EGU Blogs - Recent Division Posts

The Breath of Forests, Cities, and Everything in Between: Eva Pfannerstill and the Air We Cannot See

Roxana S. Cremer — Thu, 24 Sep 2026 09:30:06 +0000

There is a slow-moving silver shape drifting over the forests and cities of North Rhine-Westphalia. From the ground, it looks almost ceremonial — a Zeppelin NT gliding through the air as though time had reversed by a century. Inside, sensors are humming. And Eva Pfannerstill is watching the data appear. She is not there to admire the view, though the Rhine-Ruhr region from the air is something. She is there because a Zeppelin, of all things, happens to be one of the most perfectly suited platforms ever devised for measuring what forests and cities exhale into the sky.

A Chemist by Curiosity

[caption id="attachment_2230" align="alignleft" width="300"] Eva Pfannerstill in a research aircraft. Photo provided by Robin Weber.[/caption] Eva Pfannerstill studied Chemistry at Friedrich-Schiller-Universität Jena. She spent an exchange semester at the Université de Montréal during her bachelor’s, and split her master’s in Chemical Biology between Jena and the NIOZ Royal Netherlands Institute for Sea Research. The sea, the lab, the open air: already the pattern was forming; science that could not sit still indoors. Her PhD followed at the Max Planck Institute for Chemistry in Mainz, where she focused on atmospheric reactivity in the Amazon rainforest. The Amazon is, in atmospheric chemistry terms, something like the beating heart of the planet. The forests there exhale vast quantities of volatile organic compounds (VOCs) molecules that are invisible, reactive, and consequential. They shape ozone levels, they seed clouds, they communicate throughout the forest. Her pioneering work there included deploying proton transfer reaction mass spectrometry instruments during challenging field campaigns, where she succeeded in closing the OH reactivity budget and elucidating the impacts of El Niño events on tropical forest chemistry.

From the Arabian Gulf to Los Angeles

She did not stay in the jungle. Beyond her achievements in terrestrial environments, Pfannerstill led shipborne campaigns in the Arabian Gulf, assessing OH reactivity and ozone formation in regions affected by anthropogenic emissions. A striking contrast to the pristine rainforest canopy, and a deliberate one. Understanding how the atmosphere behaves at its extremes, both the wildest and the most human-altered, is how you begin to understand the middle ground where most people actually live. Then came California. Until fall 2023, she was a Feodor Lynen Postdoctoral Fellow at the University of California, Berkeley, using aircraft-based measurements to map emissions. These years produced some of her most widely noticed work. Flying instruments over Los Angeles, she and her colleagues mapped the city’s chemical fingerprint from the air. Focusing on what is being actively emitted by the city into the atmosphere , in real time, at the scale of entire neighborhoods, excluding secondary processes and transport in the atmosphere. Her 2024 paper showed that temperature-dependent emissions dominate aerosol and ozone formation in Los Angeles. A finding with immediate implications for air quality policy in a warming world. [caption id="attachment_2224" align="alignright" width="350"] Photo provided by Sascha Kreklau.[/caption]

As temperatures rise, the vegetation and human activity below breathe out more; and what they breathe out shapes the air that people breathe in.

Home to Jülich, and Up into the Sky

Since March 2024, she holds a W1 Junior Professorship at the University of Cologne under the Jülich Model—a tenure-track position—and since October 2024 she leads a Helmholtz Investigator Group at the Forschungszentrum Jülich. The Helmholtz Investigator Group is a competitive program designed to give exceptional early-career researchers the independence to build something genuinely their own. For Pfannerstill, that something involves a Zeppelin. Her group is investigating how the increased frequency and intensity of drought, heat, and herbivory stress caused by global warming changes the composition and amount of gases that plants emit — and what that means for the atmosphere above our heads. The direction of that change is not obvious in advance. Stressed trees behave differently from healthy ones; they emit different molecules, in different proportions, and those differences cascade through atmospheric chemistry in ways that current models cannot yet reliably predict. A Zeppelin is an ideal platform for this kind of research. It can fly low and slowly, carrying a lot of instrumentation just like a research plane, which makes it highly useful for airborne eddy covariance flux measurements: direct, real-time measurements of what the landscape below is actually emitting. You are not sampling the accumulated history of the air. You are catching the molecules as they leave. During the first test flight in late 2024, Pfannerstill and her colleague Dr. Georgios Gkatzelis were on board to check the instruments. Among other things, they aim to investigate how household chemicals contribute to air pollution in the cities of the Rhine-Ruhr metropolitan region, and to compare the Zeppelin’s flux measurements with long-term measurements from weather towers. The pilots performed various maneuvers — rapid ascents and descents, pitch adjustments, circling — to test whether the airship’s own movements affect the data. The major measurement campaigns are planned to start in 2026 and 2028, with the Zeppelin flying over North Rhine-Westphalia — and possibly also over Belgium and the Netherlands. The forests of NRW, the industrial Ruhr, the Rhine corridor: all of it will be read, chemically, from the air. [caption id="attachment_2221" align="alignleft" width="200"] Photo by Oles Pata.[/caption] She is thirty-something, leading her own group, flying a Zeppelin over one of the most densely populated regions of Europe, and asking what the air above it is trying to tell us. It is, all things considered, a reasonable place to have ended up — for someone who could never quite stay indoors. Dr. Eva Pfannerstill leads the Young Investigator Group “Biogenic Emissions and Air Quality Impacts” at Forschungszentrum Jülich and is a Junior Professor at the University of Cologne. Her group is recruiting — including a PhD position focused on Zeppelin-based airborne measurements.

1st International Training School on Urban Water Management and Nature-based Solutions for Sustainable Cities

Christina Orieschnig — Thu, 24 Sep 2026 08:00:45 +0000

From 7-8 September 2026, the 1st International Training School on Urban Water Management and Nature-based Solutions for Sustainable Cities was held in Munich, Germany. Organised by researchers from the Technical University of Munich, the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, and the University of Cagliari in collaboration with the International Association of Hydrological Sciences (IAHS), the event was supported through the European Geosciences Union (EGU) Training School Programme. For two days, Munich became a classroom for the next generation of researchers working on how to design sustainable and climate-resilient cities. The training school brought together 16 PhD candidates and Master's students from 13 countries for two days of deep dives into the key challenges and emerging approaches in sustainable urban water management. Through lectures, practical exercises, and interactive discussions, participants explored how hydrological, ecological, technical, and social perspectives must be considered to support more sustainable water-sensitive cities. Particular emphasis was placed on climate-resilient urban planning, innovative monitoring approaches in urban ecosystems, and the fate and treatment of micropollutants in urban water cycles. In addition to providing advanced scientific training, the school offered a valuable interdisciplinary platform for networking and knowledge exchange among early career researchers from diverse academic backgrounds. Conversations were lively and curious, and new friendships and connections were made across oceans and disciplines. Thanks to the support of the Carl Friedrich von Siemens Foundation, the event could be hosted under excellent conditions in Munich, surrounded by the green spaces and waterways of the Schlossgarten Nymphenburg. Participants benefited from the outstanding facilities of the venue as well as opportunities to gain practical insights into urban water management and climate adaptation strategies implemented within the city.

Studying cities from above and below

The first day focused on three thematic blocks addressing current challenges in sustainable urban development. Sessions covered nature-based solutions for disaster risk reduction and urban climate resilience by Dr. Elena Cristiano and Dr. Andrea Reimuth, green infrastructure planning for climate adaptation by Prof. Stephan Pauleit, and the occurrence and fate of micropollutants in urban water systems by Dr. Felicia Linke. The second day emphasised hands-on learning and field-based experiences to get a sense of design, monitoring, and engineering challenges. During a guided visit to Munich's sewer network and wastewater infrastructure, organised in cooperation with Munich's municipal wastewater utility, participants gained first-hand insights into urban drainage systems and modern stormwater management practices. This was a highlight for many students, some of whom had never seen such infrastructure up close. Realizing the hidden flows of water and effluents underneath the city and the technical and engineering challenges related to maintaining such a system gave the students a new perspective on how the water management of a large city depends on invisible infrastructure. At the same time, the visit also highlighted where the city’s capacity to absorb extreme rainfall is challenged, sparking a hot debate on the role of blue-green infrastructure and nature-based solutions in closing that gap. [caption id="attachment_14206" align="aligncenter" width="1278"] Combined lectures, field activities, and hands-on exercises enabled participants to translate scientific concepts into practical skills relevant to their own research. © Andrea Reimuth und Maria Magdalena Warter[/caption] Keeping with the practical theme, a half-day field workshop in Nymphenburg Park was led by Dr. Maria Magdalena Warter, introducing participants to monitoring and sampling techniques for urban ecosystems. Different analytical methods were presented and applied under real field conditions, enabling participants to connect theoretical concepts with practical applications relevant to their own research projects. Drinking water quality was tested directly in the park and found to be of great quality - a testament to Munich’s water supply.

Scientific exchange and networking across scientific and geographic borders

One of the most highly valued aspects of the training school was the opportunity for interdisciplinary exchange among participants from fields including engineering, hydrology, ecology, and urban planning. The international and interactive character of the event fostered lively discussions between participants and invited experts, leading to new scientific perspectives and professional networks that will hopefully inspire participants to keep connecting with peers across disciplines. The combination of scientific lectures, group activities, practical exercises, and field excursions stimulated discussions on emerging research questions and potential future collaborations. By bringing together early career scientists and leading experts in a focused learning environment, the training school successfully fulfilled the core objectives of the EGU Training School Programme while strengthening the international community working on urban water management and nature-based solutions. It is events like these that are valuable opportunities for early career researchers and we are grateful for the support of our partners and colleagues.

Beyond ‘black and white’: rethinking continental drift and land bridges through plate tectonics and orogenic bridges

jbkoehl — Wed, 23 Sep 2026 08:00:41 +0000

In this essay, Jean-Baptiste Koehl reflects on the origin of a 100-year-old divide within the geoscience community and explores how tectonics and paleontology may be brought closer together through the concept of orogenic bridges. Disclaimer: The reflections presented here reflect my perspective grounded in my own research and experience. One of the most iconic interdisciplinary achievements in the geosciences is the integration of the fossil record, igneous and sedimentary rock units, fold-and-thrust belts, and even past glaciations on continents now separated by wide oceans, which helped lay the foundations of continental drift and, eventually, modern plate tectonics. Paleontology is a highly specialized field at the intersection of the geosciences and biology, requiring advanced understanding of anatomy, evolution, sedimentology, and ecology (learn more on the EGU SSP blog). Tectonics is an interdisciplinary field that investigates the deformation and evolution of Earth’s lithosphere using tools and concepts from structural geology, geophysics, seismology, geochronology, geochemistry, petrology, geomorphology, stratigraphy and sedimentology, volcanology, mineralogy, and planetary sciences. While tectonicists and paleontologists are exchanging in some aspects of the geosciences (e.g., dating of sedimentary strata and deformation episodes using paleostratigraphy), these interactions are limited and it seems to me that paleontologists do their thing and tectonicists do theirs, as if separated by an invisible rift, like an old wound that never healed. Have you noticed a similar pattern? Let us rewind a little to understand the potential cause to this divide. Land bridges versus continental drift In the early 20^th Century, paleontologists discovered comparable terrestrial fossils in hundred-million-year-old sedimentary rocks on continents now separated by large oceans. Their solution to this problem was to propose that narrow, now sunken land bridges once connected the continents and allowed terrestrial organisms to migrate between them (Fig. 1; Gregory, 1929; Schuchert, 1931; von Ihering, 1931). Figure 1: Map of the so-called land bridges proposed by paleontologists in the early 20^th Century. Modified after Dolphin (2009). Coincidentally, Alfred Wegener proposed his hypothesis of continental drift (Wegener, 1929), which was at first rejected by the geoscience community (especially paleontologists; Gregory, 1929; Schuchert, 1931; von Ihering, 1931). Although others gradually added weight to Wegener’s hypothesis (e.g., du Toit, 1927), it is only upon the discovery of mid-ocean ridges and seafloor spreading (Hess, 1962; Vines & Matthews, 1963) that Wegener’s idea became widely accepted. In contrast, land bridges were completely dismissed from then on and, although it may sound intuitively correct, psychology suggests that it might have been too hasty. Psychological bias(es): the Black-and-White dilemma Do you remember rejecting an idea at first only to accept it later and completely dismiss what you first believed? Or have you ever made one little mistake and started believing yourself incompetent? Or ever thought that you had ruined your diet and health by eating this one doughnut? Does sticking to your diet only 99% of the time mean to you that you are failing and that you might as well eat whatever you want? Then you might be prone to dichotomous thinking. Dichotomous thinking bias, also known as “black-and-white” or “all-or-nothing” thinking bias, is a cognitive bias through which one thinks in absolute extremes with no middle ground (Bonfá‐Araujo et al., 2021). Not only does this distort reality, but it also hinders problem solving and may typically lead (among others) to interpersonal conflicts and loss of self-confidence. Upon discovery of seafloor spreading, land bridges and parts of the fossil record that did not fit continental drift were completely dismissed. Some of these included the migration of primates from western Africa to South America at ca. 40–35 Ma (Montheil et al., 2026), i.e., well after the presumed opening of the South Atlantic Ocean at ca. 125–100 Ma. Another example is the convergence of Late Cretaceous dinosaur tracks towards the Gulf of Guinea–northeastern Brazil corridor (Jacobs et al., 2024). Both fossil records suggest a terrestrial connection between South America and western Africa after the opening of the South Atlantic. However, instead of revisiting some concepts of continental drift to find a compromise, paleontologists have been exploring migration via long-distance rafting on floating island of vegetation debris (Montheil et al., 2026). While such events are possible, they require a demanding chain of conditions: small animals and/or plants on a raft of mangrove detached from riverbanks or coastlines during a storm or flood, floating thousands of km across the ocean with no fresh water and no food for one to two weeks (Houle, 1998), at the mercy of strong currents and waves, not knowing how to swim. How likely is it that they would (1) survive the journey, (2) swiftly adapt to the new environment (climate, food chain), (3) survive long enough to find potential mates (who, just like them, survived the crossing) to reproduce, and (4) that a sufficiently diverse genetic cohort of individuals survived the crossing to ensure species survival? Pretty low I would say. Up to now, tectonicists and paleontologists have been looking at the opposite ends of the same elephant, thinking of land bridges and continental drift as incompatible frameworks (Fig. 2). Reality is not “all black” or “all white” and some concepts underlying Land Bridge Theory may be reconciled with Continental Drift and modern plate tectonics. Figure 2: The elephant and the blind parable illustrating how limited, subjective experience shapes individual realities and, potentially, interpersonal conflicts. From Hey (2024). The compromise: moving away from “all-black” and “all-white” If Continental Drift Theory was 100% correct and Land Bridge Theory 100% erroneous, only oceanic crust should be found on the ocean floor between the rifted continents, which is not the case. Looking more closely at the location of inferred land bridges (Fig. 1), a pattern emerges. All the land bridges inferred by paleontologists (e.g., Gregory, 1929; Schuchert, 1931; von Ihering, 1931) coincide with major transform faults, microcontinents, regions of anomalously thick (c. 15–40 km thick; i.e., not entirely oceanic) crust offshore, and continental salients (i.e., broad regions of continental crust jutting outward into oceanic domain – e.g., Rio Grande Rise and Walvis Ridge in the South Atlantic; Fig. 3), which laid the foundation of Orogenic Bridge Theory (Koehl & Foulger, 2025). Figure 3: Global correlation of presumed land bridges, major transform faults, anomalously thick offshore crust, microcontinents, and rift-orthogonal orogens. Modified after Koehl & Foulger (2025). We propose a framework that reconciles the tectonic and paleontological records, suggesting that narrow, emerged corridors and groups of islands may have locally connected the rifted continents beyond initial breakup, including at the location of the so-called land bridges (Fig. 4; Koehl & Foulger, 2025). During rifting, continental crust is not thinned uniformly and some barriers (e.g., old orogens) oriented obliquely to the propagating rift may locally delay breakup and facilitate the formation of transform faults and microcontinents (e.g., Koehl, 2025; Koehl & Mottram, 2025; Longley et al., 2024). A potential formation mechanism for orogenic bridges is through enhanced friction between the asthenosphere and lithosphere (basal shear), which occurs preferentially along N–S- and E–W-trending axes (e.g., Doglioni et al., 2015; Vérard et al., 2012). Extension-parallel orogenic structures in the lower crust and upper mantle are stretched for extended periods through ductile shearing, thus creating differential plate movements with adjacent orogenic structures parallel to the extension direction and, thus, in the formation of major transform faults and delayed breakup. Potential causes of basal shear include Earth’s axial spin and/or tidal forces (e.g., Moon and Sun gravitational pull; Doglioni et al., 2015; Zaccagnino & Doglioni, 2022). Orogenic bridges provide potential migration routes for terrestrial species for some time after the onset of seafloor spreading where the crust has been thinned quicker, e.g., westwards migration of rodents, primates, and lizards (Montheil et al., 2026) and eastward migration of hoatzins (birds with weak flight capabilities; Mayr et al., 2011), Turdidae (passerine birds; Dantur et al., 2026), and Asteraceae (plant of daisy family; Katinas et al., 2013; Fig. 4). When considered together with island hopping or short-distance rafting on vegetation islands, “orogenic bridges” could be a powerful compromise to reconcile the fossil and tectonic records. Figure 4: Formation of transform faults and microcontinents between northeastern Brazil and western Africa along inherited rift-orthogonal thrusts. From Koehl & Foulger (2026). A more recent case further illustrates the concept of “orogenic bridges”. In the Bay of Mount St Michel in northwestern France, the Bishop of Coutances regularly walked from the mainland to Jersey during the Middle Age. Jersey is now separated from the mainland by a 20 km wide shallow sea. Structural studies have revealed that, back then, the island was connected to coastal villages by a narrow strip of land above a now submerged Alpine thrust (Lefort et al., 2021). Despite differences in timescale, this anecdote shows that inherited thrusts can temporarily enable the dispersal of terrestrial species across generally submerged terrains and that compromises are key to scientific progress. Much work remains to further test and constrain existing orogenic bridges. Promising avenues include synergies between industries and researchers on the interpretation of recent seismic reflection and geophysical data and IODP initiatives at the proposed orogenic bridges and geodynamic modelling to constrain potential key controlling parameters. Fancy joining the fun? I am only an email away!

References

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Shaping the PS Division: Call for Community Engagement

Salvatore Buoninfante — Tue, 22 Sep 2026 08:52:07 +0000

Credit: Anna Kotova (distributed via imaggeo.egu.eu) [Imaggeo - Geoscience].

Dear EGU Planetary & Solar System Sciences (PS) Division, The Planetary & Solar System Sciences blog is back! In this post, we will examine how to participate in defining the PS Division, activities, procedures, and deadlines. We dedicate our comeback post to our readers, who sit at the heart of this community. The EGU Planetary & Solar System Sciences (PS) Division is built by volunteers, for the community it serves. The more colleagues who contribute, the better our Division can represent and reflect our diverse voices. Every contribution matters, and regardless of your availability or experience level, there are opportunities for you to help shape our Division. Below, we summarize the main engagement opportunities within our Division.

EGU General Assembly

The annual EGU General Assembly is Europe’s largest and most prominent geosciences event, which attracts around 20,000 scientists from all over the world. The scientific sessions cover all disciplines in the Earth, planetary and space sciences, including oral, poster and PICOs (interactive presentations that combine the advantages of both orals and posters). Aside from the disciplinary sessions, which cover topics selected by each scientific Division (or programme group), the meeting also features many Union-wide sessions. These include Great Debates and Union Symposia, inter- and transdisciplinary sessions, medal lectures, short courses, and Education and Outreach sessions. The General Assembly remains, above all, an opportunity for scientists to stay up to date on topics of interest and an unmissable annual occasion for networking and new collaborations, as well as a way to reconnect with researchers and professionals working across Europe and the rest of the world. Abstracts and other open-access uploaded materials from all previous General Assemblies are available on EGUsphere, the Union’s central repository for open-access scientific materials. The General Assembly features a job centre, artists-in-residence, and a newsletter, EGU Today, which highlights sessions, events, and exhibitions each day of the meeting. These and other activities, as well as the scientific sessions, are often announced on GeoLog, the EGU blog, as well as EGU’s social media channels. The EGU General Assembly also organises press conferences in a dedicated Press Centre at the meeting.

