EOS

It takes Pluto 248 years to complete one journey around the Sun. Humanity has known of its existence for less than half of that time, and we are still discovering the myriad ways that Pluto is unlike other celestial objects. Among other oddities: Pluto is the only object beyond Neptune’s orbit to have an atmosphere.

But that might not always be the case.

Because Pluto experiences such a drastic change in the amount of sunlight it receives throughout its 2-century year, planetary scientists have theorized that Pluto’s nitrogen-dominated atmosphere might come and go with its seasons. Now, new research suggests that Pluto’s atmospheric pressure is beginning to drop, potentially heralding atmospheric collapse ahead of Plutonian winter.

Power of the Occult

Pluto was discovered in 1930, but astronomers didn’t detect its atmosphere until 1988. They carefully observed as Pluto briefly blocked the light from a distant star and noticed that the starlight traveled through a thin gaseous layer of mostly nitrogen, with a little bit of methane, carbon monoxide, and hydrocarbons. This method of detection, called stellar occultation, allows scientists to monitor the bulk properties of Pluto’s atmosphere, like the height and pressure, as well as some finer details like atmospheric waves and the presence of haze.

Then in 2015, NASA’s New Horizons spacecraft flew through the Pluto system. It provided the clearest pictures to date of Pluto’s atmosphere and revealed surprising complexity. Since then, planetary scientists have continued to monitor the dwarf planet’s atmosphere via occultations.

Pluto’s atmosphere and surface ice, like in the smooth western half of the heart-shaped Tombaugh Regio, regularly exchange nitrogen particles. The details of these surface-air exchanges partially govern where and how quickly the atmosphere will freeze out during Plutonian winter. Credits: NASA/JHUAPL/SwRI, Public Domain

“Stellar occultations provide a snapshot of the physical properties of Pluto’s atmosphere [at] a given time. The path that the starlight takes through a thin atmosphere is a function of its composition as well as the temperature and density profiles,” Amanda Sickafoose, a planetary scientist at the Planetary Science Institute in Tucson, Ariz., told Eos via email. Sickafoose is the lead author on the new discovery.

But occultations happen only when Pluto and a background star line up just right, which is maybe once or twice a year. What’s more, given how subtle the signal from Pluto’s atmosphere is, the answers inferred from one telescope and analysis method might differ from those of another method. These challenges make it difficult for astronomers to put together a uniform and cohesive dataset that shows the subtle changes in Pluto’s atmosphere over time.

An Almost Airless Winter

Sickafoose and her colleagues sought to overcome these challenges by compiling Pluto occultation data spanning 1988–2023, including 10 new occultations from 2017 to 2023, and analyzing them in a consistent way. The observations were made at more than 15 different telescope sites around the world. But by reanalyzing the data in a uniform way, the team minimized telescope-specific differences and was able to tease out details of how Pluto’s atmosphere has evolved.

The team’s analysis showed that Pluto’s upper and lower atmospheres have responded differently to weakening sunlight.

“In terms of size and pressure, we find that Pluto’s atmosphere remained roughly stable from the New Horizons flyby in 2015 through 2021,” Sickafoose said. “Our most recent datasets in 2022 and 2023 suggest that the pressure has dropped, at a level of 16%, in the lower atmosphere.”

As Pluto’s atmosphere cools down, the haze particles in its atmosphere will fall down as nitrogen snow. Credit: NASA/JHUAPL/SwRI, Public Domain

The data also indicate that while Pluto’s upper atmosphere remains haze free, its lower atmosphere haze has started to clear up. Astronomers have noted the change in haze before and suspect that haze particles are snowing down as Pluto’s atmosphere cools. The team published these results in The Planetary Science Journal in July.

“This is great work!” said Perianne Johnson, a Pluto climate scientist at Purdue University in West Lafayette, Ind., who was not involved with this research. “We are hoping to identify slight changes in Pluto’s atmosphere, and it can be difficult to ascertain if reported differences are truly changes to the atmosphere or just differences between the way two scientists processed the data and different assumptions they made about unknown atmospheric properties. In this work, we can trust that the reported changes to the atmospheric pressure are real.”

Nitrogen Snow

Like many trans-Neptunian objects (TNOs), Pluto’s orbit is very noncircular and angled steeply from the ecliptic plane. Its temperature changes drastically throughout its year, depending on how far it is from the Sun. Since the discovery of Pluto’s atmosphere, astronomers have theorized that the atmosphere may freeze out, or collapse, as Pluto’s temperature drops.

Astronomers “anticipated a drop in pressure sometime in the upcoming decades, based on atmospheric models that consider things like Pluto’s orbit, the amount of Sun received at different locations on its surface, and the surface ice properties,” Sickafoose said.

“Pluto is the best studied TNO, and what we learn about Pluto helps put other TNOs in context.”

These data suggest that that collapse might be starting. And while a 16% drop in atmospheric pressure may sound small, Johnson said, “it is important to note that that change occurred over a period of just a few years, which is only a few percent of Pluto’s orbital timescale. So this is rapid, exciting change and is indicative of ice condensation occurring somewhere on Pluto.”

Most theories predict that once the collapse starts, Pluto’s atmospheric pressure will continue to drop for more than 150 years before eventually bouncing back in the 23rd century. Pinning down when and how fast the collapse happens holds clues for where atmospheric nitrogen is condensing and snowing down onto Pluto’s southern hemisphere ice deposits.

The next opportunity for high-quality occultation observations of Pluto is in 2027 and could verify whether atmospheric collapse is imminent.

“Occultations are an incredibly powerful tool for observing the distant solar system from Earth,” Johnson said. “Pluto is the best studied TNO, and what we learn about Pluto helps put other TNOs in context.”

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, K. M. S. (2026), Pluto’s atmosphere may be collapsing, Eos, 107, https://doi.org/10.1029/2026EO260288. Published on 11 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: AGU Advances

Leaf area index, which measures the ratio of leaf area to ground area, is commonly used by researchers to track foliage coverage and ecosystem health. One consequence of global warming, observed by satellite remote sensing, has been a long-term increase in leaf area index. This Earth “greening” is predicated on increased terrestrial carbon uptake under increasing CO2.

Chang et al. [2026] examine water controls on vegetation greening by isolating structural (e.g. leaf area index, LAI) and physiological (e.g., water use efficiency, WUE) impacts under increasing CO2. Their analysis shows worldwide patterns of increased plant water stress (PWS) and ecological drought, attributed to soil moisture, atmospheric aridity, and regional climate. This study demonstrates water limits on Earth greening emerging from local interdependencies between the carbon and water cycles. 

Attribution of variables, including meteorological factors (air temperature, Ta; and net radiation, Rn), soil and atmospheric aridity (VPD; surface soil moisture, SMsurf; and root-zone soil moisture, SMroot), and atmospheric CO2 to the changes of PWS indicated by ESILAI over the past four decades with a Random Forest model. ESILAI is the evaporative stress index that accounts for dynamical changes in Leaf Arae Index (LAI). a. Spatial distribution of dominant factor; b. Area ratio for the distribution of each dominant factor in a. Credit: Chang et al. [2026], Figure 7

Citation: Chang, Q., Wang, L., Barnes, M. L., Ficklin, D. L., Benson, M. C., & Novick, K. A. (2026). Widespread increase in global plant water stress obscured by greening. AGU Advances, 7, e2025AV002243. https://doi.org/10.1029/2025AV002243

—Ana P. Barros, Editor, AGU Advances

Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Editors’ Vox is a blog from AGU’s Publications Department.

When studying the subsurface of the Earth, scientists commonly use geophysical inverse modeling, which aims to infer key physical properties, like geological structures, from indirect observations. But these modeling techniques are typically high-dimensional and computationally demanding. To overcome these limitations, the scientific community is embracing Bayesian inference methods, which could offer a solution by integrating prior geological knowledge with observed data, enabling systematic uncertainty quantification.

A new article in Reviews of Geophysics explores recent advances in Bayesian methods for modeling the Earth’s subsurface from indirect geophysical data. Here, we asked the authors to give an overview of geophysical inverse modeling, how scientists use Bayesian inference, and what challenges remain.

In simple terms, what is geophysical inverse modeling?

Many decisions depend on what lies beneath our feet: where to drill, whether carbon dioxide can be stored safely, how groundwater may move, or where a hidden fault may create risk. Yet most of the subsurface cannot be observed directly. Geophysical surveys provide clues by measuring seismic waves, electromagnetic fields, gravity, and other responses of the Earth. Inverse modeling works backward from those measurements. Scientists propose an underground model, use physical laws to predict the signals it would produce, compare those predictions with the observations, and revise the model. The result is not a photograph, but a scientifically constrained description of underground structures and properties.

Conceptual overview of the multidisciplinary landscape of geophysical inverse modeling in subsurface applications. Credit: Liu et al. [2026], Figure 1

What are the benefits and limitations of using geophysical inverse modeling?

Geophysical inverse modeling can investigate large and deep regions without extensive drilling or excavation. It helps estimate rock velocity, electrical resistivity, density, porosity, fluid content, and the shape of faults, aquifers, or reservoirs. Its central limitation is that the data are noisy, incomplete, and unevenly informative. Different underground models can therefore produce very similar measurements. A single “best” model may look more certain than the evidence allows, while important alternatives remain hidden. For practical decisions, the key question is not only whether an image looks sharp. It is whether the remaining ambiguity could change a prediction or action, such as a drilling location, a monitoring plan, or a safety assessment.

What is Bayesian inference?

Bayesian inference is a way to update what we believe when new evidence arrives. A “prior” represents geological knowledge and plausible underground scenarios before the latest measurements are used. A “likelihood” describes how well each scenario explains the observed data, while accounting for measurement noise and modeling errors. Combining the two gives a “posterior,” a probability-weighted collection of scenarios that remain plausible after the evidence is considered. Rather than producing only one answer, Bayesian inversion shows which features are strongly supported, which remain uncertain, and how alternative interpretations compare. Those scenarios can then be carried forward into predictions and decisions, connecting data, models, possible outcomes, and action.

How has Bayesian inference improved subsurface modeling?

Bayesian inference has shifted the goal from finding one preferred underground model to evaluating a range of plausible models and predictions. This makes uncertainty an explicit result rather than an afterthought. Scientists can identify poorly constrained regions, reveal trade-offs between properties, combine different data types, and estimate the risk of costly misinterpretation. Bayesian analysis can also help determine which additional measurement would be most valuable. Recent gradient-informed methods use derivatives to navigate large model spaces more efficiently when the simulator is differentiable. Deep learning can represent realistic geological patterns, accelerate expensive physical simulations, and support rapid repeated inference. Together, these advances make uncertainty more useful for monitoring, planning, and decision-making.

