officers led by Alan Stevens, moved to quell the movement and most likely to kill its leader. What followed was a fatal confrontation in Kolloa: over 300 Dini ya Msambwa followers, armed mainly with spears, faced off with colonial security forces in what came to be called the Kolloa Affray.

Pkech and at least 28 followers were killed, along with Stevens, two other British nationals and an African askari (soldier). Oral testimonies suggest that between 44 and 50 people were killed – 29 during the event itself, and 15 to 20 others later succumbing to wounds sustained in the fighting. At least 176 Dini ya Msambwa members present at the standoff were imprisoned. Seven of them were executed for their direct involvement.

This event led to increased repression of Pokot communities and suspected Dini ya Msambwa leaders and followers.

The colonial administration confiscated over 5,600 cattle and deployed a special police force in the region. Residents were forced into hard labour on district roads as part of communal punishment. Hundreds of adherents were thrown into colonial jails and detention camps near the district administrative centre, Kapenguria.

The exact number of Dini ya Msambwa followers today is hard to assess as many choose to remain discreet for their own safety. However, the growing visibility of branches like Dini ya Roho Mafuta Pole ya Africa (African Religion of the Gently Anointing Spirit) indicates the movement’s enduring significance in Pokot society.

Dini ya Roho attracts approximately 4,000 members weekly for worship and yearly for Kolloa commemorations. In the church’s doctrine, the deaths at Kolloa are reinterpreted as a selfless act of sacrifice in fulfilment of peace for the community. Since its official registration in 2012, the church has gained growing influence.

Silencing through legal reform

In 2013, the UK government issued a formal apology and paid £19.9 million (US$26.5 million) in compensation to 5,228 Mau Mau veterans. The compensation was related to Britain’s brutal suppression of the Mau Mau uprising (1952–1960), also known as the “Kenya Emergency”. This was a large-scale anti-colonial rebellion during which more than 150,000 Kenyans were detained without trial in a vast system of camps and fenced villages. Here, torture, forced labour and systematic abuse were widespread.

The Mau Mau case secured an official apology and compensation for colonial-era torture. It also demonstrated that legal redress for historical injustices was possible.

Yet, it was also a strategic concession by the UK government.

It was limited in scope, restricted to a specific group (those tortured during the Emergency), and designed to avoid setting a broad legal precedent.

Since then, the UK has enacted a new law – the Overseas Operations Act – that imposes strict legal limits on claims related to the actions of British troops abroad, effectively barring historical claims.

Worse still, under the legal doctrine known as divisibility of the Crown, claimants must prove that abuses were ordered by the UK government in London, not just carried out by colonial administrators.

In the case of Kolloa, where documentation is sparse and most evidence comes from oral testimonies, this is an almost impossible task.

Further, unlike the Mau Mau case, which gained global attention, Kolloa has remained largely absent from mainstream narratives. The Kenyan government has lacked political will to put pressure on Britain and has itself seen the movement as dangerous. It remained banned until 2012, after the new constitution strengthened protections for freedom of religion and beliefs.

Without strong advocacy from the Kenyan state, Britain has no diplomatic incentive to revisit or acknowledge Kolloa.

Is there still hope for justice?

One promising path is international litigation. In 2022, the Talai clan from Kenya’s Nandi and Kipsigis communities – themselves victims of colonial brutality – brought a case against the UK at the European Court of Human Rights. Their efforts could set a precedent for groups like Dini ya Msambwa seeking redress beyond British courts.

Back home, Kenya’s devolved county government of West Pokot has also given representatives from the church more freedom to speak openly. While the group remains cautious about challenging the national government directly, there’s a growing movement for memorialisation, truth telling and intergenerational dialogue.

For Dini ya Msambwa, the fight is about more than financial compensation. It is about being seen, heard and remembered. The group’s struggle touches on deeper questions of dignity, memory and the right to practise their faith with pride instead of fear and resentment.

The Conversation

Chloé Josse-Durand receives funding from Newcastle University and the Leverhulme Trust.

ref. Kenya’s 1950 Kolloa massacre: Britain won’t own up to its colonial violence but communities need closure – https://theconversation.com/kenyas-1950-kolloa-massacre-britain-wont-own-up-to-its-colonial-violence-but-communities-need-closure-262133

Le système de santé mondial peut se reconstruire après la réduction de l’aide américaine : voici comment

Source: The Conversation – in French – By Jonathan E. Cohen, Professor of Clinical Population and Public Health Sciences, Keck School of Medicine and Director of Policy Engagement, Institute on Inequalities in Global Health, University of Southern California

Les coupes budgétaires drastiques du gouvernement américain ont plongé une grande partie du secteur de la santé mondiale dans un climat de peur et d’incertitude. Autrefois fleuron de la politique étrangère américaine et évaluée à quelque 12 milliards de dollars par an, la santé mondiale a été reléguée au second plan dans un département d’État réorganisé autour de l’agenda « America First ».

Quelle que soit l’issue de la crise actuelle, très différente de ce qu’on a connu par le passé.

Ayant passé 25 ans de ma carrière dans le domaine de la santé mondiale et des droits de l’homme, et enseignant aujourd’hui cette matière à des étudiants de deuxième cycle en Californie, je suis souvent interrogé sur la possibilité, pour les jeunes, d’espérer un avenir dans cette filière. Ma réponse est un oui retentissant.

Plus que jamais, la santé mondiale a besoin de l’engagement, de l’humilité et de la vision de la nouvelle génération, afin de ne plus être tributaire des aléas politiques d’un seul pays. Et plus que jamais, je suis convaincu que cela est possible.

Pour comprendre d’où vient mon espoir, il est important de rappeler ce qui a conduit l’engagement des États-Unis dans la santé mondiale à la situation critique dans laquelle il se trouve aujourd’hui. Et comment une réponse historique à des maladies spécifiques a paradoxalement rendu les systèmes de santé africains vulnérables.

Maladie et dépendance

Il y a plus de vingt ans, le domaine de la santé mondiale tel que nous le connaissons aujourd’hui est né de la riposte internationale au VIH/sida, l’une des pandémies les plus meurtrières de l’histoire de l’humanité. Cette maladie touchait principalement les personnes en âge de procréer et les bébés nés de parents séropositifs.

La création du Plan présidentiel américain d’aide d’urgence à la lutte contre le sida (Pepfar) en 2003 était à l’époque le plus grand programme bilatéral jamais mis en place pour lutter contre une seule maladie. Il a redéfini la santé mondiale pour les décennies à venir, avec les États-Unis au centre. Même si les donateurs et les enjeux se sont multipliés au fil des ans, le domaine est resté marqué par ses origines : le leadership américain dans la lutte contre le VIH/sida.

Le Pepfar a placé les pays africains dans une situation d’extrême dépendance vis-à-vis des États-Unis. Nous en voyons aujourd’hui les résultats, et ce n’est pas la première fois. La crise financière mondiale de 2008 avait déjà réduit l’aide au développement dans le domaine de la santé, ce qui avait suscité une nouvelle réflexion sur le financement et la mobilisation des ressources nationales.

Pourtant, les États-Unis ont continué à financer la lutte contre les maladies en Afrique par le biais de contrats importants avec des universités et des organismes américains. Cela se justifiait par l’urgence du problème, le renforcement des systèmes de santé africains grâce au Pepfar et le devoir moral du pays le plus riche du monde.

Avec la montée du populisme de droite et les effets polarisants de la Covid-19, la santé mondiale allait être considérée par de nombreux Américains comme une « affaire d’élites ». Pendant la pandémie, on a opposé à tort santé publique et économie. Pour les experts, c’est pourtant l’inverse : une population en bonne santé est la condition d’une économie solide.

Cette incompréhension a éloigné une partie de l’opinion des recommandations sanitaires des experts. L’impératif de « vacciner le monde » et de jouer un rôle de premier plan dans la sécurité sanitaire mondiale ne bénéficiait pas d’un soutien suffisant au niveau national. Cet appel à la vaccination n’a pas pesé lourd face aux priorités monopolistiques de l’industrie pharmaceutique, l’isolement et les inquiétudes économiques de millions d’Américains.

