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Publication date: 15 September 2026

Source: Advances in Space Research, Volume 78, Issue 6

Author(s): Jalil Beyramzad, Kamran Daneshjoo, Esmaeel Khanmirza

Publication date: 15 September 2026

Source: Advances in Space Research, Volume 78, Issue 6

Author(s): D.S. Khabituev, Yu.V. Yasyukevich, V.G. Fainshtein, S.A. Yazev, A.B. Beletsky, E.I. Danilchuk, V.A. Ivanova, A.V. Oinats, M.V. Kravtsova, K.G. Ratovsky, I.D. Tkachev, V.P. Lebedev, V.P. Tashlykov, R.V. Vasilyev, G.A. Zherebtsov, A.V. Medvedev, S.N. Ponomarchuk, A.V. Podlesnyi, S.S. Alsatkin, I.I. Kovalev

Each summer, researchers from Hokkaido University returned to the Qaanaaq Ice Cap in northwestern Greenland to measure changes in the ice surface using aluminum poles drilled into the ice. Their 13-year record shows how the ice cap changed from 2012 to 2025.

Lord Howe Island sits about 600 kilometers (370 miles) off the New South Wales coast, a crescent of rainforest and sea cliffs that draws visitors to its beaches and birdlife. Few people realize they are standing on the worn-down remains of a volcano.

The Antarctic ozone hole in 2025 was one of the smallest in decades—a testament to the continuing success of international action to protect Earth's ozone layer, which shields us from the sun's harmful ultraviolet rays, according to a new report from the World Meteorological Organization (WMO).

Do forests cool the planet or warm it? It’s a deceptively simple question with no clear answer. The catch is that the same forest can push climate in opposite directions at once.

Forests are widely viewed as climate change mitigators—and planting trees as a partial climate solution—because they absorb carbon dioxide. Yet that framing is incomplete. Trees also release reactive gases called biogenic volatile organic compounds (BVOCs) that can influence cloud formation, contribute to air pollution, and extend the atmospheric lifetime of methane, a greenhouse gas that can trap about 80 times as much heat as carbon dioxide.

Although largely invisible to the public, BVOC emissions are significant. They account for roughly 90% of the global mass of nonmethane volatile organic compounds entering the atmosphere [Khan et al., 2025]. In natural habitats, forest trees are the dominant sources of BVOCs. They’re responsible for the familiar scent of pine stands and the bluish haze often seen above dense tropical canopies. Agricultural crops and wetlands are major sources in rural regions. In cities, BVOC emissions come primarily from parks, street trees, and remnant woodlands.

Accounting for the competing effects of BVOCs has become increasingly important for climate scientists, especially as forest habitats and footprints shift and land use patterns continue to change worldwide [Wang et al., 2024]. Better understanding whether, where, and to what extent these plant emissions affect the atmosphere will allow researchers to improve forecasts of air quality, cloud formation, and future warming.

From Leaves to Clouds

Whether forests cool or warm the planet depends on how BVOCs behave once they leave the foliage.

Cloud-shaping plant chemistry begins with photosynthesis in sunlit leaves.

Cloud-shaping plant chemistry begins with photosynthesis in sunlit leaves. From there, the normal steps of plant metabolism synthesize and release BVOCs. Globally, isoprene makes up the largest share of BVOC emissions and is especially emitted from many broad-leaved trees. Additional volatiles, such as monoterpenes and sesquiterpenes, are released in smaller amounts, often by conifers and stressed vegetation.

Once airborne, these invisible vapors oxidize rapidly and condense into microscopic specks known as secondary organic aerosols (SOAs). As SOAs drift and collide, they can grow into cloud condensation nuclei, the tiny seeds around which water droplets form. Particles larger than about 1 micrometer, about 1/100 the diameter of human hair, can influence cloud brightness and longevity, as well as Earth’s energy balance. The result is a chain of interactions that begins at the level of individual leaves and extends to regional and global climate systems.