EGU General Assembly 2027 session proposal

The next EGU General Assembly in Vienna (April 4–9, 2027) is now in preparation, and the call for session proposals is open until September 23rd 2026. We ask for your support in preparing the PS programme with new scientific session ideas whether to existing sessions or new ones. A variety of possibilities are available: scientific sessions, short courses, geopanels, ad-hoc meetings, and improvements to previously proposed sessions, including topics of interest to the PS Division and hot topics for the planetary and space science communities. Our goal is to help the PS Division members to have the best experience EGU can offer. When preparing a proposal, please always review the EGU convener rules and recommendations, as they evolve over time. How many conveners can be included in the proposal? Session proposals require a convener team of 2 to 5 members. Convener rotation for recurring sessions is highly encouraged. The convener teams shall be diverse across gender, career stage (with explicit inclusion of Early Career Scientists), and institutional/geographic affiliation. Teams fulfilling all three criteria automatically receive the EGU Equality, Diversity, and Inclusion (EDI) session logo once all members update their online EGU profiles. Note that conveners cannot serve as session chairs during the time block in which they are giving an oral presentation; however, they can be co-authors, and poster presentations are permitted. Where to submit your session proposal? For the 2027 General Assembly, the PS programme spans 7 primary groups:

Terrestrial Planets: covers terrestrial planets, their environments, and moons. The sessions will focus on processes of the planetary interior, surface, atmosphere, exosphere and magnetosphere, studied through observation, modeling, and experimental methods.
Outer Planets System: focuses on the study of the complex systems associated with the giant planets and Pluto. The study includes not only planetary interiors, but also atmospheres and the interaction of magnetospheres with rings. This group is open to contributions from observational, experimental, computational, and theoretical investigations on these topics.
Small bodies: asteroids, comets, TNOs, meteors, and interplanetary dust: covers all minor objects in the Solar System at all heliocentric distances, including their physical properties, formation, and evolution. The group welcomes theoretical, observational, experimental, and remote-sensing contributions.
Space Weather and Space Weathering: covers topics related to the interaction between the solar/stellar winds or high energy particles and different objects in our heliosphere or in other solar systems, including interactions with magnetised and unmagnetised bodies, surfaces of planets, moons and asteroids, as well as comparative planetology.
Exoplanets and Origins and evolution of Planetary Systems: covers exoplanet detection, atmospheric and interior characterization, formation mechanisms of planetary systems, and evolution.
Life in the cosmos: Astrobiology and Planetary Habitability: includes studies not only on the origin, but also on the maintenance of life in the Solar System and in exoplanetary systems. This is addressed through the study of prebiotic chemistry, as well as the evolution and proliferation of primitive or complex life.
Planetary and Solar System exploration: Mission Support, Instruments, Observations, Applications, Analogues: covers the latest advancements and discoveries in mission support, instrumentation, observational techniques, applications, and analogues. These sessions will focus on methodologies used to study planetary bodies, moons, and other celestial objects.

EGU sessions can be multidisciplinary and are actually encouraged to be so. During the submission process you can indicate the sub-programme groups with which you would like your session to be co-organized. Among the various opportunities, this year there are also proposal submissions for:

Inter- and transdisciplinary sessions (ITS), designed to bridge Earth and planetary sciences studies or integrate broader social, economic, and policy disciplines.
Geoscience & Society (GS), dedicated to education, outreach, ethics, policy, and geoscience communications.
Short courses (SC), interactive forums focused on skill-building, training, and open software relevant to multiple Divisions.
Geopanels (GP), high-level panels addressing current research topics, of interest to a broad range of Earth, planetary, and space sciences.

Ready to submit? Gather your colleagues and submit your session proposal(s) by the deadline, September 23. Thank you for your continued contributions to the PS Division, and we look forward to receiving your proposals! For further information and any clarifications, please refer to the official website: EGU27 - General convener guidelines and rules.

Awards and medals

You can nominate a colleague, lecturer or mentor who made a significant contribution to the geosciences or Division fields. Recommend them for one of the various prizes and medals that EGU awards each year!

Type of awards and medals

Among the most prestigious medals awarded by the EGU are: the Alfred Wegener Medal, for atmospheric, hydrological or ocean sciences; the Arthur Holmes Medal, for solid earth geosciences; the Jean Dominique Cassini Medal for planetary and space science. These are bestowed upon scientists of exceptional international standing in the relative field of the medal. In addition, the Alexander von Humboldt Medal is awarded to scientists who have achieved outstanding research in developing regions for the benefit of people and society. These medals, along with the Union Awards granted for outstanding results in journalism, engagement and outreach, are Union-level accolades. Each Division has also its own medal, bestowed on scientist that produce exceptional contributions to the Division field. The PS Division has the David Bates Medal and the Runcorn-Florensky Medal. EGU also wants to promote and engage early career scientists. For that reason, the union also bestows a special award upon each Division dedicated to outstanding ECSs. The EGU’s Council selects four outstanding candidates among all the Divisions and awards them the prestigious Union-level Arne Richter Award for Outstanding Early Career Scientists. Winners of EGU medals and awards can be nominated as EGU ambassadors. In this role, they are delegated to attend meetings hosted by other organisations and to offer special presentations and lectures labelled as EGU contributions. For further information and a complete list of all the awards and medals visit the official website: EGU - Awards & medals.

Nomination procedure

If you want to nominate your colleagues for an award or a medal please read carefully the nomination procedure. Submissions will be open next year, from 15 January to 15 June, so you still have time to prepare a compelling and convincing nomination!

Grants

EGU provides funding opportunities for training schools, as well as for conference series such as the Angioletta Coradini Conferences and Galileo conferences. The training schools are intended to provide training opportunities to young scientists, by bringing together experts on a particular topic, and financial support for the early career scientists through travel grants, field trips or lectures. The Angioletta Coradini Conference series is named in honour of an Italian astrophysicist and planetary scientist, and aimed at innovative research related to all themes of space science research. The Galileo Conferences address current topics of particular interest to the geoscience community with a 3 to 5-day meeting divided into keynote presentations, debates, and roundtable discussions. Presentations and discussions must be treated confidentially. These conferences are evaluated through a rigorous review process, and the organization is supported by professionals. The scientific program is defined by an organizing committee composed of at least one member familiar with the venue and an EGU delegate. Conference organizers are then required to publish an article on the conference topic and eventually on the conference proceedings. A financial support of up to 8000€ is provided for the participation of ECS, for web hosting, organizational support and tools. EGU supports not only scientific research but also outreach and communication, which is why it launched, in November 2015, an annual Public Engagement Grant, that awards the 3-4 top candidates 2000€ each for funding their own outreach project. Any project is welcome: podcasts, movies, comics, experiments and many more. The only limit, apart from your imagination, is the non-commercial use of your product and the EGU membership. For more information on the grant please refer to the official website: EGU - Outreach - Public Engagement Grants. We look forward to receiving your proposals, and thank you for your continued support to the Planetary & Solar System Sciences Division!

Written and edited by Gabriele Boccacci, Giulia Nejat, Janko Trisic Ponce and Salvatore Buoninfante

Icons credit: [Alphavector, Canva AI Elements Lab, Eucalyp-amethyststudio Lab, Prayogi M-Edwin M, とくめいとななし (Toku & Nana), Jenzon Lopez-Sketchify Education, Kester-sparklestroke, sketchify, Chelsea-Gonzales-Sketchify Education] via Canva.com.

When ozone enters a leaf: why the details matter for Earth system models

Ceren Moral — Fri, 18 Sep 2026 11:00:01 +0000

(Schematic cross-section showing leaf stomatal O_3 uptake, chloroplast oxidative stress, and the resulting downregulation of Earth's global photosynthetic carbon uptake (GPP)) We usually think of ozone as a shield high in the atmosphere or as an air pollutant that harms human lungs near the ground. But plants also “breathe” ozone. Through microscopic pores called stomata, leaves take in carbon dioxide for photosynthesis—and ozone can enter through the same doorway. Once inside a leaf, ozone forms reactive compounds that disrupt photosynthesis and alter stomatal behaviour. At the scale of a single leaf, this is a physiological stress response. At the scale of the planet, it can affect gross primary production (GPP): the total amount of carbon plants take up through photosynthesis. Because GPP is one of the largest carbon flows in the Earth system, even modest errors in its representation can influence how we understand the land carbon cycle. Yet there is a complication. Land-surface models do not all translate ozone exposure into plant damage in the same way. Our recent study in Geoscientific Model Development asked a simple but consequential question: if the same land model sees the same weather and the same ozone, how much do its answers depend on the mathematical “rules” used to represent ozone stress? From ozone in the air to ozone inside a leaf Ambient ozone concentration alone does not tell us how much damage a plant experiences. Ozone must first reach the leaf surface and then pass through the stomata. Uptake therefore depends on wind and turbulence, leaf boundary layers, stomatal opening, light, temperature, humidity, and soil water availability. A dry plant may close its stomata and take up less ozone even when the surrounding concentration is high; under brighter and wetter conditions, open stomata may admit a larger dose. Models handle this pathway with an ozone-stress parameterization: a compact set of equations that decides three things. First, how much ozone enters the leaf? Second, does the flux exceed a damage threshold? Third, how does accumulated exposure suppress photosynthesis and stomatal conductance—and how quickly does the plant “forget” earlier exposure as leaves turn over or conditions change? These choices may sound technical, but they encode very different biological assumptions. A single threshold applied to all vegetation treats forests, shrubs, grasses, and crops as if they tolerated ozone similarly. A linear response assumes that each additional unit of ozone dose causes the same increment of damage. A strong memory term can allow injury to accumulate for too long, while a rapid decay can underestimate persistent stress. The modelling comparisons and validation inside CLM5 To isolate these choices, we implemented and compared three widely used ozone-stress schemes—Sitch, Lombardozzi, and Li—within the Community Land Model version 5 (CLM5). All simulations used a common model configuration, meteorological forcing, and hourly near-surface ozone fields for 2005–2014. We also designed mixed experiments that placed thresholds and response functions from the older schemes inside the Li framework. These mixed runs were not recalibrated; their purpose was diagnostic, allowing us to trace differences to model structure rather than to unrelated settings.We then compared simulated GPP with two complementary observational benchmarks. MODIS provides broad satellite-based coverage, while FLUXNET towers measure exchanges of carbon between ecosystems and the atmosphere at individual sites. The two views are not interchangeable: satellites offer spatial reach, whereas flux towers provide process-rich, high-frequency observations. Together, they allow a more demanding evaluation across latitude bands, biomes, seasons, and plant functional types. The same ozone for very different global losses Every ozone scheme reduced global GPP relative to a simulation without ozone stress—but by very different amounts. The no-ozone experiment produced 132.0 petagrams of carbon per year. The Li scheme reduced this total by 12.8%, to 115.14 petagrams of carbon per year, close to independent global benchmarks. The Lombardozzi scheme reduced GPP by 23.5%, to 100.98 petagrams of carbon per year. In other words, the estimated loss differed by more than a factor of two even though the atmospheric forcing and host land model were held constant. [caption id="attachment_5799" align="alignnone" width="1024"] Figure 2. Spatial patterns and zonal gradients of decadal-mean gross primary production (GPP).[/caption] (Global distribution of decadal-mean (2005–2014) GPP and corresponding zonal-mean profiles simulated by CLM5 under: (a) the ozone-free baseline (I2000), (b) the Li parameterization scheme, (c) Li framework with Lombardozzi thresholds and function, (d) Li framework with Sitch thresholds and function, (e) the Lombardozzi parameterization scheme, and (f) the MODIS satellite benchmark. Neglecting ozone stress leads to marked tropical GPP overestimation, while different ozone schemes produce distinct spatial constraints. Adapted from Fig. 1 of Zhou et al. (2026), licensed under CC BY 4.0.) The contrast was clearest in high-flux regions. The Lombardozzi formulation accumulated ozone damage strongly and retained a longer memory of exposure, leading to pronounced suppression in low latitudes. The Li formulation used vegetation-specific flux thresholds, separate nonlinear responses for photosynthesis and stomatal conductance, and damage decay linked to leaf turnover. Among the ozone schemes, it showed the most consistent agreement with observed GPP patterns across annual, seasonal, and monthly scales. That result does not mean that adding ozone automatically fixes a land model. In several temperate and boreal ecosystems, the no-ozone baseline already matched FLUXNET better than the ozone-stress experiments. Ozone stress can correct an existing overestimate in one region while worsening an underestimate elsewhere. The apparent success of a parameterization therefore depends on the host model’s baseline behaviour, including its treatment of canopy physiology, phenology, water limitation, and sub-grid vegetation diversity. Where should the next generation of models go? Our comparison points to a broader lesson: representing ozone is necessary, but the form of that representation should be dynamical. Future schemes should move beyond one-size-fits-all thresholds. They should allow ozone sensitivity to vary among vegetation types and regions, represent photosynthesis and water loss separately, and connect damage and recovery to leaf age, canopy structure, phenology, and soil moisture. [caption id="attachment_5805" align="alignnone" width="1024"] Figure 3. Global total GPP for the no-ozone simulation, four ozone-stress experiments, and MODIS (top), and the relative GPP reduction caused by each ozone scheme (bottom). Adapted from Fig. 10 of Zhou et al. (2026), licensed under CC BY 4.0.[/caption] Better observations will be central to this effort. Flux towers and satellite products can constrain different parts of the problem, while ozone fumigation experiments provide direct evidence of how plant species respond. Emerging measurements of canopy structure and plant traits may eventually help models replace broad vegetation categories with more continuous, biologically meaningful controls. The stakes extend beyond model elegance. Surface ozone changes with emissions, atmospheric chemistry, weather, and climate. If models misrepresent how plants take up ozone or recover from it, they may misjudge ecosystem productivity and the strength of the terrestrial carbon sink. Our results show that uncertainty does not come only from how much ozone is in the air. It also comes from what the model believes happens after ozone reaches a leaf. This blog post is based on a manuscript accepted for publication in Geoscientific Model Development.

This post has been edited by the editorial board

References:
1. Zhou, P. et al. (2026). “Benchmarking ozone stress parameterizations in CLM5: a global mechanistic assessment of thresholds and memory effects.” Geoscientific Model Development, 19, 5491–5513. https://doi.org/10.5194/gmd-19-5491-2026

Looks can be deceiving: Why high coral cover does not always mean high reef productivity

Jacqueline Behncke — Thu, 17 Sep 2026 08:49:54 +0000

When most people imagine a coral reef, they picture clear, warm, sunny tropical waters. However, the coral communities of Hong Kong live in a vastly different setting. In the shadows of one of the most densely populated coastlines in the world, these corals persist under highly turbid conditions, receiving relatively little light over the year. Water conditions are also highly seasonal, with large changes in temperature, rainfall and nutrient loads between the wet and dry seasons. These environmental conditions are challenging for coral organisms that normally depend heavily on optimal temperatures, high light and low nutrients to thrive. And yet, Hong Kong’s coastal waters still support highly diverse coral communities (> 90 hard coral species), including locations where corals cover much of the seabed. [caption id="attachment_3855" align="aligncenter" width="1024"] Figure 1: Examples of high coral-cover, but low net ecosystem productivity, communities found in Sharp Island variably dominated by (a) cactus corals (Pavona) and (b) branching corals (Acropora). Note: these images taken during rare conditions of good visibility in Hong Kong. Scale bar is 50 cm wide. (Photo credit: Yu-De Pei)[/caption] This makes Hong Kong a useful natural laboratory for determining how coral communities might function under future coastal conditions, where climate change and coastal development may make conditions more challenging for corals to thrive. A central motivation for this study was to look beyond coral cover as the default way of judging how well a coral community is doing. High coral cover can tell us that corals are present and persisting but does not necessarily tell us how the whole community is functioning. To address this, we measured net ecosystem production, a measure of whether a whole community is producing more organic carbon through photosynthesis than it consumes through respiration, at several sites across Hong Kong. [caption id="attachment_3857" align="aligncenter" width="1024"] Figure 2: The gradient flux system deployed in a coral community at about 3 m water depth at Sharp Island, Hong Kong to measure net ecosystem production rates from dissolved oxygen exchange across the benthic boundary layer. (Photo credit: Markus Rummel)[/caption] When net ecosystem production is positive, it means the community is net productive in terms of organic carbon. When it is negative, the community consumes more organic carbon than it is producing. One striking result from the study was that even sites with moderate to high coral cover had low or negative net ecosystem production. In other words, visually coral-rich communities were not necessarily highly productive at the community scale. This pattern of low or negative net ecosystem production was observed in both the wet and dry seasons. This does not mean that these corals are “failing”. Rather, it shows that survival, coral cover and ecosystem productivity are related but not interchangeable. Our findings suggest that visual surveys of coral cover and diversity should be combined with direct measurements of biogeochemical processes whenever possible to improve understanding of the community’s underlying function. The study also showed the difficulty of measuring reef function in a highly heterogeneous coastal environment. We had also hoped to measure carbonate cycling, including whether the community was building or losing calcium carbonate reef structure. However, in Hong Kong’s highly dynamic coastal setting, those measurements were not robust enough to interpret confidently, so we chose not to include them in the final study. Rather than over-interpreting uncertain data, we focused on the measurements we could support confidently. Future work combining organic carbon cycling with carbonate cycling will help build a more complete picture of how these communities function. The wider implication of this study is that coral communities living under marginal environmental conditions, such as those found in the urbanized coastal waters of Hong Kong, may persist through alternative pathways that do not match the classic clear-water reef model. Assessing their future trajectories requires measuring function directly, rather than relying solely on visual metrics of the community. Hong Kong’s corals show that a coral community can persist under difficult conditions, but persistence alone does not tell the full story. To understand the future of coral reefs, especially in increasingly urban and turbid coastal waters, we need to measure not only what a reef looks like, but also what it is doing. Read the paper in Biogeosciences: King, T. B., Pei, Y.-D., Bennett-Williams, J., and Wyatt, A. S. J.: Net ecosystem production of coral communities persisting under marginal environmental conditions, Biogeosciences, 23, 6267–6286, https://doi.org/10.5194/bg-23-6267-2026, 2026.

Hydrothermal alteration in volcanic settings: Remaining research challenges

Agata Poganj — Thu, 17 Sep 2026 05:13:11 +0000

Why should you care about hydrothermal alteration in volcanic systems?

When people think of volcanoes, they imagine large, devastating eruptions and lava streams gushing from the summit of an edifice. However, even when volcanoes are not visibly 'active', there can be more lurking below the surface. Hydrothermal alteration is one of the important and often less-talked-about culprits that changes dome-forming rocks and minerals from within. It can occur in parallel with other processes, and, therefore, it might flow under the radar. As a matter of fact, one in five historical volcanic collapses recorded since 1500 AD have been caused by hydrothermal alteration. Good thing that today's post will cover the whys, hows and know-how of hydrothermal alteration.

What is hydrothermal alteration?

Hydrothermal alteration is a product of magmatic and meteoric interaction inside the volcanic structure. It occurs when hot hydrothermal fluids, concoctions made up of magmatic volatiles and groundwater, come into contact with host rocks. Minerals get dissolved, and incorporated into the fluid, thereby changing the chemical and mineralogical composition of volcanic rocks. Additionally, a hydrothermal system depends on faults and fractures that transport hot fluids through permeable lithology. The surface expression of hydrothermal activity can be documented in the form of crater lakes, fumaroles, hot springs, and mineral deposits at the volcanic summit. As temperature decreases further away from the heat source, mineral phases incorporated in the fluid will precipitate. All of these changes act in spatiotemporal cycles, waxing and waning microstructural integrity of the volcanic rocks. Physical property changes that arise from hydrothermal alteration can influence the behaviour of volcanoes. Therefore, hydrothermal alteration can quietly re-engineer a volcano from the inside, turning rocks into weak, clay-rich masses or overpressurised caps. Rock weakening, fluids, and pressure strongly influence where and how a volcano collapses or explodes.

What does hydrothermal alteration do?

Primary lithology and mineralogy are among the determinators of how alteration will affect physical and mechanical behaviour. Dense, coherent lavas typically retain higher strength due to low porosity and their tight-knit structures. Because of the lack of permeable pathways, it is harder for fluid to penetrate the rock and alter it. In contrast, fragmented rocks such as breccias and pyroclastic deposits with higher porosity can more easily facilitate hydrothermal fluids. With the added caveat that pyroclastic rocks can sometimes undergo welding/cementation, resulting in increased strength and compaction. A more common process in volcanic environments is argillic alteration that weakens rocks via clay formation and leaching. Depending on the mechanisms involved, both porosity-increasing and porosity-decreasing are documented in dome-forming materials. Hydrothermal fluids often dissolve original feldspar and mafic phases, replacing them with weak clays (e.g., smectite, kaolinite), thereby increasing porosity and reducing strength, stiffness, and cohesion. The result is a ''rotten rock'', a mechanically compromised rock mass, which can fail under relatively low stress. These altered zones can form laterally continuous, mechanically weak layers that act as slip surfaces. Because they are often buried beneath more competent rocks, they may remain undetected until a sudden failure/collapse occurs. On the other hand, precipitation that fills pores and fractures reduces permeability but might either decrease or increase strength. While this may locally strengthen the rock, it also shuts off permeable pathways. The resulting isolation can allow pore pressures to build up beneath sealed caps, increasing the likelihood of explosive behaviour. The destabilisation caused by the impact, therefore, depends not only on whether rocks are weakened, but also on how altered zones interact with fluid flow and stress distribution across the volcano. [caption id="attachment_13353" align="aligncenter" width="780"] A schematic of eruption styles in volcanic settings, showing potential trigger mechanisms (e.g., magma/fluid injection; landslide; sulphur sealing; lake drainage). Source: Montanaro et al. (2022)[/caption]

How to detect and measure hydrothermal alteration on site?

