Carbon cycle feedbacks play a key role in past climate variations and may also have a significant impact on future climate. However, it was not until the early 2000s that general circulation models (GCMs) of the climate started to include carbon cycle feedbacks on climate change. The results of the first two climate-carbon GCMs were compared in a paper published in Tellus. Following those first model runs, many other such ‘Earth System Models (ESMs)’ have been developed and compared as part of the Coupled Climate-Carbon Cycle Model Intercomparison project (C4MIP). Modelled changes in global land and ocean carbon storage have been routinely compared using a simple formalism that assumes a linear dependence of global land and ocean carbon storage on both atmospheric CO2 increase and global warming. This 𝛽-𝛾 formulation has been very helpful to identify the zeroth-order reasons for differences between ESM projections, but it is unable to reproduce the saturating time-evolution of global land and ocean carbon storage as simulated by the C4MIP models. In this paper, we summarise work to date on modelling the coupled climate-carbon cycle system, and suggest an update to the 𝛽–𝛾 formulation to include a representation of sink saturation as well as the timescale dependencies of land and ocean carbon uptake. Our new approach adds half-saturation constants, 𝜅, for quasi-equilibrium land and ocean carbon increases with CO2, and land and ocean timescales, 𝜏, that approximate how quickly this quasi-equilibrium is approached. This new ‘𝛽–𝛾–𝜅–𝜏’ formulation reproduces the C4MIP results with much greater accuracy than the existing 𝛽–𝛾 formulation, without requiring any additional ESM runs to be analysed.
Ocean stratification plays a crucial role in regulating climate and marine ecosystems. This study investigates global ocean stratification changes over a 26-year period (1992-2017) from the ECCOv4r4 ocean state estimate. We quantify stratification trends using the depth anomaly of the ocean's center of mass (COM), defined as the excess depth of the COM relative to a fully mixed reference state. The global depth anomaly has increased at a steady rate of 0.66 cm per decade, corresponding to a significant 1% stratification increase per decade. The global mean squared buoyancy frequency has increased at a similar rate, albeit with larger interannual variability, making it a less robust metric. The primary driver of stratification increase is the upper ocean warming, with a nearly perfect correlation between the global depth anomaly and the ocean heat content. Depth anomalies are mapped spatially for the upper 2000 m water column, showing large spatial heterogeneity. Most of the stratification increase occurs in Indo-Pacific tropical regions and along western boundary currents, with local rates more than five times higher. Salinity changes provide a secondary contribution, dominant only in polar regions. In contrast, stratification has weakened in most of the North Atlantic sector during the same period.
O presente trabalho discute a relevância da criação de uma Universidade Intercultural Indígena no Brasil. Para tanto, realizou-se uma comparação entre as experiências dos estudantes indígenas da Universidade Federal de Goiás (UFG) com os da Universidad Autónoma Indígena Intercultural (UAIIN) na Colômbia. Na UFG, os pesquisadores indígenas enfrentam desafios relacionados à adequação de seus estudos a modelos acadêmicos eurocentrados. Já na UAIIN, as práticas de ensino-aprendizagem têm como propósito fortalecer suas línguas, culturas e seus saberes ancestrais. Essa análise evidencia a necessidade de um espaço acadêmico que respeite as especificidades culturais dos povos indígenas, promovendo justiça epistêmica e um ambiente intercultural. A criação de uma Universidade Intercultural Indígena no Brasil representa um avanço significativo na valorização dos saberes ancestrais e na consolidação do protagonismo indígena no cenário acadêmico nacional e internacional.
Este artículo analiza la creación de universidades autónomas, o más precisamente, universidades indígenas. En términos de escala macro, las universidades indígenas están repartidas en diferentes partes del mundo. Específicamente, México, seguido de Estados Unidos y Nueva Zelanda, son las primeras nacionalidades en presentar estas formaciones. En Brasil, desde 2006 bajo gestión autónoma en Río de Janeiro, se crea la Universidade Pluriétnica Indígena Aldeia Maracaná. En México existen aproximadamente 17 universidades autónomas, administradas por el SEPE, y aquí nos centraremos en la Universidad Autónoma Comunal de Oaxaca (UACO). Una universidad emblemática con relación a sus personajes como Jaime Luna, Floriberto Díaz y las luchas por el sentido de la comunalidad.