Overview of Bayesian inference approaches for geophysical inverse problems. RW-MCMC enables general-purpose uncertainty quantification without requiring gradients. Ensemble-based methods offer efficiency in high-dimensional, weak non-linear, and non-Gaussian settings. Gradient-informed techniques leverage posterior geometry for improved sampling when gradients are available. Differentiable Bayesian frameworks combine physics-based modeling, machine learning, and automatic differentiation. Credit: Liu et al. [2026], Figure 2

What is Differentiable Bayesian Inversion, and what are its benefits?

Differentiable Bayesian Inversion, or DBI, is not a single new sampling algorithm. It is a unifying framework for linking geological knowledge, physical or learned simulators, models of measurement uncertainty, and Bayesian inference in one computational workflow. “Differentiable” means that software can track how a small change in an underground model affects the predicted data and how plausible that model is. Automatic differentiation can calculate these sensitivities through the full workflow. This common computational language allows physics-based models and machine-learning components to work together rather than remain separate boxes. Because the framework is modular, individual components can be improved or replaced. DBI could support faster, geologically realistic, uncertainty-aware inversion for monitoring and operational decisions.

What challenges remain?

The largest challenge is scale. Real three-dimensional problems may contain millions of unknowns, and every candidate model can require an expensive seismic, electromagnetic, or flow simulation. Plausible answers may also form several disconnected geological scenarios that are difficult to explore. AI models used to represent geology and fast surrogate simulators introduce further risks: they may fail when field conditions differ from their training data, and their errors can distort uncertainty estimates. Progress will require efficient differentiable solvers, more robust samplers, better uncertainty calibration, and validation on realistic field data. Gradient-free and hybrid methods will remain essential when models are not differentiable. The aim is not to eliminate uncertainty, but to identify which uncertainties matter and use them wisely.

—Mingliang Liu (mingliangliu@sdu.edu.cn; 0000-0002-5783-4490), Shandong University, China, and Stanford University, United States; Dario Grana (0000-0003-4220-053X), University of Wyoming, United States; Klaus Mosegaard (0000-0001-5292-5249), University of Copenhagen, Denmark; Mrinal K. Sen (0000-0002-5525-0467), The University of Texas at Austin, United States; Minghui Xu (0000-0001-9567-5569), Stanford University, United States; and Tapan Mukerji (0000-0003-1711-1850), Stanford University, United States

Editor’s Note: It is the policy of AGU Publications to invite the authors of articles published in Reviews of Geophysics to write a summary for Eos Editors’ Vox.

Citation: Liu, M., D. Grana, K. Mosegaard, M. K. Sen, M. Xu, and T. Mukerji (2026), How can we make better decisions about what lies underground?, Eos, 107, https://doi.org/10.1029/2026EO265036. Published on 10 September 2026. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

This is the highest-resolution image of the Sun ever taken.

It was captured by the Daniel K. Inouye Solar Telescope (DKIST) in Hawaii, the largest solar telescope in the world, on 14 April 2025.

The image zooms in on a small patch of the Sun’s surface in visible light. The whole image spans 5,800 kilometers (3,604 miles) horizontally and 4,350 kilometers (2,703 miles) vertically, covering a mere 0.0004% of the Sun’s surface. Each pixel is 6 kilometers (3.7 miles) per side.

Take a close look at the grid-like pattern and see if you can spot small swirls among the feathered edges.

A high-resolution image of the Sun at 416 nanometers taken by the Inouye Solar Telescope. Credit: NSF/NSO/AURA/MPS, CC BY 4.0

Here are two spots with swirling plasma.

The inset here zooms in on a small patch of the Sun’s surface with the telltale swirl of Kelvin-Helmholtz instabilities (KHI) just tens of kilometers across. Credit: NSF/NSO/AURA/MPS, CC BY 4.0 Another region of the same image shows even more KHI fingerprints, suggesting that these instabilities might be common on the Sun’s surface. Credit: NSF/NSO/AURA/MPS, CC BY 4.0

The tiny swirls and vortices are called Kelvin-Helmholtz instabilities, and this is the first observational confirmation that they exist on the Sun. The swirls are manifestations of a physical process that could play a crucial role in how the Sun’s plasma bubbles and bursts.

“Kelvin-Helmholtz instabilities are one of the fundamental instability processes in magnetofluids, fluids, and gases,” said David Kuridze. Kuridze studies plasma in the solar atmosphere at the National Solar Observatory (NSO) in Boulder, Colo., and is colead researcher on the discovery.

“We did not set out to find Kelvin-Helmholtz instabilities,” added colead researcher Friedrich Wöger, who studies flow dynamics of the solar photosphere at NSO. “The experiment was targeted at finding the most efficient way to reach the diffraction limit of the telescope. And the nice thing is, not only did we succeed with that but we also found Kelvin-Helmholtz instabilities.”

Kelvin-Helmholtz instabilities might be everywhere on the Sun. Credit: NSF/NSO/AURA/MPS, CC BY 4.0 When Plasmas Flow By

Kelvin-Helmholtz instabilities (KHI) are caused by the edges of two streams of fluid flowing past each other at different speeds. And “fluid” is quite a broad term, geophysically speaking. Scientists have spotted these swirls and vortices in estuaries and oceans, as well as in Earth’s clouds; the skies of Mars, Jupiter, and Saturn; and interactions between the solar wind and planetary magnetospheres, Kuridze explained.

Astronomers have long suspected that KHI exist on the Sun’s surface. The solar photosphere is a fluidlike plasma, so it would make sense for it to follow the same rules as any other fluid, albeit with the added complication of the Sun’s magnetic field. What’s more, the existence of KHI could explain some of the Sun’s more mysterious phenomena, like braided magnetic field lines, eruptions, and the ultrahot corona.

“Kelvin-Helmholtz instabilities are a very effective mechanism to twist and bend magnetic structures” and generate magnetic energy, Kuridze said.

“One of the big questions is, How much energy can these vortices create and transport up into the outer atmosphere of the Sun, and is it enough to heat it up to millions of degrees kelvin?” Wöger said.

But until recently, actually spotting these instabilities on the Sun’s surface was impossible. Picking out small vortices within the solar plasma requires specialized instruments installed on solar telescopes, and previous generations of solar telescopes were simply not powerful enough to see them. When DKIST came online in 2019, its 4-meter (13-foot) mirror immediately changed the game by allowing astronomers to view the bubbling, boiling solar surface at several wavelengths and at smaller scales than ever before.

“DKIST’s resolving capacity is equivalent to finding a quarter from a distance of 50 kilometers,” said Michail Mathioudakis, a solar astrophysicist at Queen’s University Belfast in the United Kingdom.

Roil and Toil

Kuridze, Wöger, and their team pushed DKIST’s resolving power to the max to zoom in on a small part of the Sun near a sunspot for a few minutes. This slow roiling is what they saw.

As the Sun’s plasma surface roils, the different flows of plasma shear against each other and create Kelvin-Helmholtz instabilities. Credit: NSF/NSO/AURA/MPS, CC BY 4.0

Here are those same two zoomed-in spots from before.

When scientists zoomed in on the high-resolution video of the Sun, they could watch KHI actively swirling. Credit: NSF/NSO/AURA/MPS, CC BY 4.0

“When we looked at these data and the movie, we immediately recognized the signature of Kelvin-Helmholtz instability,” Wöger said.

After they spotted the telltale signs of KHI, the observing team asked their modeling partners to simulate the motions of the Sun’s magnetically influenced fluidlike plasma, or magnetohydrodynamics, at a similarly high resolution. Creating simulations with the level of detail needed to compare with the DKIST observations requires phenomenal computational power and likely wouldn’t have happened without these observations as motivation, Wöger said.

Those simulations, based on fundamental physics and fluid dynamics principles, confirmed that the vortices captured by the DKIST images were likely created by KHI. The DKIST observations show that KHI might be ubiquitous across the Sun’s surface. This discovery was published in Nature in August.

“Models of the solar atmosphere have shown indications of this instability, but the paper has identified this physical process observationally in some of the smallest astrophysical scales,” said Mathioudakis, who was not involved with the research. “What surprised me the most is that this discovery was made with a relatively simple imaging setup and does not involve complex instrumentation, calibration issues, or data inversions. It will therefore stand the test of time.”

Small Swirls, Big Energy

“This is a very notable observation because Kelvin-Helmholtz instability in photospheric shear flows has been predicted theoretically for decades, but the relevant spatial scales were simply too small to resolve directly,” said Claire Foullon, a solar and space physicist at the University of Exeter in the United Kingdom.

“What is more surprising is how DKIST reveals it to be so widespread,” Foullon added. “Rather than being an occasional phenomenon, the observations suggest that this may be a fundamental part of the small-scale dynamics of the magnetized photosphere.” Foullon was not involved with the new discovery.

“There’s always this nice tension between simulation and observation.”

As KHI swirl around and around in the solar photosphere, they can twist up magnetic fields and store up energy. All that energy has to go somewhere, and many solar scientists think it might contribute to heating up the Sun’s corona.

“We are effectively seeing, for the first time, dynamics on the scales at which the magnetic foot-points of the corona are being continually stirred and restructured,” Foullon said.

The degree to which KHI contribute to coronal heating is still unknown, as is whether KHI exist on even smaller physical scales on the Sun. These might remain open questions for a while, Kuridze said, as observers figure out ways to push DKIST to even smaller physical scales and as simulations stretch farther to match.

“There’s always this nice tension between simulation and observation,” Wöger said. “When we see something [in observations], then we’re pushing the numerical simulations. And sometimes in the numerical simulations you see something, and then we’re trying to see whether it actually exists on the Sun.”

—Kimberly M. S. Cartier (@astrokimcartier.bsky.social), Staff Writer

Citation: Cartier, K. M. S. (2026), Sharpest-ever image of the Sun shows small but mighty swirls, Eos, 107, https://doi.org/10.1029/2026EO260285. Published on 10 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Source: AGU Advances

A process known as the biological carbon pump (BCP) moves organic carbon from near the ocean’s surface to the ocean floor. That carbon often stays there for hundreds or thousands of years, making the BCP a primary source of carbon sequestration in the oceans. Scientists have thought that relatively large phytoplankton are more efficient at exporting carbon to the deep ocean than tiny cyanobacteria, but new research from Zhang et al. now calls that belief into question.