Ce contexte a préparé le terrain pour le retrait brutal de l’Amérique de la santé mondiale au début de l’année 2025. Lorsque le Département de l’efficacité gouvernementale (Department of Government Efficiency) a visé l’USAID, beaucoup considéraient la santé mondiale comme un vestige de la réponse initiale au VIH/sida, comme une excuse pour permettre à d’autres gouvernements de réduire leurs dépenses de santé, ou encore comme un secteur réservé à une élite. Une cible facile que la Maison-Blanche ne pouvait ignorer.

C’est pourtant là que réside l’espoir. Née autour d’une seule maladie, façonnée par le soft power américain et portée par un cercle restreint d’experts, la santé mondiale a aujourd’hui l’occasion de se réinventer en profondeur. On pourrait voir naître un nouveau pacte sanitaire mondial, où les gouvernements africains bâtiraient eux-mêmes des systèmes de santé robustes, avec une communauté internationale présente en soutien discret.

Une occasion de reconstruire en mieux

Pour établir un nouveau pacte mondial pour la santé en Afrique, le premier changement doit consister à passer de la lutte contre quelques maladies précises à l’objectif de garantir, pour chacun, la santé et le bien-être tout au long de la vie.

Plutôt que de laisser les systèmes de santé se définir uniquement par la réponse au VIH/sida, à la tuberculose ou au paludisme, l’Afrique doit développer des systèmes intégrés qui privilégient :

  • les soins primaires, qui rapprochent les services répondant à la plupart des besoins de santé des communautés

  • la promotion de la santé, qui permet aux individus de prendre en main tous les aspects de leur santé et de leur bien-être

  • les soins de longue durée, qui aident tous les individus à fonctionner et à maintenir leur qualité de vie tout au long de leur existence.

Aucune tendance mondiale ne rend ce changement plus urgent que le vieillissement de la population. Ce phénomène, lié à l’allongement de l’espérance de vie et à la baisse de la fécondité, touchera tous les pays. Bientôt, la proportion de personnes âgées dépassera celle des enfants. Les sociétés auront alors besoin de systèmes de santé intégrés, capables d’accompagner les patients dans la gestion de plusieurs maladies à la fois.

Elles n’ont pas besoin de programmes fragmentés, sources d’avis médicaux contradictoires, des interactions médicamenteuses dangereuses et une bureaucratie paralysante. Le temps presse pour opérer ce changement en profondeur.

Deuxièmement, il est nécessaire de réorienter les relations entre les pays à faible revenu et les pays à revenu élevé vers un investissement commun au service des besoins locaux. Cela commence à se produire dans certains endroits, et cela exigera des sacrifices plus importants de la part de toutes les parties.

Les gouvernements à faible revenu doivent consacrer une plus grande part de leur PIB aux soins de santé. Cela suppose de s’attaquer aux nombreux facteurs qui entravent la redistribution des richesses, de la corruption à la dette, en passant par l’absence de fiscalité progressive. Les États-Unis et les autres pays à revenu élevé doivent payer leur juste part, tout en partageant les décisions sur la manière dont les biens publics mondiaux – vaccins, surveillance des maladies et professionnels de santé – sont répartis et distribués dans un monde interconnecté.

Troisièmement, il est nécessaire de changer le discours sur la santé mondiale dans les pays riches tels que les États-Unis, afin de mieux répondre aux préoccupations des électeurs hostiles à la mondialisation elle-même. Cela signifie qu’il faut répondre aux craintes réelles des citoyens qui pensent que les mesures de santé publique leur coûteront leur emploi, les obligeront à fermer leur entreprise ou favoriseront les intérêts de l’industrie pharmaceutique. Il faut justifier la santé mondiale en des termes auxquels les gens peuvent s’identifier et adhérer, c’est-à-dire aider à sauver des vies sans assumer la responsabilité des systèmes de santé d’autres pays.

Cela passe par des alliances improbables entre ceux qui croient au leadership des pays dits du Sud et ceux qui ont une vision plus isolationniste du rôle de l’Amérique dans le monde.

Un leadership en retrait

Ne vous y méprenez pas. Je ne compte pas sur cette administration américaine, ni sur aucune autre, pour réinventer la santé mondiale en des termes plus adaptés aux tendances actuelles en matière de maladies, plus équitables entre les nations et plus pertinents pour les électeurs américains.

Mais je ne le souhaite pas non plus. Pour créer la santé mondiale de demain, le leadership ne doit pas venir uniquement des États-Unis, mais plutôt d’un engagement commun de la communauté des nations à donner et à recevoir en fonction de leurs capacités et de leurs besoins. Et c’est là une vraie source d’espoir.

The Conversation

Jonathan E. Cohen 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. Le système de santé mondial peut se reconstruire après la réduction de l’aide américaine : voici comment – https://theconversation.com/le-systeme-de-sante-mondial-peut-se-reconstruire-apres-la-reduction-de-laide-americaine-voici-comment-262827

Arbres urbains ou toitures réfléchissantes : quelle est la meilleure solution pour les villes afin de lutter contre la chaleur ?

Source: The Conversation – in French – By Ian Smith, Research Scientist in Earth & Environment, Boston University

Les arbres comme ceux-ci à Boston peuvent aider à rafraîchir les quartiers pendant les journées chaudes. Yassine Khalfalli/Unsplash, CC BY

Lorsque la chaleur estivale s’installe, les villes peuvent commencer à ressembler à des fours, car les bâtiments et les chaussées emprisonnent la chaleur du soleil, tandis que les véhicules et les climatiseurs rejettent davantage de chaleur dans l’air.

La température dans un quartier urbain dans lequel il y a peu d’arbres peut être supérieure de 5,5 degrés Celsius à celle des quartiers voisins. Cela signifie que la climatisation fonctionne davantage, mettant le réseau électrique à rude épreuve et exposant les habitants aux pannes de courant.

Il existe des mesures éprouvées que les villes peuvent prendre pour rafraîchir l’air, par exemple planter des arbres qui fournissent de l’ombre et de l’humidité, ou créer des toitures réfléchissantes qui réfléchissent le rayonnement solaire vers l’atmosphère au lieu de l’absorber.

Mais ces mesures sont-elles efficaces partout ?

Nous étudions les risques liés à la chaleur dans les villes en tant qu’écologistes urbains, et analysons l’impact de la plantation d’arbres et des toitures réfléchissantes dans différentes villes et différents quartiers. Nos conclusions peuvent aider les villes et les propriétaires à mieux cibler leurs efforts pour lutter contre la chaleur.

La magie des arbres

Les arbres urbains offrent une protection naturelle contre la hausse des températures. Ils apportent de l’ombre et libèrent de la vapeur d’eau par leurs feuilles, un processus similaire à la transpiration humaine. Cela refroidit l’air ambiant et atténue la chaleur de l’après-midi.

L’ajout d’arbres dans les rues, les parcs et les jardins résidentiels peut changer sensiblement la température ressentie dans un quartier, les quartiers arborés étant près d’1,7 °C plus frais que ceux qui le sont moins.

Deux cartes de New York montrent comment la végétation correspond aux zones plus fraîches en fonction de la température
La comparaison des cartes de la végétation et de la température de New York montre l’effet rafraîchissant des parcs et des quartiers plus boisés. Sur la carte de gauche, les couleurs plus claires correspondent aux zones moins boisées. Les zones claires de la carte de droite sont plus chaudes.
NASA/USGS Landsat

Mais planter des arbres n’est pas toujours simple.

Dans les villes chaudes et sèches, les arbres ont souvent besoin d’être irrigués pour survivre, ce qui peut mettre à l’épreuve des ressources en eau déjà limitées. Les arbres doivent survivre pendant des décennies pour atteindre une taille suffisante afin de fournir de l’ombre et libérer assez de vapeur d’eau pour réduire la température de l’air.

Les coûts d’entretien annuels, estimés à environ 900 dollars américains annuels par arbre à Boston, peuvent dépasser l’investissement initial de plantation.

La difficulté, c’est que les quartiers urbains denses, où la chaleur est la plus intense, sont souvent trop encombrés de bâtiments et de routes pour permettre la plantation d’arbres supplémentaires.

Comment les toitures réfléchissantes peuvent aider pendant les journées chaudes

Une autre option consiste à recourir aux toitures réfléchissantes. Recouvrir les toitures d’une peinture réfléchissante ou utiliser des matériaux de couleur claire permet aux bâtiments de réfléchir davantage la lumière du soleil vers l’atmosphère au lieu de l’absorber sous forme de chaleur.