These interactions are dynamic, not fixed. Rising temperatures generally amplify BVOC emissions. A 2°C–3°C rise in mean global temperature is expected to increase total BVOC emissions by 30%–45% worldwide. High-latitude, nutrient-limited ecosystems are especially sensitive. Researchers have found, for example, that isoprene emissions from Arctic sedges are exceptionally temperature sensitive, suggesting that warming could produce disproportionately large increases in emissions from these ecosystems.

But if temperatures rise beyond the range that plants can tolerate or warming is paired with prolonged drought, then photosynthesis can falter, and BVOC emissions can be suppressed. The system thus comprises a powerful and delicate feedback, in which plants respond to climate while simultaneously helping to regulate it through their effects on the clouds above.

A Climate Paradox

The paradox is that identical molecules released by living plants can either cool or warm Earth, depending entirely on the conditions in the atmosphere when and where they enter it (Figure 1).

Fig. 1. The same compounds emitted by forests can either cool or warm the atmosphere depending on background pollution levels and atmospheric chemistry. BVOCs, biogenic volatile organic compounds; NOx, nitrogen oxides. Credit: Mary Heinrichs/AGU

In cleaner air, the balance tilts toward a cooling effect of BVOCs. As SOAs seed clouds, droplet numbers increase, and clouds grow brighter. They reflect more of the Sun’s energy back into space. The longer those droplets persist, the more they extend a thin planetary shade over the landscape below.

Recent model estimates suggest that BVOC-driven aerosol effects may have a radiative cooling effect between −2.0 and −0.4 watts per square meter [Bellouin et al., 2020]. This value is smaller than the roughly 2–3 watts per square meter of warming from carbon dioxide currently. Nevertheless, the effect is large enough to shape regional weather and cloud feedbacks.

Under polluted skies, however, the same emissions can have the opposite effect. In the presence of nitrogen oxides from tailpipe exhaust, power plant emissions, and other combustion sources, for example, BVOCs help generate ozone, a greenhouse gas found in urban smog. They can also disrupt the chemistry that normally removes methane from the atmosphere, allowing it to remain aloft longer and trap more heat.

These warming pathways partially offset the cooling produced by biogenic aerosols, although current evidence indicates that the global cooling effect remains larger overall, with substantial regional variation and uncertainty among warming effects.

Temperature, sunlight, drought, and pollution thus determine whether forests act as air conditioners or furnaces with respect to warming.

The Air People Breathe

The consequences of plant vapors are not confined to clouds and climate. Biogenic volatile organic compounds (BVOCs) can also contribute to pollution.

The consequences of plant vapors are not confined to clouds and climate. BVOCs themselves can also contribute to pollution that exacerbates respiratory health conditions and leads to increased hospital emergency room visits and premature deaths.

Photochemical reactions in the air can intensify quickly above traffic corridors and rooftops, especially under summer sunlight. The ground-level ozone and SOAs (an important component of fine particulate matter) formed through reactions of BVOCs with nitrogen oxides are both harmful forms of air pollution. Ozone inflames airways in our lungs, worsens asthma, and is linked to higher mortality. Fine particles small enough to penetrate deep into the lungs are associated with heart disease, stroke, and premature death.

Haze hangs over Los Angeles, as seen from the Hollywood Hills. Credit: David Iliff/Wikimedia Commons, CC BY-SA 3.0

The risk is greatest where dense populations and human-caused emissions overlap with strong biogenic emissions, a scenario that characterizes places like Los Angeles, Atlanta, and Beijing. Even with stricter vehicle tailpipe standards and other emissions controls, ozone pollution persists in many cities around the world as heat, sunlight, and mixed emissions from anthropogenic and natural sources continue to interact.

A Gray Area of Greening Cities

Urban vegetation is one of the most visible tools that cities have for confronting another public health threat: extreme heat. Trees reduce heat exposure by shade- and evapotranspiration-driven cooling. They can also help filter pollutants from the air and are associated with benefits for mental health and well-being.

But not all trees are chemically equivalent. A recent meta-analysis covering 357 plant species found that broad-leaved trees such as oaks produce markedly different blends of BVOCs than pines and other conifers [Bao et al., 2023]. For example, 78% of broad-leaved trees emit isoprene, compared with only 48% of conifers, whereas 93% of conifers emit monoterpenes.