Detecting and quantifying hydrothermal alteration is difficult because different methods tell a part of the alteration story, and data interpretation depends on resolution, surface exposure, and integration with field or laboratory data. Electromagnetic methods such as resistivity and magnetotellurics are effective for mapping conductive, fluid-rich, clay-bearing zones and delineating hydrothermal flow structures, including clay caps and upflow regions. However, they do not identify alteration mineralogy on their own. Aeromagnetic inversion can map subsurface altered volumes to depths highly dependent on the setting (at Mt. Ruapehu ~500 m), because hydrothermal alteration commonly destroys ferrimagnetic minerals and lowers magnetization; however, magnetic lows are not uniquely diagnostic because some fresh fine-grained lavas can show similarly low susceptibility. Hyperspectral imaging is highly effective for mapping surface mineralogy and alteration styles, and newer models can also predict density, porosity, stiffness, and strength from spectral fingerprints, but the method is restricted to exposed surfaces and can be hidden by tephra, snow, ice, vegetation, or supergene weathering. Muon tomography adds a different constraint by imaging internal density variations and tracking short-term density changes linked to hydrothermal dynamics, making it a useful complement to resistivity, magnetics, and laboratory rock-property data rather than a replacement for them. Alteration intensity can be estimated from secondary mineral assemblages, geochemical indices such as CIA, and rock magnetic parameters, but CIA is best treated cautiously because its interpretation can be biased by protolith, grain size, sediment recycling, and metasomatic overprint, unless paired with petrography and broader geochemistry. Together, electrical, magnetic, hyperspectral, and muon datasets can reveal altered, saturated, mechanically weak zones that often cluster on steep flanks and around domes. There has been an increasing number of case studies exercising a multidisciplinary approach, that are more informed and accurate in constraining hydrothermal alteration and detangling its complicated influence. [caption id="attachment_13360" align="aligncenter" width="754"] An example of what hydrothermal alteration does to Merapi volcano. Source: Heap et al. (2019)[/caption]

All of the colours of the alteration rainbow

[caption id="attachment_13356" align="alignright" width="183"] Highlighting heterogeneity in altered volcanic rocks from La Soufrière de Guadeloupe.[/caption] Hydrothermal alteration is often described in terms of mineralogical “zones,” each associated with distinct conditions, temperatures, and fluid compositions. These zones can be visually recognisable by colour, offering clues for interpreting subsurface processes.

Argillic clay-dominated alteration often appears as pale, soft, and earthy material—whites, creams, and light grays. Advanced argillic zones, containing minerals like alunite and kaolinite, may display bleached, bright white, or even have pinkish hues.
Silicic alteration is one of those processes that can increase rock strength. It can include locally vuggy silica with white, grey to bluish tones due to quartz enrichment.
Propylitic alteration, characterised by chlorite, epidote, and calcite, commonly gives rocks a greenish colour and is usually associated with greater strength and structural integrity than clay-rich zones.
Iron oxides appear red, orange, and yellow because of the presence of hematite and goethite. Be warned that these hues can be telling of either hydrothermal oxidation or surface weathering.
Neon green and bright yellow surface sulfur precipitates can be markers of active degassing, but they are better treated as fumarolic surface products than as a primary alteration facies.

These variations are not solely aesthetic—they provide field geologists with some macroscopic clues about the alteration state of the volcano. It goes without saying that colourful rocks are not a foolproof method of determining alteration. They are fun and CAN BE indicators.

Some outstanding questions

Heterogeneity and sampling: Anyone who has climbed a volcano can tell you – volcanoes are a hot mess! With so many different alteration zones, host rocks, and phases, saying that volcanoes are heterogeneous is an understatement. And how do you sample an area like that? Which samples do you prioritise? The most fragile-looking ones or the most volumetrically abundant? Additionally, if you are dealing with a degassing volcano, acessing and sampling active, deep-seated hydrothermal systems will be technically difficult, leaving gaps in real-time observation. Scale and complexity: There is definitely a disconnect between well-constrained, sample-scale laboratory measurements and edifice-scale numerical models that require input parameters. The scarcity of petrophysical properties for altered volcanic rocks limits large-scale stability modelling, and simplified cross-sections often fail to capture the true heterogeneity of alteration zones. One of the more exercised approaches in recent history has been the use of 3D models that investigate the impact of alteration on dome stability. Even if conceptualised, these types of models show how far alteration can damage a volcanic edifice, and coupled with appropriately upscaled physical and mechanical input parameters, they are creating a new era for hydrothermal research. Spatiotemporal evolution: The time and space scales of alteration are poorly understood and difficult to constrain, with estimates ranging from years to thousands of years based on stratigraphy and radiometric dating. Superimposed alteration zones make it difficult to determine whether different mineral assemblages represent discrete events or varying conditions along the system, leaving their relative chronology unresolved. Drill cores from geothermal fields such as Irruputuncu (Chile) and Los Humeros (Mexico) can provide rare windows into alteration at depth, but these still account for a few boreholes and may not fully capture spatial variability. At Los Humeros, there are no clear trends between alteration facies and intensity, which might coincide with multiple hydrothermal events, of no avail in detangling a single alteration history. Literature and figures for those who want to learn more:

Siebert, Lee, Tom Simkin, and Paul Kimberly. Volcanoes of the World: Third Edition. University of California Press, 2010.
Montanaro, Cristian, Emily Mick, Jessica Salas-Navarro, et al. ‘Phreatic and Hydrothermal Eruptions: From Overlooked to Looking Over’. Bulletin of Volcanology 84, no. 6 (2022): 64. https://doi.org/10.1007/s00445-022-01571-7.
Sanchez, Rachelle, Gabor Kereszturi, Antonio M. Álvarez-Valero, Mercedes Suárez, Geoff Kilgour, and Georg Zellmer. ‘Timescales and Processes of Hydrothermal Alteration at Te Maari Tongariro, New Zealand: Insights Utilizing Petrographic and Mass Balance Techniques’. Journal of Volcanology and Geothermal Research 473 (2026): 108570. https://doi.org/10.1016/j.jvolgeores.2026.108570.
Ní Nualláin, K. D., C. E. Harnett, A. Hrysiewicz, M. J. Heap, T. R. Walter, and M. Rosas-Carbajal. ‘From Alteration to Avalanche: A 3D Framework for Exploring Hydrothermal Weakening of Lava Domes’. Journal of Volcanology and Geothermal Research, 16 February 2026, 108566. https://doi.org/10.1016/j.jvolgeores.2026.108566.
Pereira, Maria Luísa, Vittorio Zanon, Isabel Fernandes, Lucia Pappalardo, and Fátima Viveiros. ‘Hydrothermal Alteration and Physical and Mechanical Properties of Rocks in a Volcanic Environment: A Review’. Earth-Science Reviews 252 (2024): 104754. https://doi.org/10.1016/j.earscirev.2024.104754.
Heap, Michael J., and Marie E. S. Violay. ‘The Mechanical Behaviour and Failure Modes of Volcanic Rocks: A Review’. Bulletin of Volcanology 83, no. 5 (2021): 33. https://doi.org/10.1007/s00445-021-01447-2.
Mathieu, Lucie. ‘Quantifying Hydrothermal Alteration: A Review of Methods’. Geosciences 8, no. 7 (2018): 245. https://doi.org/10.3390/geosciences8070245.
Heap, Michael J., Valentin R. Troll, Alexandra R. L. Kushnir, et al. ‘Hydrothermal Alteration of Andesitic Lava Domes Can Lead to Explosive Volcanic Behaviour’. Nature Communications 10, no. 1 (2019): 5063. https://doi.org/10.1038/s41467-019-13102-8.

(This post was reviewed by Samira Yalla, whose thoughts and comments helped improve the clarity of the article. I am thankful that she took the time and effort to provide feedback)

Bridging the Gap: How Virtual Reality is Helping the Next Generation of Geoscientists

Editorial team 1 — Wed, 16 Sep 2026 08:00:57 +0000

Deciphering Earth’s geological history is no easy feat. For undergraduate students beginning their journey in geology, identifying a rock and drawing connections with relevant geodynamic processes occurring over millions of years can be a challenge. In this week’s blog post, Phillip Ruscia explains how virtual reality (VR) and the High Immersion Virtual Experiences (HIVE) research lab at the University of Toronto are bridging the "abstraction gap" and preparing the next generation of geoscientists.

[caption id="attachment_44111" align="alignleft" width="143"] Phillip Ruscica, University of Toronto, Canada[/caption]

Geodynamic processes span millions of years and vast spatial scales, far beyond what anyone can witness in a single lifetime. To reconstruct past geological processes, geologists analyze pieces of evidence, such as a segment of a fold, a fossil in a limestone, or a striation on a rock. For an expert, a marine fossil becomes a tropical sea teeming with life; for a student, however, this leap of imagination can be a significant challenge.

The Problem of Abstraction in Geoscience

In the “Earth History” undergraduate course at the University of Toronto Scarborough campus (UTSC), students explore roughly 4 billion years of geological history, focusing on how geodynamic processes shaped our planet’s atmosphere, oceans, biology, and climate. The course traditionally emphasizes hands-on identification of fossil, rock, and mineral specimens in weekly labs and links them to larger geological processes, such as ocean formation, subduction, mountain-building, erosion, and deposition. The link between these processes and the physical rock record is rarely clear to students. Students struggle to grasp the three-dimensional nature of these processes and to connect a local observation to its regional story. Part of the problem is that the specimens students analyze carry little of what would make them meaningful. For example, a marine fossil in a lab drawer has been stripped of the sea it once inhabited. Another challenge is that pristine samples bear little resemblance to the imperfect, weathered rocks and fossils students will eventually encounter in the field. Bridging this gap requires more than examining a specimen up close — it requires letting students step inside the environments and timescales a specimen has been removed from. This is precisely where immersive technology earns its place in the geoscience classroom.

A marine fossil in a lab drawer has been stripped of the sea it once inhabited.

A New Kind of Facility: Immersive Virtual Reality

Virtual Reality (VR) is an immersive technology that simulates an entirely digital world where the user feels a sense of “presence” through a stereoscopic headset and haptic per-hand controllers. In this digital space, there are essentially no limits on what can be seen or done. Once immersed, users can explore the limitless nature of the digital world, where real and created objects seamlessly blend with whatever behaviours, guidance, gamification, and active learning the activity calls for. Objects can be captured directly through photogrammetry, modelled or AI-generated from real-world references, or made wholly fictional, as in video games. Their behaviour can follow real data or depart from it entirely — changing how they move, appear, and respond. In our applications, real data drives the components that matter most: the visual detail, behaviour of key objects, and the actions available to the user. To bring VR into the course, we established the DPES HIVE, a dedicated VR facility at UTSC supported by a $100,000 departmental research grant. The HIVE houses seven specialized stalls, each equipped with a custom smart wall and high-end hardware, including the HTC Vive Pro 2 and Meta Quest 3 headsets. The layout is designed for maximum pedagogical support. Each student has their own “play area” for movement, while supervisors can monitor the student’s view on external monitors. This setup allows hands-on, tailored support, ensuring that even students new to VR can successfully navigate the digital world.

A Three-Stage Pedagogical Arc: From “Specimen-to-Setting-to-Stone”

To address the abstraction gap and the disconnect between theory and fieldwork, we structured the practical component of the course into three escalating stages:

Stage 1: Building Core Skills in the Lab

Students first use traditional methods to identify fossil, rock, and mineral specimens through hands-on practicals with physical samples. This allows students to learn the core skills of observation and classification. In our course, fossil identification focuses on Silurian-Devonian fossils from Southern Ontario, Canada.

**Stage 2: Deep Immersion in VR – Ocean Floor VR App**

Stage 2 utilizes our newly developed Ocean Floor VR application, designed to introduce students to VR while reinforcing fossil identification. This application features four visually distinct ocean zones - the epipelagic, mesopelagic, bathypelagic, and the combined abyssopelagic/hadopelagic. As students “descend” through each zone, they encounter fossils in an original environment or setting. Each environment features unique characteristics, such as water depth, lighting, grain size, and even marine species swimming throughout the scene. Students can pick up and examine digital fossils, consult information panels, and answer questions via the university’s academic web platform integrated directly into the VR experience. By the time students complete the exercise, a fossil hand-sample is no longer an isolated object – it holds an ocean and the millions of years that shaped it. [embed]https://youtu.be/kxmeNpgotDQ[/embed]

A fossil hand-sample is no longer an isolated object – it holds an ocean and the millions of years that shaped it.

Stage 3: Virtual and Physical Field Trip into the Devonian!

With VR familiarity established, the final stage focuses on exploring a stone quarry, where Devonian fossiliferous limestone is well exposed. Here, students transition from “ideal” specimens to real-world challenges. In a VR replica of the quarry, students work in pairs to identify rock types and geological features, such as joints, striations, and imperfect fossils often half-hidden in the rock. Using a virtual compass, they also measure the trend of joints and striations. By practicing these skills in VR first, students are better prepared for their in-person field trip to the quarry. In both formats (virtual and in-person), students also discuss the region’s geological history since the Devonian, helping them connect the physical rock record to the geological processes that shaped the area. https://youtu.be/gSgnoKIagF0

The Limitless Role of VR in Teaching and Research

We continue to evolve through student feedback, refining our design with a steady goal: to send the next generation of geoscientists into the field not only better prepared for fieldwork but with the trained ability to perceive deep time and the planet-scale processes that a single specimen can only hint at. As the DPES HIVE evolves, we hope the “specimen-to-setting-to-stone” arc is more than just a course sequence; it is a template for the future of geoscience education—one we believe could extend to any field. VR also has meaningful potential in research. For example, we're working on a "VR-crystal experience" that enables atomic-scale exploration of crystal structures. Students can manipulate lattices, measure parameters, and classify minerals while interactively visualizing symmetry, bonds, and 3-dimensional atomic arrangements. We also have VR applications in development for visualizing the results of ecological modelling. The goal is to transfer expert knowledge of environmental problems, along with concepts such as “uncertainty” and “risk”, to stakeholders, policymakers, scientists, and the public. Because VR allows us to combine real data with simulated behaviours, the potential is truly limitless. Interested in bridging immersive visualization into your work? We'd love to hear from you!

Arhonditsis, G.B., Neumann, A., Ruscica, P., Javed, A., Daxberger, H., 2023. Integration of Bayesian Inference Techniques with Mathematical Modeling, in: Reference Module in Earth Systems and Environmental Sciences. Elsevier, p. B9780323907989000767. https://doi.org/10.1016/B978-0-323-90798-9.00076-7 

Ruscica, P., Daxberger, H., Resch, G., Hadzovic, A., Dalili, S., Arhonditsis, G.B., 2026. Transforming education and research with extended reality technologies: How virtual reality can shape the future of data interactions in earth and environmental sciences. Ecol. Inform. 93, 103535. https://doi.org/10.1016/j.ecoinf.2025.103535

Great Names in Geomorphology A–Z: Ralph Bagnold

wioletaporebna — Tue, 15 Sep 2026 13:25:39 +0000

Ralph Alger Bagnold (3 April 1896 – 28 May 1990) was a British engineer, geomorphologist, desert explorer, and soldier. His work fundamentally changed our understanding of sediment transport. His pioneering studies of wind-blown sand and desert dunes established a quantitative, physics-based approach to aeolian geomorphology. Bagnold’s scientific career was closely connected with his fascination with deserts. As an officer in the British Army, he spent years in North Africa and used his periods off leave to explore parts of the Sahara. His expeditions across the Libyan Desert combined exploration with systematic observations of dunes, sand movement, and desert landscapes. [caption id="attachment_3058" align="alignright" width="279"] On a 1932 desert exploration (source: Long Range Desert Group, https://lrdg.hegewisch.net/)[/caption] Rather than simply describing dunes and other aeolian landforms, Bagnold sought to understand the physical processes responsible for their formation and movement. After leaving active military service in the 1930s, he constructed a wind tunnel and conducted experiments on sand transport, connecting field observations with laboratory measurements and physical theory. Bagnold’s most influential work, The Physics of Blown Sand and Desert Dunes, was published in 1941. His studies of saltation, the characteristic hopping motion of sand grains, helped establish relationships between wind velocity, grain size, and the rate of sediment transport. His approach provided a framework for understanding how processes operating at the grain scale contribute to the development and migration of dunes. He also investigated sediment transport in water, the behaviour of granular materials, river meanders, and bedload transport. His 1966 US Geological Survey publication, An Approach to the Sediment Transport Problem from General Physics, applied physical principles to sediment transport in flowing water and became an important contribution to fluvial geomorphology and sediment transport research. Bagnold’s scientific legacy extends beyond Earth. The Bagnold Dunes, an active dune field on the northwestern flank of Mount Sharp in Gale Crater on Mars, were informally named in his honour. NASA’s Curiosity rover investigated these dunes as part of its exploration of the Martian surface, providing an opportunity to study dune dynamics under conditions very different from those on Earth. [caption id="attachment_3060" align="alignleft" width="300"] Location of Bagnold Dune Field (source: Curiosity Rover’s Location Map, NASA, https://science.nasa.gov/mission/msl-curiosity/location-map/).[/caption] The connection is more than symbolic. Bagnold pioneered the study of how wind moves sand grains on Earth, while the investigation of the Bagnold Dunes allows scientists to examine how similar processes operate in Mars’ much thinner atmosphere and under lower gravity. In this sense, questions first explored by Bagnold in the deserts of Earth have become part of planetary geomorphology. Bagnold’s influence on geomorphology is also commemorated by the European Geosciences Union (EGU) through the Ralph Alger Bagnold Medal, established by the EGU Geomorphology Division to honour his scientific achievements. The medal is awarded annually to a scientist who has made an outstanding contribution to the field. [caption id="attachment_3062" align="alignright" width="292"] The Ralph Alger Bagnold Medal designed by József Kótai.[/caption] Importance Ralph Bagnold was one of the pioneers of physics-based geomorphology, demonstrating how fundamental physical principles can be used to explain sediment transport. His work on the movement of sediment across aeolian and fluvial environments, linking laboratory experiments, field observations, and physical theory, provided a quantitative foundation for understanding one of the fundamental processes shaping landscapes. Did you know? Bagnold was not only a scientist but also played a significant role in the history of the Second World War. Drawing on his extensive experience of desert travel and navigation, he helped establish the Long Range Desert Group in 1940, a British reconnaissance unit operating deep behind enemy lines in the North African desert. He was awarded the Order of the British Empire in 1941 and was elected a Fellow of the Royal Society in 1944. Selected Works Bagnold R.A. 1936. The movement of desert sand, Proceedings of the Royal Society of London, Series A, Mathematical and Physical Sciences, Vol. 157, No. 892, pp. 594–620. Bagnold R.A. 1941. The Physics of Blown Sand and Desert Dunes, Methuen, London, pp. 265. Bagnold, R.A. 1966. An approach to the sediment transport problem from general physics, U.S. Geological Survey Professional Paper 422, pp. I1-I37, DOI: https://doi.org/10.3133/pp422I. Bagnold R.A. 1974. The Physics of Blown Sand and Desert Dunes, Springer Dordrecht, pp. 265, DOI: https://doi.org/10.1007/978-94-009-5682-7. Bagnold R.A. 1987. Libyan sands: travels in a dead world, Michael Haag, London, pp. 288. Whose next? Now it’s your turn! Which geomorphologist whose surname begins with the letter “C” should be featured in the next post? Share your suggestions in the comments.

El Niño shouldn't stay in the classroom: Why everyone should understand one of Earth's most influential climate patterns

Hedieh Soltanpour — Mon, 14 Sep 2026 08:26:09 +0000

Floods in one region. Droughts in another. Wildfires intensifying across already dry landscapes, while elsewhere intense rainfall triggers landslides and infrastructure disruption. At first glance, these hazard events may seem entirely unrelated. After all, what could a flood on one side of the world possibly have to do with a drought on the other? Yet many of these seemingly disconnected events can be traced back to the same climate phenomenon developing thousands of kilometres away in the tropical Pacific Ocean: El Niño. Chances are you have heard of El Niño and its adverse impacts in news reports from around the world. At the time of writing, El Niño is once again developing in the tropical Pacific. As it builds over the coming months, it is expected to add further warmth to an already warming planet while increasing the likelihood of weather extremes across many regions of the world. While most people are familiar with hazards such as floods, droughts and wildfires, relatively few outside the scientific community are aware of the global climate pattern that can influence them all. This blog aims to explain what El Niño is, how it develops, why it can influence weather across the globe, and which regions are typically most affected. At the end of the blog, I will touch on the question that first inspired me to write it: whether El Niño can be considered a natural hazard. The main sources of information for this blog are the World Meteorological Organization (WMO), National Oceanic and Atmospheric Administration’s (NOAA) Climate Prediction Center (CPC), and recent news reports. All sources have been carefully cited throughout.

What is El Niño and why "El Niño"?