Ces toitures peuvent réduire la température à l’intérieur d’un immeuble sans climatisation d’environ 1 à 3,3 °C et peuvent réduire la demande maximale de climatisation jusqu’à 27 % dans les bâtiments climatisés, selon une étude. Elles peuvent également procurer un rafraîchissement immédiat en réduisant les températures extérieures dans les zones densément peuplées. Les coûts d’entretien sont aussi plus faibles que ceux liés à l’expansion des forêts urbaines.

Deux ouvriers appliquent de la peinture sur un toit plat
Deux ouvriers appliquent un revêtement blanc sur le toit d’une maison mitoyenne à Philadelphie.
AP Photo/Matt Rourke

Cependant, tout comme les arbres, les toitures réfléchissantes ont leurs limites. Elles sont plus efficaces sur les toits plats que sur les toits en pente recouverts de bardeaux, car les toits plats sont souvent recouverts de caoutchouc qui emprisonne la chaleur et sont exposés à un ensoleillement plus direct l’après-midi.

Les villes disposent également d’un nombre limité de toits susceptibles d’être convertis. Et dans les villes qui comptent déjà de nombreux toits de couleur claire, quelques toitures supplémentaires pourraient contribuer à réduire les coûts de climatisation dans ces bâtiments, mais elles n’auraient pas beaucoup d’effet à l’échelle du quartier.

En évaluant les avantages et les inconvénients des deux stratégies, les villes peuvent concevoir des plans adaptés à leur situation pour lutter contre la chaleur.

Choisir la bonne combinaison de solutions de refroidissement

De nombreuses villes à travers le monde ont pris des mesures pour s’adapter à la chaleur extrême, avec des programmes de plantation d’arbres et de toitures réfléchissantes qui imposent des exigences en matière de réflectivité ou en encouragent l’adoption.

À Detroit, des organisations à but non lucratif ont planté plus de 166 000 arbres depuis 1989. À Los Angeles, les codes du bâtiment exigent désormais que les toits des nouvelles constructions résidentielles respectent des normes de réflectivité spécifiques.

Dans une étude récente, nous avons analysé le potentiel de Boston pour réduire la chaleur dans les quartiers vulnérables de la ville. Les résultats montrent comment une stratégie à coût maîtrisé pourrait apporter des bénéfices significatifs en matière de refroidissement.

Par exemple, nous avons constaté que la plantation d’arbres peut refroidir l’air de 35 % de plus que l’installation de toitures réfléchissantes dans les endroits où il est possible de planter des arbres.

Cependant, la plupart des meilleurs emplacements pour planter de nouveaux arbres à Boston ne se trouvent pas dans les quartiers qui en ont le plus besoin. Dans ces quartiers, nous avons constaté que les toitures réfléchissantes constituaient un meilleur choix.

En investissant moins de 1 % du budget annuel de fonctionnement de la ville, soit environ 34 millions de dollars, dans 2 500 nouveaux arbres et 3 000 toitures réfléchissantes ciblant les zones les plus à risque, nous avons constaté que Boston pourrait réduire l’exposition à la chaleur pour près de 80 000 habitants. Cela permettrait de réduire la température de l’air l’après-midi en été de plus de 0,6 °C dans ces quartiers.

Bien que cette baisse puisse sembler modeste, il a été démontré que des réductions de cette ampleur diminuent sensiblement les maladies et les décès liés à la chaleur, augmentent la productivité et réduisent les coûts énergétiques liés à la climatisation des bâtiments.

Toutes les villes ne bénéficieront pas de la même combinaison. Le paysage urbain de Boston comprend de nombreux toits plats et noirs qui ne réfléchissent qu’environ 12 % de la lumière solaire, ce qui rend les toitures réfléchissantes qui réfléchissent plus de 65 % de la lumière solaire particulièrement efficaces. Boston bénéficie également d’une saison de végétation relativement humide qui favorise le développement d’un couvert forestier urbain luxuriant, rendant ces deux solutions viables.

Deux images aériennes montrent des couleurs de bâtiments très différentes dans deux villes
Phoenix, à gauche, compte déjà de nombreux toits de couleur claire, contrairement à Boston, à droite, où les toits sont principalement sombres.
Imagerie Google 2025

Dans les endroits où il y a moins de toits plats et sombres pouvant être convertis en toitures réfléchissantes, la plantation d’arbres peut apporter davantage de bénéfices. À l’inverse, dans les villes où il reste peu d’espace pour planter de nouveaux arbres ou où la chaleur extrême et la sécheresse limitent la survie des arbres, les toitures réfléchissantes peuvent être une meilleure solution.

Phoenix, par exemple, compte déjà de nombreux toits de couleur claire. Les arbres pourraient être une option, mais ils nécessiteraient un système d’irrigation.


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Apporter les solutions là où les gens en ont besoin

La création de zones ombragées le long des trottoirs peut avoir un double effet en offrant aux piétons un endroit pour s’abriter du soleil et en rafraîchissant les bâtiments. À New York, par exemple, les arbres de rue représentent environ 25 % de la forêt urbaine totale.

Les toitures réfléchissantes peuvent être plus difficiles à déployer pour les autorités publiques, car elles nécessitent la collaboration des propriétaires. Cela signifie souvent que les villes doivent proposer des mesures incitatives. Louisville, dans le Kentucky, par exemple, accorde des rabais pouvant aller jusqu’à 2 000 dollars aux propriétaires qui installent des matériaux de toiture réfléchissants, et jusqu’à 5 000 dollars aux entreprises commerciales dotées de toits plats qui utilisent des revêtements réfléchissants.

Deux graphiques montrent les améliorations
À Boston, la plantation d’arbres (à gauche) et l’augmentation de la réflectivité des toitures (à droite) se sont avérées des moyens efficaces pour refroidir les zones urbaines.
Ian Smith et al. 2025

De telles initiatives peuvent contribuer à étendre les bénéfices des toitures réfléchissantes dans les quartiers densément peuplés qui ont le plus besoin d’être rafraîchis.

Alors que les changements climatiques entraînent une augmentation de la fréquence et de l’intensité des vagues de chaleur urbaine, les villes disposent d’outils puissants pour faire baisser la température. En prêtant attention à ce qui existe déjà et à ce qui est faisable, elles peuvent trouver la meilleure stratégie en fonction de leurs besoins et de leurs réalités.

La Conversation Canada

Lucy Hutyra a reçu des subventions du gouvernement fédéral américain et de fondations telles que le World Resources Institute et le Burroughs Wellcome Fund pour ses recherches sur le climat urbain et les stratégies d’atténuation. Elle a reçu une bourse MacArthur 2023 pour ses travaux dans ce domaine.

Ian Smith 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. Arbres urbains ou toitures réfléchissantes : quelle est la meilleure solution pour les villes afin de lutter contre la chaleur ? – https://theconversation.com/arbres-urbains-ou-toitures-reflechissantes-quelle-est-la-meilleure-solution-pour-les-villes-afin-de-lutter-contre-la-chaleur-262412

My research team used 18 years of sea wave records to learn how destructive ‘rogue waves’ form – here’s what we found

Source: The Conversation – USA – By Francesco Fedele, Associate Professor of Civil and Environmental Engineering, Georgia Institute of Technology

Rogue waves have captivated the attention of both seafarers and scientists for decades. These are giant, isolated waves that appear suddenly in the open ocean.

These puzzling giants are brief, typically lasting less than a minute before disappearing. They can reach heights of 65 feet (20 meters) or greater and often more than twice the height of surrounding waves. Once a nautical myth, rogue waves have now been observed around the world. Because they’re so tall and powerful, they can pose a danger to ships and offshore structures.

To rethink what rogue waves are and what causes them, I gathered an international team of researchers. Our study, published in Nature Scientific Reports, sheds light on these oceanic giants using the most comprehensive dataset of its kind.

By analyzing 18 years of high-frequency laser measurements from the Ekofisk oil platform in the central North Sea, we reached the surprising conclusion that rogue waves aren’t just freak occurrences. They arise under the natural laws of the sea. They are not mysterious, but somewhat simple.