Este texto ofrece una reflexión orientada a historizar y analizar los postulados políticos que antecedieron la creación de la Universidad Intercultural del Estado de México (UIEM). Para ello, se recurre a testimonios y documentos legados por diversos protagonistas, indígenas y no indígenas, quienes participaron directamente en el proyecto de formación de la Universidad Autónoma Intercultural de México "Foxite" (UAIMF), así como en la formación de una propuesta de educación bilingüe y pluricultural surgida de un movimiento etnopolítico local; ambos procesos constituyen antecedentes directos de la UIEM. A partir del análisis de estos materiales, se concluye que la decisión de omitir los apellidos “indígena” o “mazahua”, así como de excluir la referencia a “Foxite” en el nombre de la universidad, responde a algo más que consideraciones semánticas: refleja disputas y acuerdos políticos entre actores locales —indígenas y no indígenas—, el gobierno del Estado de México y el gobierno federal mexicano. Se argumenta, además, que este cambio de nombre ha tenido y sigue teniendo repercusiones prácticas en la forma en que actualmente se conciben y aplican conceptos transversales dentro del modelo universitario intercultural mexicano, así como en la estructura político-administrativa de la institución. Para ilustrar cómo se aterrizan cotidianamente en las aulas de la UIEM nociones como interculturalidad, identidad indígena y reivindicación étnica, se recogen las experiencias de un profesor-investigador de la UIEM, quien participa como coautor de este escrito.
O objetivo deste artigo é explorar as ligações entre a multiplicação de histórias ameríndias e a pluralidade epistemológica na universidade. A partir de um estágio de pesquisa na Universidade Federal do Sul da Bahia (UFSB), no Brasil, o objetivo é reunir as preocupações dos pós-graduandos indígenas da Universidad Nacional Autónoma de México (UNAM) sobre o racismo e o valor político de compreender a história como um diálogo ou uma disputa sobre o passado, com a experiência pluriepistemológica construída nas últimas duas décadas no Brasil. Descrevo três práticas de pluralização epistemológica na UFSB, articuladas com a produção e ensino de histórias ameríndias Maxakali e Pataxó: 1) “Encuentro de Saberes” com xamãs e artistas Maxakali, 2) ligação entre a história produzida por acadêmicos Pataxó e a de estilo nacionalista do sul da Bahia, e 3) descrição da prática pedagógica da professora Pataxó Adriana Pesca, na UFSB.
Este artigo investiga a relação entre a cultura e uma universidade indígena, analisando os desafios e as possibilidades presentes nas ações da Universidade Pluriétnica da Aldeia Marakanã na concepção, organização, produção e execução do evento Transfluências de Saberes. A pesquisa deste artigo busca compreender como a Universidade Indígena, em compartilhamento de saberes, mas protagonizando os processos, pode contribuir para a (re)existência cultural, a decolonização do conhecimento e a formação de lideranças indígenas. A partir de uma revisão da literatura e com um olhar particular para a relevância do Transfluências de Saberes, buscamos compreender de que modo iniciativas que promovem o encontro entre saberes originários/tradicionais, acadêmicos e políticos, como este evento, podem contribuir para a construção de um espaço mais decolonial para a universidade ocidentalizada, visando que a academia possa abarcar os saberes silenciados pelo epistemicídio histórico e corrente. Costurado em três vozes femininas: uma antropóloga, uma psicanalista e uma liderança indígena, o artigo discute a importância da interculturalidade, da autonomia indígena e da articulação entre os saberes tradicionais e os conhecimentos acadêmicos.