These emissions are also highly sensitive to climate. Another meta-analysis found that warming increased isoprene emissions globally by an average of 107% and monoterpene emissions by 60%, whereas drought reduced them by 27% and 33%, respectively [Chen et al., 2026]. Thus, the trees planted to cool tomorrow’s cities may behave differently under tomorrow’s climate conditions than they do today.

Reducing nitrogen oxide pollution decreases ground-level ozone formation, yet expanding urban tree cover may increase emissions of reactive BVOCs that offset these decreases.

This uncertainty creates a challenge for policymakers. Reducing nitrogen oxide pollution decreases ground-level ozone formation, yet expanding urban tree cover may increase emissions of reactive BVOCs that offset these decreases depending on species choice and local conditions.

A pioneering 2024 survey by the California Department of Transportation evaluated more than 260 commonly used roadside plants for their potential to contribute to ozone and fine particulate formation. The report identified willows (Salix spp.), American sweet gum (Liquidambar styraciflua), sycamores (Platanus spp.), gum trees (Eucalyptus spp.), and several oak species (Quercus spp.) among the highest BVOC emitters. In contrast, all pines (Pinus spp.) and other conifers were categorized as comparatively low emitters.

The survey’s findings underscore that urban greening strategies are not chemically neutral. Species selection can shape local atmospheric composition and influence whether vegetation improves or inadvertently worsens air quality. Questions of urban forestry, once framed mainly around shade and aesthetics, are increasingly considering how trees affect atmospheric chemistry.

Challenges for Atmospheric Modeling

Climate modelers must address three main challenges to translate the chemistry and behavior of BVOCs into realistic simulations of the atmosphere.

The first is accurately estimating the magnitudes of BVOC emissions themselves. Some analyses report uncertainties in modeled emissions estimates approaching or exceeding 100% [Wang et al., 2021]. Even for a single compound, such as isoprene, emissions can vary substantially depending on ecosystem composition. In some regions, updated land cover data reduced estimated emissions modestly, whereas in others they more than doubled them relative to estimates based on conventional land cover maps [Opacka et al., 2021].

BVOCs and their oxidation products can travel far beyond forested regions, influencing atmospheric processes well downwind of their sources.

The second challenge is that BVOC oxidation in the atmosphere remains incompletely understood. A major limitation for models has been the difficulty of representing the thousands of intermediate reactions involved in this chemistry. Recent work shows that incorporating more detailed oxidation mechanisms into current models can significantly alter predictions of SOA formation and its climatic effects, narrowing some of the models’ largest uncertainties [Zha et al., 2023].

The third challenge is one of scaling. Observations from high-altitude monitoring stations have shown that air masses containing BVOCs and their oxidation products can travel far beyond forested regions, influencing atmospheric processes well downwind of their sources [Okamoto and Tanimoto, 2016]. To capture these effects, models must account for processes occurring in individual leaves and then accurately simulate the transport and chemical evolution of BVOCs throughout the atmosphere [Guenther et al., 2012].

Although these difficulties limit our ability to resolve BVOC-driven climate feedbacks, available models have clearly revised the standard view of forests as passive carbon sinks.

Tracking the Chemical Pulse of Forests

New tools are narrowing gaps between living ecosystems and the climate models built to represent them. For decades, scientists estimated BVOC emissions by combining vegetation maps with average emission rates for different plant types and equations describing how emissions change with temperature and sunlight. In these models, forests were represented largely as static patches on a grid, with broad vegetation categories standing in for the diversity and responsiveness of real ecosystems. That simplified picture is now giving way to a far more observational, data-rich view of Earth’s vegetation.

The Model of Emissions of Gases and Aerosols from Nature (MEGAN) is one example of how that transition is occurring. MEGAN estimates BVOC emissions by combining information about terrestrial vegetation with data on environmental conditions that influence emissions. Its latest generation, MEGANv3.2, improves upon earlier versions by estimating emission factors from measurements of individual plant species rather than relying on fixed categories of plant functional types.