27,500 sea states

We analyzed nearly 27,500 half-hour wave records, or sea states, collected between 2003 and 2020 in the central North Sea. These records, taken every 30 minutes, describe how elevated the sea surface was compared to the average sea level. They include major storms, such as the Andrea wave event in 2007.

Several structures standing in the sea.
A complex of platforms on the Ekofisk oil field in the North Sea.
BoH/Wikimedia Commons, CC BY-SA

Under normal conditions, waves arise from wind blowing over the sea surface. It’s like when you blow over your cup of coffee and form small ripples on the surface. At sea, with enough time and space, those ripples can turn into large waves.

We focused on understanding what causes waves to suddenly go rogue and rise far above their neighboring waves. One proposed theory is based on modulational instability, a phenomenon described by complex mathematical models. I’ve revised these models in the past, as my work suggests that this theory doesn’t fully explain what causes rogue waves in the open ocean.

A diagram showing the height of waves in different sea states, with the tallest reaching about half the height of a large commercial boat.
Sea states record the height of waves and show when some waves rise high above sea level.
U.S. Government Accountability Office

When waves are trapped within a narrow channel, the modulational instability theory describes their rippling movement well. However, it starts to fall apart when you look at the real ocean. In open environments such as the North Sea, waves are free to propagate from multiple directions.

To understand the difference, imagine a crowd of spectators leaving a stadium after a football game. If the exit is a long, narrow hallway with tall walls, people are forced to move in a single direction. Those at the back push forward, and some may even climb over others, piling up between the confining walls. This catastrophic pileup would resemble a rogue wave, caused by their confinement.

In contrast, if the stadium’s exit opens onto a wide field, spectators can disperse freely in all directions. They don’t push on each other, and they avoid pileups.

Similarly, researchers can generate rogue waves in a confined channel in the lab, where they obey modulational instability. But without the confinement of a channel, rogue waves usually won’t follow those physics or form the same way in the open sea.

Our team knew we had to study the open sea directly to figure out what was really going on. The real-world data my team examined from the North Sea doesn’t line up with modulational instability – it tells a different story.

A sailboat caught in the swell of a tall wave, under a cloudy sky
Rogue waves are much taller than the others around them.
John Lund/Stone via Getty Images

It’s just a bad day at sea

We analyzed the sea state records using statistical techniques to uncover patterns behind these rare events. Our findings show that instead of modulational instability, the extreme waves observed more likely formed through a process called constructive interference.

Constructive interference happens when two or more waves line up and combine into one big wave. This effect is amplified by the natural asymmetry of sea waves – their crests are typically sharper and steeper than their flatter troughs.

Rogue waves form when lots of smaller waves line up and their steeper crests begin to stack, building up into a single, massive wave that briefly rises far above its surroundings. All it takes for a peaceful boat ride to turn into a bad day at sea is a moment when many ordinary waves converge and stack.

These rogue waves rise and fall in less than a minute, following what’s called a quasi-deterministic pattern in space and time. This type of pattern is recognizable and repeatable, but with touches of randomness. In an idealized ocean, that randomness would almost vanish, allowing rogue waves to grow to nearly infinite heights. But it would also take an eternity to witness one of these waves, since so many would have to line up perfectly. Like waiting for Fortuna, the goddess of chance, to roll a trillion dice and have nearly all of them land on the same number.

In the real ocean, nature limits how large a rogue wave can grow thanks to wave breaking. As the wave rises in height and energy, it can’t hold itself beyond a certain point of no return. The tip of the wave spills over and breaks into foam, or whitecap, releasing the excess energy.

The quasi-deterministic pattern behind rogue waves

Rogue waves aren’t limited to the sea. Constructive interference can happen to many types of waves. A general theory called the quasi-determinism of waves, developed by oceanographer Paolo Boccotti, explains how rogue waves form, both in the ocean and in other wave systems.

For example, for turbulent water flowing through a confined channel, a rogue wave manifests in the form of an intense, short-lived spike in vortices – patterns of spinning swirls in the water that momentarily grow larger as they move downstream.

While ocean waves seem unpredictable, Boccotti’s theory shows that extreme waves are not completely random. When a really big wave forms, the waves in the sea around it follow a recognizable pattern formed through constructive interference.

We applied Boccotti’s theory to identify and characterize these patterns in the measured North Sea wave records.

The giant waves observed in these records carry a kind of signature or fingerprint, in the form of a wave group, which can reveal how the rogue wave came to life. Think of a wave group like a small package of waves moving together. They rise, peak and then fade away through constructive interference. Tracking these wave groups allows researchers to understand the bigger picture of a rogue event as it unfolds.

As one example, a powerful storm hit the North Sea on Nov. 24, 2023. A camera at the Ekofisk platform captured a massive 55 foot (17 meter) rogue wave. I applied the theory of quasi-determinism and an AI model to investigate the origin of this extreme wave. My analysis revealed that the rogue event followed these theories – quasi-determinism and constructive interference – and came from multiple smaller waves repeatedly stacking together.

Left: Stereo video footage of a powerful storm in the North Sea on Nov. 24, 2023, recorded at the Ekofisk platform.
Right: The wave group signature of the recorded rogue wave.

Recognizing how rogue waves form can help engineers and designers build safer ships and offshore platforms – and better predict risks.

The Conversation

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

ref. My research team used 18 years of sea wave records to learn how destructive ‘rogue waves’ form – here’s what we found – https://theconversation.com/my-research-team-used-18-years-of-sea-wave-records-to-learn-how-destructive-rogue-waves-form-heres-what-we-found-260900

Women in STEM face challenges and underrepresentation – this course gives them tools to succeed

Source: The Conversation – USA – By Filomena Nunes, Professor of Physics, Michigan State University

Women with strong networks and communities are most likely to succeed in the STEM fields. LWA/Dann Tardif via Getty Images

As a graduate student in physics, I was often the only woman in the room. As I gained more experience, I learned valuable lessons about the scientific community and how to better advance my career. Once I started mentoring female graduate students, I realized that many of them had also felt alienated around some scientists, an experience that chipped away at their confidence or the passion for their work.

Over two decades of doing research and mentoring students, I have compiled some tools that give women the power to improve their own experiences in the STEM world. In 2019, I turned these resources into an experiential course called Tools for Women in STEM. Although the course is designed for women, all genders are welcome.

There are many reasons women are underrepresented in STEM, including bias and stereotypes, but also workplace cultures and the absence of policies for work-life balance. A report from the American Association for University Women makes recommendations for improving the retention of women in STEM careers: ensuring women are getting the mentoring they need, supporting a work-life balance and creating a welcoming culture.

This is all easier said than done. Despite the many programs and initiatives implemented across the country since 2010, when the AAUW report came out, the percentage of women in many fields of science, technology, engineering and math continues to stay very low, with a trend that is flat at best. Even if they come into the field, many choose to leave.

What does the course explore?

To help young women navigate their professional lives in STEM, I start by taking each student on a personal journey, beginning by contextualizing their experiences in STEM. Students reflect on the shame triggers that can make them feel like they’re not good enough even when their record is stellar, as well as any biases they may have about others. Self-awareness is an essential starting point.

Students then work on skills with real-life impact, ranging from networking at meetings and building effective relationships with mentors to negotiations, dealing with harassment and exploring leadership roles. This is done through in-class activities and often followed up with practice in their real life.

Two women, one older and one younger, sitting in front of a computer screen.
Strong relationships with mentors can help women succeed in the STEM field.
Willie B. Thomas/DigitalVision via Getty Images

What does the course prepare students to do?

Prepped by videos and papers, students practice these skills and discuss strategies in small groups. This model provides an opportunity for collaboration and for assimilating and sharpening all the skills covered in the course.

Take mentoring as an example. Students practice reaching out to potential mentors and establishing a new mentoring relationship. Through discussion, students learn to both receive and provide useful feedback. When students have a safe, trusting environment, they’re more inclined to try out new things.

During the last month of the course, students practice communicating effectively in a wide range of circumstances characteristic of a STEM career. They focus on one type of communication each week: scientific presentations, posters, research group meetings and outreach, all important skills in a STEM job that aren’t always formally taught.