Using sediment traps placed at a depth of 1,000 meters in the South China Sea paired with multiple years of observations of surface phytoplankton communities, the authors show that about two thirds of the carbon sequestered in the ocean comes not from eukaryotic microalgae, but from another major group: cyanobacteria. These tiny, often unicellular prokaryotic phytoplankton are so named because of the blue-green color seen when they grow in large colonies. The main reason cyanobacteria play a larger role is that much of the carbon from microalgae is lost on its journey to the deep ocean but carbon from cyanobacteria is not. These findings could change how models of ocean carbon sequestration are constructed and hold implications for our understanding of how the BCP will shift in response to climate change, the authors say.

Evidence of taxon-specific divergence in carbon sequestration comes from the amino acid carbon isotope signatures found 1,000 meters deep, which allowed the researchers to tie the carbon they collected to phytoplankton groups at the surface. The authors found that production of carbon and phytoplankton structure at the surface vary considerably by season and corresponding nutrient availability. But surprisingly, the efficiency and origin of carbon collected deeper down do not change much by season.

The linked processes of aggregation and ballasting, in which carbon from cyanobacteria is incorporated into larger clumps that also contain other minerals, help cyanobacteria carbon sink more efficiently and reduce its loss during sinking by limiting microbial degradation. These findings may explain why high-latitude systems dominated by large phytoplankton do not always exhibit higher organic carbon sequestration efficiency compared to low-latitude oligotrophic gyres rich in cyanobacteria, the authors note. (AGU Advances, https://doi.org/10.1029/2025AV002148, 2026)

—Nathaniel Scharping (@nathanielscharp), Science Writer

Citation: Scharping, N. (2026), Tiny cyanobacteria may be the secret heroes of ocean carbon sequestration, Eos, 107, https://doi.org/10.1029/2026EO260283. Published on 10 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Authors: Lakshman Srikanth and David Petley

This article was first published on the UNDRR PreventionWeb site.

A hazard event occurs. Imagine that the first report says 20 people have died. By the evening, the number is 27. The following day, authorities report 23. A week later, some people initially reported missing are confirmed alive, while others previously listed as injured have died. Which number is correct? 

The obvious answer is the latest one. 

But the problem is more complicated than changing numbers over time.

Before we can count disaster fatalities, we need to answer a set of more fundamental questions: What exactly was the event? Which deaths were caused by it? How directly were they connected? And what evidence do we have?

Disaster fatality data are therefore not simply collected. They are interpreted, classified, attributed, verified, and revised. This is part of a broader challenge in disaster loss and damage databases, where definitions, thresholds, reporting practices and data sources can strongly influence what ultimately gets recorded – a pattern documented in studies of missing data in the Emergency Events Database (EM-DAT) , loss-data fallacies and flood loss databases .

Here we focus specifically on the challenges of accounting for disaster fatalities.

Before counting deaths, we need to define the event and the causal pathway

Consider what happened during Typhoon Maysak in southern China in July 2026 . Heavy rainfall associated with a storm caused flooding in Guangxi, where a reservoir embankment was breached and a snake-breeding farm was flooded. Around 800-900 snakes escaped, including venomous species. Several people were bitten and at least one person died following a snakebite. Reports also indicated delays in accessing medical care contributed to the circumstances surrounding the fatality. An illustrative causal pathway of the reported snakebite fatality is represented in Figure 1:

Figure 1: Illustrative causal pathway for reported snakebite fatality during Typhoon Maysak

So how should this death be recorded? As a snakebite death? A flood-related death? A consequence of the reservoir failure? A typhoon-related death? Or an indirect disaster fatality?

There is no universally obvious answer because each label answers a slightly different question. Mortality registries typically seek the underlying cause of death: the disease, the injury or the circumstances that initiated the chain leading to death. Disaster databases, instead, often link deaths with a particular hazard event, including direct and indirect consequences.

Therefore, the same fatality can occupy several positions in a causal chain. It may be a “snakebite death” in a health or mortality registry, a “reservoir breach consequence” in infrastructure analysis, a “rainfall-related death” or a “flood related indirect death” in a disaster database. None of these labels are necessarily wrong. A disaster fatality can thus pass through multiple interpretive layers before becoming a database entry, and each layer may legitimately produce a different label. 

This distinction matters because disaster databases often use the event as their basic unit of analysis. Yet defining the boundaries of an event can itself be difficult, particularly when hazards cascade or occur simultaneously. A tropical cyclone can generate heavy rainfall, flooding, landslides, infrastructure failures and secondary impacts, while a single fatality may result from several links in that chain. The challenge is therefore not only to count deaths, but to decide which event and causal pathway those deaths belong to.

Typhoon Maysak’s official death toll rose from 39 to159 over the six weeks, according to the South China Morning Post . Several causal chains may be established to better understand the reasons for the deaths due to the event. A hypothetical causal pathway of disaster deaths is presented in Figure 2.

Figure 2: Hypothetical (not event verified) causal pathway associated with a tropical cyclone (darker boxes are hypothetical additions) Defining the main event (start point of the causal chain)

Disaster databases often require an event as the unit of analysis, although defining one event is difficult. A World Meteorological Organization (WMO) / United Nations Development Programme (UNDP)review of 91 post-disaster needs assessments (PDNAs) highlights recent efforts by WMO to develop a globally accepted standard for determining the temporal or spatial extent of a hazard event. 

The same document also highlights that only 20% of the PDNAs involved consultations with the National Hydrological and Meteorological Services. This matters directly for fatality attribution because understanding the initiating hazard and its evolution requires hazard expertise. If a report says “landslide deaths,” hazard experts may help determine whether the event was rainfall-triggered, earthquake-triggered, construction-related, mining-related, or part of a compound flood-landslide event. If a death follows a dam breach, hydrological and infrastructure expertise can help distinguish the initiating rainfall, the failure mechanism, downstream flood wave and later exposure pathway. 

The WMO Cataloguing of Hazardous Events approach offers one potential building block. By providing events with unique identifiers, recording temporal and spatial parameters, it can help link related or cascading hazards and associated impacts. This does not completely remove uncertainty, but it helps prevent complex chains from being flattened into one misleading hazard label. 

Defining the temporal boundary

Not all deaths due to disasters happen immediately. The Hillsborough stadium disaster, for example, caused 94 immediate deaths and 766 injuries, with 300 hospitalizations, in 1989. According to a contemporary timeline , the latest recognized death due to the event – the 97th – was confirmed in 2021, 32 years after the incident. The delayed death was recognized because a documented causal chain remained. Many disasters lack comparable long-term records and institutional follow-up. This creates systematic differences in what can later be recognized.

Physical injury is not the only pathway through which a disaster may contribute to later mortality. Hillsborough survivors also experienced long-term trauma, and some died by suicide . Disasters may contribute to trauma, bereavement, displacement, social isolation or substance-related harm, and these pathways can contribute to later mortality. Establishing causation for an individual case is, however, more difficult than identifying increased mortality at the population level.

While counting deaths, we are actually counting reports about deaths

Much of what we know about disaster fatalities comes through an information system that is itself imperfect. A death that occurs in a remote community with little media coverage may never enter an international database. A death in a major city may generate dozens of independent reports. Official emergency management sources may record events requiring institutional intervention while smaller events remain undocumented. Comprehensive disaster databases therefore often need to combine official records with media reports, local sources and other forms of evidence.

Disaster deaths also get lost in the noise of conflicting reports on the actual death toll. The landslide in Papua New Guinea in May 2024 illustrates this. Early media articles indicated over 2,000 individuals buried while other articles reported 670 deaths and, later, 200. That is a difference of about 1,800 individuals from the earliest estimate. Uncertainty arises not only because sources provide different numbers, but because they may be counting different things — such as estimated people buried, estimated deaths, confirmed or recovered bodies, directly affected people, or retrospective estimates.

Similar irregularities in media reporting that results in high uncertainty are common in outlier events such as earthquakes. The Kashmir earthquake in 2005 with an epicenter in Muzaffarabad affected Azad Jammu and Kashmir region administered by Pakistan, Khyber Pakhtunkhwa, areas in Afghanistan, and some areas of Jammu and Kashmir region, India. The death toll in Pakistan ranges from 87,350 to more than 100,000 – an uncertainty of almost 13,000 people.

Reports may also be in vernacular languages, use local hazard terminology, or translated differently across languages. A term translated as “landslide” may refer to a debris flow, slope collapse, embankment failure, quarry wall failure, construction-site collapse or broader rain-related ground failure. Official district-level statements may give only aggregate numbers such as “five dead, 20 injured”, without explaining whether the deaths occurred by drowning, collapse, electrocution, explosion, disease, evacuation accident or delayed medical access. These examples show that hazard datasets must work with partial visibility, language effects and evolving source quality. 

Actual deaths ≠ reported deaths ≠ verified deaths ≠ database deaths.

The database is therefore not simply a mirror of reality. It is also a record of what became visible, what could be verified and what could be attributed from the available evidence.

This raises a broader question: if disaster fatality data are inherently evolving, uncertain and dependent on how events and causal pathways are defined, what should a good disaster fatality accounting system look like?

What should we do differently? Build on existing data systems

More research is needed on the standardization of disaster fatality accounting and on the requirements for disaster fatality registries at different levels – from local and national systems to global disaster databases. 

There are already useful examples to build on. In landslide death mapping, specific methodologies and databases have been developed, including NASA’s Global Landslide Catalog and the Global Fatal Landslide Database . Recent work has also proposed frameworks for linking landslide inventories with loss and damage reporting . At the global level, EM-DAT provides a major compilation of disaster-related losses and impacts. The emerging WMO approach to cataloguing hazardous events could provide another important building block, by supporting more consistent identification and linking of hazard events.

Connect multiple sources and causal pathways

A key requirement is to move beyond reliance on a single source of information and systematically combine multiple sources, with mechanisms for corroboration, verification and revision.

The opportunity is to move towards interoperable and mineable disaster fatality datasets that recognize the complexity of compiling, interpreting, attributing and maintaining fatality information. 

Such systems should not only record how many people died but also preserve the causal pathway through which deaths occurred. This could allow fatality data to be used not only for counting impacts, but also for understanding where vulnerabilities emerge along the disaster chain and where risk reduction measures might intervene. 