Using MEGANv3.2 together with time-varying satellite observations of vegetation and meteorological reanalysis data, Wang et al. [2024] estimated that average annual global BVOC emissions from 2001 through 2020 amounted to about 835 million metric tons, including 348 million tons of isoprene and 185 million tons of monoterpenes.

The atmosphere responds not simply to how much vegetation is present but to what grows where and how vegetation is influenced by its changing environment.

The new model also illustrates why representing vegetation accurately matters. Although global isoprene emissions declined slightly during the study period, regional patterns differed sharply under varying influences from changes in vegetation, temperature, soil moisture, and atmospheric carbon dioxide [Wang et al., 2024]. In Europe, for example, higher temperatures helped increase emissions, whereas higher soil moisture was more important for increasing emissions in East and South Asia.

Earlier generations of MEGAN had shown the importance of vegetation type on BVOC emissions. Guenther et al. [2012] found that tropical forests, which cover less than a fifth of Earth’s land surface, account for roughly 80% of the isoprene and terpenes emitted by vegetation and about half of other plant-emitted volatiles, whereas other forested ecosystems covering a similar area contribute only about 10% of total emissions.

Such early estimates helped establish a fundamental principle that newer models are now able to examine in greater detail: The atmosphere responds not simply to how much vegetation is present but to what grows where and how vegetation is influenced by its changing environment.

Sensing Biogenic Volatiles from Orbit

Satellites are also driving much of the shift toward better data and improved understanding. Instruments such as the Tropospheric Monitoring Instrument (TROPOMI) aboard the European Space Agency’s Sentinel-5P satellite can detect atmospheric formaldehyde, a compound formed when isoprene oxidizes in air. Because isoprene is the dominant BVOC emitted by many forests, formaldehyde serves as a large-scale chemical fingerprint of plant emissions.

From hundreds of kilometers overhead, satellite instruments like TROPOMI and the Cross-track Infrared Sounder now allow a comparison of modeled emissions with real atmospheric chemistry across continents rather than at only a scattering of field sites.

Measurements of atmospheric formaldehyde reveal regions where vegetation releases large quantities of reactive gases. Because formaldehyde forms during the oxidation of plant-emitted compounds such as isoprene, these observations provide a global view of the chemical exchanges linking forests, clouds, air quality, and climate. These data, collected by the Sentinel-5P satellite, reflect averaged formaldehyde concentrations across the globe from 1 March to 31 May 2026. Credit: Sentinel-5P Product Algorithm Laboratory; contains modified Copernicus Sentinel-5P/TROPOMI data

Satellite observations have already revealed that even widely used emission inventories can contain substantial regional biases. For example, a prior version of MEGAN was found to overestimate total African isoprene emissions by 22%—and emissions in the central African rainforest by 43%—while underestimating emissions from southern deciduous forests by 21% [Marais et al., 2012]. Satellite observations have also shown that some mismatches between observations and models arise not from incorrect emissions estimates, but from incomplete understanding of atmospheric oxidation chemistry, particularly that of isoprene [Wells et al., 2020].

Other satellites observe plants more directly. Missions such as NASA’s Orbiting Carbon Observatories (OCO-2 and OCO-3) measure solar-induced fluorescence emitted by chlorophyll during photosynthesis. Because the amount and composition of BVOC emissions can change with plant productivity and metabolic activity, these data help to determine when ecosystems are active and how emissions respond to drought, heat waves, and seasonal change.

Continuing to Reveal Ecosystem Influences

The behaviors of clouds, aerosols, and tropical ecosystems still pose major challenges for atmospheric modeling, as does resolving the detailed chemistry of BVOCs. Thousands of reactions happen in air and aerosol droplets, and no satellite or global model can track them all in full.

Yet the atmosphere above forests is no longer being inferred and approximated from temperature curves or simplified assumptions. Innovative models and observing technologies are linking forest emissions to the beat of photosynthesis itself and revealing how ecosystems continuously influence climate, clouds, and air quality through dynamic chemical exchanges once treated as background noise.

References

Bao, X., et al. (2023), A meta-analysis on plant volatile organic compound emissions of different plant species and responses to environmental stress, Environ. Pollut., 318, 120886, https://doi.org/10.1016/j.envpol.2022.120886.