We wrap up the course with a “Women in STEM” outreach event that is fully created and implemented by the students themselves. This event has ranged from organizing a STEM research fair, speaking to undergrads about bridges between STEM and real life, and collecting sticky notes from researchers about their experiences in STEM.

A chalkboard covered in post it notes.
Graduate students in the Tools for Women in STEM course collected sticky notes about other researchers’ experiences in the STEM field as part of the course.
Filomena Nunes

As students work together in a safe, trusting environment, they develop their own voices and gain confidence. And the connections established during the course can continue throughout their graduate program.

Why is this course relevant now?

Today, women in STEM have higher expectations for their workplace than those of previous generations, and they are less tolerant of toxic environments. Courses like this can empower students to advocate for a better experience and promote a healthy culture for women in STEM.

Women aren’t the only group underrepresented in STEM. Instruction that tailors these lessons to the challenges faced by other identity groups could help many other students succeed.

Uncommon Courses is an occasional series from The Conversation U.S. highlighting unconventional approaches to teaching.

The Conversation

Filomena Nunes receives funding from NSF and DOE.

ref. Women in STEM face challenges and underrepresentation – this course gives them tools to succeed – https://theconversation.com/women-in-stem-face-challenges-and-underrepresentation-this-course-gives-them-tools-to-succeed-261505

The new NextGen Acela trains promise faster travel and more seats – but arrive as US rail faces an uncertain future

Source: The Conversation – USA – By David Alff, Associate Professor of English, University at Buffalo

The new Acela trains are scheduled to start running on the Northeast Corridor soon. Courtesy of Amtrak

When former President Joe Biden unveiled his US$1.9 trillion infrastructure plan in 2021, he found the perfect place to go public: Philadelphia’s 30th Street Station rail yard.

Over the din of crackling wires and grumbling engines, the president made his case for revitalizing the country’s roads, ports, airports and rail lines.

Behind Biden sat rows of gleaming Amtrak trains. Among them was a prototype of NextGen Acela, a sleek machine engineered to deliver the fastest passenger service in American history.

On Aug. 28, 2025, NextGen will finally hit the rails, after years of delays.

As the author of a book on the Northeast Corridor, the rail line that connects Boston, New York, Philadelphia and Washington, I know this new train cannot come soon enough for many seaboard riders, even though it launches at a time of diminished political will for passenger rail.

Interior of modern train with seats with red headrests
Red headrests distinguish first-class cars from business class on the NextGen Acela trains.
Courtesy of Amtrak

Rail renaissance under fire

The French-designed, American-manufactured NextGen arrives years late due to mechanical defects and failed simulation tests mandated by the Federal Railroad Administration. The new Acela will begin whisking passengers along the corridor after a chaotic year that saw downed wires, busted circuit breakers and brushfires disrupt Amtrak operations.

Gone is Amtrak’s White House champion, railfan-in-chief Biden, replaced by Donald Trump, whose one-time adviser, Elon Musk, called Amtrak a “sad situation,” and who proposed replacing the government-owned carrier with private competitors.

Man in suit and blue baseball cap speaks behind a lectern in front of a train with an urban skyline in the background
Former President Joe Biden delivers remarks at an Amtrak 50th anniversary event in Philadelphia in 2021.
AP Photo/Patrick Semansky

Amtrak CEO Stephen Gardner resigned in March 2025, and, in May, Amtrak cut 450 employee positions.

NextGen Acela promises an American rail renaissance in a moment when federally sponsored trains are fighting for their lives, as Biden’s infrastructure ambitions fall to an administration bent on cutting government costs.

These contradictions, however, are nothing new.

Not-so-fast trains

America’s love-hate relationship with fast trains stretches back to October 1964, when Japanese National Railways opened its Shinkansen high-speed line between Tokyo and Osaka.

Japan’s iconic 130-mph bullet train entranced audiences, many of whom saw footage of the new service during televised coverage of the Tokyo Olympics.

High-speed bullet train crosses bridge between skyscrapers
A Shinkansen high-speed bullet train passes through Tokyo.
Richard A. Brooks/AFP via Getty Images

Americans wanted their own bullet train but were reluctant to pay the massive infrastructural costs of a Shinkansen system. When Congress passed the High-Speed Ground Transportation Act of 1965, it prioritized the development of trains over the reconstruction of tracks, power systems and maintenance facilities.

The resulting services underperformed.

On Dec. 20, 1967, a gas turbine train manufactured by United Aircraft topped 170 mph while testing in New Jersey. But when the so-called TurboTrain entered service, it managed an average pace of just 63 mph on the weaving track between New York and Boston.

The electric-powered Metroliner, which began service in 1969, boasted similar potential but rarely held triple-digit speeds in service and broke down so often that its carrier, the Penn Central Railroad, struggled to keep the trains running between New York and Washington.

Historians usually regard these high-speed forays as resounding failures.

But riders loved them.

Technical flaws aside, both the TurboTrain and Metroliner were a hit with northeastern riders, so much so that Amtrak retained the Metroliner brand until 2006, long after it had retired the ‘60s-era trains.

Reflecting in 1999, rail journalist Don Phillips expressed disbelief “that those dogs were actually popular with the riding public.”

The birth of Acela

Amtrak opened a new era of high-speed rail in 2000 when it launched Acela Express.

Derived from France’s acclaimed TGV design, Acela carries passengers at speeds up to 150 mph on the Northeast Corridor.

Like the Metroliner before it, Acela suffered from design problems and mechanical faults, including cracked yaw dampers and brake discs, which temporarily sidelined the trains.

Rail writer Joseph Vranich described Acela as both “Amtrak’s crown jewel” and a “remarkable fiasco.”

And yet riders flocked to the service. Acela became one of Amtrak’s most popular and lucrative trains – so attractive that it lured business travelers off regional airlines.

When Acela entered service in 2000, Amtrak trains claimed just 37% of air-rail traffic between New York and Washington. By 2021, it had 83%. Between New York and Boston, that figure jumped from 20% to 75%.

Passengers stand on platform waiting to board a train
Acela trains are popular and lucrative for Amtrak, in part because they draw so many business travelers.
Anna Moneymaker via Getty Images

Acela 2.0

Now, NextGen Acela takes up the fraught legacy of American high-speed rail. What can we expect of the new train?

NextGen is faster than the original Acela but will not set any world speed records. Its top velocity of 160 mph falls short of global benchmarks set by China’s Fuxing, which hits 217 mph, and Japan’s newest Shinkansens, which reach 200 mph.

With better tracks and signals, NextGen could conceivably ramp up to 186 mph, though such speeds won’t be possible anytime soon.

For now, NextGen will make do with an imperfect corridor. The train’s lightweight design means faster acceleration and lower energy consumption. An enhanced dynamic tilting system will let carriages lean into curves on the corridor’s twisting track, so they lose less speed on turns. The original Acela also tilted, but not as much.

Modern white-and-red bathroom with changing table open
The NextGen Acela bathrooms are more spacious and have more touchless features than the previous design.
Courtesy of Amtrak

The upgraded onboard experience includes winged headrests, seat-side USB ports and 5G Wi-Fi. More importantly, each NextGen train can seat 82 more passengers than its predecessor. When Amtrak’s full fleet of 28 NextGens enters service, sending the first-generation trains into retirement, Acela service capacity will have increased by 4,728 seats.

This figure may be the train’s greatest achievement in a congested region at a time when Amtrak is posting record ridership.

The effects of the Northeast’s post-pandemic passenger surge are nowhere more visible than the Philadelphia rail yard where Biden spoke four years ago. Amtrak is constructing a new maintenance shop beside the Schuylkill River that will service NextGen trains and cement Philly’s role in the railroad’s addition of a million annual seats to its non-Acela corridor trains. Powered by conventional electric locomotives, these slower, cheaper “Regionals” accounted for 77% of corridor ridership in 2024 and will continue to carry the bulk of northeastern passengers.

Meanwhile, a quarter-mile south of the maintenance shop, America’s third-busiest passenger hub, 30th Street Station, is receiving a generational overhaul with a new food court, exterior plaza, shops and underground access to rapid transit.

These projects demonstrate the economic power of fast, frequent trains in Philly and throughout trackside communities of the Northeast. America’s embattled but resilient high-speed rail tradition may never be the world’s best, but even incremental improvements, like NextGen, cannot help but transform the places they serve.