Preserve how the evidence evolves

Finally, the evolution of the evidence itself should be preserved. A fatality database should not simply replace yesterday’s estimate with today’s number. It should retain the trajectory of the information: what was initially reported, what was subsequently verified or revised, what evidence led to the revision, and what remains uncertain.

In other words, a disaster fatality database should preserve not only the number of deaths, but also the event, the causal pathway, the evidence and the evolution of our understanding.

When we say that a disaster killed 20 people, we are not simply reporting a number. We are making a series of decisions about what the event was, how deaths were connected to it, what evidence was available, and how certain we are. Those decisions are often invisible once the number enters a database.

Improving disaster fatality accounting is therefore not simply a data-management exercise. It is part of improving how we understand disaster risk itself.

Why better counting matters

This matters because disaster fatality data are not only used to describe what happened. They are also used to measure whether disaster risk is being reduced. The Sendai Framework includes a global target to substantially reduce disaster mortality by 2030. We therefore use disaster fatality data to assess progress towards reducing disaster risk. But how confidently can we claim progress if the way disaster deaths are identified, attributed, classified and revised remains so difficult to standardize?

Further examples and an evolving compilation of disaster fatality data and sources are available in Deaths, injuries, evacuations due to hazard events as part of the  Disaster Risk Intelligence Hub .

Lakshman Srikanth is a Senior Advisor at Deltares, working on disaster risk management, & resilience. His work focuses on disaster vulnerability and risk assessment, risk management planning, and translating evidence and data into practical approaches for reducing disaster risk.

Return to The Landslide Blog homepage Text © 2026. The authors. CC BY-NC-ND 3.0
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The Arctic is often described as a distant frontier. In reality, it is one of the most consequential regions on the planet.

For 2 decades, the Arctic Report Card (ARC) has provided an annual, peer-reviewed assessment of environmental conditions across the Arctic, helping scientists, decisionmakers, industries, and communities understand how one of Earth’s fastest-changing regions is evolving. Issued annually since 2006, the report has become one of the world’s most trusted syntheses of Arctic observations and research.

The ARC’s importance stems from a simple truth: The Arctic matters far beyond the Arctic.

Changes unfolding across the region influence weather, climate, ecosystems, economies, transportation networks, and security interests around the globe. As Arctic temperatures continue to rise faster than the global average and sea ice continues its long-term decline, what happens in the far north increasingly affects people, organizations, and governments everywhere.

 
Related

•  Arctic Report Card Finds a New Home With AGU
•  Government Pulls Funding for the Arctic Report Card
•  Arctic Report Card Will Move Ahead Without NOAA
 

Despite the ARC’s value, NOAA recently announced that it will no longer facilitate or support the report’s development. Under this decision, NOAA says it will continue to collect and make available Arctic data, but it will no longer provide the important coordination, review management, communications support, and other resources that have historically enabled publication of the report card.

The announcement that a uniquely valuable scientific resource would be disrupted at a time when understanding Arctic change has never been more important raised serious concerns for many in the Arctic research community. Researchers emphasized that the ARC serves not only scientists but also policymakers, educators, industry stakeholders, and communities seeking reliable information about ongoing environmental change.

Fortunately, the ARC will continue.

AGU has announced that it is partnering with the University of Colorado Boulder Cooperative Institute for Research in Environmental Studies (CIRES) and the University of Alaska Fairbanks (UAF) to support the 2026 ARC effort and the report’s editorial team.

This partnership reflects a recognition shared across the scientific community: Continuity matters. Long-term observational records become more valuable with every passing year. Regular assessments such as the ARC provide critical context, helping connect individual observations into a coherent picture of change.

One of the most visible consequences of Arctic change is the opening of new maritime pathways.

As seasonal sea ice retreats, routes that were once inaccessible for much of the year are becoming increasingly navigable. This shift carries not only significant economic opportunities but also environmental challenges. Shipping companies, logistics providers, and governments are all watching closely how changing Arctic conditions could reshape global trade routes, reduce transit times between major markets, and alter patterns of maritime activity.

Richard Spinrad, an oceanographer and former NOAA administrator, presents the 2024 Arctic Report Card at the AGU Annual Meeting in Washington, D.C. Credit: Beth Bagley/AGU

At the same time, operating in Arctic waters remains complex and risky. Weather variability, sea ice dynamics, and rapidly changing environmental conditions require robust observational data and scientific analysis to support navigation, risk management, and long-term planning. The ARC helps provide exactly that kind of information.

The Arctic is also attracting growing attention from a national security perspective.

Several strategically important nations share Arctic coastlines. Increased activity across Arctic waters has heightened interest in maritime awareness, monitoring capabilities, and regional infrastructure. Scientific observations and environmental intelligence help inform understanding of operating conditions across the region, supporting everything from navigational safety to situational awareness.

The value of Arctic information extends below the surface. Interest in seabed resources and terrestrial mineral deposits across and adjacent to the Arctic has grown substantially in recent years. Accessing and operating in these environments requires a deep understanding of changing weather patterns, permafrost conditions, sea ice trends, and environmental risks. Reliable scientific assessments help inform planning decisions, infrastructure investments, and long-term management considerations.

In addition—and critically—the ARC serves far more than just the scientific community.

Commercial fisheries depend on observations and analyses that help them understand changing ocean conditions and ecosystem shifts. Arctic waters support important fisheries in their own right, but the Arctic also serves as a bellwether for broader changes occurring across Northern Hemisphere marine systems. Understanding these trends can help inform fisheries management and operational planning well beyond the Arctic alone.

The Arctic Report Card has never been solely about documenting environmental change. It is about providing society with the information needed to understand and respond to that change.

Similarly, maritime shipping and logistics companies monitor Arctic environmental conditions to evaluate emerging routes, assess operational risks, and support strategic planning. Insurers and reinsurers rely on environmental data and climate information when evaluating risk exposure across a number of sectors affected by changing Arctic conditions, including shipping, fisheries, infrastructure, and more.

In each case, informed decisions are absolutely critical. Those decisions depend on trustworthy observations, expert analysis, and a consistent record of environmental change over time. The ARC has become an essential source of that crucial information.

Maintaining the continuity of this annual assessment ensures that all the various people who need this information, including decision-makers, researchers, communities, and industries, continue to have access to trusted information about one of Earth’s most consequential regions.

The Arctic Report Card has never been solely about documenting environmental change. It is about providing society with the information needed to understand and respond to that change.

As the Arctic continues to transform, the need for rigorous observations, expert assessment, and trusted scientific communication will only grow. Supporting efforts like the ARC is therefore not simply an investment in Arctic science; it is an investment in the information infrastructure that helps communities, economies, and governments navigate an increasingly interconnected world.

And that is why the Arctic Report Card remains so important, not just for the Arctic but for all of us.

—Chris Avery, Director, Science Assessment, AGU; and Kristen Averyt Hinton, Executive Vice President, Science, AGU 

Citation: Avery, C. and Averyt Hinton, K. (2026), The Arctic Report Card matters more than ever; AGU joins partners to publish in 2026, Eos, 107, https://doi.org/10.1029/2026EO260291. Published on 9 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Mexico City has an atmospheric puzzle: Air quality policies have significantly reduced concentrations of many primary pollutants such as carbon monoxide, sulfur dioxide, and nitrogen oxides, but decreases in the amount of ozone, a secondary pollutant, have leveled off in recent years. This apparent contradiction is part of what the scientific literature describes as the “ozone paradox.” Could air temperatures be the key to this conundrum?

The ozone paradox has implications for health and safety. Unlike stratospheric ozone, elevated ozone concentrations near ground level are associated with respiratory tract inflammation, increased susceptibility to lung infections, and aggravation of existing respiratory diseases. Further, ozone can impede the growth of certain plants and can make them more vulnerable to disease and damage from insects and severe weather.

Ozone in the troposphere remains a challenge for Mexico City’s public health and policymakers. Unlike other pollutants emitted directly from car exhaust or industry, ozone forms when precursor pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) interact with sunlight through photochemical reactions. Under favorable atmospheric conditions, more heat and more sunlight can increase the efficiency of ozone formation. As temperatures rise, so does the efficiency of atmospheric reactions related to ozone production. This dynamic was identified decades ago [Sillman and Samson, 1995; Jacob and Winner, 2009; Nolte et al., 2021] and reaffirmed by our most recent analysis of atmospheric data collected in the Mexico City area between 2000 and 2021 [Castro et al., 2025].

Our data revealed that high-ozone episodes occur most frequently at the end of the dry season, particularly during April and May, and again in winter. The April–May peak coincides with intense solar radiation and rising ambient temperatures, creating ideal conditions for ozone formation. The winter peak, on the other hand, is related to atmospheric stagnation and a compressed boundary layer that traps pollutants near the surface [Castro et al., 2025].

A Complex History of Air Pollution

The ozone paradox is especially relevant in Mexico City because the region has a long and complex history of air pollution management.

The ozone paradox is especially relevant in Mexico City because the region has a long and complex history of air pollution management. The metropolitan area, located at high elevation and surrounded by mountains, has meteorological and topographic conditions that often limit pollutant dispersion.

During the late 20th century, the city became widely known for severe air pollution episodes associated with rapid urban growth, industrial activity, traffic emissions, and frequent atmospheric stagnation. Since then, air quality policies have substantially improved the situation, but ozone remains one of the most persistent challenges.

For more than 20 years, Mexico City has addressed these issues with ambitious environmental policies. The city’s comprehensive “ProAire” programs, for example, included expansion of the Metrobús system, reforestation efforts, and environmental education. Additionally, the city introduced requirements for low-sulfur fuels, vehicle inspection programs, and measures to reduce industrial and transportation emissions.

These efforts should not be underestimated. They have successfully reduced several ozone precursors and primary pollutants and represent one of the most important urban air quality management experiences in Latin America. Mexico City’s long-term air quality monitoring network has also made it possible to evaluate the effectiveness of these policies and to identify new atmospheric challenges as they emerge.

So why do ozone levels remain high, even when levels of its precursor pollutants decrease?

Scientists have concluded that the missing piece of the puzzle may be temperature. The average maximum surface temperature in Mexico City’s metropolitan area increased from 32.5°C to 33.2°C between 2000 and 2021. This increase of almost 1°C, although modest, acts as a catalyst, accelerating the chemical efficiency of ozone formation [Sillman and Samson, 1995; Jacob and Winner, 2009].

Ozone is becoming a defining pollutant of a warming and chemically complex urban atmosphere.

