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Author(s): K. Zsukovszki, I. Papp, and L. P. Csernai

Using fully kinetic three-dimensional particle-in-cell (EPOCH) simulations, we investigate resonant planar nanoantenna configurations supporting localized surface plasmon resonances in hydrogen-rich media under irradiation by 795 nm femtosecond laser pulses with intensities of 1017–1019 W/cm2. The s…

[Phys. Rev. E 114, 035210] Published Thu Sep 10, 2026

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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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.

Rising sea levels and storm surges could cost $855 billion in economic losses across Australia by the end of the century, according to new research, the first of its kind in Australia.

From the Vredefort Dome in South Africa (the world's oldest and largest known meteorite impact structure) to the volcanic lakes of the Great Rift Valley in Kenya, Africa's landscapes hold some of Earth's oldest stories. Morocco's M'Goun UNESCO Global Geopark records more than 200 million years of geological history, while Tanzania's Ngorongoro-Lengai landscape brings together a vast caldera, an active volcano and the fossil record of Olduvai Gorge.

The Anthropocene became part of the zeitgeist after Nobel laureate Paul Crutzen launched the idea in 2000. This is the notion that a crescendo of human impacts has recently propelled Earth out of the relatively stable climatic conditions of the Holocene epoch, during which human civilization developed and flourished, to produce a new kind of planet.

Canada's last epishelf lake drained into the Arctic Ocean following the 2020 breakup of the Milne Ice Shelf and will not recover, a new study confirms.

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.

Indonesia's Mount Anak Krakatau has erupted again this week, sending plumes of volcanic ash high into the sky and disrupting hundreds of flights. More than 300,000 passengers have been affected.

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.

Southeast Asia has spent decades trying to tackle haze from forest fires. Yet every few years, the region finds itself breathing it again. The transboundary environmental problem has become a recurrent phenomenon in the region.

Since the 1950s, the Tibetan Plateau has experienced pronounced warming and wetting. However, an overall shift toward wetter conditions does not necessarily mean that drought risk has diminished. On the contrary, against the backdrop of continued warming, compound hot-dry events—characterized by the simultaneous occurrence of high temperatures and drought—have become an increasingly important climate risk across the plateau.

SummaryHessian–vector products (HVPs) provide matrix-free access to second-order information in full-waveform inversion (FWI), enabling the use of truncated-Newton updates with improved convergence. This may result in enhanced imaging of small-scale scatterers in strongly heterogeneous, high-contrast media. In the time domain, standard adjoint-based HVP derivations are often presented either via perturbation theory or via a Lagrangian (Lagrange-multiplier) framework. Although these routes are formally equivalent, their correctness hinges on a precise treatment of transpose/adjoint placement, boundary/endpoint terms, and the discrete inner product used by the numerical solver. Revisiting these derivations, we show that a commonly used Lagrangian expression for the first HVP contribution can be incorrect when the wave equation operator L is not symmetric, and that rewriting the first term of the HVP, $\mathcal {H}_1$, using L† (or equivalently, swapping the contraction order) requires accounting for the associated boundary terms, where the L† indicates the adjoint of L. To resolve this ambiguity, we provide a complete Lagrangian formulation that explicitly incorporates initial and boundary conditions, together with a Green-identity-based treatment that distinguishes purely algebraic transpose identities from true operator adjoints obtained by integration by parts. We validate the resulting gradient and HVP expressions against reference HVPs computed by automatic differentiation (AD) using an independent JAX computational graph, which we term FDCompGraph. FDCompGraph reproduces the same discrete time stepping, source/receiver injection, and convolutional perfectly matched layer (CPML) treatment as the PDE solver, enabling apples-to-apples validation after matching wavefields under identical discretization and CPML settings. Using the first-order velocity–stress acoustic vertically transversely isotropic (VTI) system with CPML (a representative case where L is non-symmetric), we demonstrate that incorrect handling of $\mathcal {H}_1$ can yield errors up to approximately 400 per cent for HVP in ε and approximately 40 per cent for HVP in δ, whereas the HVPs in Vp and ρ are numerically unaffected. We further assess numerical errors unique to HVP evaluation, which requires perturbed wavefields and their time/space derivatives. In acoustic VTI tests using the damping sponge boundary condition, we observe HVP sensitivity losses of approximately 10 per cent amplitude compared with the results obtained using the CPML boundary condition. These errors may be difficult to diagnose because the commonly used finite-difference check, H δm ≈ g(m + δm) − g(m), is itself a linear approximation, particularly when the gradient g is computed using wavefields affected by the same imperfect boundary absorption. To make accurate HVPs practical at scale, we develop Devito–Hdm, a storage- and I/O-efficient Devito-based engine for co-simulating the required forward, adjoint, tangent, and second-adjoint system, with CPML-consistent checkpointing and partially on-the-fly correlations. As an application, we perform three-parameter VP–ε–δ acoustic VTI FWI using Newton–CG across models with increasing scatterer density and compare it against standard NLCG and L-BFGS. This application shows that incorporating HVP information overall yields a more reliable recovery of small-scale scatterer perturbations at approximately the same computational cost.