Este artículo compara las experiencias de dos instituciones interculturales de educación superior en México, surgidas desde iniciativas comunitarias y una convergencia de diversos actores sociales, incluyendo organizaciones no gubernamentales, comunitarias, líderes locales y sectores progresistas de la Iglesia católica. Estas instituciones buscan construir una propuesta educativa integradora, manteniendo una estrecha relación con las comunidades indígenas que las albergan, mientras enfrentan desafíos estructurales que las colocan en desventaja frente a otras universidades del país. Se analizan dos programas académicos pioneros en sus campos: la Licenciatura en Educación Intercultural y la Licenciatura en Economías Solidarias. A través de estos casos, se retrata la coherencia de proyectos educativos que no solo forman individuos, sino que también sientan las bases para un cambio estructural orientado hacia la justicia social y la sostenibilidad comunitaria.
Pretende-se com este texto, refletir narrativamente sobre dois contextos plurais de formação docente específicos que atendem populações indígenas no Brasil, com a Faculdade Indígena Intercultural (FAINDI) da Universidade do Estado de Mato Grosso (UNEMAT) com a Licenciatura em Pedagogia Intercultural e com a Universidade Pedagógica Nacional (UPN) situada na Cidade do México, que conta com o curso de Licenciatura em Educação Indígena (LEI). A proposta compõe a pesquisa que resultou na tese de Doutorado em Educação na região Centro Oeste. Foram entrevistados 13 docentes formadores/as, sendo selecionados alguns fragmentos para este texto. A discussão está fundamentada no método da Pesquisa Narrativa (Clandinin e Connelly, 2015) e em autorias brasileiras e mexicanas indígenas e negras para pensar sobre os contextos das diferenças étnicas e culturais desta atuação docente. Defende-se a ideia de que a docência em contextos indígenas e interculturais é um fenômeno complexo permeado pelas aprendizagens que se dão em suas experiências formativas, de trabalho e da própria dinâmica das vidas atravessadas por uma dimensão da corpóreo-afetiva-intercultural de escuta sensível e atenta aos desafios e potencialidades provocadas em diferentes contextos das aldeias à universidades indígenas e interculturais com potencialidades pedagógicas interculturais que nos convidam à contracolonizar e compreender a universidade como Território Indígena.
Many important questions in Earth system science require an integrated understanding on the duration of processes such as mass flows, particularly for components of the Earth system that are interconnected and are changing rapidly due to human activity. This type of questions require an integrated and general approach to study timescales of Earth system processes. A number of publications in Tellus have been fundamental to establish the basis for such a general approach. In this contribution, I present a review on how Tellus helped to define the basis to study timescales of Earth system processes, establishing the definitions of timescale metrics such as age, transit-, and turnover time. In addition, I present an overview of an expanded theory based on recent progress in hydrology and carbon cycle science where new methods to study timescales for time-dependent systems out of equilibrium have been recently developed. The new theory facilitates the study of timescale problems in which rates of mass flows are changing fast and interacting nonlinearly with other system components. I discuss the application of the theory to studying the time required to remove anthropogenic carbon dioxide from the interconnected atmosphere-land-ocean system, the time that anthropogenic reactive nitrogen spends in the natural environment, and the time that methane spends in the atmosphere. Overall, the new theory helps to clarify concepts and expands the range of scientific questions to problems on the anthropogenic perturbation of timescales of Earth system processes.
Nutrient limitation is widespread among microbial decomposers of plant litter, as they often feed on substrates with much wider carbon (C)-to-nutrient ratios than those of their biomass. How they cope with nutrient (especially nitrogen, N) limitation remains an open question. Possible responses include: upregulating N acquisition; respiring excess C and thus lowering microbial C-use efficiency (CUE, ratio of C used for growth over C taken up); or retaining N more efficiently in microbial biomass growing in N-poor litter. We tested these hypotheses using a minimal model of litter decomposition that includes preferential N acquisition, CUE, and N recycling efficiency as parameters, resulting in alternative model variants. Parameters encoding microbial responses to N limitation were fitted to more than 500 litter decomposition curves, which trace how litter N changes as a function of litter C in individual litter cohorts. The model indicates that preferential N acquisition is upregulated at high litter C:N ratios, but the performance of model variants with flexible N acquisition was worse than that of the other variants, suggesting that microbes might respond to N limitation by regulating CUE or N recycling. CUE decreased with increasing litter C:N when N was not recycled from senescent biomass and N recycling efficiency increased with increasing litter C:N when CUE was fixed. Both these model variants (flexible CUE or N recycling efficiency) had high fitting performance. Moreover, flexible N recycling supported higher microbial growth rates compared to flexible CUE. These model results indicate that flexible N recycling can explain patterns in N import and release in litter, while also being a physiologically more beneficial response to cope with N limitation than regulation of CUE.