The COVID-19 lockdown offered an unusual opportunity to study this phenomenon. During this period of reduced mobility, emissions of several primary pollutants decreased, but ozone did not decline in the same proportion. These data indicate that reducing NOx alone reduces the chemical removal of ozone by nitric oxide, but VOCs, sunlight, and high temperatures continue to favor ozone production [Peralta et al., 2021].

Mexico City is not an isolated case; other large urban regions around the world have also faced difficulties reducing ozone, even after achieving important reductions in primary emissions. A study of air quality during the COVID-19 lockdown in northern China saw similar results: Surface-level quantities of NOx decreased by about 60%, while surface-level ozone increased by a factor of 1.5 [Shi and Brasseur, 2020]. This broader context suggests that ozone is becoming a defining pollutant of a warming and chemically complex urban atmosphere.

Quantifying the Relationship Between Heat and Ozone

A relatively small temperature increase can have a disproportionately large effect on ozone formation.

Using data from the RAMA (Red Automática de Monitoreo Atmosférico) and REDMET (Red de Meteorología y Radiación Solar) networks, we identified a clear exponential relationship between ozone concentrations and temperatures in Mexico City between 2000 and 2021 (Figure 1), with a model fit to the data explaining more than 70% of the variation in peak ozone levels. Essentially, each additional degree of warming produces a progressively larger peak in ozone concentration [Castro et al., 2025].

Fig. 1. Maximum daily ozone (O3) concentrations show an exponential relationship with maximum daily surface temperature (T) on the basis of measurements collected from 2000 to 2021 by the RAMA (Red Automática de Monitoreo Atmosférico) and REDMET (Red de Meteorología y Radiación Solar) networks. R2 is the coefficient of determination and indicates the proportion of variation in the maximum daily ozone concentration accounted for by the exponential fit. Credit: Castro et al. [2025]

Importantly, our results show that ozone does not respond to temperature in a simple linear way and help to explain why ozone episodes may continue even when long-term emission control policies are in place. A relatively small temperature increase can have a disproportionately large effect on ozone formation when other conditions are favorable. These conditions include intense solar radiation, the presence of stagnant air masses, and sufficient availability of precursor gases.

This dynamic is most visible during the “ozone season” from March to May, when high solar radiation and stagnant air masses prevent pollutants from dispersing in the atmosphere. These conditions are no longer just seasonal anomalies; they are expected to become more frequent or more intense as climate change progresses [Estrada et al., 2023]. In this context, ozone management is not only an air quality issue but also a climate adaptation challenge.

The city is running a race where the finish line, clean air, is receding farther and farther because of global warming.

The relationship between heat and ozone is also connected to urbanization. Large cities modify their local climate through the urban heat island effect, which can increase surface temperatures relative to surrounding rural areas. In Mexico City, this effect interacts with regional climate warming, local emissions, and basin meteorology. Together, these factors can create a more reactive atmosphere than the one that existed 2 decades ago.

The city is running a race where the finish line, clean air, is receding farther and farther because of global warming.

The Way Forward: Integrated Policy

Our findings highlight a critical challenge for urban planning. If temperatures continue to rise, technological advances in vehicles and industry could be partially offset by the increased chemical efficiency of the atmosphere [Nolte et al., 2021]. The next generation of policies must recognize that ozone control requires a more integrated strategy.

First, ozone mitigation should consider the balance between NOx and VOC emissions. Because ozone formation depends on nonlinear chemistry, reducing only one group of precursors may not always produce the expected response. More detailed control of VOC emissions from fuels, solvents, industry, traffic, and consumer products may be necessary, especially during the ozone season.

Second, air quality policy should be linked to meteorological forecasting. High-ozone episodes often occur under predictable combinations of high temperature, intense solar radiation, atmospheric stagnation, and limited vertical mixing. Short-term actions during these periods could help reduce peak exposures, particularly for vulnerable populations such as children, older adults, outdoor workers, and people with respiratory disease.

Air quality strategies cannot exist in isolation. They must be integrated with climate change adaptation and mitigation goals.

Third, reducing the urban heat island effect should be considered part of ozone management. Measures such as increasing urban vegetation, protecting green areas, using reflective materials, improving building efficiency, and reducing heat emissions from transport and infrastructure can contribute to climate adaptation while also helping to reduce conditions favorable for ozone formation.

Fourth, long-term monitoring must continue. Mexico City’s atmospheric monitoring networks are essential because they allow scientists to distinguish between emission-driven trends and climate-driven changes. Without continuous measurements of pollutants and meteorological variables, it would be much more difficult to understand why ozone remains persistent despite reductions in other pollutants.

To protect public health, air quality strategies cannot exist in isolation. They must be integrated with climate change adaptation and mitigation goals. In megacities like Mexico City, reducing emissions is no longer enough; we must also address the urban heat island effect and prepare for a fundamentally more reactive and hotter atmosphere.

Mexico City’s experience with the ozone paradox offers a useful lesson for other megacities. The challenge ahead is not only to emit less but also to understand how a warmer atmosphere changes the effectiveness of traditional pollution control strategies. Ozone is therefore more than an air pollutant; it is a signal of how climate change can reshape urban environmental risks.

References

Castro, T., et al. (2025), Evolution of tropospheric ozone and surface temperature in Mexico City from 2000 to 2021, Atmosphere, 16(12), 1379, https://doi.org/10.3390/atmos16121379.

Estrada, F., et al. (2023), State and perspectives of climate change in Mexico: A starting point, cambioclimatico.unam.mx/.

Jacob, D. J., and D. A. Winner (2009), Effect of climate change on air quality, Atmos. Environ., 43(1), 51–63, https://doi.org/10.1016/j.atmosenv.2008.09.051.

Nolte, C. G., et al. (2021), Regional temperature-ozone relationships across the U.S. under multiple climate and emissions scenarios, J. Air Waste Manage. Assoc., 71(10), 1,251–1,264, https://doi.org/10.1080/10962247.2021.1970048.

Peralta, O., et al. (2021), Ozone over Mexico City during the COVID-19 pandemic, Sci. Total Environ., 761, 143183, https://doi.org/10.1016/j.scitotenv.2020.143183.

Shi, X., and G. P. Brasseur (2020), The response in air quality to the reduction of Chinese economic activities during the COVID-19 outbreak, Geophys. Res. Lett., 47, e2020GL088070, https://doi.org/10.1029/2020GL088070.

Sillman, S., and P. J. Samson (1995), Impact of temperature on oxidant photochemistry, J. Geophys. Res., 100(D6), 11,497–11,508, https://doi.org/10.1029/94JD02146.

Author Information

Telma Castro (telma@atmosfera.unam.mx), Oscar Peralta, and Salvador Reynoso-Cruces, Instituto de Ciencias de la Atmósfera y Cambio Climático, Universidad Nacional Autónoma de México, Mexico City; Harry Alvarez-Ospina, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City; and Alejandro Salcido, Instituto Nacional de Electricidad y Energías Limpias, Cuernavaca, Mexico

Citation: Castro, T., O. Peralta, S. Reynoso-Cruces, H. Alvarez-Ospina, and A. Salcido (2026), The ozone paradox: A growing cost of a warmer atmosphere, Eos, 107, https://doi.org/10.1029/2026EO260284. Published on 9 September 2026. Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Source: AGU Advances

Fieldwork is a vital part of geoscience research, allowing scientists and students to directly observe, interact with, and collect data about Earth processes that cannot be replicated in the lab.

Because fieldwork involves traveling to remote locations and living in close quarters under demanding conditions, it can also lead to circumstances in which personal boundaries are crossed or safety is compromised. Shared housing, uneven power structures between students and professionals, remote locations, and long workdays can increase the likelihood of harmful field interactions.

Although the National Science Foundation, the largest agency funding field-based research, provides safety guidelines for fieldwork, many researchers in the geosciences report a range of problematic behaviors, from bullying to discrimination to sexual harassment.

Gold et al. conducted an anonymous survey of 289 AGU members to assess the frequency of harmful field interactions (excluding severe cases of violence or misconduct), which types have the most impact, and why incidents may go unreported. The researchers also asked participants what could be done to make geoscience field research safer and more inclusive.

In the survey, participants were asked whether they had experienced or witnessed harmful behaviors, including aggression and hostility, social harassment, undermining of work, inappropriate sexual behavior, assumptions and stereotyping, and violations of personal privacy.

Participants identified instances and provided additional details, such as whether they experienced or observed the harmful behavior, the relationship between perpetrator and victim, the career stage in which the event occurred, whether the field site was in a remote or accessible location, and whether the incident was reported or not.

Eighty percent of survey participants reported experiencing at least one harmful field interaction during fieldwork; the average respondent reported five harmful interactions. Though identity-based harmful behaviors, such as inappropriate sexual behaviors and assumptions or stereotyping, were commonly reported, respondents consistently identified behaviors related to professional conduct such as gatekeeping, sabotage, and devaluation of work as the most negatively impactful. Women and nonbinary researchers were disproportionately affected by devaluation of their work, bullying, unwanted sexual attention, and invasions of privacy. Career stage also affected study respondents: Early-career researchers were more likely to face incidents such as uncomfortable sleeping situations and pressure to drink alcohol. Some harmful behaviors, such as pressure to engage in unsafe activities and bullying, were more common at remote worksites.

Seventy-five percent of the most impactful instances went unreported, highlighting a need for improved safety and inclusion training, enforced codes of conduct, and independent reporting pathways to ensure that geoscience fieldwork can be safe, fair, and ethical for all participants. (AGU Advances, https://doi.org/10.1029/2026AV002402, 2026)

—Rebecca Owen (@beccapox.bsky.social), Science Writer

Citation: Owen, R. (2026), Four in five researchers report harmful interactions during geoscience fieldwork. A new survey suggests a path forward., Eos, 107, https://doi.org/10.1029/2026EO260286. Published on 9 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Single-celled algae within delicate glass-like needles, Pseudo-nitzschia diatoms may be tiny, but they can play a huge role in the ecosystems they occupy.

“Domoic acid is rough. It’s a neurotoxin. It’s nerve damage.”

When types of Pseudo-nitzschia that make domoic acid proliferate during harmful algal blooms off California’s coast, marine mammals, seabirds, and humans who eat toxin-laced fish and shellfish can become gravely ill.