Bellouin, N., et al. (2020), Bounding global aerosol radiative forcing of climate change, Rev. Geophys., 58(1), e2019RG000660, https://doi.org/10.1029/2019RG000660.

Chen, J., et al. (2026), Global variability in isoprenoid emissions: Divergent responses to warming and drought driven by physiochemical controls, Plant Cell Environ., 49(8), 5,294–5,312, https://doi.org/10.1111/pce.70536.

Guenther, A. B., et al. (2012), The Model of Emissions of Gases and Aerosols from Nature version 2.1 (MEGAN2.1): An extended and updated framework for modeling biogenic emissions, Geosci. Model Dev., 5(6), 1,471–1,492, https://doi.org/10.5194/gmd-5-1471-2012.

Khan, M. A. H., et al. (2025), Isoprene emissions, oxidation chemistry and environmental impacts, Atmosphere, 16(3), 259, https://doi.org/10.3390/atmos16030259.

Marais, E. A., et al. (2012), Isoprene emissions in Africa inferred from OMI observations of formaldehyde columns, Atmos. Chem. Phys., 12(14), 6,219–6,235, https://doi.org/10.5194/acp-12-6219-2012.

Okamoto, S., and H. Tanimoto (2016), A review of atmospheric chemistry observations at mountain sites, Prog. Earth Planet. Sci., 3, 34, https://doi.org/10.1186/s40645-016-0109-2.

Opacka, B., et al. (2021), Global and regional impacts of land cover changes on isoprene emissions derived from spaceborne data and the MEGAN model, Atmos. Chem. Phys., 21(11), 8,413–8,436, https://doi.org/10.5194/acp-21-8413-2021.

Wang, H., et al. (2021), A long-term estimation of biogenic volatile organic compound (BVOC) emission in China from 2001–2016: The roles of land cover change and climate variability, Atmos. Chem. Phys., 21, 4,825–4,848, https://doi.org/10.5194/acp-21-4825-2021.

Wang, H., et al. (2024), Regional to global distributions, trends, and drivers of biogenic volatile organic compound emission from 2001 to 2020, Atmos. Chem. Phys., 24(5), 3,309–3,328, https://doi.org/10.5194/acp-24-3309-2024.

Wells, K. C., et al. (2020), Satellite isoprene retrievals constrain emissions and atmospheric oxidation, Nature, 585(7824), 225–233, https://doi.org/10.1038/s41586-020-2664-3.

Zha, Q., et al. (2023), Oxidized organic molecules in the tropical free troposphere over Amazonia, Natl. Sci. Rev., 11(1), nwad138, https://doi.org/10.1093/nsr/nwad138.

Author Information

Dennis Clark (drdennisclark@gmail.com), Arizona State University (retired), Tempe

Citation: Clark, D. (2026), Chemical conversations between forests and the sky affect air quality, clouds, and more, Eos, 107, https://doi.org/10.1029/2026EO260295. Published on 18 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.

Venus’s pale face enshrouds a hostile reality unfolding beneath its clouds, one that’s inhospitable for life-forms as we know them. Acidic downpours and a crushing carbon dioxide–rich atmosphere lead to blistering surface temperatures of about 467°C (872°F) and atmospheric pressure about 93 times that of sea level on Earth.

Yet the clouds themselves, made almost entirely of sulfuric acid, have held astrobiologists’ curiosity for decades, especially in the upper reaches where the ambient conditions can host liquids and organic molecules brought by meteorite showers. Some see the clouds as an opportunity to test whether life-forms not only can survive concentrated sulfuric acid but also rely on it instead of on water.

In recent years, Massachusetts Institute of Technology planetary scientist Sara Seager and her team have demonstrated how the chemical bonds in amino acids and nucleic acid bases—the building blocks of proteins and DNA and RNA, respectively—can survive in concentrated sulfuric acid. The more concentrated sulfuric acid gets, the fewer water molecules are present to trigger the hydrolysis that breaks the molecule’s chemical bonds.

“This shouldn’t even be happening, and yet it does.”