Hundreds of years ago, every few years around Christmas, Peruvian fishermen noticed that unusually warm waters would replace the normally cold, nutrient-rich waters along their coast. As these warm waters often arrived during the Christmas season, they are said to have named the phenomenon El Niño, Spanish for "the little boy/child". For many years, it was believed to be a local event affecting only the Peruvian coast. It was not until the 1960s that scientists recognised it as part of a much larger ocean-atmosphere system spanning the tropical Pacific, capable of influencing weather patterns triggering natural hazard events in many parts of the world [2; 7]. But what exactly were these fishermen observing? El Niño happens when the ocean surface temperatures across the central and eastern equatorial Pacific Ocean become warmer than usual (Fig 1) (for more on the mechanisms behind El Niño, see the further reading at the end of this post). This also changes the jet streams, which lead to changes in wind directions fuelling more severe storms in some parts of the world, while drying out others [10]. During El Niño, trade winds weaken and this pushes back warm water east, toward the west coast of the Americas. Once initiated, such events can last for 12 to 18 months (sometimes even go up to 24 months). El Niño occurs irregularly every 2 to 10 years, with an average recurrence interval - the average time between successive events - of around 4.5 years, typically increasing global temperatures and driving more extreme weather and rainfall patterns [2; 10]. NOAA declares El Niño conditions when sea-surface temperatures in the central-eastern equatorial Pacific are at least 0.5°C above average and the warming is expected to persist for at least three consecutive months, and characteristic changes are also observed in the atmosphere [6; 7]. [caption id="attachment_11358" align="aligncenter" width="511"] Figure 1. Schematic showing normal Pacific conditions compared with El Niño conditions in 1997. Image credit: NOAA Ocean Exploration [/caption]

A brief look at El Niño events past and present

In NOAA's El Niño-Southern Oscillation (ENSO) record, which begins in 1950, several prominent El Niño events stand out, including those of 1972-73, 1982-83, 1997-98 and 2015-16. ENSO combines changes in tropical Pacific Ocean temperatures with related shifts in atmospheric pressure [6]. More recently, the 2023-24 El Niño was classified by the World Meteorological Organization (WMO) as one of the five strongest events on record [6; 8]. And now we are experiencing another major El Niño. NOAA formally declared El Niño conditions in June 2026, and the event has continued to strengthen. Current forecasts indicate a greater than 90% chance that it will become a very strong El Niño during autumn and winter 2026-27. Forecasts also suggest that its eventual strength could rival some of the strongest El Niño events in the modern observational record [3].

The geography of El Niño’s impacts

Not all regions of the world are affected by El Niño, and even within a region, impacts can be different both spatially and seasonally. Each El Niño event is unique, with its effects depending on factors such as its intensity, duration, timing and interaction with other climate drivers [10;11]. However, generally speaking, the cycle tends to create drought and heat across Australia, around southern and central Africa, in India and in parts of South America, including in the Amazon rainforest. Heavy precipitation, meanwhile, could hit the southern tier of the US / southern South America, parts of the Middle East and south-central Asia [11]. Zooming in on the geography of El Niño in the US provides a good example of how these effects can vary from one place to another. During El Niño, warmer waters in the tropical Pacific can shift the Pacific jet stream south of its neutral position. This tends to bring warmer and drier conditions to parts of the northern United States and Canada, while the Gulf Coast and southeastern United States generally experience wetter-than-normal conditions and an increased risk of flooding [7] Looking at India, El Niño can disrupt the monsoon, potentially reducing or altering seasonal rainfall, with important consequences for agriculture and water resources. However, the relationship is not always straightforward, as the strength of the monsoon is also influenced by other atmospheric and oceanic factors. Therefore, an El Niño event does not necessarily mean drought across India [4]. For a map of typical global El Niño impacts, check out NOAA Climate.gov website.

Is El Niño a natural hazard?

As Kamal Kishore of the UN Office for Disaster Risk Reduction puts it, "An El Niño is not, in itself, a disaster. Nor is it necessarily even a hazard" [2]. Rather, it is a large-scale climate phenomenon capable of influencing hazards ranging from droughts and floods to wildfires and tropical cyclones in different parts of the world. From a disaster risk reduction perspective, this makes the question particularly interesting. Perhaps the most useful way to think about El Niño is not simply to ask whether it is a hazard itself, but to ask what hazard scenarios it could generate, intensify or make more likely, and where. Earlier in 2026, forecasters were already warning that El Niño was likely to develop. Since then, some of its anticipated influences have begun to appear. In Indonesia, El Niño-related drying has intensified drought conditions and increased wildfire risk, while in India it has contributed to below-average monsoon rainfall. El Niño conditions have also been linked to aspects of Typhoon Dolphin's unusual behaviour: the storm formed exceptionally far east in the Pacific and travelled over warm ocean waters for much longer than a typical western Pacific typhoon [8]. At the same time, other major extremes and disasters have occurred, including severe heatwaves and wildfires in France throughout the summer of 2026 and the devastating glacier-triggered flash flood along the Nepal-Tibet border on 26 August 2026. Their occurrence during an El Niño year does not mean that El Niño caused them. This is precisely why attribution matters: which hazards can reasonably be linked to El Niño, and which are driven mainly by other climatic or environmental processes? From a multi-hazard perspective, this distinction is exactly why I think it is useful to perceive El Niño not as a catch-all explanation for extreme events, but as a large-scale climate driver capable of creating or amplifying hazardous conditions across different regions. By changing rainfall, temperature and atmospheric circulation, it can favour drought in one place, flooding in another, and conditions conducive to heatwaves or wildfires elsewhere.

Why should we care?

El Niño should not only concern scientists and disaster managers. A basic public understanding of the phenomenon can help people make sense of changing hazard conditions, recognise why certain risks may be increasing, and interpret warnings more critically. El Niño is one of the most closely monitored climate phenomena in the world, yet, as WMO Secretary-General Celeste Saulo has emphasised, forecasts alone do not prevent disasters - people and preparedness do. Forecasts are only useful when we understand what they mean and know how to act on them. Knowing what El Niño is makes it easier to understand why forecasters anticipate floods in some regions, droughts in others, and how communities can prepare accordingly. At a more everyday level, knowing that we are in an El Niño phase can encourage people to pay closer attention to local forecasts and official warnings, particularly when travelling or planning activities in areas where certain hazards may become more likely. As a final word, if El Niño can act as a driver of different hazard scenarios across different parts of the world, understanding that connection becomes part of preparedness itself. Be aware that El Niño can influence many hazards - but do not blame El Niño for everything.

Please read more:

https://www.preventionweb.net/hubs/el-nino https://oceanservice.noaa.gov/facts/ninonina.html https://education.nationalgeographic.org/resource/el-nino/

References

[1] Bureau of Meteorology . Tropical Climate Update. Australian Government Bureau of Meteorology, issued 25 August 2026, available at: https://www.bom.gov.au/climate/tropical-note/ (last access: 2 September 2026). [2] Glantz, M. H. (Ed.): Once Burned, Twice Shy? Lessons Learned from the 1997-98 El Niño, United Nations University Press, Tokyo, Japan, 294 pp., available at: https://www.preventionweb.net/files/1864_VL102131.pdf (last access: 22 July 2026), 2001. [3] Kishore, K.: A “Super El Niño” would be a test for our disaster risk governance systems, United Nations Office for Disaster Risk Reduction (UNDRR), available at: https://www.undrr.org/news/kamal-kishore-super-el-nino-would-be-test-our-disaster-risk-governance-systems (last access: 22 July 2026), 2023. [4] Met Office: El Niño declared for 2026 as Pacific warms, available at: https://www.metoffice.gov.uk/blog/2026/el-nio-declared-for-2026-as-pacific-warms (last access: 31 August 2026), 2026. [5] National Oceanic and Atmospheric Administration (NOAA): FAQs, Pacific Marine Environmental Laboratory, available at: https://www.pmel.noaa.gov/elnino/faq (last access: 31 August 2026), n.d. [6] NOAA Climate.gov: December 2023 El Niño update: Adventure!, available at: https://www.climate.gov/news-features/blogs/enso/december-2023-el-nino-update-adventure (last access: 31 August 2026), 2023. [7] NOAA Ocean Exploration: What is El Niño?, National Oceanic and Atmospheric Administration, available at: https://oceanexplorer.noaa.gov/ocean-fact/elnino/ (last access: 31 August 2026), 2020. [8] Reuters. How climate change and El Niño supercharged Typhoon Dolphin, Reuters, 13 August 2026, available at: https://www.reuters.com/business/environment/how-climate-change-el-nio-supercharged-typhoon-dolphin-2026-08-13/ (last access: 2 September 2026), 2026. [9] World Meteorological Organization (WMO): El Niño weakens but impacts continue, available at: https://wmo.int/news/media-centre/el-nino-weakens-impacts-continue (last access: 31 August 2026), 2024. [10] World Meteorological Organization (WMO): Strong El Niño expected to intensify, available at: https://wmo.int/news/media-centre/strong-el-nino-expected-intensify (last access: 31 August 2026), 2026a. [11] World Meteorological Organization (WMO): WMO: Prepare for El Niño, available at: https://wmo.int/news/media-centre/wmo-prepare-el-nino (last access: 31 August 2026), 2026b. Blog post edited by: Harriet Thompson and Navakanesh M Batmanathan

Challenges in accessibility and code quality of the climate models that underpin our understanding of climate change

Ceren Moral — Fri, 11 Sep 2026 11:00:38 +0000

Climate models help us understand how the climate system works, project future climate change, and provide evidence that supports international assessments such as exposed on the IPCC. At this point, there is a fundamental question that is rarely discussed and solved: Can we access and reproduce the climate models used throughout the history of the Coupled Model Intercomparision Project (CMIP)? In our recent study, we explored this question by assessing the accessibility and software quality of climate models that participated in CMIP. Why reproducibility matters Reproducibility is one of the foundations of science. In principle, independent researchers should be able to examine the methods used in a study and verify the results. These results must be exactly the same obtained by other researcher groups. For computational science, and especially climate science, this means that source code, configuration files, documentation, and model settings should ideally remain accessible over time. Without them, reproducing simulations becomes extremely difficult, even when the scientific publications themselves are available. Also, this is very important for educating new generations of climate modelers, as it is essential to have clear, reproducible code and experiments to understand why certain decisions and implementations were made in the past when developing the models.

Climate models are particularly challenging because they are developed over decades by large international teams and contain millions of lines of code. As models evolve, older versions can become difficult to locate, maintain, or even identify. Looking back across the history of CMIP To investigate how accessible climate models actually are, we examined models from all historical CMIP phases; from CMIP1 to CMIP6. CMIP7 still under development nowadays. Our approach was focused on search for publically available model code, contact institutions and modelling centres when code was not available, evaluate licensing conditions, assess documentation and usability, and analyse software quality in the models that could be obtained. Despite the central role of CMIP in climate science, we were able to obtain only a fraction of the models that have participated through its history. Many early models have simply not been preserved, while others remain inaccessible because of licensing restrictions, institutional policies, or uncertainties regarding intellectual property rights. One of the most striking findings was the complete absence of recoverable source code from CMIP1 and CMIP2. These models played an important role in the development of modern climate science, yet many have effectively become part of a lost digital heritage. The scientific publications describing them still exists, but the software itself is often unavailable. Preserving model source code is not only about reproducibility today. It is also about preserving scientific knowledge for future generations. Are climate models following software engineering best practices? Access to code is only one part of the reproducibility challenge. Once source code is available, another question emerges: How maintainable and understandable is it? To explore this issue, we analyse the climate models using FortranAnalyser, a toll specifically designed to assess scientific software written in Fortran (the most widely used programming language in the climate models). Newer models achieved higher software quality scores than older models. The results suggest that climate modelling groups are increasingly adopting better software development practices and paying greater attention to maintainability and reproducibility. Beyond climate science: preserving reproducible research Although this study focuses on climate models, its implications extend far beyond the climate science community. Modern research increasingly relies on complex software systems, and when source code is unavailable, poorly documented, or inadequately preserved, reproducibility becomes difficult to achieve regardless of the discipline. The challenges identified in this work are therefore not only technical, but also organisational and cultural. To address these challenges, we argue that final versions of scientific software, including climate models, should be preserved in long-term public repositories together with their documentation, configuration files, and licensing information. Adopting open-source practices and routinely evaluating software quality can strengthen transparency, improve trust in scientific results, and make research more accessible to future generations. Climate models represent decades of scientific investment, collaboration, and accumulated knowledge. Ensuring that future researchers can understand, inspect, reproduce, and build upon these systems is essential for the continued advancement of climate science and computational research more broadly. After all, preserving scientific knowledge does not end with publishing a paper. Sometimes, it begins with preserving the code behind it.

This blog post is based on a manuscript accepted for publication in Geoscientific Model Development.

This post has been edited by the editorial board

Will Antarctic ice shelves embark on their last journey soon?

Clara Burgard — Fri, 11 Sep 2026 07:36:03 +0000

Ice shelves, the floating margins of the Antarctic ice sheet, play an important role in the estimation of future sea-level rise. By their presence, they act as a brake on the flow from the grounded ice sheet to the ocean and therefore modulate how much of this ice is added to the ocean. As the atmosphere and ocean warm, melt is occurring at their surface and at their base, putting their existence under threat. In this context, the future of ice shelves looks grim. When can we expect them to disappear and what’s the main driver behind it? This is what we explored in a recent study…

[Note: As this paper was not published in open access (due to very high publication costs), we can unfortunately not share the figures in this blog post. Please check out the paper directly here if you have access to Nature or to its preprint version here.]

A climatic limit of viability for ice shelves?

The presence of ice shelves is governed by a fragile balance between mass gain and mass loss at their boundaries with the grounded ice sheet, the atmosphere and the ocean. If the mass loss exceeds mass gain, an ice shelf is bound to disappear on the long term. Based on the observation that ice shelves do not exist in the warmest parts of the Antarctic Peninsula, the idea of a climatic limit of viability linked to a given atmospheric threshold has been explored in the past 60 decades. This was reinforced by the collapse of the ice shelves Larsen A-B in 1995 and Larsen B in 2002, which were mainly driven by hydrofracturing. Hydrofracturing occurs when surface meltwater favours the propagation of crevasses and eventual disintegration of the ice shelf.

However, such a collapse can only occur if the ice shelf is weak enough. And this can be the result of (1) melt at the surface, through the atmosphere, (2) melt at the base, through the ocean and (3) mass loss and mass gain through ice dynamics (see Fig. 1 in the paper). In our study, we therefore decided to look beyond only the atmosphere-ice interface and also look at the other boundaries. We define the limit of viability as the moment when mass loss at the surface, at the base and at the front exceeds the maximum possible mass gain from the grounded ice sheet to the ice shelf (grounding-line flux for the experts). Our limit of viability therefore represents the ocean and atmosphere conditions for which it is almost impossible that an ice shelf maintains its current shape in the long term because it loses more mass than it gains.

Reaching non-viability

To investigate this limit of viability we inferred several estimates of (1) ice-shelf surface and basal conditions from several climate simulations (CMIP6) under a low and a high-emission scenario until 2300 and (2) a limit for the maximum mass gain from the grounded ice sheet from an ice-sheet model. Due to large uncertainties, we decided to set the calving flux (the icebergs) to zero (if you’re interested in their minimal effect on our results, check out the supplementary figures of our paper). This way, we could estimate a likelihood of reaching non-viability based on the whole group of simulations (across several climate models, and several methods to estimate basal conditions and ice-sheet bedrock conditions).

We find that the time of reaching likely non-viability strongly depends on the scenario (see Fig. 2 in the paper). Only 1 out of the 64 ice shelves becomes likely non-viable by 2300 in the low-emission scenario. By contrast, 38 out of 64 ice shelves become likely non-viable by 2300 in the high-emission scenario. While 2300 might seem far away, the number of ice shelves being likely non-viable by 2150 already reaches 26, showing that this is not necessarily a problem of the far-future.

Our results show that current choices to change emission pathways could significantly affect the likelihood of the long-term loss of most Antarctic ice shelves.

Drivers of non-viability

The next step of our analysis was to examine if the limit of viability is mainly linked to the atmosphere or if there is more at play behind the curtains. To do so, for each simulation, we looked at the proportion of mass loss to the atmosphere and to the ocean. We found that the ocean is by far the main driver for reaching non-viability (Fig. 4 in the paper). In both scenarios, ocean-induced melt at the base of the ice shelves explains more than half of the mass loss needed to reach non-viability for all ice shelves that reach non-viability.

Our results show that, while the final trigger for collapse might likely come from surface meltwater, long-term disappearance of ice shelves is mainly driven by ocean warming.

What now?

Once again, this study shows how vulnerable the icy environments of our planet are. Our current choices of greenhouse gas emissions impact the mighty ice sheets. Their loss represents several meters of global sea-level rise. The long response times of the ocean and ice should be a warning to act as fast as possible to avoid high-impact long-term consequences.

If you got curious, check out the whole paper here!

Burgard C., Jourdain, N.C., Mosbeux, C., Caillet, J., Mathiot, P., and Kittel, C. (2025): “Ocean warming threatens the viability of 60% of Antarctic ice shelves”, Nature, doi: 10.1038/s41586-025-09657-w.

Edited by Mirjam Paasch and Leah Sophie Muhle

Methane in India: Why precise measurements and cutting-edge technology matter for climate action

Roxana S. Cremer — Wed, 09 Sep 2026 12:21:41 +0000

The looming El Niño is likely to hit hard this year, bringing bracing moments to the already warming world. Extreme weather events are no longer just anomalies; they have become far too common in this new reality. It’s clear that our environment is under unprecedented stress. Experts warn of the costs of inaction: between 1995 and 2024, nearly one million lives have been lost due to climate-related disasters globally, with direct economic damages soaring to nearly 4 trillion Euros. Consequently, environmental risks, including extreme weather events as well as biodiversity loss and ecosystem collapse, ranked as the top two global risks in terms of severity over the next decade (The Global Risks Report, 2026). The urgency for collective climate action has never been clearer. In response to this crisis, countries around the world are stepping up efforts to enhance their Monitoring, Reporting, and Verification (MRV) systems. These systems are crucial not only for improving transparency and accountability but also for effectively tracking and reducing greenhouse gas (GHG) emissions (e.g., UNECE-MRV). Among GHGs, methane has emerged as an important concern (e.g., Global Methane Initiative, UN Climate Action). Methane warms the atmosphere approximately 25 times more than carbon dioxide over a 100-year period. At the same time, unlike carbon dioxide that stays in the atmosphere unaltered for centuries, methane breaks down in about a decade.

That shorter lifetime and high global warming potential make methane one of the fastest levers available for slowing near-term warming.
IPCC, 2021

In 2021, nearly 160 countries signed the Global Methane Pledge, committing to cut methane emissions by 30% by 2030 (Global Methane Pledge). But for such a commitment to be meaningful, countries must know how much methane they emit that eventually stays in the atmosphere, where and how those sources are distributed, and how to mitigate them without hampering economic stability. For India, one of the fastest-growing economies amid large emissions and climate change mitigation, the question has been difficult to answer.

Why is India’s methane difficult to address?

India’s methane footprint is substantial and distributed across multiple sectors. India has one of the world’s largest cattle populations, which is a major source of methane. Adding to that, rice paddies contribute to seasonal methane emissions: emissions increase during the monsoon, the main rice-growing season in much of the country, as flooded fields create ideal conditions for methane-producing microbes. Coal mines, landfills, wastewater systems, and parts of the oil and gas sector are other contributors. Before implementing emission-reduction strategies, it is crucial to estimate methane emissions accurately. This is to identify prioritized sectors or regions for effective mitigation.

According to India’s Fourth Biennial Update Report (MoEFCC., 2024), India emits 19.6 teragrams of methane compared to around 608 teragrams of global emissions each year. But the global methane inventories draw a different figure for India.

The widely used global inventory, the Emissions Database for Global Atmospheric Research (EDGAR; Crippa et al., 2022), often estimates higher methane emissions in India than the national inventory.

Figure 1. Sector-wise anthropogenic emission components over India. Enteric fermentation from livestock (43%) dominates, followed by wastewater treatment, agricultural soils, and fuel exploitation (Crippa et al., 2022; Bloom et al., 2021; Kaiser et al., 2012).

In simple terms, an inventory is an accounting of emissions from different human activities and sectors across the country. These estimates are generally built using a bottom-up approach, where emissions are calculated from activity data such as livestock numbers, rice cultivation area, or coal production, combined with emission factors.

Traditional methods that rely on statistical estimates or the interpolation of localized information to represent the country are highly incapable of reflecting reality.
Mathew et al., 2026

These global inventories are essential, but they do not directly support informed decision-making for effective emission-reduction strategies. For instance, emission factors may not fully capture Indian conditions, and activity data may be incomplete or outdated. Thus, the accuracy of emission estimates across India is questioned, despite their importance to climate mitigation plans. Without sufficient observationally driven information and a robust estimation technology, it has been difficult to determine which emission estimate is closer to reality and where to prioritize mitigation efforts.

Looking at methane from space

To move beyond activity-based estimates alone, we turned to atmospheric observations. A key instrument in our study is TROPOMI, the TROPOspheric Monitoring Instrument aboard the European Space Agency’s Sentinel-5P satellite that scans the globe daily. It measures the spectral absorption of light corresponding to methane molecules in the atmosphere.