SummaryDip is often read from a regularized electrical resistivity tomography (ERT) image without a parameter-specific uncertainty. Image-resolution measures describe how an inversion blurs the resistivity field, but they do not give a noise-dependent limit for the dip of a geological interface. We derive that limit from the 2.5-D forward operator using Fisher information and a Cramér–Rao bound (CRB). The background resistivity is profiled out in log-data space. For a specified structural family, the dip standard error satisfies $\sigma _\theta \ge \sigma /\left\Vert \partial g_0/\partial \theta \right\Vert _{P_{C_0}}$. We also derive a marginal bound for unknown geometry and a first-order bias caused by structural misspecification. Tests with a 30-electrode dipole–dipole array show that the maximum-likelihood estimate attains the CRB when the fitted family is correct. At 3 % noise, the single-parameter floor is 0.14–0.50○ and the geometry-marginalised floor is 0.33–0.72○. Holding a coupled geometry parameter one cell away from its true value instead produces a 3–5○ dip bias. This is 6–25 times the formal floor. An ablation attributes most of the bias to thickness, width, or depth rather than resistivity contrast. The result is conditional on the chosen model family: the CRB measures noise-limited precision within that family, whereas the bias measures the cost of using the wrong geometry. For the cases tested here, improving an independent geometric constraint is therefore more useful than further reducing data noise.

Researchers have developed a method for extrapolating sea surface temperatures from sparse data that is significantly more accurate than other commonly used computational methods and slightly more accurate than the best-performing AI model, while taking a fraction of the time to train. The work has implications for both short-term weather forecasting and longer-term climate predictions.

Across southern Europe, increasingly extreme heat, wildfire and intense rainfall are forcing planners to consider how one event can alter the risk of the next. Portugal's exceptionally wet winter and another summer of wildfire risk are an example of this. As a professor of architecture and climate change adaptation who has been following the cyclical nature of weather extremes in the Pinhal Interior region since the deadly 2017 fires, I explain why prevention must connect forests, settlements, slopes and waterways.

Radiation from space is constantly entering Earth's atmosphere, but how much of it reaches the altitudes used by commercial aircraft depends not only on height and location, but also on the activity of the sun. A new study based on high-altitude balloon measurements over southern Israel has mapped these changes through the atmosphere and found that radiation levels at aviation altitudes rise as solar activity falls.

Researchers at The University of Manchester have developed a new physics-based artificial intelligence approach that, for the first time, enables accurate global-scale predictions of how dissolved organic carbon moves between seawater and marine sediments, a crucial but previously unquantifiable component of the planet's carbon cycle.

Geochemical studies of volcanic rocks from Baffin Island, Canada, and Iceland suggest that some of the water dating back to Earth's formation may still be preserved deep within the planet. However, it has remained unclear which minerals could store such quantities of water under the extreme conditions of Earth's interior.