We describe the coordination of ORCESTRA, a field campaign designed to advance understanding of how mesoscale convective processes influence Earth's climate. ORCESTRA harmonized the execution of eight sub-campaigns that spanned the tropical North Atlantic from 10 August to 30 September 2024. The ORCESTRA sub-campaigns performed measurements from three research aircraft, a research vessel, two ground stations, and EarthCARE, a new Earth Explorer Satellite. These platforms performed thousands of atmospheric soundings, supported a rich constellation of active and passive remote sensing, conducted a wide variety of in situ measurements, and deployed autonomous sensors in the air and sea. Together with its measurements, ORCESTRA is being accompanied by extensive numerical experimentation to advance the development of a new generation of more physical climate models.
Despite the urgency to mitigate climate change, global greenhouse gas concentrations are still increasing, and even global emissions are still growing. Furthermore, the global sinks-both natural and technical-are not improving rapidly enough. Therefore, discussion and investigations to utilize solar radiation modification (SRM) have resurfaced. Stratospheric Aerosol Injection (SAI) is one of the most studied methods, particularly using sulfate aerosols. However, sulfate SAI includes several risks, such as deposition of acidic aerosol particles on the Earth's surface, increasing acidification and ozone depletion, and changing weather patterns. Here we propose an alternative approach, namely Organic Stratospheric Aerosol Injection (OSAI). The OSAI is initiated by an injection of isoprene or monoterpenes, which, according to our conceptual investigations and global model simulations, seem to be plausible candidates for this purpose. The organic SAI is likely to avoid some of the problems inherent to sulfate SAI, even though further research is needed in terms of its potential influences on stratospheric heating and the ozone layer. While SRM is still preferably avoided, our results suggest that organic aerosols may be an alternative to sulfate for further consideration if it is deemed a viable and necessary option.
Radiance observations from microwave sounders have become one of the most valuable sources of information that is used in Numerical Weather Prediction (NWP). However, uncertainties in the land (and sea-ice) surface modelization do not permit optimal use of channels that receive a mixed contribution from the surface and the troposphere (i.e., low-peaking channels). In the context of the preparation of the Arctic Weather Satellite (AWS) mission, the HARMONIE-AROME model was run to evaluate the impact of assimilating the low-peaking channels of existing instruments using the so-called “dynamic emissivity method.” The aim of this work was also to build the best possible version of HARMONIE-AROME data assimilation system (3D-Var and 4D-Var) before the launch of the AWS instrument that happened in August 2024 and to be ready to assimilate the data as soon as the instrument was declared operational in June 2025.
Snowflakes play a crucial role in weather and climate. A significant portion of precipitation that reaches the surface originates as ice, even when it ultimately falls as rain. Contrary to the popular image of symmetric, dendritic crystals, most large snowflakes are irregular aggregates formed through the collision of primary ice crystals, such as hexagonal plates, columns, and dendrites. These aggregates exhibit complex, fractal-like structures, particularly at large sizes. As a result of this structural complexity, each aggregate snowflake is unique, with properties that vary significantly around the mean-variability that is typically neglected in weather and climate models. Using a physically based aggregation model, we generate millions of synthetic snowflakes to investigate their geometric properties. The resulting dataset reveals that, for a given monomer number (cluster size) and mass, the maximum dimension follows approximately a lognormal distribution. We present a parameterization of aggregate geometry that captures key statistical properties, including maximum dimension, aspect ratio, cross-sectional area, and their joint correlations. This formulation enables a stochastic representation of aggregate snowflakes in Lagrangian particle models. Incorporating this variability in the Monte-Carlo super-particle model McSnow improves the realism of simulated fall velocities, enhances growth rates by aggregation, and broadens Doppler radar spectra in closer agreement with observations.