Those satellite measurements, when analyzed with complex radiative transfer equations and numerical techniques, give information on the total methane in a vertical column of air extending from the Earth’s surface to the top of the atmosphere.
Schneising et al., 2023 and Mathew et al., 2026

This quantity is called XCH4, or the dry-air column-averaged methane mixing ratio. Because TROPOMI provides broad coverage at relatively fine spatial resolution, it allows us to observe methane across agricultural regions, urban areas, industrial belts, wetlands, and coastlines. Methane sources are spread across a vast and diverse landscape. Satellite observations help us see methane emission patterns at a broader spatial scale, though they do not directly distinguish sector-wise emissions.

However, satellite data alone are not enough, since methane observed over a particular place does not necessarily originate there; winds transport and mix gases over long distances.
Mathew et al., 2026

Bringing together space-borne measurements, surface observations, and models

[caption id="attachment_2165" align="alignright" width="260"] Figure 2. Illustration of the study domain and satellite retrieval. Basemap retrieved from Natural Earth (Public domain).[/caption] To transform what the satellite sees into emissions, we implemented the atmospheric transport model WRF-GHG (Weather Research and Forecasting Model coupled with GHG modules), thereby enabling us to understand the effects of atmospheric dynamics. With the model, we represented how methane can be emitted, transported, mixed, and distributed through the atmosphere. It also helped us understand how methane emissions peaking over agriculture-dominated regions of India, such as the Indo-Gangetic Plain, are transported, and how a shallow atmospheric boundary layer during winter intensifies their accumulation near the surface. We then compared the simulated methane fields with TROPOMI XCH4 observations. Where the model and the satellite agreed, we had more confidence in the emissions used in the model. Where they differed, it indicated that the underlying inventories likely required correction. Acknowledging the complexities of the atmospheric model, we emphasize a major challenge for India’s methane science: the ground-based methane monitoring network remains limited.

Inverting the problem

Figure 3. Illustration of the inverse modeling framework.

The central analytical step in our study is Bayesian inversion. Generally, atmospheric modeling works 'forward' in atmospheric science and climate applications: if we assume a certain set of emissions, what should the atmosphere look like? Inversion flips that question around. It asks: given what we actually observe in the atmosphere, what emissions must have generated it? Simply put together, think of it as reconstructing a recipe from a finished dish. You compare the taste against your best initial guess of the ingredients, identify where the simulation falls short, and adjust until the two align. In our case, the "recipe" is the true or optimized emissions, the initial guess of ingredients is the EDGAR global emission inventory, and the "taste" is the TROPOMI observation.

Bayesian inversion in this context works backward — using satellite measurements of atmospheric methane to estimate how much was released at the source, with the help of a model that simulates how methane travels through the atmosphere.

In our study, the Bayesian framework systematically calculates the corrections needed at the level of individual Indian states. Crucially, it also quantifies uncertainty, so rather than a single number, we obtain a range of plausible emissions that is consistent with the observations. While inversion techniques lead to powerful transformations of observational space into parameter space, the resulting solutions can also be challenged by the nature of the observations, which raise issues of existence, uniqueness, and the degree of independence of solutions.

What we found

Our inversion analysis estimated India’s anthropogenic methane emissions at 21.9-24.9 teragrams per year (Tg/year). The confidence in our estimates is within a range of 3.3 Tg/year. Our satellite-inferred methane emission estimate is lower than the values reported for India in global inventories, but is around 19% higher than the emissions reported in India’s Fourth Biennial Update Report. In other words, India appears to emit less methane than global databases claim, but more than the national report suggests. These findings support the argument that global inventories overestimate India’s methane emissions and suggest that national estimates need further refinement. Our study acknowledges some limitations, including sparse ground-based methane observations in India for validation, possible uncertainties in satellite retrievals, and the reliance on certain model assumptions and approximations.

Why this matters for climate policy

The implications of this work go far beyond improving a methane estimate on paper. Climate policy depends on knowing where emissions come from, how they vary across sectors and regions, and where mitigation efforts can have the greatest effect. If methane emissions are underestimated, important sectors such as livestock, rice cultivation, or waste management may not receive enough policy attention. If it is overestimated in global inventories, that can distort international comparisons and climate negotiations. Better estimates help answer practical questions: which sectors matter most, where emissions are concentrated, and where monitoring or mitigation should be prioritized.

Inaccurate information that fails to capture the complexity of the sources can lead to poorly designed policies, potentially exacerbating the country's economic burden
Nisbet et al., 2019; Steinebach et al., 2024

Consider agriculture, for instance; agriculture plays an essential role in the Indian economy, ensuring food security. Inadequately devised climate action plans increase risks for farmers who are already vulnerable to climate change, thereby reducing agricultural yields and triggering economic and food crises. Hence, properly devised, better-informed sectoral prioritization for emissions reduction is crucial not only for environmental sustainability and climate change mitigation but also for the country's economic stability. Beyond regional applications, the techniques demonstrated in this study are highly scalable and adaptable, helping countries worldwide tackle methane emissions with greater confidence and accuracy.

Methane cannot be managed effectively unless it is measured credibly, which must be interpreted with robust scientific tools
Mathew et al., 2026

India urgently needs a stronger methane monitoring network. The current inverse estimates suffer from such precise and accurate measurements from a dense ground-based measurement network. Expanding continuous atmospheric monitoring across India’s diverse regions would improve inversion estimates, strengthen satellite validation, and better capture regional and seasonal patterns. When we get the numbers right, we stand a much better chance of getting the response right. To decode the response, we need innovative technology to leverage credible measurements. Integrating satellite technology into methane emission estimates across the region via inverse techniques is not merely a scientific advancement; it’s a critical tool for climate action. By such advancements, we are not just investing in technology; we are investing in climate and economic stability, ultimately leading to a future grounded in environmental equity, sustainability, and resilience. This post is based on the ACP article, Mathew, T. A., Pillai, D., Sukumaran, J., et al. (2026): Leveraging TROPOMI observations and WRF-GHG modeling towards improving methane emission assessments in India. The research was conducted at the Greenhouse Gas Modeling, Measurements, and Applications (GMA) Laboratory, Indian Institute of Science Education and Research (IISER) Bhopal, India, in collaboration with the Institute of Environmental Physics, University of Bremen, Germany, and the Space Physics Laboratory, Vikram Sarabhai Space Centre (ISRO), India. Copyright statement All figures are licensed under Creative Commons Attribution 4.0 International License (CC BY 4.0). Figure 2 uses Natural Earth (public domain) coastline data as a base layer; all rendering, symbology, and annotations are original.

The Hidden Topography of the Deep Earth

Editorial team 1 — Wed, 09 Sep 2026 08:00:34 +0000

Travel across the globe and you will see landscapes change along the way. But what if the same were true inside Earth? What if the landscapes we see on the surface also exist deep within?

[caption id="attachment_43570" align="alignleft" width="150"] Ankit Barik from Johns Hopkins University[/caption]

In this week’s Geodynamics 101 post, Ankit Barik, Assistant Research Scientist at Johns Hopkins University, explores the hidden topography deep inside our planet and why do they matter.

[caption id="attachment_43611" align="alignright" width="281"] Figure 2: A dynamo simulation showing a convecting core inside. The colors inside show temperature and magnetic field lines are colored by the radial magnetic field.[/caption] The only fluid part of the Earth's interior is the outer core, which undergoes vigorous turbulent convection and maintains our planet’s magnetic field through a process called the dynamo. Geodynamo theorists and planetary scientists have been trying to recreate this process on computer since the 90s (Glatzmaier & Roberts, 1997). Since then, the models have grown remarkably good enough to reproduce the Earth's magnetic field not just what looks like today, but how it likely behaved millions of years in the past. However, most of these models till date were built considering the core-mantle boundary (CMB) to be a perfectly smooth surface (as shown in an example simulation in Figure 2). But...

Is the CMB really smooth?

Let's start with what we already know for certain. Earth is not a perfect sphere; geometrically speaking the shape is an oblate-spheroid, which means it bulges slightly at the equator and flattens at the poles, a signature of its own spin. Strikingly, it is not restricted to the surface only. The same rotational flattening extends all the way down to the core-mantle boundary. Geodetic studies tell us that the CMB is about 9 km flatter at the poles compared to the equator. So even 2,900 km beneath our feet, Earth's rotation leaves its mark! But that's just the broad brushstroke. The real question is whether there's finer details hiding underneath it. The first hints came in the late 80s when scientists first pulled signs of smaller-scale topography from Earth's gravity data (Bowin, 1986). Since then, seismological investigations have played a key role in deciphering the shape of this hidden boundary, using the rumble of earthquakes (normal modes, P-waves, S-waves). Different seismic models still disagree with each other in the details (Koelemeijer, 2021). But when you average across them, a picture starts to emerge — a weighted map of ridges and valleys 2,900 km down (Figure 1).

So it turns out that the CMB is not smooth!

Which leaves us with the obvious next question: what could possibly carve mountains and valleys into a boundary buried at the bottom of the mantle?

Well, the view depends on where you stand!

We're used to thinking of Earth's surface being shaped by water, wind, ice and rock chemistry (the exogenic processes). But mantle dynamics, volcanism and tectonics (the endogenic processes) matter just as much. And of these, the mantle takes the lead. (If you want to explore more on this, Rafael Monteiro da Silva's blog is a great place to start.) As it convects slowly over millions of years (drifting at tens of centimeters per year), the mantle pushes the lithosphere up in some places and lets it sink in others, sculpting what's called dynamic topography (a story explained beautifully in Fred Richard's blog).

But now delve deeper into the Earth's interior, down to the core-mantle boundary. Here, the perspective flips entirely. The core fluid is racing along at about 0.5 mm per second, a hundred thousand times faster than the mantle above it. From the core's point of view, it's the mantle that now seems frozen in place. Like water sculpting ripples into a stone riverbed, the fast-moving core presses against this "stationary" mantle, carving topography into the CMB that persists for long stretches of geological time. And etched into this boundary are its most striking features: the large low-shear-velocity provinces (LLSVPs) and the ultra-low velocity zones (ULVZs). Both are made of material that's heavier than the mantle around it. Because it's so dense, this material sinks and settles at the bottom instead of being swept along by mantle flow, piling up over hundreds of millions of years and pushing the CMB downward wherever it sits. The smaller, even denser ULVZs collect right at the edges of these piles, adding extra bumps of their own. So LLSVPs and ULVZs don't just sit on CMB topography, they help create it.

Once you know the reason behind CMB topography, the next question is whether it matters. Think of the Himalayas: they wring the monsoon clouds dry on their southern flank, keeping Nepal and northern India lush and green, while leaving the Tibetan plateau on the other side parched. A single ridge of topography reshapes an entire climate system. If mountains can do that at the surface, it shouldn't be surprising that topography deep down does something just as consequential to the flow above it. So,

what does this rough boundary actually do?

Length-of-Day (LOD) Variation

We tend to treat 24 hours as fixed, but Earth's day actually stretches and shrinks by milliseconds over time, on cycles ranging from years to decades (Figure 3, left). Scientists have long suspected the culprit lies at the core-mantle boundary itself, where the twisting force (torque), driven by topography, gravitational and electromagnetic, drives this variation (Gross, 2015). As molten iron flows past the carved topography, it builds up uneven pressure across these bumps, generating a fluid pressure torque, which makes the core and mantle exchange spin, i.e. if the outer core speeds up, the mantle and crust must slow down to compensate. Since we can only measure the spin of the solid Earth (not the hidden core), this slowdown or speedup of the mantle is exactly what shows up as decadal fluctuations in Figure 3 (left, marked b) -- tiny changes in LOD that recur over roughly 20–30 year cycles. [caption id="attachment_43654" align="aligncenter" width="1024"] Figure 3: Left: Length-of-Day (LOD) variations on different periodicities (from Gross, 2015). Right: A simple model of torque exerted on topography (Glane & Buffett, 2018).[/caption] There's another interesting aspect. When we talk about "core convection", it's easy to picture the entire outer core churning as one turbulent mass. But, that's not the scenario. Just beneath the CMB, there is a layer where fluid arranges itself into distinct density bands rather than being mixed fully. You can think of it like oil sitting on top of water. Growing evidence (Braginsky, 1999, Buffett, 2014) suggests that this stably stratified layer resists the vertical mixing seen elsewhere in the core, with lighter fluid stably layered above denser fluid below. As a result, the core flow cannot easily glide over the mantle's "inverted mountains" and it gets blocked against these bumps, amplifying the upstream pressure buildup. Recent studies (Glane & Buffett, 2018, Monville et al., 2025) show when a steady current of liquid iron moves through this layer in a magnetic field, it generates slow, decadal waves (Figure 3, right), which combined with the blockage effect, enhance dissipation and produce the net torque responsible for the multi-millisecond LOD variations. Perhaps this shouldn't come as a surprise. These deep waves behave much like Lee waves in the ocean, generated when currents flow over underwater ridges (Bell Jr., 1975). The same physics that ripples through our oceans, it turns out, is also quietly nudging the clock at the center of the Earth.

Increase in heat flux

[caption id="attachment_43663" align="alignright" width="300"] Figure 4: Convection with rough boundaries in a non-rotating regime showing increasing in temperature (red marked) near boundary. (Zhu et al., 2017)[/caption] Imagine a pot of boiling water with a lid on top. The water churns wildly but at the lid, the fluid calms; a thin, quiet film clings there. Heat can't ride the fast currents through this stillness; instead, it has to creep across like a bottleneck. This is the viscous boundary layer that acts like an invisible blanket. Now, scar that lid with ridges and bumps. As the calm film tears apart, it lets the chaos reach to the boundary. With the blanket gone, heat rushes through instead of creeping. This is exactly what happens at CMB (shown in Figure 4). So a rough CMB opens a wider door for heat to escape. And since that heat powers the dynamo generating the magnetic field, even a boundary's texture shapes the planet's deepest engine.

Conclusion

Topography, it turns out, is everywhere — not just on the surfaces we walk on, but on boundaries buried deep within our planet. Where fluid meets a rough boundary, that roughness does real work: it generates torque, enhances heat flux, and at large scales can even trigger three-dimensional turbulence. Interestingly, this isn't just an Earth story either. The same reasoning extends to the interior of Icy moons (e.g. Titan), where ice-ocean topography may play a similar role (Kvorka et al., 2018).

This is a departure from the smooth-boundary picture that has long shaped our understanding of convection and magnetic field generation and it marks

a new frontier for fluid dynamics in planetary interiors!

The field is catching up: topography experiments (such as the Coraboloid at UCLA, the Topographic Rotating Convection (ToRoCo) at the University of Rochester and the ERC project THEIA) paired with novel numerical studies are beginning to light the path towards study of fluid flow interactions with topography in planetary interiors.

References

Bowin, C. (1986). Topography at the core‐mantle boundary. Geophysical Research Letters, 13(13), 1513–1516. https://doi.org/10.1029/GL013i013p01513 

Braginsky, S. I. (1999). Dynamics of the stably stratified ocean at the top of the core. Physics of the Earth and Planetary Interiors, 111(1), 21–34. https://doi.org/10.1016/S0031-9201(98)00143-5 

Buffett, B. (2014). Geomagnetic fluctuations reveal stable stratification at the top of Earth's core. Nature, 507(7493), 484–487. https://doi.org/10.1038/nature13122

Glane, S., & Buffett, B. (2018). Enhanced Core-Mantle Coupling Due to Stratification at the Top of the Core. Frontiers in Earth Science, 6. https://doi.org/10.3389/feart.2018.00171 

Glatzmaier, G. A., & Roberts, P. H. (1997). Simulating the geodynamo. Contemporary Physics, 38, 269–288. https://doi.org/10.1080/001075197182351

Gross, R. S. (2015). 3.09—Earth rotation variations – long period. In G. Schubert (Ed.), Treatise on geophysics (second edition) (pp. 215–261). Elsevier. https://doi.org/10.1016/B978-0-444-53802-4.00059-2 

Koelemeijer, P. (2021). Toward Consistent Seismological Models of the Core–Mantle Boundary Landscape. In H. Marquardt, M. Ballmer, S. Cottaar, & J. Konter (Eds.), Geophysical Monograph Series (1st ed., pp. 229–255). Wiley. https://doi.org/10.1002/9781119528609.ch9 

Kvorka, J., Čadek, O., Tobie, G., & Choblet, G. (2018). Does titan’s long-wavelength topography contain information about subsurface ocean dynamics? Icarus, 310, 149–164. https://doi.org/10.1016/j.icarus.2017.12.010 

Zhu, X., Stevens, R. J. A. M., Verzicco, R., & Lohse, D. (2017). Roughness-Facilitated Local $1/2$ Scaling Does Not Imply the Onset of the Ultimate Regime of Thermal Convection. Physical Review Letters, 119(15), 154501. https://doi.org/10.1103/PhysRevLett.119.154501

ECS Spotlight: Can Weather Analogues forecast Europe’s Wind and Rainfall Extremes?

Valerio Lembo — Tue, 08 Sep 2026 13:03:21 +0000

Extreme rainfall and strong winds can each cause major disruption. When they occur together—or within only a few days of each other—their combined impacts can be even more severe. Heavy rainfall may saturate soils and increase flood risk, while strong winds can damage infrastructure, disrupt transport and bring down trees or power lines. Forecasting these events is essential for early-warning systems, yet extremes are particularly difficult to predict because they are rare and often influenced by local processes. In our recently published study in Geoscientific Model Development, we explored whether past atmospheric conditions could help us forecasting isolated and compound wind and precipitation extremes across Europe. Searching the past similar atmospheric conditions Our approach is based on atmospheric analogues. The idea is simple: when the current large-scale atmospheric circulation resembles a situation observed in the past, the weather that followed that historical situation may provide information about what could happen next. We combine these analogs with a stochastic weather generator (SWG). After identifying a set of similar atmospheric states, the generator randomly moves through their historical evolutions to produce possible future weather sequences. We developed two versions of this approach. For extreme precipitation, the HC-SWG combines the weather generator with atmospheric analogues selected from ECMWF ensemble reforecast/hindcast (HC). For extreme wind speed, the MA-SWG uses multivariate analogues (MA) derived from two atmospheric variables: geopotential height at 500 hPa and sea-level pressure. Together, these variables describe both the mid-tropospheric and near-surface circulation associated with wind extremes. Each approach generates an ensemble of 100 forecast trajectories. We tested them at nine European locations representing different climatic conditions. The forecasts were evaluated at lead times of up to ten days. How skillful were the forecasts? Both stochastic weather generators showed useful skill in forecasting extreme events. The HC-SWG reproduced the timing of many observed heavy-precipitation events and performed particularly well for moderate extremes. The MA-SWG also captured the occurrence of many wind extremes, although its performance varied more between locations, especially for the rarest events. When compared with ECMWF forecasts, both stochastic approaches provided added value across the studied locations. Their probabilistic forecasts generally represented the observed distributions and forecast uncertainty more realistically. In several cases, the ECMWF ensemble covered a relatively narrow range of possible outcomes, whereas the stochastic forecasts generated a broader distribution that was closer to observations. However, both approaches tended to overestimate the magnitude of some of the most intense events. This distinction is important: the models could often correctly identify that an extreme would occur, even when its forecasted intensity was too high. Forecasting compound extremes We then combined the precipitation and wind forecasts to investigate compound events. We considered simultaneous events, in which extreme rainfall and wind occurred at the same time, as well as sequential events, in which one extreme followed the other within one to five days. At Atlantic-influenced locations such as Brest and Bergen, for example, strong winds were more frequently followed by heavy precipitation. This is consistent with the passage of Atlantic storm systems, which can bring strong winds before their associated rainfall. Other locations displayed a different ordering or similar frequencies of the two possible sequences. The models overestimated sequential events at some stations, particularly when longer time windows were considered. Nevertheless, they reproduced many of the main spatial features of compound wind and precipitation extremes. Looking ahead The location-dependent performance highlights one limitation of the method: large-scale atmospheric analogues cannot fully represent local influences such as topography and other small-scale processes. Moreover, the relatively short ECMWF reforecast archive restricts the availability of suitable analogues to the rarest circulation states. Future research could explore calibration techniques to reduce intensity biases, improve analogue selection and extend the approach to other hazards and geographical regions. Despite these limitations, our findings demonstrate that the atmosphere’s past can provide valuable information about its near future. Combining atmospheric analogues, numerical reforecasts and stochastic simulations offers a flexible and computationally efficient approach for forecasting both isolated and compound weather extremes. These results do not suggest that stochastic weather generators should replace numerical weather prediction. Instead, they show how analogue-based methods can complement dynamical forecasts, for example through statistical post-processing and the generation of large ensembles at a relatively low computational cost. They may therefore provide valuable support for early-warning systems, particularly for compound hazards that remain challenging for existing forecasting tools. The full study is available in Geoscientific Model Development: Krouma and Messori (2026), “Ensemble forecasts of isolated and compound wind and precipitation extremes in Europe using HC-SWG (v3.1) and MA-SWG (v1.1) Stochastic Weather Generators”. [caption id="attachment_2746" align="alignnone" width="255"] Fig. Simulating Compound Rain and Wind Events Across Europe for 1 and 5 day forecast window. Rain–wind denotes events in which extreme rainfall precedes extreme wind, whereas wind–rain denotes events in which extreme wind precedes extreme rainfall. Values represent the difference between the observed and simulated numbers of events.[/caption]

Joining the dots: From overlooked disaster impacts to inclusive disaster risk reduction

Hedieh Soltanpour — Mon, 07 Sep 2026 08:52:20 +0000

A note from the Natural Hazards Division editorial team

We would like to open this blog post with our sincere condolences in response to the devastating multi-hazard flash flood that occurred in Nepal and Tibet in late August. In the face of such suffering, messages like this risk sounding hollow. Still, we, as the Natural Hazards Division editorial team, wish to express our solidarity with all families and communities affected and with those making huge sacrifices to support the recovery effort. This blog post broadly discusses the question, “Are all disasters recorded equally?”, and its implications for inclusion in disaster risk reduction (DRR). To do so, the piece first explores how the manifestation of disasters is shaped by risk - the relationship between hazard, vulnerability and exposure. Following this, I explore how these underlying conditions influence which impacts communities experience, and how inclusive DRR can support more equitable preparation for and recovery from disasters.