For Amtrak’s corridor region, the stakes have never been higher.

Read more of our stories about Philadelphia.

The Conversation

David Alff is a member of the Empire State Passenger Association.

ref. The new NextGen Acela trains promise faster travel and more seats – but arrive as US rail faces an uncertain future – https://theconversation.com/the-new-nextgen-acela-trains-promise-faster-travel-and-more-seats-but-arrive-as-us-rail-faces-an-uncertain-future-256675

San Francisco and other cities, following a Supreme Court ruling, are arresting more homeless people for living on the streets

Source: The Conversation – USA – By Stephen Przybylinski, Assistant Professor of Geography, Michigan State University

A person walks past a homeless encampment in the Skid Row community in Los Angeles in June 2024. Mario Tama/Getty Images

Homelessness is on the rise in the United States, and in some places, it is becoming more common for the police to arrest someone for sleeping or living in a public space.

In June 2024, the Supreme Court issued a ruling, Grants Pass v. Johnson, that determined it is constitutional to issue citations to or arrest homeless people, even when there is no available shelter.

The ruling reversed earlier federal appeals court rulings from 2019 and 2022 that determined cities cannot enforce anti-camping laws against homeless people if there are not enough shelter beds available for them.

The Supreme Court’s ruling also determined that the Eighth Amendment’s prohibition on cruel and unusual punishments does not protect homeless people from laws criminalizing resting in public places.

As someone who has spent more than a decade researching homelessness and speaking with unhoused communities, I have seen firsthand how enforcement of such laws imposes unavoidable hardships on homeless people and makes it harder for them to find a stable home.

A woman wearing a white pantsuit walks alongside a few people in a street that is littered in front of a few large buildings.
Los Angeles Mayor Karen Bass visits the site of a city-led sweep of a homeless encampment in Van Nuys, Calif., on July 31, 2025.
David Pashaee/Middle East Images/AFP via Getty Images

A rise in punitive action against homelessness

In 2024, there were an estimated 771,480 people in the U.S. who experienced homelessness on a single night, the highest number ever recorded.

Since June 2024, almost 220 local measures have passed that restrict or ban acts like sleeping, sitting or panhandling in public in cities that include Phoenix; Gainesville, Florida, and Reno, Nevada.

The rate of unsheltered homelessness, meaning homeless people who are sleeping in places that are not meant for humans to rest in, like parks or cars, is the highest in California.

After the Supreme Court’s decision, California Gov. Gavin Newsom issued an executive order in July 2024 that directs state agencies and departments to adopt new policies that remove homeless encampments. Those are temporary outdoor living spaces used by homeless people, often on public or private property.

Following this executive order, more than two dozen California cities and towns adopted or considered adopting sweeping bans on homeless encampments.

Not every leader has embraced this approach of what some observers call criminalizing homelessness. Los Angeles Mayor Karen Bass, for example, rejected criminalizing homelessness as “backwards” in June 2024.

Nevertheless, many cities are enforcing existing and new bans on homeless encampments more aggressively than before the Supreme Court decision – despite evidence that such enforcement is not effective in dealing with the problem of homelessness.

The impacts of aggressive enforcement

Research shows that arresting someone without a home for sitting, resting or sleeping in a public place does not reduce homelessness.

Instead, encampment sweeps and camping bans typically displace people from one area to another, while discarding or destroying their personal belongings in the process, such as identification cards, medications and sleeping gear.

This approach also wastes public resources by paying groups to throw away people’s belongings instead of investing that money into actual housing solutions, like creating more affordable housing options.

Homeless encampment sweeps by police or other government officials are also shown to make people living in camps sicker, leading to increases in hospitalizations and even deaths among those dependent on drugs or alcohol.

A punitive shift in San Francisco

San Francisco is an example of an American city with a relatively large homeless population that has taken a more aggressive approach to enforcing bans on homeless encampments over the past year.

A few weeks after the Supreme Court decision, then-San Francisco Mayor London Breed promised to be “very aggressive” in removing homeless encampments. She also said that “building more housing” would not solve the homelessness crisis.

City data shows that in the 12 months since the Supreme Court ruling, San Francisco police had arrested more than 1,000 homeless people for living in a public space – a scale of enforcement rarely seen in the city’s past. In the year leading up to the ruling, 111 people were arrested for illegal lodging

San Francisco identified approximately 8,300 homeless city residents in 2024.

In June 2025, I conducted a survey of 150 homeless people in San Francisco. About 10% of those people who gave a reason for a recent arrest reported being jailed for lodging without permission. Another 6% said they were arrested for trespassing.

In the same survey, which is part of an ongoing project, 54% of homeless San Francisco residents reported being forced to move from a public space at least once.

Another 8% reported being cited for another reason related to trespassing.

A less aggressive path in Portland

Other western American cities with large homeless populations have taken slightly different approaches to removing homelessness encampments since June 2024.

Portland, Oregon, for example, began enforcing a new daytime camping ban in July 2024. But Portland police have only made 11 arrests of homeless people for camping-related violations over the past year.

Other homeless people in Portland have received police citations for other offenses, like trespassing.

As part of my June 2025 study, I surveyed 150 homeless Portland residents. About 49% of respondents reported having been arrested at some point in their lives. Though no respondents were arrested for camping in a prohibited place, 68% of people I spoke with reported that police or other government officers forced them to leave a public space at some point over the past year.

And 13% of those who gave a reason for being cited by police said it was for camping in a prohibited place. Another 11% of homeless people were cited for some other reason related to living without shelter.

As part of the study, I also interviewed residents who had been arrested while living on the street. One Portland resident I interviewed – who asked not to be named to preserve their anonymity – told me they lost the chance to rent an apartment because they were arrested in 2023 on a preexisting, unrelated warrant after a police officer checked their ID – just days before they were supposed to pick up their keys.

“Many unhoused people have warrants simply for failing to appear after being cited for sitting or resting in public space,” they said. “I was supposed to go get the keys and, bam, I got picked up. I was arrested and went to court. Just me being in jail for five, six or five days screwed it all. I didn’t show up to get the keys, and then (the landlord) couldn’t get ahold of me, and they had no idea what was going on.”

The weeklong jail stay not only pushed this person back onto the street, but it also put them back onto a waiting list for housing – where they remain in 2025.

A person wearing a dark sweatshirt and hat holds onto a wheelchair as a man crouches in front of a tent next to the wheelchair.
A volunteer helps a person into his tent after relocating him from one park to another in Grants Pass, Oregon, in March 2024.
AP Photo/Jenny Kane

Looking ahead

The Supreme Court’s 2024 ruling did not mandate that cities criminalize homelessness. But it effectively gave cities the green light to do so without fear of violating people’s constitutional protections.

The effects of this ruling will be further felt with President Donald Trump’s July 24, 2025, executive order that ended federal support for approaches like Housing First, a policy that prioritizes providing homeless people with housing, before any other needed help. The order also calls for involuntarily committing homeless people with mental illness to mental health institutions.

As more cities consider tougher encampment ordinances, I think it is worth considering if more punitive measures really address homelessness. Decades of evidence suggest they won’t.

Instead, arresting homeless people often deepens their poverty, increases displacement and diverts public funding away from the real solution – stable, affordable housing.

The Conversation

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

ref. San Francisco and other cities, following a Supreme Court ruling, are arresting more homeless people for living on the streets – https://theconversation.com/san-francisco-and-other-cities-following-a-supreme-court-ruling-are-arresting-more-homeless-people-for-living-on-the-streets-262664

4 laws that could stymie the Trump EPA’s plan to rescind the endangerment finding that underpins US climate policies

Source: The Conversation – USA (2) – By H. Christopher Frey, Glenn E. Futrell Distinguished University Professor of Environmental Engineering, North Carolina State University

U.S. Interior Secretary Doug Burgum, left, takes a selfie with Energy Secretary Chris Wright, center, and EPA Administrator Lee Zeldin in front of the Trans-Alaska oil pipeline. AP Photo/Jenny Kane

The Trump administration’s plan to unravel many of the nation’s climate policies hinges on rescinding what’s known as the endangerment finding. But its strategy for doing that appears to run afoul of several federal laws.