“Domoic acid is rough. It’s a neurotoxin. It’s nerve damage,” said Dave Bader, chief operations and education officer at the Marine Mammal Care Center, which rescues and cares for sick and injured marine mammals in Los Angeles County. Mass strandings of domoic acid–poisoned California sea lions on the county’s beaches were once rare but have become common in recent years. The toxin spreads through the food web as animals eat the diatoms and each other, but only some animals suffer.

This California sea lion’s curved neck and nose in the air are signs of domoic acid poisoning. Credit: Marine Mammal Care Center

In Southern California, Pseudo-nitzschia diatoms are a natural part of the phytoplankton community. For millennia, phytoplankton blooms have been tied to upwelled nutrients, which surge during La Niña and decline during El Niño. But the blooms have become more frequent and more toxic. “There’s just much more domoic acid than there used to be,” said Clarissa Anderson, an oceanographer at the University of California, San Diego’s Scripps Institution of Oceanography.

Worldwide, harmful algal blooms are growing more harmful, often for both global reasons like climate change and ocean acidification and local reasons like nutrient levels in wastewater runoff.

But how big a role do local factors play? To find out, Anderson and her colleagues modeled Pseudo-nitzschia diatoms and coastal processes in Southern California to discover how much the urban area’s wastewater and runoff affect blooms and domoic acid in a study published in Harmful Algae.

Proliferating Diatoms and Toxins

Southern California’s 23 million residents create a tremendous amount of wastewater. Treatment removes pathogens, but nutrients like nitrogen persist. Of the nitrogen that flows from land to sea in this region, nearly all of it—97%—comes from wastewater, explained Marco Sandoval-Belmar, an oceanography postdoctoral researcher at the University of California, Los Angeles, and lead author of the study. Of the remaining nitrogen, 2% is from urban or agricultural runoff. Less than 1% is natural.

Pseudo-nitzschia reproduce rapidly with nitrogen as long as they have other nutrients, particularly silicon, which they need for their glassy shells. If silicon is in short supply, the diatoms can’t reproduce, but if they still have nitrogen, they keep making domoic acid. Silicon in the region, mainly found in upwelled water, has dwindled for decades, said Anderson. With less silicon rising from the deep and more nitrogen coming from land, diatoms can become domoic acid factories.

Anderson, Sandoval-Belmar, and their colleagues added a model of how Pseudo-nitzschia proliferate and produce toxin to a widely used model of coastal ocean processes and biogeochemistry. They simulated Southern California’s coastal ocean over the years 2006 to 2017, including the nutrient-filled wastewater and runoff released into the ocean over that time. To check how closely the model run mimicked real-world blooms, they compared it to data collected as part of the Southern California Coastal Ocean Observing System over the same time frame. A second model run with clean water flowing off the coast simulated what domoic acid levels would have been like without nutrients from land.

The Los Angles Hyperion Water Reclamation Plant’s treated wastewater is released into the ocean via an underwater outfall. While most wastewater at Hyperion is still conventionally treated, advanced treatment methods are now being prototyped. Credit: Doc Searls/Flickr, CC BY-SA 2.0

According to the model runs, nitrogen from land increased domoic acid levels within 15 kilometers of the shore by about 25% on average. But these modeled toxin levels were patchy; in some places domoic acid levels increased by more than 50%. “Especially super near the major [wastewater] outfalls, there is a lot more modeled production of domoic acid,” Sandoval-Belmar said.

This algal bloom, seen off the coast of Northern California in December 2025, was responsible for the deaths of at least 9 whales near Kodiak Island, Alaska. Scientists hope that research into harmful algal blooms off the coast of Southern California could help improve understanding of blooms farther north, like this one. Credit: MODIS Land Rapid Response Team, NASA GSFC

Modeling makes a strong case that “nutrients are having an impact and widening the window of opportunity for blooms in Southern California,” said Kyla Kelly, water quality program manager at the California Ocean Protection Council, which partially funded the research. Kelly hopes that similar modeling can help reveal drivers of blooms farther north as well. “A handful of research is showing there’s different drivers in the northern versus southern California Current system, which encompasses Oregon and Washington,” she said. Blooms to the north have been linked with unusually warm water, which often occurs during El Niño.

Making Harmful Algal Blooms Less Harmful

Whenever people ask Anderson what can be done to stop harmful algal blooms, she pauses.

“They’ve been around for millennia. We’re not going to just stop these blooms.”

“It’s really a hard thing to answer, because they’ve been around for millennia. We’re not going to just stop these blooms,” she said, adding that Pseudo-nitzschia diatoms can also be helpful because they are food for marine life and generate oxygen.

But the toxin the diatoms produce is more of a problem than the blooms themselves. “We can’t prevent these events, but we can lower their total impact,” Bader said. “If we remove the wastewater outfall from the equation, we don’t have a problem really anymore, or we have a problem that’s a much different scale,” he said. Smaller blooms with less domoic acid would reduce the threat to wildlife.

This image shows the forecasted probability of domoic acid off the coast of Southern California during a Pseudo-nitzschia bloom in spring 2025, according to the C-HARM (California-Harmful Algae Risk Mapping) model run by NOAA. Credit: NOAA ERDDAP

Methods exist to scrub nearly all nitrogen from wastewater, and there is an appetite to tackle land-based sources of nitrogen in California, Kelly said. “The State Water Resources Control Board is considering water quality regulations to address ocean acidification, eutrophication, and the effects of anthropogenic nutrients on ocean waters,” Kelly wrote in an email to Eos. In addition, some wastewater treatment plants have pledged to reduce nutrients on their own. But it is not a simple fix: The changes will be costly and take decades to implement.

Though Southern California’s enormous population is contributing to the nitrogen problem, it also means there is no shortage of coastal residents looking out for animals in distress. “Keeping an eye on the ocean helps,” said Sandoval-Belmar.

—Lisa S. Gardiner (@lisasgardiner.bsky.social), Science Writer

Citation: Gardiner, L. S. (2026), Wastewater can take harmful algal blooms from bad to worse, Eos, 107, https://doi.org/10.1029/2026EO260282. Published on 8 September 2026. Text © 2026. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Enough satellite and drone imagery is now available to allow some initial analysis of the landslide that started the 26 August 2026 debris flow in Nepal and Tibet.

Much has been written over the last ten or so days about the tragic debris flow that has caused such high levels of damage and loss of life in Tibet and Nepal. The various narratives have at times been excellent, simply wrong, reflective and/or challenging. Loyal readers will know that I tend not to write about events that are being well-covered by others, so I have resisted writing whilst I have been on leave with my daughter Holly.

But it is interesting to note that little has been written about the landslide that started the terrible cascade of events. It is worth some reflection ahead of a detailed analysis that will come from the group convened by Dan Shugar to interpret the event.

There is an incredibly useful compendium of satellite images on a website compiled by the Hidenori Watanave Laboratory at The University of Tokyo. This includes images from Planet Labs, Vantor and Landsat 9 in a very accessible format. It is worth a look, not least because it has imagery of the site of the landslide both before and after failure. Of course, there is also some drone footage of the aftermath that was posted to LinkedIn by Guoxiong Zheng. This allows us to start to understand the landslide itself, but we are going to need better data to fully understand this event.

The site of the landslide was [28.2921, 85.5271]. The most recent Google Earth imagery of this site is heavily shadowed, but there is a good image from 2017:-

Google Earth image from 2017 showing the site of the 26 August 2026 landslide in Nepal.

The Watanave Lab imagery collection has a Planet Labs image from 25 August 2026 showing the site. This is lower resolution than the Google Earth image:-

Planet Labs image from 25 August 2026 showing the site of the 26 August 2026 landslide in Nepal. Image via Watanave Lab.

Comparing the two sets of images, I don’t see much that would have indicated that a failure was incipient. Indeed, perhaps the lack of obvious change is a surprise.

The Watanave Lab imagery has two post-failure images, of which this one is the more useful:-

Planet Labs image from 28 August 2026 showing the aftermath of the 26 August 2026 landslide in Nepal. Image via Watanave Lab.

Two caveats here – first, the image is draped on a DEM that won’t accurately reflect the post-failure topography (see the drone footage below). And second, there is cloud in the imagery that becomes draped on the topography, which is of course an error.

The site of the landslide had a highly complex morphology, with very steep slopes and perhaps a strongly developed overhang. One might hypothesise that this oversteepened upper slope failed catastrophically, triggering failure on the lower slope. There has been much conjecture that climate change might have played a role, and the increased occurrence of these events in general is very likely to be climate-related, but I am uncertain as to whether this particular event has a climate change signature. It is entirely possible that this was a progressive failure in a slope that was both oversteepened and deteriorating.

It is entirely possible to construct a climate change narrative for this event, but it cannot be assumed.

The landslide itself is very large. The source zone is about 2,000 metres long and the elevations are about 5,140 metres at the crown and 3,990 metres at the toe, so about 1,150 metres. This is a very steep slope.

The landslide generated a seismic signal the equivalent of a M=5.7 earthquake, indicating a volume in the order of 100 million cubic metres.

The imagery clearly shows that the shear surface was in bedrock, not within the ice or at the ice-rock boundary. It is interesting to look at the images collected by drone. This is the upper portion of the landslide scar:-

The upper part of the scar from the 26 August 2026 landslide in Nepal. Image from drone footage posted to LinkedIn by Guoxiong Zheng.

At the crown, the interface between the glacier and the bedrock is clear, confirming that this was primarily a bedrock landslide. The scar has a weak wedge shape in this area (?), probably indicating that the failure exploited existing weaknesses (as you’d expect). Is there a hint that the shear surface is weathered? I suspect so, but it is hard to be certain.

Lower down, the landslide scar is more planar and is covered with debris left behind and that has fallen from the exposed scar:-

The lower part of the scar from the 26 August 2026 landslide in Nepal. Image from drone footage posted to LinkedIn by Guoxiong Zheng.

This has now left a very steep slope, albeit one without overhangs, so the potential for further collapses needs to be considered.

The geomorphology of this area, and the slopes along the channel downstream, are now going to evolve. This could involve further collapses in the coming years.

A much more detailed review of this landslide is needed. It will be all too easy to focus on the debris flow and its terrible impacts – and this is important – but we must not lose sight of the need to understand the initial failure too.

Finally, I have seen quite a lot of commentary that this event was in some way unprecedented in scale. It was not. Three much larger landslides and debris flows are recorded in valley fills in the Pokhara area of Nepal. These events are related to earthquakes that occurred in ∼1100, 1255, and 1344 AD – i.e. in the medieval period. These three events generated about 5 km3 of sediment.