What gets recorded?

The magnitude 7.8 Gorkha earthquake hit Nepal’s Gorkha District on 25 April 2015, causing almost 9000 fatalities, injuring approximately 18,000 people, and affecting over 5.5 million people [1]. As Nepal’s deadliest disaster since 1934 [2], the event received international media attention, humanitarian assistance and funding for recovery and reconstruction efforts. Small-scale events, such as frequent river inundation of the Bagmati River into informal riverside settlements in the Kathmandu Valley during the annual monsoon season, cause significant disruption to the lives of residents. For instance, the September 2024 floods in the Kathmandu Valley caused floodwater to rise to “2.5 times the bankfull water extent”, resulting in devastating damage to homes, infrastructure and transport [3]. However, despite the widespread disruption, this was not reflected in the scale of reporting and assistance during and after the event. Understanding the difference in the scale of and response to these two events can be characterised by the concept of intensive and extensive risk. In the context of DRR, a broadly accepted definition of risk is: “The potential loss of life, injury, or destroyed or damaged assets which could occur to a system, society or a community in a specific period of time, determined probabilistically as a function of hazard, exposure, vulnerability and capacity.” [4] Building on this definition, intensive risk (such as that associated with the Gorkha 2015 earthquake) relates to higher-severity, low- to mid-frequency events that have a high overall impact. Conversely, extensive risk (associated with regular monsoon-triggered flooding in the Kathmandu Valley) concerns lower-severity, high-frequency events that often have a devastating impact on affected communities yet may be localised in spatial or temporal extent [5]. Figure 1 illustrates this distinction on simplified axes of frequency and impact [6]. [caption id="attachment_11273" align="aligncenter" width="374"] Figure 1: Illustration of intensive and extensive risk on axes of frequency and impact (Image credit: UNDRR, 2026).[/caption] Intensive risk can be shaped by high population density and the exposure of assets during high-magnitude events, such that it is dependent upon how hazard, exposure, vulnerability and capacity change over time. On the other hand, extensive risk is closely interlinked with underlying drivers of risk, including poverty and deprivation, that disproportionately affect marginalised communities through indirect impacts. These types of impacts result from the ripple effects of direct impacts across space and time, affecting multiple sectors, but may not be observed equally.

What becomes visible?

According to the Centre for Research on the Epidemiology of Disasters, 110.2 million people were affected by natural hazards in 2025 [7]. However, this represents only a snapshot of the total global impact of disasters, owing to a reporting bias towards higher-magnitude, lower-frequency events. The reporting of impacts that are difficult to quantify or are poorly captured by conventional disaster impact assessments, including cultural, social, and environmental impacts, represents a significant proportion of the total impact caused by disasters, as captured in Figure 2 [8]. [caption id="attachment_11281" align="aligncenter" width="358"] Figure 2: Ilustration of the indirect disaster impacts that may be overlooked (Image credit: UNDRR, 2022).[/caption]

What receives attention and funding?

Underreporting of indirect impacts associated with extensive disasters is significant because the events that hazard managers, funders, and the wider public discuss and prioritise directly inform DRR strategies and, most significantly, who is protected from future harm. Although the cumulative impact of extensive events causes significant damage, these events are often understudied due to factors including lower priority status and a lack of funding [9]. Indeed, over time and space, the incremental impacts of smaller disasters can be equal to or greater than those of larger disasters [10], such that the ripple effect of an event spreads far beyond the initial direct impacts. To better understand how communities are affected by smaller disasters and indirect impacts, a more comprehensive approach to disaster management is critical: inclusive DRR.

Whose risk is addressed?

DRR provides a crucial framework to reduce disaster impacts. This is particularly important for impacts resulting from extensive events that disproportionately affect marginalised communities who may be more vulnerable. According to the United Nations Office for Disaster Risk Reduction (UNDRR): “Disaster risk reduction is aimed at preventing new and reducing existing disaster risk and managing residual risk, all of which contribute to strengthening resilience and therefore to the achievement of sustainable development.” [11] Marginalised communities that are often excluded from mainstream DRR include, but are not limited to, the following groups:

elders,

ethnic minority groups,

Indigenous groups,

LGBTQIA+ people,

migrants, refugees and/or people seeking asylum,

people with disabilities,

women, and

young people.

Members of these groups may be socio-economically marginalised, particularly when individuals or groups have overlapping intersectional social identities which can compound exclusion and, in turn, the severity of impacts experienced [12]. Marginalised groups, including those listed above, may already experience infringement of their rights, have barriers to full engagement with civic life, and be limited from engaging in DRR processes, all of which contribute towards overlapping social vulnerabilities and systemic barriers to inclusion [13]. These challenges are exacerbated by current threats such as discriminatory bias in AI tools, rising populism and polarised politics which undermine support for inclusive DRR practices more broadly [13]. As such, it is clear that a tailored approach to DRR is required to ensure that no one or no community is left behind in developing effective strategies – this is where inclusive DRR comes in. This approach to DRR is significant in that inclusion of marginalised groups is centred at all stages of the development and implementation process, as opposed to being an “optional add-on” [13]. Inclusive DRR is significant, as it recognises that the development of a disaster is far less about the hazard event itself and more about the socio-economic and political context which shapes how impact manifests.

Why does this matter?

Given these pressing challenges, it is crucial to centre inclusion whilst developing and refining effective DRR strategies. Existing practices can be tailored to support inclusion by centring traditional and community knowledge in decision-making processes, ensuring sustainable involvement of affected groups in the development of DRR strategies, partnering with existing community organisations to support change, and sharing learnings and expertise across social movements [14]. Inclusive DRR is not only about reducing the impacts of individual disasters, but also about addressing the underlying drivers of risk and the cumulative impacts of multiple extensive events. The interconnections between extensive risk and inclusive DRR strategies in reducing disaster impacts are significant, not only for those most affected by disasters but for society at large. By developing more inclusive, community-centred actions, the impact of events can be mitigated, driving the shift towards genuine inclusion in preparing for and responding to disasters.

References

[1] Tonnelier, M., Delforge, D., Bhandari, M.P., Devleesschauwer, B., Haathat shapes how impacts manifest, Speybdoes this matterk, N., and Charalampous, P. Years of Life Lost due to the 2015 Gorkha earthquake in Nepal. BMC Public Health. 2026; 26(1): 1444. doi: 10.1186/s12889-026-27054-4. [2] Sapkota, S. N., Bollinger, L., and Perrier, F. Fatality rates of the M w ~8.2, 1934, Bihar–Nepal earthquake and comparison with the April 2015 Gorkha earthquake. Earth Planets and Space. 2016; 68(1): 40. doi: 10.1186/s40623-016-0416-2. [3] Talchabhadel, R., Panthi, J., Pandey, V.P., Rakhal, B., Ghimire, G.R., Bista, S., Bhattarai, S., Poudel, S., Bhattarai, Y., Prajapati, R., Thapa, B.R., Nepal, B., and Sharma, S. Yesterday’s extremes, today’s new normal: flood risk in the Kathmandu Valley, Nepal. Natural Hazards. 2025; 121, 19409–19423. doi: 10.1007/s11069-025-07524-5.

[4] United Nations Office for Disaster Risk Reduction (UNDRR). The Sendai Framework Terminology on Disaster Risk Reduction: Definition: Disaster risk. 2017 [cited 9 August 2026]. Available from: https://www.undrr.org/terminology/disaster-risk.

[5] Hallegatte, S., Vogt-Schilb, A., Rozenberg, J., Bangalore, M., and Beaudet, C. From Poverty to Disaster and Back: a Review of the Literature. Economics of Disasters and Climate Change. 2020; 4(1), 223–247. doi: 10.1007/s41885-020-00060-5. [6] United Nations Office for Disaster Risk Reduction (UNDRR). Intensive and extensive risk. 2026 [cited 10 August 2026]. Available from: https://www.preventionweb.net/understanding-disaster-risk/key-concepts/intensive-extensive-risk. [7] Delforge, D., Below, R., Wathelet, V., Tonnelier, M., Alonso, A., and Speybroeck, N. 2025 Disasters in Numbers. Brussels, Belgium: Centre for Research on the Epidemiology of Disasters (CRED). 2026 [cited 2 August 2026]. Available from: https://files.emdat. be/reports/2025_EMDAT_report.pdf. [8] United Nations Office for Disaster Risk Reduction (UNDRR). The invisible toll of disasters. 2022 [cited 10 August 2026]. Available from: https://www.undrr.org/explainer/the-invisible-toll-of-disasters-2022. [9] Osuteye, E., Johnson, C., and Brown, D. The data gap: An analysis of data availability on disaster losses in sub-Saharan African cities. International Journal of Disaster Risk Reduction, 2017; 26, 24 33. doi: 10.1016/j.ijdrr.2017.09.026. [10] Brennan, M.E. and Danielak, S. Too small to count? The cumulative impacts and policy implications of small disasters in the Sahel. International Journal of Disaster Risk Reduction. 2022; 68, 102687. doi: 10.1016/j.ijdrr.2021.102687. [11] United Nations Office for Disaster Risk Reduction (UNDRR). The Sendai Framework Terminology on Disaster Risk Reduction: Definition: Disaster risk reduction. 2017 [cited 2 August 2026]. Available from: https://www.undrr.org/terminology/disaster-risk-reduction. [12] Crenshaw, K. Demarginalizing the Intersection of Race and Sex: A Black Feminist Critique of Antidiscrimination Doctrine, Feminist Theory and Antiracist Politics. University of Chicago Legal Forum. 1989; 1–31. Available from: http://chicagounbound.uchicago.edu/uclfhttp://chicagounbound.uchicago.edu/uclf/v ol1989/iss1/8. [13] Blanchard, K. Intersecting Emergencies: Understanding Emerging Risks and Inclusive Futures. 2025 [cited 2 August 2026]. Available from: https://www.drrdynamics.com/publications. [14] Pertiwi, P.P. Unpacking collaboration in disability-inclusive disaster risk reduction. In S. Grech, S. and Weber, J., editors. An Introduction to Disability Inclusive Disaster Risk Reduction: Intersecting Terrains. Abingdon, Oxon: Routledge; 2026. ISBN: 9781003353188. Post edited by: Hedieh Soltanpour and Navakanesh M Batmanathan

eDNA4Hydrology

Bettina Schaefli — Thu, 03 Sep 2026 08:00:49 +0000

What flows around comes around

For centuries, hydrologists have studied the flow of water through landscapes near and far. We measured flow rates, mapped aquifers and followed invisible paths of raindrops through soil and bedrock. Hydrology is a meticulous, beautiful science that has taught us much over the years. From the water cycle, surface water in rivers, wetlands and snowpack and groundwater deep and shallow, this is what we were taught as young aspiring hydrologists. Now, as we are starting to understand our ecosystems better over time, it has become clear that water carries more than just hydrogen and oxygen. It also carries life, but in particular the invisible genetic traces that organisms leave behind as they move through water. Much like a loose strand of hair unintentionally left behind at a crime scene, organisms passing through a water body – however briefly, leave their genetic fingerprint behind. One could almost say that in hydrology, the water always tells. We call it the gene pool of evidence.

Where traditional hydrology meets molecular biology

On the surface, the disciplines could not look more different. Hydrology and the geosciences have deep roots in physics, chemistry and process-based understanding. Molecular biology, driven by genomics and biology, is rooted in understanding life on earth as a whole. At the same time, the hydrological cycle does not respect such disciplinary boundaries. A simple water sample from hillslopes, groundwater, snowmelt or urban runoff does not only reveal chemical properties but also an entire world of biological communities living in these environments, waiting to be discovered and tell their story. Considering the information contained in a simple water sample’s isotope and geochemical composition – from origins, residence times, and evaporative histories, it isn’t surprising that the environmental DNA (eDNA) in a drop offers a whole other evidence base through which we can understand even more aspects of water movement, flow pathways, and ecosystem interactions that were previously invisible. At the same time, eDNA incorporates hydrological aspects into biodiversity monitoring, carrying the water flows legacy across time and space, allowing us to track flow paths, ecosystem changes and interactions between organisms and their environments. A recent landmark review paper on how eDNA connects hydrology and biology laid out the untapped potential of how eDNA could help us address unsolved questions about water movement through catchments. While it may be a nuisance for biologists trying to pinpoint the origin of a certain species, the movement of water and transport of genetic material through the surface and subsurface is precisely what makes eDNA interesting for hydrologists.

Hydrologists and Biologists unite

With the idea to bridge the longstanding gap between geoscientists and biologists, a new collaborative research network, eDNA4Hydro, has been created by Dr. Natalie Ceperley, Dr. Yvonne Schadewell, and others. By connecting researchers across fields, their goal is to foster interdisciplinary collaboration and reshape how we study aquatic and terrestrial ecosystems. I (Maria Magdalena Warter) joined this network last year after meeting Natalie and Yvonne at EGU, and getting excited about sharing this interdisciplinary journey with like-minded researchers. A stranger to eDNA before, I am now part of this emerging interdisciplinary research field and can honestly say that it broadened my hydrological horizon and ecological understanding. Because water and sediment have a better genetic memory than most witnesses, I believe that the use of eDNA in hydrology and geosciences will play an important role in the future. [caption id="attachment_14060" align="alignleft" width="225"] Sampling at Steinsee/Steingletscher/ Wysbach in Canton Bern, Switzerland in June 2026. © Sabine Röthlin[/caption] Over the years, the number of publications integrating eDNA into hydrological research has steadily increased. Examples from high mountain streams in Switzerland to urban aquatic systems in Germany, to analyzing hydrological timeseries and subsurface stromflow, to name just a few, clearly show– eDNA is everywhere just waiting to be decoded. Even more so, the investigation of eDNA bound to sediment, which accumulates flood after flood and year after year in lakes and dam reservoirs, also offers new insights into flow and transport dynamics. Through dating the sediment layers, we can actually reconstruct the environmental history and past changes in biological communities in contrasted environments. eDNA is revealing unprecedented insights into hydrological processes. Paired with biogeochemistry, it becomes an unbeatable duo for exploring and understanding complex environments. The eDNA4Hydro network was founded by Yvonne Schadewell and Natalie Ceperley, together with Peter Chifflard and Olivier Evrard. Yvonne’s research spans biodiversity patterns, molecular ecology, and ecosystem linkages across terrestrial and aquatic environments. Natalie’s research spans from glacier melt in Alpine environments to evaporation from dry-land savannas. Peter’s research focuses on fine-scale hydrological connectivity, water flow pathways, biogeochemical processes, and the impacts of global environmental change on terrestrial and aquatic ecosystems, while Olivier focuses on eDNA bound to sediments to reconstruct spatial and temporal variations of sediment sources and associated contaminants in contrasted environments. Designed to be a catalyst, the eDNA4hydro network combines exactly the strengths of biological and geoscientific expertise to shed light on pressing water-related challenges in a fast-changing environment. The network provides a platform for researchers of all backgrounds to exchange knowledge, develop and compare new methodologies, and jointly explore and advance the boundaries of the fields of hydrology and geosciences. eDNA is the bridge between disciplinary boundaries that helps us to advance our understanding of water dynamics, connectivity, sediment transport, surface-subsurface water as well as human-environment interactions. It is like nature’s forensics, no warrant needed. New members always welcome.

Edited by B. Schaefli

The Geodynamics Awakens: Star Wars Planets and Earth’s Geological History

Editorial Team 4 — Wed, 02 Sep 2026 08:00:04 +0000

Star Wars is one of the most influential science-fiction worlds created in our time. The central theme revolves around the struggle between the tyrannical Galactic Empire and the rebels trying to bring it down. Star Wars has many reasons to pull you in: iconic lightsaber duels, technological advancements such as hyperspace travel, and perhaps most importantly for a geologist: a remarkable number of habitable planets in the galaxy. The planets in the Star Wars galaxy also has diverse flora and fauna. Planets with lava, ice, forests, deserts, inhabited by various species like large, cunning wookiees and crafty Anzellans. But how realistic are these planets they inhabit? To try and answer that question, today we go on a “planetary” quest around our solar system or the Milky Way galaxy and try to find twins of Star Wars planets, but we don’t yet have the technology of hyperspace travel. Therefore, today we turn towards our own planet, Earth, which has undergone dramatic geological changes, and see if different stages of its evolution can match conditions of some planets in the Star Wars galaxy. So let’s begin our “geodynamic” quest by travelling back to the beginning of Earth’s history. The young Earth was not the blue and green planet it is today.

Mustafar: Revenge of the Sith and the Hellish Earth.

Mustafar is a volcanic planet in Star Wars. It is shown as glowing bright red and is covered in volcanic fields and lava flows. It is the backdrop of the iconic duel between Obi-Wan Kenobi and Anakin Skywalker. [caption id="attachment_43865" align="alignright" width="300"] Artist’s impression of the early Hadean Earth, when intense volcanism and widespread lava fields may have made our planet look surprisingly like Mustafar (Image Credit: NASA's Goddard Space Flight Center Conceptual Image Lab).[/caption] The hellish condition that Obi-Wan had to endure at Mustafar could possibly be found 4.5 billion years ago on Earth. This geologic interval is called the Hadean, when Earth had intense volcanism. The surface of the Earth probably had similar lava fields with traces of stable crust. The atmosphere during that time would have been significantly different. It was probably thicker, with more CO₂ and sulphur. The surface temperature might also have been fairly hot. So, kudos to Obi-Wan Kenobi for surviving there! Let’s move on from all the volcanic planets. It’s getting Hoth out there.

The Phantom Menace of Plate Tectonics

At some point in Earth’s history, plate tectonics began to operate, which shaped the planet in multiple ways. Tectonic plates are created in mid-oceanic ridges and are destroyed at subduction zones. Over millions of years, this movement of tectonic plates cause continents to come together and later break apart. Supercontinents can break apart through continental rifting, often accompanied by an increased volcanic activity. This volcanism releases CO₂ into the atmosphere, which strengthens the greenhouse effect and potentially warms Earth. During different phases of the supercontinent cycle, either during rifting and breakup or mountain building during collision, a lot of fresh, unweathered rocks are exposed. Chemical weathering of these rocks removes CO₂ from the atmosphere, which can also cause cooling. If CO₂ removal becomes greater than the amount being supplied by volcanism, the climate can cool. As ice cover expands, it reflects more sunlight into space, causing further cooling through the ice-albedo feedback.

The Empire Strikes Back: Hoth and Snowball Earth

[caption id="attachment_43847" align="alignright" width="300"] Artist’s impression of a Snowball Earth, when ice may have covered much of the planet during the glaciation periods, making it similar to Hoth (Image credits: Oleg Kuznetsov).[/caption] Hoth is a rocky planet covered by ice and glaciers. Temperatures on Hoth were always frigid and are known to drop to -60^oC. Hoth hosted the Echo rebel base and was the temporary headquarters of the Rebel Alliance. This base was attacked by the Galactic Empire in the Battle of Hoth. A major defeat for the Rebels it was! The conditions on Hoth remind me of snowball Earth, a condition when a large section of Earth’s surface was covered by ice. Earth has experienced such episodes in its history. Between roughly 720 and 635 million years ago, Earth experienced a large-scale cooling event during the breakup of the supercontinent Rodinia. But Snowball Earth would not last forever. The ice-covered surface would reduce weathering, and therefore the removal of CO₂ from the atmosphere would be significantly less. Eventually there would be enough CO₂ in the atmosphere to increase the greenhouse effect and melt the ice.

Return of the Jedi: Endor, and a Warmer Earth

Endor is actually a moon in a very remote part of the galaxy. It is covered in dense woodlands, tall mountains, and is home to the Ewoks. It has a warm climate. Due to its remote location, it was a perfect place for the Galactic Empire to establish a shield generator, intended to protect the incomplete Death Star, also known as the planet destroyer. In the Battle of Endor, the Rebel Alliance and Ewoks destroyed the shield generator. The Death Star was also destroyed along with Emperor Palpatine and Darth Vader. It was a monumental victory. Earth has also experienced periods that were much greener and warmer than today owing to the greenhouse effect. During such greenhouse periods, such as the Cretaceous, Earth had high CO₂ and the oceans were warmer. These conditions can very well represent the geology and atmospheric conditions of Endor. So, we have seen that plate tectonics can dramatically shape a planet’s climate and morphology. But will it continue forever? What happens when, in a “geologically” distant future, plate tectonics ceases to exist? [caption id="attachment_43841" align="aligncenter" width="500"] Reconstruction of a warm, forested Earth during warm periods analogous to Endor.(Image credit: Alfred-Wegener-Institut/J. McKay)[/caption]

No Hope at Tatooine?