The endangerment finding is a 2009 determination by the Environmental Protection Agency that six greenhouse gases, including carbon dioxide, contribute to climate change and therefore pose a threat to public health and welfare.

The scientific evidence of these threats has gotten stronger in the years since the endangerment finding was made. That evidence is laid out in multiple national and international reports written by hundreds of scientists who reviewed the data and research.

In contrast, the EPA’s proposal to now rescind the endangerment finding is based in part on a new Department of Energy report written by five people, named as the “Climate Working Group.” All five have been outspoken critics of mainstream climate science. Energy Secretary Chris Wright said he handpicked the group to write the report.

The group’s report cherry-picks information and misrepresents uncertainties. Some scientists whose studies it cites have complained that the authors misrepresented their research. Others are speaking out about factual problems with the report.

I have served in the federal government and on numerous scientific federal advisory committees, and I’ve seen firsthand the rigorous requirements that federal agencies are supposed to meet so that scientific information they disseminate can be trusted by the public.

The Energy Department and the EPA seem to have run afoul of four laws in particular that may be tricky for the administration to get around.

1. Has the Energy Department produced a credible report?

A casual reader might think the Energy Department climate report is credible.

Its inside cover affirms that it “is being disseminated … in compliance with” the Information Quality Act. The word “disseminated” means that this is a final report and not just a draft.

The Information Quality Act, passed by Congress in 2000, requires “ensuring and maximizing the quality, objectivity, utility, and integrity of information (including statistical information) disseminated by Federal agencies.”

An image of the title page pointing out important problems.
The author annotates the title page of the Energy Department’s report.
Christopher Frey

This law is the basis for federal guidance on scientific peer review for all agencies. It also requires agencies to provide the public with an opportunity to request corrections in final reports if they were not properly developed or lack balance, accuracy and objectivity. The agency decides whether to grant the request, but there is an appeals process.

Government scientific products considered final also must have previously undergone independent external peer review conducted in an “open and rigorous manner,” according to the White House Office of Management and Budget.

One author of the Energy Department’s report stated that the report was reviewed by “eight scientists/administrators employed by the DOE.” However, this does not meet the government’s standards for implementing the law, which requires a public record of review by scientific experts not affiliated with the department that issued the report.

2. Agencies cannot cherry-pick groups to give answers they want

The Federal Advisory Committee Act of 1972, or FACA, addressed concerns that “special interest groups” could “exercise undue influence” in promoting “their private concerns” on “matters in which they have vested interests.”

The law requires a public process for creating and appointing groups to advise the government and requires that the properly appointed group operates in public view and takes public comments along the way.

According to the DOE’s own guidance, “FACA applies when a group is asked to render advice or recommendations as a group and not a collection of individuals.”

Thus, the group chosen to write the department’s report falls within the scope of FACA. The law requires that a committee representing a fair balance of viewpoints be chartered under FACA and that members be appointed only after a public nomination process with public opportunity to comment on the list of candidates.

Once appointed, a balanced group is also required to deliberate in public and receive public comments in formulating their report. That didn’t happen.

3. Federal agencies cannot be arbitrary or inconsistent in rulemaking

The Administrative Procedure Act of 1946 requires federal agencies to allow public participation in rulemaking processes and to follow consistent procedures and practices when developing regulations.

The law prohibits actions that are “arbitrary and capricious” – meaning decisions made without justification or regard for facts – or an “abuse of discretion.”

Agencies are expected to examine relevant data. They must not only follow applicable laws, such as FACA, but also must follow procedures established to implement those laws, such as balanced membership of the committee and opportunity for public comment when formulating the report.

A schematic of different laws and their impact
Four federal laws that apply to the EPA’s effort.
Christopher Frey

4. Science Advisory Board review is also required

The EPA is also subject to the Environmental Research, Development and Demonstration Authorization Act of 1978. The act mandated that the EPA must establish a Science Advisory Board. It also requires that agency make available to its Science Advisory Board relevant scientific and technical information on any “proposed criteria document, standard, limitation, or regulation.”

The board must be given time to review the scientific and technical basis of the proposed action – in this case, the disseminated Energy Department report – now that the EPA is using this report to inform its regulatory action.

Under the Information Quality Act, the EPA may not develop a regulation based on a draft report.

The EPA’s Science Advisory Board website lists zero members as of mid-August 2025. On Jan. 28, 2025, the EPA dismissed all of the board’s previous members. Nominations for new board members were due on June 2. At best, it will be months before the EPA can seat a new Science Advisory Board because of time needed to complete the selection, appointment and ethics review processes.

An annotated screenshot of the EPA’s Science Advisory Board website shows no members as of Aug. 11, 2025.
EPA

Either the EPA could follow the law and suspend any proposed actions until the Science Advisory Board is available, or accept legal risk for not following the Environmental Research, Development and Demonstration Authorization Act.

What’s next?

These laws exist to protect the public by preventing the federal government from being unduly influenced by narrow interests when disseminating evidence that informs policy decisions. Science-based agencies such as the Energy Department and the EPA have a legal requirement to follow the science.

The public has a chance to comment on the EPA’s proposal to rescind the 2009 endangerment finding and greenhouse gas vehicle standards until Sept. 15, 2025. And although the Energy Department disseminated its report as a final version, the department is accepting public comments on the report through Sept. 2.

For both, the most effective comments are evidence-based and not merely opinion.

The National Academies of Sciences, Engineering and Medicine, independent nonprofit institutions that advise the government, announced in early August that they will conduct a fast-track review of the science on whether greenhouse gas emissions endanger public health and welfare to submit as a public comment.

Because the Energy Department report is presented as final, it is also subject to the “request for correction” process under the Information Quality Act within 60 days of its initial release.

Given the Energy Department report’s legal vulnerabilities, the Trump administration could consider withdrawing the report and starting over with a legally and scientifically valid approach. If these vulnerabilities are not corrected and the EPA rescinds the endangerment finding based on the Energy Department report, years of litigation are likely to slow the administration’s efforts.

The Conversation

Dr. H. Christopher Frey is currently a professor of environmental engineering at North Carolina State University. He has served on numerous scientific advisory committees, including the U.S. Environmental Protection Agency FIFRA Scientific Advisory Panel (2004-2006), Science Advisory Board (2012-2018), and Clean Air Scientific Advisory Committee (2008-2015). He was chair of CASAC from 2012 to 2015. He has served on study committees of the National Academies of Science, Engineering, and Medicine. He served at EPA from 2021 to 2022 as Deputy Assistant Administrator for Science Policy and from 2022 to 2024 as Assistant Administrator for Research and Development and Science Advisor. While in federal service he co-chaired the National Science and Technology Council Committee on Environment.

ref. 4 laws that could stymie the Trump EPA’s plan to rescind the endangerment finding that underpins US climate policies – https://theconversation.com/4-laws-that-could-stymie-the-trump-epas-plan-to-rescind-the-endangerment-finding-that-underpins-us-climate-policies-262952

US has slashed global vaccine funding – if philanthropy fills the gap, there could be some trade-offs

Source: The Conversation – USA (3) – By Amy E. Stambach, Professor of Cultural Anthropology and International Studies, University of Wisconsin-Madison

Bill Gates gives a baby in a woman’s arms a rotavirus vaccine in Ghana in 2013. Pius Utomi Ekpei/AFP via Getty Images

The U.S. government is relaxing federal vaccine requirements and cutting vaccine research and development funding here at home. Elsewhere, it’s going even further.

The Trump administration has stopped funding Gavi, a global initiative that helps millions of children in low-income and medium-income countries get vaccinated against measles, cholera and other preventable diseases. Gavi, the Vaccine Alliance, is an international organization that collects money from government and private donors. It spends around US$1.7 billion annually to buy and deliver vaccines.

Gavi has helped vaccinate over 1.1 billion children in 78 countries since 2000. Those vaccinations, according to the alliance, have prevented more than 18 million deaths from meningitis, diphtheria, tetanus, polio and other deadly diseases – saving more than $250 billion in health and economic costs.

In 2024, the U.S. was its third-biggest funder – after the U.K. and the Gates Foundation. It contributed $3.7 billion between 2000 and early 2025.

The Biden administration had promised to kick in $1.6 billion over five years beginning in 2026, plus another $300 million for the rest of 2025.