In a study published in the Proceedings of the National Academy of Sciences of the United States of America, the team shows that some peptides—or chains of amino acids—can also remain intact in concentrated sulfuric acid. And they can go a step further, folding into a distinctive knot shape called an omega loop that could give these chains biological functions.

“This shouldn’t even be happening, and yet it does,” said coauthor Janusz Petkowski, an astrobiologist at Wrocław University of Science and Technology in Poland. He’s a longtime collaborator of Seager’s, who will assume an appointment at the University of Toronto in October.

In finding these shapes, the team has done away with the assumption that concentrated sulfuric acid destroys every peptide it comes in contact with. The finding could mean expanding the search for signs of life beyond Earth to new environments previously considered too hostile to support biological functions.

On Omega Loops

Omega loops are one of many shapes peptides can fold into in nature and are typically known to occur in water-based chemistry. Scientists didn’t think such bonds could exist in concentrated sulfuric acid; it was thought that the presence of excess protons and hydrogen bonds would inhibit folding or unfurl any 3D structure.

In the new work, researchers tested three synthesized peptides. While in water, the peptides arranged themselves as flat sheets without folding. In concentrated sulfuric acid, they folded into omega loops.

Not every peptide can remain stable in the acid, let alone fold. A few years ago, Seager’s team reported dipeptides degrading in the acid. But the latest study has astrobiologists reconsidering commonly held assumptions about organic compounds’ behavior in the medium.

“The cool part is they find some peptides are stable, some are not,” said Martin Rahm, a quantum chemist and astrobiologist at Chalmers University of Technology who was not involved in the study. Commenting on the omega loop, he said, “Seemingly, this is not like a random coil.”

However, Rahm was “less sure” about interpreting these peptides as bearing omega loops. Researchers used a spectroscopic technique called nuclear magnetic resonance to identify the structures, applying a magnetic field to the peptides and observing their atoms realign. But the researchers’ modeling software wasn’t designed to interpret structures in sulfuric acid–based media.

Though concentrated sulfuric acid is a “severely understudied” solvent, according to Petkowski, he said the team took care to adopt controls to avoid bias in their structural models, finding the three peptides tested bore omega loops of “slightly” different curvatures. The loops reemerged under every assumption they varied and tested for.

Life in an Acid Environment

It may be too early to speculate whether these omega loops have biochemical functions, in part because the study itself doesn’t necessarily point to this. “If they all fold into the same thing (omega loops), that might actually be bad for life,” Rahm said. The reason is that none of the peptides would fold into the other structures necessary for life as we know it, such as sheets and helices.

“From an astrobiological point of view, there could be sulfuric acid in many places and likely on Venus. So then, understanding what could survive in it, what kind of chemistry that can happen, would be important regardless [of] if it’s related to life or not.”

“There is a lot of work ahead of us,” Petkowski said. While he agreed with Rahm about the ubiquity of omega loops not necessarily pointing to life, he noted the team has only just begun experimenting with various peptides, exploring the many possible shapes peptides can fold into and amino acid sequences beyond the ones found in life on Earth. “One of the avenues of research is essentially looking at sulfuric acid as a solvent for life.”

“From an astrobiological point of view, there could be sulfuric acid in many places and likely on Venus,” Rahm said. “So then, understanding what could survive in it, what kind of chemistry that can happen, would be important regardless [of] if it’s related to life or not.”

That way, he added, “we can understand what we find when we go there.”

—Karthik Vinod (@karthikvin2000), Science Writer

Citation: Vinod, K. (2026), Venusian sulfur clouds might not be so inhospitable after all, Eos, 107, https://doi.org/10.1029/2026EO260298. Published on 18 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.

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

Extreme heat events are an increasing threat to human health and ecosystem sustainability. While their rising frequency under global warming is well documented, much less is known about how their seasonality is changing, including whether extreme heat is occurring earlier or later in the year, potentially catching societies and ecosystems unprepared.

Ivanovich et al. [2026] characterize global changes in the seasonality of extremely dry and humid heat events using data from the Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) over the period 1980-2024. Changes in seasonality are assessed by comparing the distribution of extreme heat events during 1980-1989 with that of the most recent decade in the historical record.