[caption id="attachment_43843" align="alignright" width="270"] The dry and barren landscape of Mars offers a glimpse of what a Tatooine like world might look like in our own Solar System (Image credit: NASA/JPL-Caltech/MSSS).[/caption] Tatooine is a desert planet, orbiting two suns. The landscape is covered with sand dunes, mountains, and canyons. There is no water at the surface, and the planet's residents have to farm water from the atmosphere. It is a very harsh planet to live in. I think Earth devoid of plate tectonics would look a lot more like Tatooine. The Earth's declining internal heat would gradually reduce tectonic activity, weakening the climate-tectonic forcing. Earth would become geologically quieter, and depending on how its climate evolved, some regions could become increasingly arid and desert-like. Let’s put our thinking caps on now and explore another possible future Earth might have. On a planet inhabited by “intelligent” life, Nature is not the only force capable of shaping the environment. Humans themselves can alter climate and ecosystems. Sometimes for the better, sometimes for worse.

Coruscant and a Dystopian future?

Now we turn to Coruscant to get a glimpse of what this alternate future might be. Coruscant is a planet which is the political and administrative centre of the Galactic Republic and the Empire. Unlike Hoth, Mustafar or Tatooine, there is no Nature left on Coruscant. The entire planet is covered by one enormous city. If we squeeze Earth’s 4.5-billion-year history into a single hour, modern humans would appear only in the very last fraction of a second. Yet we have had an enormous impact on Earth. The word Anthropocene comes from anthropos, meaning human, and kainos, meaning new. It is the proposed geological epoch where human activity is becoming an increasingly dominant force shaping Earth’s climate and ecosystems, at a rate which is extreme on a geologic timescale. But of course, Earth becoming one gigantic city is still a science fiction scenario, but comparison with Coruscant raises an interesting question: if humanity survives for millions of years, how much of the planet will still be shaped by nature, and how much will be shaped by us? A final question: How does Luke Skywalker manage to breathe on every planet he visits? Perhaps the Force is really strong with him!

References:  
1. Bressan, D. (2022, May 4). The geology of star wars – bressan-geoconsult. Bressan-Geoconsult.Eu. http://www.bressan-geoconsult.eu/the-geology-of-star-wars/
2. Lemon, K. (2015, December 17). Jedi geology or sith science: The force was calling. Blogspot.Com. https://britgeopeople.blogspot.com/2015/12/jedi-geology-or-sith-science-force-was.html
3. Earth as the inspiration for star wars planets. (2026). Banthaskullcom. https://www.banthaskull.com/story/news_earth_as_the_inspiration_for_star_wars_planets

From Storm to Landscape: High Resolution for Climate Risk

annavdb — Tue, 01 Sep 2026 14:00:22 +0000

Welcome to ”Climate Change through a Geomorphological Lens”, a blog series exploring the changing climate from a geomorphological perspective. This first post was inspired by a single figure in the Intergovernmental Panel on Climate Change's Sixth Assessment Report [1]. It compares precipitation change per degree Celsius of warming across different climate models and observations for three time categories: global mean, 24-hour extremes, and sub-1-hour extremes. Figure 1 shows that observed changes per degree of warming are five times greater for sub-hourly extremes than for daily extremes. In other words, heavy rainfall increases roughly five times more for events lasting less than an hour than for events lasting a full day. In comparison, the regional climate model (RCM/CRM) shows only a small difference between daily and hourly rainfall. This gap matters because risk assessments often rely on daily rainfall data and regional-scale projections of erosion and landscape change, yet erosion responds to hourly rainfall that averages out in the daily rainfall data. Moreover, the hourly rainfall is just the trigger. The damage comes later, as landslides, debris flows, and sediment pulses reshape channels and create new hazards [7]. [caption id="attachment_3036" align="aligncenter" width="300"] Figure 1: Precipitation change per degree of warming (% °C⁻¹) across three time scales. Rainfall changes intensify with shorter timescales — from about 2–3% per increase in degrees Celsius for the global mean to over 15% per increase in degrees Celsius for sub-hourly extremes. The colored bars compare estimates from observations (black), global climate models (GCM and GCM constrained, yellow and red), and regional climate models (RCM/CRM, blue). Source: IPCC 2021.[/caption] With our changing climate, understanding these short-term rainfall extremes is becoming more important. The key question is not only how much rain the landscape will receive, but also when it will fall and how the landscape will respond during these extreme events. This is not a hypothetical question. In just two hours on 29 May 2016, a small catchment in southern Germany - site of the devastating Braunschbach flash flood - received 131 mm of rain, with a peak five-minute intensity of 157 mm/h [4,5]. As a result, the Orlacher Bach transformed into a debris flow that buried part of the town under 42,000 m³ of boulders, gravel and mud. The resulting flow reached a height of 3.5 m and damaged more than 80 buildings, five of which were destroyed [4]. [caption id="attachment_3039" align="aligncenter" width="1024"] Figure 2. Damage caused by the 29 May 2016 flash flood in Braunsbach, Germany. Photo: Kai Pfaffenbach/Reuters, 30 May 2016.[/caption] Landscape Evolution Models (LEMs) help predict geomorphological changes over years to millennia, but they must capture the storm hours that move sediment [2]. However, high-resolution modelling requires large amounts of data and substantial computing power, making it impractical to replay every plausible extreme event at hourly resolution. Surrogate modelling offers a bridge: a few detailed process-based simulations can train a fast, inexpensive surrogate model, opening thousands of rainfall and landscape scenarios at a fraction of the cost [3]. It can also make sensitivity analysis of LEM parameters affordable, revealing which parameters most strongly control simulated output (e.g. discharge, sediment flux) [6]. The aim is not to perfectly reconstruct events whose details were never observed, but to use the available information to identify where, when, and under what rainfall conditions major geomorphic change is likely. This approach turns the missing hours of past disasters into information that can help prevent the next one. References: 1. IPCC 2021 - Climate Change. The Physical Science Basis: Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (1st ed.). Cambridge University Press. https://doi.org/10.1017/9781009157896 2. Coulthard, T., & Skinner, C. (2016). The sensitivity of landscape evolution models to spatial and temporal rainfall resolution. Repository@Hull (Worktribe) (University of Hull), 4(3), 757–771. https://doi.org/10.5194/esurf-4-757-2016 3. Donnelly, J., Abolfathi, S., Pearson, J., Chatrabgoun, O., & Daneshkhah, A. (2022). Gaussian process emulation of spatio-temporal outputs of a 2D inland flood model. Water Research, 225, 119100. https://doi.org/10.1016/j.watres.2022.119100 4. Laudan, J., Rözer, V., Sieg, T., Vogel, K., & Thieken, A. H. (2017). Damage assessment in Braunsbach 2016: data collection and analysis for an improved understanding of damaging processes during flash floods. Natural Hazards and Earth System Sciences, 17(12), 2163–2179. https://doi.org/10.5194/nhess-17-2163-2017 5. Öztürk, U., Wendi, D., Crisologo, I., Riemer, A., Agarwal, A., Vogel, K., López‐Tarazón, J. A., & Korup, O. (2018). Rare flash floods and debris flows in southern Germany. The Science of The Total Environment, 626, 941–952. https://doi.org/10.1016/j.scitotenv.2018.01.172 6. Skinner, C., Coulthard, T., Schwanghart, W., Wiel, M. J. V. D., & Hancock, G. R. (2018). Global sensitivity analysis of parameter uncertainty in landscape evolution models. Geoscientific Model Development, 11(12), 4873–4888. https://doi.org/10.5194/gmd-11-4873-2018 7. Yanites, B. J., Clark, M. D., Roering, J. J., West, A. J., Zekkos, D., Baldwin, J. W., Cerovski‐Darriau, C., Gallen, S. F., Horton, D. E., Kirby, E., Leshchinsky, B., Mason, H. B., Moon, S., Barnhart, K. R., Booth, A. M., Czuba, J. A., McCoy, S., McGuire, L. A., Pfeiffer, A., & Pierce, J. (2025). Cascading land surface hazards as a nexus in the Earth system. Science, 388(6754). https://doi.org/10.1126/science.adp9559

Book Review: Invisible Women by Caroline Criado Perez

Jacqueline Behncke — Mon, 31 Aug 2026 08:59:03 +0000

Our previous book recommendations were the nonfiction books Blue Machine – How the Ocean Shapes our World by Helen Czerski and Below the Edge of Darkness by Edith Widder as well as the thriller The Swarm by Frank Schätzing. This time, we are stepping away from the ocean. Our next book recommendation is "Invisible Women: Exposing Data Bias in a World Designed by Men" by Caroline Criado Perez, a nonfiction book published in 2019. While it is not an ocean-themed book, we recommend it nonetheless. The book reveals how much of the world's data is based on male norms, resulting in a world primarily designed for men. This causes a range of problems for women across areas like medical research, urban planning, safety, and opportunity. Perez supports her arguments with numerous studies, explores possible reasons behind these gaps, and offers approaches to closing them. Here we highlight some of the everyday- as well as science-focused issues she raises.

A few familiar examples

Some of the more prominent examples have entered public debate: office temperatures set too low for women, the underdiagnosis of female autism, or the misdiagnosis of women experiencing heart attacks with atypical symptoms. But Perez documents many more. Equipment — tools, uniforms, seatbelts — designed for male bodies leads to more accidents for women. Voice recognition systems perform worse on women's voices, even though it should be easier to with womens voices because of speech speed and pronounciations. Public toilets consistently fail to account for women's longer average bathroom time. Female scientists doing fieldwork in places like Alaska are forced to wear overalls designed for male bodies, putting them at risk of frostbite. The underrepresentation of women in medical research is particularly alarming. Because women metabolize drugs differently than men, dosages calibrated on male subjects can lead to women being overdosed and some drugs that benefit men may be harmful or even fatal to women.

Bias against women in academia

Bias against female scientists starts early and society has made less progress than we might think:

🎨

"[F]ollowing decades of 'draw a scientist' studies where children overwhelmingly drew men, a recent 'draw a scientist' meta-analysis was celebrated across the media as showing that we were becoming less sexist. [...] Where in the 1960s only 1% of children drew female scientists, 28% do now."

Nearly three in four children still picture a scientist as male. These biases get encoded into technology too. Perez gives the example of someone searching for 'computer programmer' on a program trained on a dataset that associates that term more closely with a man than a woman — the algorithm could deem a male programmer's website more relevant than a female programmer's. With the Guardian reporting that 72% of US CVs never reach human eyes, the consequences of such bias are substantial.

The disadvantages add up for women pursuing academic careers. Unpaid domestic work is a good starting point:

🍳

"A 2010 US study [...] found that female scientists do 54% of the cooking, cleaning and laundry in their household, adding more than ten hours to their nearly sixty-hour work week, while men's contribution (28%) adds only half that time."

This unequal burden has measurable career consequences:

🎓

"Married mothers with young children are 35% less likely than married fathers of young children to get tenure-track jobs, [...] and among tenured faculty 70% of men are married with children compared to 44% of women."

The disadvantage extends to recognition:

📄

"[S]everal studies have found that women are systematically cited less than men. [...] Over the past twenty years, men have self-cited 70% more than women[…] — and women tend to cite other women more than men do."

And even informal evaluations reflect this bias:

⭐

"An analysis [...] of 14 million reviews on the website RateMyProfessors.com found that female professors are more likely to be 'mean', 'harsh', 'unfair', 'strict' and 'annoying'. [… M]ale professors are more likely to be described as 'brilliant', 'intelligent', 'smart' and a 'genius'."

Physical barriers persist too. Female fieldwork scientists in places like Alaska are forced to wear overalls designed for male bodies, putting them at risk of frostbite.

Perez also makes the economic case: closing the gender data gap isn't just the right thing to do — it's a sound investment. Invisible Women is dense with information and covers an important topic. We recommend it highly.

Summary of the August 26th, 2026, Himalayan flash flood

Bettina Schaefli — Fri, 28 Aug 2026 16:31:50 +0000

At the time of preparing this blog entry, we are less than 48 hours after the catastrophe which has hit the Himalaya. While the flow of new information continues, it is useful to summarize and clarify the key points around this event.

WHAT? The massive destruction was caused by a flash flood. It was such a high energy that is rarely seen. Numerous videos can be found online.

WHERE? The cause of the flash flood was a major glacier collapse and landslide, on the North slope of Langtang Lirung (7234 m) and Tsangbu Ri (6781 m) mountains in Nepal. The side valley reaches the valley along which lies the Tibet–Nepal border: the river is called Donglin Tsangpo in Tibet and Lhende Khola in Nepal. After reaching the ill-fated Gyirong/Rasuwa border post, the flood re-entered Nepal and swept down the Trishuli River valley, across the entire country, and then to India.

A GLOF? Before and after satellite photo comparison such as this one show no trace of a glacial lake prior to the event. Hence there seems to have been no glacial lake outburst flood (GLOF). The flash flood was made of river water, ice and lots of rocks and debris. In the aftermath of the main event of August 26^th, a smaller lake grew behind a new dam of debris, yet the water level is already sinking.

AN EARTHQUAKE? Initial reports said the mass movement was triggered by a magnitude 4.4 earthquake. Subsequent analysis by the USGS shows that there was no tectonic event, instead it is the mass movement itself that has triggered ground vibrations. Its energy is equivalent to a magnitude 5.2 earthquake, which is over 1000 times more energy than following the 2025 Blatten event in Switzerland.

VIBRATIONS. Seismic records from Nepali observation stations show that the flash flood caused ground vibrations that lasted for over two hours. Here is a seismogram example from a station that is 60 km away from the source of the event, and at the closest point still 20 km away from the Trishuli River. Further seismic analyses are ongoing.

FAR REACHING. The long duration and far-reaching impact of the flood is unfortunately confirmed by casualties in the Chitwan district, in the southern foothills of Nepal, too. This district is at over 100 km distance downstream. It has been reported that flood alert stations were simply swept away before they could send a message.

POWER. If you ever wondered how big boulders are transported and arrive to surprising locations in a mountain landscape, this video provides a relevant yet shocking answer.

VOLUME. For now, there are only preliminary estimates of the volume of the initial mass movement, on the order of a half to 10 million cubic metres. How much additional material was swept away along the flood’s path has not yet been estimated. For comparison, the gigantic Flims rockslide about 10 thousand years ago moved approximately 12’000 million cubic metres of rock.

IMPACT. The flash flood’s consequences on Nepal and also Tibet are terrifying: the number of casualties will be high, and the environmental and economic impact long-lasting. We commend the efforts of the rescue teams for their relentless efforts, and hope and pray for their success in the field.

Together, the two authors, Shiba and György have designed and implemented the Seismology at School in Nepal program starting 2017 (website). The program offers direct training to schoolteachers, free educational materials, and has built a school seismic network with fully open data. The program is effectively increasing awareness and preparedness of the population.

Edited: B. Schaefli

Regional Reference Frames: Keeping Track of a Deforming Earth

Leire Retegui-Schiettekatte — Fri, 28 Aug 2026 09:00:48 +0000

You are observing the construction of a bridge that will be initiated on the two banks of a river simultaneously, in such a way that the works will eventually meet in the middle of the river. You wonder, how do they make sure that the construction on the two sides will stay aligned with the millimeter precision that this project requires? You are aware of previous constructions where small miscalculations led to embarrassing results, such as the Laufenburg bridge between Germany and Switzerland (2003) [1] or the Gokhale Bridge in Andheri, Mumbai (India, 2024) [2]. In your case, you fully trust the construction team's skills and are sure all the distances have been double-checked. However, a question may still bother you. All construction distances are computed with respect to fixed points with known coordinates on each bank of the river, which were previously aligned. But what if the ground has moved since then, causing misalignment in the reference points and, therefore, in the whole construction? In other words, how do we ensure a robust and well-known physical reference for the construction? If you had a geodesist friend by your side, they would probably explain to you that this difficult task is achieved through geodetic reference frames, which consist of a set of physical points (reference stations) with precisely determined coordinates and velocities. To be reliable, these reference frames must account for the invisible, continuous change on and beneath the Earth’s surface. In this blog post, we will explore the drivers that change the shape of the Earth, how a reference frame can account for these changes, and the role of regional reference frames in monitoring changes on regional levels. Why does the Earth’s surface constantly deform, and how can it be monitored? Earth is a complicated structure and nothing like the perfect blue sphere we see in photographs from space. That image is beautiful, but misleading. The Earth is commonly approximated by a reference ellipsoid (Fig. 1), which [caption id="attachment_6003" align="alignleft" width="300"] Fig 1. Schematic representation of the geocentric reference ellipsoid fitted to the Earth’s surface, with its center coinciding with the Earth’s center of mass. (Credit: Emlid)[/caption] provides the mathematical foundation for modern geometric reference frames such as the International Terrestrial Reference System (ITRS). Although convenient for positioning, this idealized surface does not fully represent Earth's complex gravity field or topography. Underneath, the crust is broken into massive slabs called tectonic plates, which drift and collide at 2 to 10 centimetres per year. Where they meet, mountains rise, or where they pull apart, new ocean floors are born. Additional geophysical processes such as melting ice caps, seismic activity or natural hazards can also modify the shape of the Earth at different scales. The ground is never truly still, and, even a perfect coordinate measured today will be slightly wrong tomorrow. [caption id="attachment_6006" align="alignright" width="300"] Fig 2: The International Terrestrial Reference System. CM represents the centre of mass. (Credit: Alexander Kehm)[/caption] This complicated problem can only be solved by having precise 3D coordinates at every point on the surface of the earth to track all these dynamic changes. The International Terrestrial Reference Frame (ITRF) aims to achieve a “near-perfect” global description of these changes, by computing the X, Y, and Z coordinates of diverse points on Earth with respect to the center of mass (CM) of the Earth as the origin. The axes form a right-angled triad, with the X and Y axes lying in the equatorial plane, while the Z-axis points towards the North Pole (Fig. 2). In practice, the frame is realized using a global set of ground stations that incorporate information on the Earth deformation. The coordinates of a point obtained at any instant (epoch) using such a global frame are also accompanied by velocities to compensate for dynamic changes due to plate movements. More details on the global reference frame are available in this previous post.

Why do regional frames exist when a global one already does? If ITRF provides a near-perfect global solution, one might reasonably ask: why do regional frames need to exist? Well, there is a high likelihood that global changes don’t reflect those within a particular region. Consider the example of India: out of a total of 1344 Global Navigation Satellite System (GNSS) stations, only three Indian GNSS stations were used to realise the ITRF2020 reference frame. Considering north-eastern India is a highly seismically active region, the limited number of stations is inadequate to represent regional variations. Thus, a regional reference frame is tailored to the region of interest, with a dense network of ground stations to better capture local phenomena that might have been ignored by the global best-fitting solution. The International Association of Geodesy (IAG) organizes regional frames into six sub-commissions: EUREF (Europe), SIRGAS (South America), NAREF (North America), AFREF (Africa), APREF (Asia-Pacific), and SCAR (Antarctica). Several countries have also developed national frameworks to monitor such activities, and the coordinates may or may not be shared beyond their borders. There might be a chance that coordinates from two different networks can be off by a few centimeters to several meters based on their frame realization strategies. Conventionally, these regional and national frames are mathematically aligned with the ITRF to ensure interoperability in positioning and location. Applications of global and regional reference frames A robust reference frame is essential to support not only construction works, but also a variety of day-to-day activities, ranging from self-driving cars and infrastructure monitoring to boundary mapping and aircraft and missile guidance systems. The applications extend to understanding the dynamics of our planet Earth caused by a variety of geophysical phenomena. Any coordinates without the frame, epoch, and station velocity are meaningless and are just random numbers. As the ground keeps moving, these frames keep the world from drifting apart. A regional reference frame offers a sentinel's view of a restless planet with rigorously tracking every subtle change, so that what begins as a millimetre of drift never silently grows into a catastrophe.