But Health and Human Services Secretary Robert F. Kennedy Jr. announced on June 26, 2025, that the Trump administration would not honor those commitments, ripping a gaping hole in Gavi’s budget.

A woman holding an infant stands in a hallway with papers affixed to the walls.
A Nicaraguan woman carries her infant after the child received a pneumococcal vaccine at a Gavi-funded clinic in 2011.
Elmer Martinez/AFP via Getty Images

Becoming more reliant on philanthropy

Kennedy criticized what he alleged was Gavi’s weak track record on vaccine safety.

Many scientists and pediatricians have disputed his rationale for cutting funding, partly because Kennedy referred to a single, contested study in his remarks that was based on 40-year-old data.

So far, Gavi’s other donors – a mix of nations, foundations, drugmakers and other corporations, including Cisco, Mastercard and Shell – haven’t said they’ll step up their support enough to plug the $3 billion hole in Gavi’s five-year plan. But several of the initiative’s biggest donors, particularly the U.K. and the Gates Foundation, have reiterated their commitments of $1.7 and $1.6 billion, respectively, to be disbursed from 2026 to 2030.

In the meantime, Gavi is trying to cut costs and is seeking new funders. Unless other governments decide to make up for the loss of U.S. funding, which so far they have not, Gavi will likely become more dependent on philanthropy than ever before.

In 2024, more than 20% of its funding came from companies and foundations. Now, the vaccine alliance wants to grow that percentage, in part by slowly gaining new donors.

In my research with collaborators on vaccine hesitancy, and through fieldwork in clinics in South Africa and Tanzania, I have seen both the strengths and weaknesses of Gavi’s reliance on the Gates Foundation and corporate donors. These donors either provide funding for vaccines or donate vaccines directly for Gavi to distribute.

While most of the media coverage of the U.S. halting its funding focuses on the fact that U.S. pullout is likely to mean that more children around the world will die, I’m also concerned about another issue.

An illustration of a medical syringe emblazoned with the Gavi vaccine alliance logo and branding.
The U.S. has ceased funding for Gavi, ripping a hole in the global initiative’s budget for the next five years.
Pavlo Gonchar/SOPA Images/LightRocket via Getty Images

Encountering some complications

When philanthropy helps fill funding gaps in the public sphere, challenges can arise.

Gavi’s vaccine programs have undoubtedly increased childhood vaccination rates. But they would be even more helpful if they could more consistently help countries build the strong and lasting vaccination systems that low-income and medium-income countries need to make sure vaccines can eventually be delivered without foreign aid.

One problem is that corporate donors and foundations don’t have to answer to voters or taxpayers in the countries they give money to. This can make it harder for countries where Gavi operates to understand philanthropic decisions.

Gavi has received more funding from the Gates Foundation than from any other private contributor. The foundation says it has disbursed or pledged, since Gavi’s launch in 2000, a total of $30.6 billion to “advance vaccines – investing in their discovery, development, and distribution.” And $7.7 billion of that sum has been “directed to Gavi” to vaccinate kids.

In so doing, the Gates Foundation, which announced on Aug. 4, 2024, that it intended to devote $2.5 billion toward improving women’s health care around the world by 2030, has helped Gavi vaccinate more children against preventable diseases than government money alone could have accomplished.

But when one donor wields that much influence, I’ve observed, tensions can follow .

I heard about such tensions at African vaccine clinics where I conducted research between 2021 and 2023.

Bill Gates in a suit and tie stands against a purple background.
Bill Gates, in 2023, speaks in Belgium about another initiative besides Gavi that the Gates Foundation is supporting, which aims to give the polio vaccine to hundreds of millions of children.
Thierry Monasse/Getty Images

Concerns about influence

At clinics across South Africa, Tanzania and other parts of sub-Saharan Africa, I spoke with doctors, nurses and public health officials working directly with Gavi-supported programs. Many of the people I interviewed acknowledged the vital role the Gates Foundation has played in expanding access to vaccines.

I am not naming the people who I interviewed to protect their confidentiality, in keeping with social science research norms.

But many expressed concern about the outsized influence that can follow when one donor gives so much money. For example, several people I interviewed said they believed they had no control over which brand of vaccines to use or which age group to vaccinate first.

“That’s all decided by donor offices – not by our own (health) ministry,” said a doctor in Dar es Salaam, Tanzania. She pointed to the walls of her clinic, plastered with promotional posters for the Gates Foundation and Gavi.

Gavi, however, says on its website that its board chooses the vaccines it invests in after extensive research.

And many of the people I interviewed said they believed that some donors push for vaccines made by companies they have invested in through their endowments and other assets.

Health workers also told me that Gates Foundation-funded reporting requirements added pressure and extra work without improving care. A district health official in rural Tanzania said his clinic had to meet strict targets set by a Gates Foundation–backed program. This meant quickly submitting forms with detailed information about numbers vaccinated and each patient’s health history – sometimes taking a toll on the quality of care.

“We’re spending more time filling out reports for the donor than talking to patients,” he said. Because the clinic had no computers and lacked a stable flow of electricity, keeping up with the paperwork was tedious.

Across interviews and locations, a common pattern emerged. I frequently heard that the Gates Foundation had helped clinics operate and pay staff with its grant money, but its programs followed a business model focused on meeting targets and showing results.

“It’s all about hitting numbers, not building systems,” one official in Cape Town, South Africa, told me. Many health care workers said this model shifted public health priorities toward the Gates Foundation’s goals at the expense of developing sustainability.

A white man in a suit and tie beholds a baby held by a Black woman in a clinic.
David Cameron tours a Gavi vaccination clinic in 2011, in Lagos, Nigeria, while serving as U.K. prime minister.
AP Photo/ Christopher Furlong

The limits of philanthropy

Funding from foreign governments can also shift local priorities, though possibly to a lesser degree than philanthropy. That’s because governments often work through bilateral agreements and are subject to diplomatic protocols and political accountability, which can temper their influence. In contrast, large foundations like the Gates Foundation may operate with more autonomyallowing them to shape programs more directly around their goals.

Ultimately, without democratic oversight or deep roots where they donate, foreign philanthropy can be seen as overriding local priorities. Donations from foundations and corporations can be perceived as exerting influence over public health goals, stirring resentment.

The Gates Foundation agrees that philanthropy cannot replace U.S. government assistance.

“There is no foundation – or group of foundations – that can provide the funding, workforce capacity, expertise, or leadership that the United States has historically provided to combat deadly diseases and address hunger and poverty,” Rob Nabors, director of the North America Program at the Gates Foundation, wrote in response to a query from me.

Nabors’ statement underscores why the end of U.S. government funding for, and involvement in, Gavi matters.

The U.S. government has historically engaged in diplomacy and forged long-term partnerships with health ministries in other countries. It has also traditionally spent billions of dollars on infrastructure, like research labs and refrigerated systems to store and transport vaccines.

Foundations typically don’t operate on the scale of government aid operations.

The Gates Foundation provided some information upon request that pointed to efforts it has made in this regard. For example, it had spent $1 billion by 2018 to support vaccine manufacturers located in developing countries and “related grantees,” working with 19 of those manufacturers in “11 countries to bring 17 vaccines to market.” It also pointed to the $15 million it announced in 2022 for a “South African specialty pharmaceutical company to support its capabilities to manufacture lifesaving routine and outbreak vaccines for Africa.”

Regardless of where its funding comes from, Gavi is essential for everyone, including Americans, because diseases like measles don’t respect borders. Because global air travel shuffles millions of people around the world daily, an outbreak of a very contagious disease anywhere can become a threat everywhere. That makes U.S. funding for Gavi not just an act of generosity toward people in other countries, but one of protecting the U.S. as well.

The Gates Foundation has provided funding for The Conversation U.S. and provides funding for The Conversation internationally.

The Conversation

Amy E. Stambach has received funding from the Council on Foreign Relations (CFR), the U.S. National Science Foundation, the Wenner-Gren Foundation for Anthropological Research and the U.S. Fulbright Scholars program. She has served as a CFR fellow with USAID.

ref. US has slashed global vaccine funding – if philanthropy fills the gap, there could be some trade-offs – https://theconversation.com/us-has-slashed-global-vaccine-funding-if-philanthropy-fills-the-gap-there-could-be-some-trade-offs-260383