The potential for even larger landslides must be considered when proposals to mitigate these hazards through the construction of even larger dams are made.

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Source: AGU Advances

In 1967, a solar storm nearly triggered World War III by jamming early-warning radar systems in the United States, causing U.S. leaders to think the Soviet Union was responsible. Though society averted catastrophe thanks to some timely intel from solar forecasters, the threat from space weather remains real and present.

Solar, or geomagnetic, storms form as the Sun expels plasma and magnetic field from its corona during coronal mass ejections. After traversing space and encountering Earth’s magnetic field, the energy can interact with conducting materials such as the crust or ocean and induce geoelectric fields. The currents destabilize electrical transmission as they flow over the extrahigh-voltage transformers that toggle electricity voltage in the grid.

Yet despite their potential for havoc, geomagnetic storms are an underquantified threat. Existing socioeconomic assessments of space weather are often siloed by discipline and overlook the relationship between geophysical drivers and the function of the power grid.

To comprehensively assess the threat from space weather, Oughton et al. developed a novel framework to estimate the economic consequences of a 1-in-250-year (250-year, in short) geomagnetic storm in the United States. The model combines physics, engineering, and economics to characterize hazards, vulnerability in the power grid, and potential socioeconomic consequences under varying storm severities.

To validate the model, the authors compared simulated effects at electric substations to measurements taken by the Tennessee Valley Authority during the 2024 Gannon storm.

During a 100-year geomagnetic storm, 3.5 million people and 91,000 businesses are predicted to lose power, with daily economic losses of $1.22 billion. A 250-year storm, the most intense storm evaluated, would affect up to 5 million Americans and more than 135,000 businesses. Such an extreme storm would cause direct losses of roughly $980 million per day and total losses of $1.81 billion per day.

The study provides a rigorous assessment of the socioeconomic hazard posed by space weather and offers direction for investment in the power grid to safeguard against future storms. The authors note that future research should examine cascading power grid dynamics and multihazard interactions, for example, if a geomagnetic storm hit during a heat wave or hurricane. (AGU Advances, https://doi.org/10.1029/2026AV002367, 2026)

—Aaron Sidder, Science Writer

Citation: Sidder, A. (2026), The economic costs of solar storms, Eos, 107, https://doi.org/10.1029/2026EO260258. Published on 4 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
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Source: Water Resources Research

Fringed with swamps and mangroves, a swath of tropical lowland forests once covered what is now the densely populated island country of Singapore. Today, buildings, pavements, and other structures have replaced more than 60% of the original land cover. Still, urban greening efforts have kept Singapore one of the greenest cities in the world.

With limited natural water resources, Singapore has made sustainable water management a top priority. Its reliance on imported water was sharply reduced through an extensive rainwater collection network of canals, drains, and 17 reservoirs, which collectively cover about two thirds of Singapore’s land area.

However, climate change and urbanization dramatically affect hydrological processes in Singapore and other tropical urban settings around the world, posing ongoing water management challenges. New simulations by Lin Xu et al. provide the first fine-resolution picture of how natural and urban hydrologies interact to affect Singapore’s long-term, island-wide water budget.

The researchers employed an ecohydrological model specifically adapted for urban environments. Unlike models often adopted in prior studies, which mostly focused on how short-term rainfall affects local-scale flood risk, this model accounts for the nuanced interplay between the properties of urban vegetation, a changing climate, and the built environment—at an hourly timescale and a spatial resolution of 250 meters. The model can also simulate multidecadal scenarios.

First, the research team evaluated how past deforestation and urbanization have changed Singapore’s energy balance today. They found milder shifts than expected, primarily attributable to reduced transpiration, the process in which leaves release water vapor into the air. As impermeable surfaces (such as roads and pavements) increased to 35%, water runoff levels increased by 16.5%. Sensible and latent heat fluxes—measurements relevant to surface energy budget and water cycling—increased by about 4.6% and decreased by 11%, respectively.

Next, the researchers evaluated how future climate change and urbanization might affect Singapore’s hydrology. Their analysis suggests that a continued decrease in transpiration by urban plants will compensate for increased evaporation and a “thirstier” atmosphere, meaning that variations in rainfall will be the main factor influencing the future of Singapore’s water budget. However, simulations of extremely dry years, such as during El Niño conditions, highlight the possibility of severe water shortages in rainwater harvesting, which is one of the four “national water taps.”

This study could help inform future water management planning and policy in Singapore. Similar approaches could be applied to other cities around the world, including other tropical cities and cities that rely on local water resources, such as Los Angeles and Jakarta, the authors suggest. (Water Resources Research, https://doi.org/10.1029/2025WR041411, 2026)

—Sarah Stanley, Science Writer

Citation: Stanley, S. (2026), A high-resolution look at Singapore’s water budget, Eos, 107, https://doi.org/10.1029/2026EO260280. Published on 4 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
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body {background-color: #D2D1D5;} Research & Developments is a blog for brief updates that provide context for the flurry of news regarding law and policy changes that impact science and scientists today. These updates are made possible through information from the scientific community. Do you have a story about how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2026. AGU. CC BY-NC-ND 3.0
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Last weekend, flash flooding in the Grand Canyon killed two, left one missing, and forced dozens to evacuate. On Monday, the National Park Service shared that approximately 40% of the Transcanyon Waterline—the national park’s only water pipeline—had been damaged or destroyed.

Considering the ongoing discourse about the struggle to allocate the limited water supply of the Colorado River, the onslaught of water may have seemed not just tragic, but confusing.

However, flooding isn’t all that uncommon in the Grand Canyon.

 Related

•  CW3E Event Summary: August 29 Grand Canyon Flooding
•  Why the Grand Canyon flash flood was so devastating
•  Dragon Bravo Fire BAER Executive Summary
 

“Flash floods are not a new thing for this canyon or for anywhere in the Grand Canyon region,” Laura Crossey, a hydrologist at the University of New Mexico, told Scientific American.

What stood out about these monsoon rains is where they fell. Last summer, the Dragon Bravo Fire burned nearly 150,000 acres and damaged or destroyed more than 100 structures along the canyon’s North Rim. The Grand Canyon was also experiencing severe drought conditions in August, according to the Center for Western Weather and Water Extremes (CW3E).

In combination, the burn scar and the drought led to soil more susceptible to debris flows.

So, when Tropical Storm Karina (itself fueled by record-breaking El Niño conditions) began fueling monsoonal rains over the eastern Grand Canyon last week, conditions were primed for flooding. One U. S. Geological Service precipitation gauge, at Bright Angel Creek below Ribbon Falls, recorded 1.16 inches of precipitation in about 45 minutes before being damaged by flood waters. Such rainfall levels had just a 2% to 4% likelihood of occurring, according to the CW3E. Another gauge, along Phantom Creek, reported an approximately 6.5-foot rise in water height over a 45-minute period.

Credit: Center for Western Weather and Water Extremes

In August 2025, after the Dragon Bravo Fire, the Department of Interior’s Burned Area Emergency Response team took to the field “to assess post-fire threats to life, property, and critical natural and cultural resources.” Though the team found that natural recovery from the fire looked likely in most areas, they also noted that the fire could lead to stabilization issues along trails, hazardous rockfalls, and potential flood events.

“This tragedy also underscores the broader reality facing parks across the Southwest. Extreme weather, wildfire and post-fire flooding are straining landscapes, communities and aging infrastructure,” said Alex Johnson, Southwest Regional Director of the National Parks Conservation Association, in a statement. “To cope, parks need dependable funding, modern emergency systems and climate-resilient infrastructure.”

—Emily Gardner (@emfurd.bsky.social), Deputy Editor

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Editors’ Vox is a blog from AGU’s Publications Department.

In an era marked by new and accelerating global challenges, we need scientific research to provide guidance and solutions. Anthropogenic changes to the Earth’s climate, ecology, and environment are unprecedented in their speed and scale; scientific observation, prediction, and innovation will be key to finding routes forward. While public trust in science remains high, policy and decision-making can remain disconnected from scientific evidence. Data show that citations of academic papers in policy documents are lagging – and papers in the physical sciences are under-cited.

The American Geophysical Union aims to address challenges like this at all scales, catalyzing discovery and solutions not just within science, but also for society.  The research published in AGU journals – already highly cited across scientific disciplines – has also been influential in policy (Figure 1), but we’ve noticed an increasing need for expanding this potential influence and making sure scientists’ voices are heard.

Figure 1. We assessed mentions of scientific articles in policy documents published in AGU journals from 1969 to 2026.

To help bridge the gap between science and policy, we’re launching a new special collection for policy and policy-related work across seven AGU journals. We hope that this special collection will serve as a home for work at the intersection of policy and Earth, space, and environmental science, and support dialogue for an international network of scientific researchers and decision-makers.

AGU Advances, Earth’s Future, GeoHealth, Global Biogeochemical Cycles, JGR: Biogeosciences, Paleoceanography and Paleoclimatology, and Space Weather are all welcoming submissions within this new special collection, including commentaries discussing emerging policy that directly impacts Earth, space, and environmental science researchers, research articles highlighting new findings with immediate or future consequences for science and society, and assessments and other evaluative work with a direct connection to our disciplines. The call for papers also includes more specific guidance for submitters to each journal.

Global challenges require global solutions, and this special collection is intended to address policy-related issues at a global scale, especially given developing regions’ disparities in access to scientific and policy-related research. However, rapid shifts in the political landscape in the United States have also brought to light the need to preserve evidence-based research and the scientific data that supports research for informed decision making.

AGU is committed to fighting for science and has launched several special initiatives in support of this, including the Impactful Datasets in Earth, Space, and Environmental Sciences special collection and, with the American Meteorological Association (AMS), the U.S. Climate Collection. Our AGU Science Policy program continues to advocate for science and for our members within the U.S., both nationally and locally.

We look forward to receiving contributions to the new Policy and Policy-Related Research Special Collection. We also recognize that the conversation doesn’t end here. AGU is committed to supporting science and society through our programming and publications and we look forward to collaborating further with our members.   

—Kristina Vrouwenvelder (kvrouwenvelder@agu.org, 0000-0002-5862-2502); and Emille Beller (ebeller@agu.org, 0009-0009-7274-0706), American Geophysical Union, United States

Citation: Vrouwenvelder, K., and E. Beller (2026), AGU launches new special collection at the nexus of science and policy, Eos, 107, https://doi.org/10.1029/2026EO265035. Published on 3 September 2026. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 2026. The authors. CC BY-NC-ND 3.0
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Editors’ Highlights are summaries of recent papers by AGU’s journal editors. Source: AGU Advances

Electrons and ions respond differently to atmospheric winds and to magnetic fields. This generates a large-scale electrical current in the “dynamo” region of the Mars ionosphere, where the electrons preferentially gyrate around the magnetic field while the ions undergo collisions with the neutrals.