References and further reading

1. Marine Digital. (n.d.). Measure twice and cut once or how the sea level prevented the construction of the bridge. Retrieved June 1, 2026, from https://marine-digital.com/article_bridge_between_germany_and_switzerland

2. Urban Acres. (2024, April 20). BMC to investigate Gokhale Bridge Barfiwala Flyover alignment error. https://urbanacres.in/bmc-to-investigate-gokhale-bridge-barfiwala-flyover-alignment-error-urban-acres/

3. Altamimi, Z., Rebischung, P., Collilieux, X., Métivier, L., & Chanard, K. (2023). ITRF2020: An augmented reference frame refining the modeling of nonlinear station motions. Journal of Geodesy, 97, 47. https://doi.org/10.1007/s00190-023-01738-w

4. Sánchez, L., Drewes, H., Kehm, A., & Seitz, M. (2022). SIRGAS reference frame analysis at DGFI–TUM. Journal of Geodetic Science, 12(1), 92–119. https://doi.org/10.1515/jogs-2022-0138

- Edited by: Leire Retegui-Schiettekatte

- Use of AI: LLMs have been used to improve language and clarity of specific parts of the text

I’M BRINGING KERNELS BACK

Editorial team 1 — Wed, 26 Aug 2026 15:26:56 +0000

Computational geodynamic models are powerful tools for understanding Earth's deep interior, but how do we know they are producing realistic results? In this week's News & Views, Alina Valop, a PhD candidate from Virginia Tech, unpacks the world of geodynamic kernels and shows how these sensitivity functions provide a computationally efficient way to benchmark mantle flow models, test viscosity structures, and bridge the gap between numerical simulations and geophysical observations. [caption id="attachment_43580" align="alignleft" width="235"] Alina Valop from Virginia Tech[/caption] “You should produce the kernels and compare them to the benchmark paper,” said my advisor. Perfect, I shall do that. And the first step is to find out what kernels are. Surely the internet will have a straightforward answer… And it did: the internet gave me kernel definitions for operating systems, statistics, and popcorn, just not geodynamic kernels. But I still needed to know whether my model was behaving correctly. Based on the literature, it came down to this: for a benchmark in a 3D mantle model, a kernel shows how the model responds when I place a density anomaly at one depth; repeating this at every depth produces a curve (Green’s function) that I could compare with a published curve. If they matched, I knew that part of my model was behaving correctly. Easy peasy, we can move on! Except we cannot, because while looking into who was using kernels and why, my advisor suggested I read Hager and Clayton (1989) to understand how kernels can be used for more than just benchmarking. Let’s state some facts:

3D geodynamic models are computationally expensive.
There’s a multitude of possible viscosity models we can assign to the mantle.
And all the while, seismic tomography has considerably more detailed and reliable data than we’ve ever had (shoutout to the EarthScope stations).
Different models often disagree in amplitude and smaller features. When you have enough parameters to adjust, you can make almost anything fit. As a professor once said, “Tell me how many cats you want to fit in your model, and we’ll make it happen.”

If only there were a computationally inexpensive way to test these models, compare them to the data we have, and narrow them to a realistic number of possibilities to commit to a 3D calculation… Spoiler alert: that’s kernels! [caption id="attachment_43584" align="alignright" width="271"] Figure 1. Five radial viscosity profiles used in the thickness experiment (W5-AA through W5-AE). Each color is one viscosity layer. The viscosity values stay fixed, while the weak 10¹⁹ Pa s layer above the CMB thickens from 200 km in AA to 2230 km in AE. Depth increases downward.[/caption] What are kernels? Kernels are sensitivity functions for theoretical density anomalies. For example, in a 1D model of the Earth with a density and viscosity assigned at each depth (Figure 1), you can systematically test how sensitive a boundary (the geoid, surface topography, or core-mantle boundary (CMB) topography) is to an anomaly at each depth. To do this, we solve the Stokes equations in a spherical shell and calculate the radial response function K_l(r) for each spherical harmonic degree. The degree tells us the horizontal size of the pattern at the boundary. Degree 2 describes the largest wavelength pattern, which is the focus of this example, while higher degrees describe smaller-scale patterns. When the value of K_l(r) is positive, a positive density anomaly at that depth contributes positively to the boundary. When it is negative, the anomaly contributes to the opposite direction. But conceptually it gets simpler: for the boundary ΔB^lm you want to identify (geoid, surface topography or CMB topography), you multiply the kernel value K_l(r) by the density anomaly δρ^lm(r) at each depth, then add the contributions from the CMB to the surface. The result (ΔB^lm) is a spherical harmonic coefficient for the geoid, surface topography, or CMB topography, depending on which kernel you calculate. In other words, the kernel tells you, “If you have a density anomaly at r depth, under your current model conditions, it will affect your boundary by this much (Figure 2).” Here is the best part: if you change your radial viscosity, the kernel response changes (Figure 3). For this experiment, you keep the density model fixed and compute a new kernel, which means you can test multiple viscosity ideas while changing only one or two parameters at a time. Density still affects the final amplitude; keeping it fixed here simply lets us see what viscosity is doing. [caption id="attachment_43586" align="alignleft" width="686"] Figure 2. Core-mantle boundary topography kernels for a uniform-viscosity, uniform-density model. Each line shows the response to a different spherical harmonic degree. The y-axis represents radius, and the x-axis represents relative response.[/caption] Case study: the lower mantle needs some zest To explain their capability, we need to consider what we want to predict. In my case, it is CMB topography. The CMB separates the solid mantle and the liquid core at ~2900 km dept and topography estimates find it to be roughly 300-4000 m (Deschamps et al., 2018; Heyn et al., 2020; Koelemeijer, 2021). However, there is no consensus on the direction, exact pattern, or amplitude of topography produced by mantle flow, only in the location of topography beneath the African and Pacific Large Low Shear Velocity Provinces (LLSVPs; Koelemeijer, 2021; Lekic et al., 2012). All this to say, CMB topography is a very useful constraint, but not a perfect answer. In this case, a kernel tells us how efficiently a density anomaly at any depth would be transmitted to the CMB (Figure 3). As the kernel shows, anomalies near the surface have negligible weight on our CMB topography observation. The density anomalies come from a geodynamicist’s close friend, aka tomography. For this example, we will use SP12RTS (Figure 3; Koelemeijer et al., 2016) and focus on degree 2, the largest-scale structure in the lower mantle and CMB. Tomography measures seismic velocity, not density, so we convert the anomalies using mineral physics (Figure 3 - C_MinPhys). In this example, we use a uniform factor of 0.25 across the range discussed by Adam et al. (2021). If only this factor changes, the predicted topography changes linearly. Density, therefore, matters for amplitude; keeping it fixed isolates the effect of viscosity. This is where Hager and Clayton’s model 5 (W5 and blue line in the kernel Figure 3) returns to the story. W5 has a relatively strong 10²² Pa s lower mantle and a weaker 10¹⁹ Pa s layer directly above the CMB. A weak D″ layer can reduce the mechanical coupling between CMB topography and convection above it (Hager & Clayton, 1989). This inspires the question: if we hold the weak-layer viscosity fixed, how much does its thickness change the CMB response? [caption id="attachment_43587" align="alignright" width="1509"] Figure 3. How the CMB topography (ΔB^lm) calculation comes together. The kernel (K_l (r) and respective figure) weights the SP12RTS tomography models at each depth (δρ^l m (r) and tomography slice). A factor of 0.25 converts velocity anomalies to density, and the contributions are added to predict CMB topography. The small graph compares the degree-2 kernels for the W5 models; radius increases from the CMB to the surface.[/caption] Models AA–AE test this question. We keep all viscosity values and the upper-mantle structure fixed; only the weak layer’s thickness changes: 200 km (AA), 400 km (AB), 900 km (AC), 1000 km (AD), and 2230 km (the whole lower mantle; AE). The result gives the maximum and minimum CMB topography calculated from SP12RTS, as shown in Table 1. [caption id="attachment_43588" align="alignleft" width="1015"] Table 1. Maximum and minimum degree-2 CMB topography predicted from SP12RTS for models AA–AE.[/caption] Almost every model in this suite produces topography within the broad range of 300–4000 m; AB falls just below it. The response is not steady as the weak layer thickens: AB is the smallest and AE the largest. And here is where you decide what still needs testing. Model AE, where the lower mantle is two orders of magnitude weaker than the transition zone, produces acceptable CMB topography, but that does not make it a realistic representation of the Earth. If we test that model in 3D (and I have), LLSVP-like piles cannot be maintained because the lower mantle is too weak. A profile also needs to satisfy the geoid or surface topography constraints, as it does the CMB topography. All this is to say that one boundary can shorten the list of possible models, but it cannot identify a unique Earth model by itself (Liu & Zhong, 2016; Steinberger & Calderwood, 2006). This work is part of a paper that explores other viscosity suites and compares different tomography models, currently in preparation for submission. Don’t stop at the CMB! Nothing about this workflow is limited to the CMB; that’s just what I like to study. The same calculation produces kernel responses for surface topography and the geoid in the current pipeline, following King and Masters (1992). These are (from a data availability standpoint) more attractive because Earth’s surface and gravity field are measured in far more detail than the CMB topography. The geoid has long been used to constrain radial mantle viscosity, including in tomography-driven flow models (Hager & Clayton, 1989; Liu & Zhong, 2016). 1D to 3D As explained, kernels cannot identify “the one” viscosity profile, and a 1D model cannot represent laterally varying piles, slabs, plumes, or the lithosphere by itself. Instead, it allows us to shortlist the candidates we want to test in 3D, using realistic geometry and time evolution. 1D gives us a filter, and we let 3D handle the regional complexity. So I am bringing kernels back to test Earth models fast. We have the best data anyone has ever had, and we should take advantage of it to go crazy with our tests. And if you’re ever asked about kernels, now you know why they’re cool, in with the old and the new!

References:

Adam, C., King, S. D., & Caddick, M. J. (2021). Mantle temperature and density anomalies: The influence of thermodynamic formulation, melt, and anelasticity. Physics of the Earth and Planetary Interiors, 319(September 2020), 106772. https://doi.org/10.1016/j.pepi.2021.106772

Deschamps, F., Rogister, Y., & Tackley, P. J. (2018). Constraints on core-mantle boundary topography from models of thermal and thermochemical convection. Geophysical Journal International, 212(1), 164–188. https://doi.org/10.1093/gji/ggx402

Hager, B. H., & Clayton, R. W. (1989). Constraints on the structure of mantle convection using seismic observations, flow models, and the geoid. In W. R. Peltier (Ed.), Mantle convection: Plate tectonics and global dynamics (pp. 657–763).

Heyn, B. H., Conrad, C. P., & Trønnes, R. G. (2020). Core-mantle boundary topography and its relation to the viscosity structure of the lowermost mantle. Earth and Planetary Science Letters, 543, 116358. https://doi.org/10.1016/j.epsl.2020.116358

King, S. D., & Masters, G. (1992). An Inversion For Radial Viscosity Structure Using Seismic Tomography. Geophysical Research Letters, 19(15), 1551–1554.

Koelemeijer, P. (2021). Towards consistent seismological models of the core–mantle boundary landscape. In Mantle convection and surface expressions (pp. 229–255). https://doi.org/10.1002/9781119528609.ch9

Koelemeijer, P., Ritsema, J., Deuss, A., & van Heijst, H. J. (2016). SP12RTS: A degree-12 model of shear- and compressional-wave velocity for Earth’s mantle. Geophysical Journal International, 204(2), 1024–1039. https://doi.org/10.1093/gji/ggv481

Lekic, V., Cottaar, S., Dziewonski, A., & Romanowicz, B. (2012). Cluster analysis of global lower mantle tomography: A new class of structure and implications for chemical heterogeneity. Earth and Planetary Science Letters, 357–358, 68–77. https://doi.org/10.1016/j.epsl.2012.09.014

Liu, X., & Zhong, S. (2016). Constraining mantle viscosity structure for a thermochemical mantle using the geoid observation. Geochemistry, Geophysics, Geosystems, 17(3), 895–913. https://doi.org/10.1002/2015GC006161

Steinberger, B., & Calderwood, A. R. (2006). Models of large-scale viscous flow in the Earth’s mantle with constraints from mineral physics and surface observations. Geophysical Journal International, 167(3), 1461–1481. https://doi.org/10.1111/j.1365-246X.2006.03131.x

EGU Campfire Geodesy – Share Your Research – 22nd Edition

Fikri Bamahry — Mon, 24 Aug 2026 13:19:46 +0000

We are excited to announce the 22nd edition of Geodesy Campfire – Share Your Research in September. The Geodesy EGU Campfire Events “Share Your Research” give (early career) researchers the chance to talk about their work. We have two exciting talks by our guest speakers, Brian Bramanto and Arash Tayfehrostami. Below, you can find the details of the topics awaiting us. We will have time to network after the presentations. Please join us on Zoom on 17th September 2026 from 13:30 to 15:00 (CEST). Register for this webinar here. Brian Bramanto @Institut Teknologi Bandung, Indonesia:

Gravimetric and geodetic techniques to monitor the subsidence case.

Brian Bramanto is an Assistant Professor in Geodesy and Geomatics Engineering at Institut Teknologi Bandung (ITB), Indonesia. He holds a Ph.D. in Geomatics from the Norwegian University of Life Sciences (NMBU). His research focuses on physical geodesy, GNSS, gravimetry, geoid modelling, and hydrogeodesy, with particular interest in understanding Earth-system processes through integrated geodetic and gravimetric observations. His work includes geoid development, groundwater and subsidence monitoring, and the application of satellite and terrestrial observations for environmental monitoring and climate resilience. Arash Tayfehrostami @K. N. Toosi University of Technology, Tehran, Iran:

GNSS Meteorology From Atmospheric Water Vapor Sensing to Improved Numerical Weather Prediction.

Arash Tayfehrostami is a Ph.D. candidate in Geodesy and Geomatics Engineering at K. N. Toosi University of Technology, Tehran, Iran. His research focuses on GNSS meteorology, atmospheric water vapor retrieval, GNSS Radio Occultation, and the integration of GNSS observations and Remote Sensing into numerical weather prediction models. His recent works explore the potential of multi-mission GNSS observations and advanced data assimilation techniques to improve atmospheric monitoring and regional weather forecasting. [caption id="attachment_4753" align="alignleft" width="293"] Image credit Baptiste Gombert (distributed via imaggeo.egu.eu)[/caption] Time to connect! After the presentations, we invite everyone in the audience to turn on their camera and microphones, if possible. Participation via the chat is of course also possible. We will start with a short introduction round to get an idea of who is in the room. So if you like to, you can already think about how to summarise your research in a few words so that mortals can also understand it! We’re also open to hear about your favourite dinosaur, your latest burnout, or the 4th element on your tasks list today. Just be there and be talking, we guarantee for the awkwardness. We are always looking for speakers for upcoming Geodesy EGU Campfire Events “Share Your Research”. Are you interested in giving a talk? Then, please express your interest by filling out this form. If you have any questions about the Geodesy EGU Campfire Event, please contact the Geodesy ECS Team via ecs-g@egu.eu. We look forward to seeing you at the Campfire!

A paper that shaped my career - Tim Eglinton on Hayes et al., 1990

Franziska Lechleitner — Wed, 19 Aug 2026 06:30:02 +0000

In this series, we ask senior researchers to reflect on how a paper or a series of contributions influenced their thinking and led to a change in their research direction and career. Our first reflection comes from Prof. Tim Eglinton, who was professor of Biogeoscience at the Department of Earth and Planetary Sciences of ETH Zurich, Switzerland until his recent retirement in 2025. Throughout his career, Tim has focused on understanding processes that govern the Earth's carbon cycle and quantifying amounts and timescales of carbon transport using a range of methods from molecular scale to global. Amongst other things, Tim’s research employed the use of compound-specific carbon isotope analysis to understand the factors that lead to the conversion of organic matter produced by the biosphere into long-term carbon sinks such as sediments and fossil fuels.

I vividly remember attending the 14^th International Meeting on Organic Geochemistry in 1989 in Paris. I witnessed a presentation by John Hayes during which he introduced both a conceptual framework for interpretation of stable carbon isotopic compositions (δ¹³C values) of biologically-derived compounds (biomarkers), as well as a novel analytical approach to measure δ¹³C values of individual compounds using isotope ratio monitoring-gas chromatography mass spectrometry (irm-GCMS; today, this is typically abbreviated as GC-irMS). The paper stemming from this presentation (Hayes et al., 1990), as well as another from the same year led by Kate Freeman (Freeman et al., 1990), were the first in a series of seminal contributions from John’s group at Indiana University that laid the foundation for compound-specific isotope analysis (now often abbreviated as CSIA) to emerge as a brand-new sub-discipline. While the approach has its roots in biogeochemistry, it has been embraced by many other disciplines, including environmental geochemistry, ecology, petroleum geochemistry, forensic science, paleoclimatology and paleoceanography, and astrobiology.

[caption id="attachment_4143" align="alignleft" width="251"] John Hayes attending a dinner at Woods Hole Oceanographic Institution in 2016. Image credit Tim Eglinton.[/caption]

A new method to revolutionize carbon isotopic analysis Although stable isotopic measurements on specific compounds had been reported previously, the methods used were typically challenging, required relatively large sample sizes, and were not conducive to the development of large datasets. The new contributions highlighted the feasibility of routinely acquiring stable carbon isotopic information of large numbers of compounds provided they were amenable to gas chromatographic separation. This was a stunning achievement. Because of the reduced sample size needed, the new method opened up the way to conducting isotopic analysis at the molecular level on many different sample matrices. The preliminary results that were presented at the meeting and in ensuing publications highlighted the extraordinary degree of isotopic variability that existed at the molecular level, with this variability largely masked in carbon isotopic data from the more conventional measurements of bulk samples. For those who were used to observing bulk-level δ¹³C values of sedimentary organic matter that varied by only a few permil, it was eye opening to see data for individual lipids from the same sample with isotopic compositions spanning over 50 permil! This was exciting because it provided clear evidence that the isotopic composition of pigment- and lipid-derived compounds in ancient sediments is linked to the carbon source of their biological precursors and the biosynthetic pathways by which the compounds were synthesized. Moreover, the results indicated that these signatures are not affected by the chemical, physical and microbial processes that impact the sediment after its deposition (diagenesis), suggesting that they may be well preserved in the geologic record. This was truly transformative because it brought together the hitherto largely separate sub-disciplines of biomarkers (chemical fossils) and stable isotope biogeochemistry. It was immediately clear that this advance represented a dramatic shift in our ability to decipher carbon sources and biogeochemical processes in modern and ancient environments. The ramifications of this exciting new approach were numerous, with immediate applications in biogeochemistry and to petroleum geochemistry (which was a major aspect of organic geochemistry at that time).

How this contribution influenced my research I was a postdoc at the time that I saw John Hayes’ presentation, shortly before starting as an Assistant Scientist at Woods Hole Oceanographic Institution (WHOI). At that time, my primary focus had been on characterizing “kerogen” – the insoluble macromolecular organic matter in ancient sediments – using pyrolysis methods (thermal decomposition at high temperatures and under absence of oxygen). Kerogen is viewed as the dominant component of organic carbon in ancient sediments and the major precursor to oil and gas upon thermal maturation of sedimentary rocks. At WHOI, I was interested in further understanding how biological organic matter is transformed to kerogen during sediment diagenesis. At that time, there was much debate about whether kerogen is compositionally heterogeneous, being derived from transformation of diverse biochemicals into complex macromolecules, or whether it reflected selective preservation of more structurally organized biopolymers that are resistant to decomposition. It struck me that exploring the isotopic composition of individual products from pyrolysis of kerogens might help to address this question. I approached John about the possibility of performing some preliminary GC-irMS measurements. He very graciously said yes, and invited me to visit his lab at Indiana University. There I had the privilege to work with his group, and obtained some initial data that proved very interesting. That opportunity to interact with such an engaging and creative group, including Kate Freeman who pioneered the applications of CSIA as part of her PhD thesis, is still vivid in my memory.

I became increasingly interested in compound-specific isotope analysis following this initial exposure to the methodology and to the burgeoning field of CSIA. However, I also became interested in another instrumental capability at WHOI - accelerator mass spectrometry (AMS) – for radiocarbon analysis. The National Ocean Sciences AMS facility was established just as I arrived at WHOI. Motivated by the scientific revelations made possible by stable isotopic measurements at the molecular level, I wondered about the feasibility of compound-specific radiocarbon analysis. As a result of the good fortune of being in the right place at the right time, some additional serendipity, and the benefit of skilled students and colleagues, we developed a gas chromatographic approach to isolate and determine natural abundance variations of radiocarbon in individual organic compounds. This became the major focus of my research from the mid-90s onwards, and it was a direct consequence of the impact of the pioneering work by John Hayes and his group. Coincidentally, John joined WHOI and served as Director of the National Ocean Sciences Accelerator Mass Spectrometry Facility between 1996 and 2005, and I had the great fortune and pleasure to interact with him on a regular basis and benefit from his scientific vision and wisdom during this period.

Publications cited: Hayes J.M., Freeman K.H., Popp B.N. & Hoham C.H. (1990) Compound-specific isotopic analyses: A novel tool for reconstruction of ancient biogeochemical processes. In Advances in Organic Geochemistry 1989, Org. Geochem. 16, 4-6, pp. 1115-1128.

Freeman, K., Hayes, J., Trendel, JM. et al. (1990) Evidence from carbon isotope measurements for diverse origins of sedimentary hydrocarbons. Nature 343, 254–256. https://doi.org/10.1038/343254a0

* Image credit: Wikimedia Commons contributors, "File:20060827 Oelschiefer Eozaen Grube-Messel Germany.jpg," Wikimedia Commons, https://commons.wikimedia.org/w/index.php?title=File:20060827_Oelschiefer_Eozaen_Grube-Messel_Germany.jpg&oldid=1249702478 (accessed August 18, 2026).