Delcourt and Mittelholz [2026] developed a “Neural-Curlometer” model – a new machine learning (neural network) computer model based on Ampere’s Law and Gauss’s Law, which they apply to analyze the magnetic field resulting from the large-scale dynamo currents and measured onboard NASA’s MAVEN satellite.

The authors find the reconstructed currents to form a hemispheric, seasonally varying vortex system in the altitude range of 125-220 km, with a transition in direction near 160 km and a correlation in the current density with the crustal magnetic field. Furthermore, the hemispheric vortex pattern is consistent with the predicted atmospheric wind circulation on Mars, as well as the transport driven by the Coriolis force and associated with seasonal CO2 condensation at the poles. The findings provide a data-driven proxy for atmospheric circulation at ionospheric altitudes and potentially serve as important new inputs for Martian general circulation models.

Left: Map of the current density of the ionospheric dynamo at 150 km altitude from the Neural-Curlometer model and using MAVEN magnetic field data in all four seasons, in the Mars Solar Orbital (MSO) frame and using a Robinson projection; the arrow lengths are proportional to the horizontal component of the current density. Right: Map of the corresponding average crustal magnetic field intensity near spring equinox. Credit: Delcourt and Mittelholz [2026], Figure 2a (left) and 2f (right)

Citation: Delcourt, T. & Mittelholz, A. (2026). Global Circulation of Martian Ionospheric Currents Revealed by Magnetometer Data. AGU Advances, 7, e2026AV002408. https://doi.org/10.1029/2026AV002408

—Andrew Yau, Editor, AGU Advances

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Humanity is certain to exceed the warming limit set by the Paris Agreement, a legally binding treaty meant to cap the world’s carbon emissions, according to a new report from the United Nations Environment Programme (UNEP). 

Now, to reduce severe threats to human health, food security, water supplies, and more, societies will need to reach net-negative greenhouse gas emissions by not only cutting those emissions, but expanding carbon dioxide removal projects, a pathway called “overshoot, peak and decline.”

The 1.5°C (2.7°F) goal “must now be approached from above.”

Following such a pathway would require virtually eliminating greenhouse gas emissions by mid-century and rapidly deploying carbon dioxide removal technologies, including conventional tactics such as planting trees and restoring ecosystems, and new ones, such as carbon capture and storage.

“This is by no means an acceptable or preferred pathway,” the report stated. “It is simply the best remaining option.”

The 1.5°C (2.7°F) goal “must now be approached from above,” Inger Andersen, the executive director of UNEP, wrote in the report’s foreword. The report is the first time that UNEP has referred to staying beneath the 1.5°C (2.7°F) warming limit as impossible rather than unlikely.

An outline of the “overshoot, peak and decline” pathway that the United Nations Environment Programme has called the “best remaining option” to prevent the worst of climate change’s impacts. Credit: UNEP

The news that Earth will likely breach this limit was expected by climate scientists: In February 2025, a pair of studies published in Nature Climate Change determined that Earth had likely already entered the 20-year period in which global temperatures would exceed 1.5°C (2.7°F). 

In order to bring global temperatures back to the 1.5°C (2.7°F) mark, Earth’s warming must not exceed 1.8°C (3.2°F), the new report states. Beyond that mark, cooling Earth back to the 1.5°C (2.7°F) level this century “becomes increasingly challenging.”

Reaching the amount of carbon dioxide removal required for the “overshoot, peak and decline” pathway would be an enormous task for the world’s governments and economies. Technologies that remove carbon from the air and store it underground are still limited in scale, and so far, just 12 projects have been successful. Just to limit warming to 1.5°C (2.7°F), even without overshooting that limit, the world would need to deploy carbon dioxide removal technologies at rates faster than those seen for solar power, which is far from the current reality. 

Scientists aren’t sure Earth’s subsurface could even store the amount of carbon necessary to keep Earth at net-zero emissions. “Just maintaining net-zero CO₂ emissions could exhaust current estimated storage capacity in sedimentary basins by 2200,” the report stated. 

 
Related

•  Read the Report: “Limiting Overshoot—Navigating Exceedance of 1.5°C and Pathways Towards Return”
•  Climate Goals Missed, U.N. Says World Must Now Remove Carbon at Scale
•  Carbon Brief: Q&A: The Current State of ‘Carbon Dioxide Removal’ Around the World
• UNEP: Overshoot Explained: 5 Things to Understand About a World Beyond 1.5°C
 

Glen Peters, a senior researcher at the CICERO Center for International Climate Research in Norway who was not involved in the UNEP report, told The New York Times that various obstacles are in the way of large-scale carbon removal projects. Large amounts of land would need to be reforested for conventional carbon removal, for instance, which could spark conflicts with agriculture. Wildfires, as well as climate change itself, could prevent or damage plant growth.

Still, a rapid upscaling of carbon dioxide removal, paired with strong governance frameworks to ensure ethical deployment, is critical, according to UNEP. Without such action, the breaching of dangerous tipping points in Earth systems, such as irreversible changes to ice sheets or the slowing of the Atlantic Meridional Overturning Circulation (AMOC), will become more likely, paired with growing human and ecological suffering. 

“We need stronger political will,” Andersen wrote. “Decisions taken now and in the next few years will determine whether viable options remain to reverse warming towards 1.5°C.”

—Grace van Deelen (@gvd.bsky.social), Staff Writer

These updates are made possible through information from the scientific community. Do you have a story about science or scientists? Send us a tip at eos@agu.org. Text © 2026. AGU. CC BY-NC-ND 3.0
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Source: Journal of Geophysical Research: Planets

This is an authorized translation of an Eos article. 本文是Eos文章的授权翻译。

木卫一（Io）是木星的第三大卫星，它不断受到木星及其另外两颗卫星——木卫二（Europa）和木卫三（Ganymede）——的引力作用而发生形变。木卫一内部由此产生的摩擦会产生极高的内部温度，从而引发遍布其表面的火山喷发。事实上，木卫一的火山活动比太阳系中任何其他天体都要活跃。

此前几乎所有对木卫一温度的观测都依赖于红外测量，而红外测量只能探测到木卫一最外层“表皮”的温度。如今，Brown等人首次测量到了木卫一的内部温度。

研究人员利用了美国宇航局“朱诺号”探测器上的微波辐射计在2023年12月和2024年2月近距离飞掠木卫一期间采集的数据，“朱诺号”自2016年以来一直在绕木星运行。

这些数据揭示了木卫一在微波波段的热辐射。微波波段的波长比红外线更长，使研究人员能够观测到木卫一表面以下数十米的深度。分析过程中，研究人员识别并剔除了部分由天空反射在木卫一表面造成的干扰信号，以确保最终获得真正反映木卫一特性的观测数据。

这些观测结果表明，木卫一表面上数十米的上层区域受到内部过程的强烈加热。与数据相符的两种可能解释是：热量可能通过近表面的导热层持续上升，或者近期熔岩流或热喷气孔释放的热量可能通过冷却的薄层地壳逸散到表面，考虑到木卫一上存在高耸的山脉，后一种解释的可能性更大。

对微波观测数据的进一步分析揭示了更多关于木卫一的信息。数据显示，木卫一的表面相对平坦，类似于地球上的平原。数据还表明，木卫一的上层密度低于固体岩石，可能类似于火山灰或浮石，而这层物质很可能位于其下方数米处密度更高的物质之上。

这些发现以及对朱诺号微波辐射计数据的进一步分析，将有助于我们更深入地了解木卫一，特别是其内部散热机制以及热量流动模式在其表面各处的差异。这项工作还有助于为未来探测木卫一或其他岩质或冰质天体的微波探测仪器的设计提供参考。(Journal of Geophysical Research: Planets, https://doi.org/10.1029/2025JE009622, 2026)

—科学撰稿人Sarah Stanley

This translation was made by Wiley. 本文翻译由Wiley提供。

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Source: Earth’s Future

Climate change is altering patterns of wildfire activity in Alaska, making fires larger and more common in some areas with historically low fire activity. Wildfires can be difficult to predict because they are affected by intricate interplays between factors including climate, ecology, and weather. But a better idea of which fire pathways are more likely is important for future fire forecasting, adaptation, and management strategies.

Littell et al. use temperature and precipitation data from an ensemble of five climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to assess how fire activity in boreal Alaska may change in the 21st century. Feeding the data into the Alaska Frame‐Based Ecosystem Code (ALFRESCO) landscape model to assess changing fire-vegetation dynamics, they present a range of fire and vegetation composition scenarios based on both moderate and high levels of future greenhouse gas emissions.

Though significant variation exists between how individual models calculate increases in burn area, the authors show that the more likely outcome under climate change, regardless of emissions pathway, is for the median annual area burned by wildfire in Alaska to increase—by more than double under a high-emissions scenario. Areas that currently see less wildfire, such as the Alaskan Arctic and western Alaska, could see up to an eightfold increase in wildfire activity. In addition, ecosystems are likely to be increasingly dominated by deciduous tree cover as spruce species are pushed out by fire.

Uncertainty over the future of Alaskan wildfires remains. Lower levels of warming combined with increased summer precipitation could keep wildfire activity within historical bounds, and the future balance of less-flammable deciduous trees to more-flammable spruce will also likely affect fire activity. The authors note one significant limitation to their current results is that the ALFRESCO model was trained on historical fire-vegetation dynamics. Future dynamics, such as increased flammability of vegetation under novel climates, could be substantially different, changing the evolution of fire activity in the region.

Key takeaways for fire managers include the fact that diversity in the age, species makeup, and spatial coverage of vegetation could potentially reduce the likelihood of larger fires. Maintaining and creating this variability in wildfire fuel through suppression, controlled burns, fuel treatments, and other methods could therefore be a useful management strategy. (Earth’s Future, https://doi.org/10.1029/2026EF008324, 2026)

—Nathaniel Scharping (@nathanielscharp), Science Writer

Citation: Scharping, N. (2026), What will the future of Alaskan wildfire look like?, Eos, 107, https://doi.org/10.1029/2026EO260278. Published on 2 September 2026. Text © 2026. AGU. CC BY-NC-ND 3.0
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