The results reveal substantial shifts in extreme heat seasonality over the past 45 years, with both dry and humid extreme heat seasons expanding across much of the globe. Importantly, these changes are often asymmetric. In regions such as western Europe and northeastern Russia, changes are dominated by an increase in pre-season extremes-analogous to springtime events in the midlatitudes. In contrast, much of the United States, eastern Europe, and eastern China have experienced stronger changes in late-season extremes.

The study also highlights important regional departures from the broader global trend. Although previous research has shown that the average warm season is lengthening substantially across the midlatitudes, some regions, including eastern Russia, have experienced a contraction of the extreme heat season. These regional asymmetries suggest that local and regional climate processes can modify, and in some areas, even outweigh the broader influence of global warming.

By revealing not only where extreme heat seasons are expanding, but also when within the year the greatest changes are occurring, these findings provide a new perspective on evolving heat risks and can help inform climate adaptation and risk-mitigation strategies.

Citation: Ivanovich, C. C., Cook, B., & McDermid, S. (2026). Extreme dry and humid heat seasons are changing asymmetrically. AGU Advances, 7, e2026AV002516. https://doi.org/10.1029/2026AV002516

—Alberto Montanari, Editor-in-Chief, 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.

Mount Timpanogos, towering 7,000 feet (2,100 meters) above Utah Valley, is more than an iconic view and beloved hiking destination. Snowmelt from mountains like these provides about 95% of Utah's water supply. Hotter, drier conditions have led to water conservation statements from both religious and state leaders.

On June 29, 2026, the snow accumulated by Switzerland's glaciers over the course of the previous winter had melted. Known as Glacier Loss Day, this date marks the point at which further melting begins to erode the glaciers' mass until snow accumulation resumes in the fall. Matthias Huss, the network head of Glacier Monitoring in Switzerland (GLAMOS), told Agence France-Presse (AFP) that this year's Glacier Loss Day was "three months too early, compared to a healthy state."

Nitrogen is a key nutrient because it fuels the growth of plankton, which forms the basis of the marine food web. Two opposing processes determine the global nitrogen cycle: nitrogen fixation and denitrification.

SummaryElectromagnetic induction logging-while-drilling tools measure real-time electromagnetic data to characterize the electrical properties of formations, thereby supporting geosteering decisions. The multiscale structures formed by heterogeneous fractures within complex reservoirs lead to electromagnetic field discontinuities, which in turn limit the accuracy of reservoir evaluation. To elucidate the mechanisms by which multiscale fracture conductivity and spatial distribution influence the attenuation of the electromagnetic field, a discontinuous Galerkin method based on vector basis functions is developed, using the open-source finite element library deal.II, for modelling complex fracture clusters. To reduce the number of elements associated with the explicit volumetric discretization of fractures and truncate the computational domain, the impedance transition boundary condition that treats the fractures as element interfaces and the perfectly matched layer approach are employed. A goal-oriented adaptive mesh refinement strategy based on element-wise residuals and interelement field jumps is adopted to flexibly refine the mesh near the transmitter–receiver system and fractures, since the complex distribution of field discontinuities induced by fracture clusters renders empirical mesh refinement inadequate. The numerical results validate the accuracy and performance of the algorithm. For a layered fracture model, the numerical accuracy is assessed by comparison with the semi-analytical solutions from the open-source software empymod. In interlaced fracture models with different in-plane dimensions, the flexibility and adaptability in modelling fractures are demonstrated by the mesh distributions after adaptive refinement. For fracture cluster models, an advantage in computational efficiency over the finite element method for complex fracture networks is demonstrated as fracture complexity increases. These results demonstrate the applicability to electromagnetic induction logging-while-drilling modelling of fractures in conductive-to-moderately resistive sedimentary formations, with improved computational efficiency and modelling flexibility.

SummaryGlobal Navigation Satellite System (GNSS) technology and Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry provide essential observational constraints for monitoring terrestrial water storage (TWS) changes. In this study, we develop a spatiotemporally constrained joint inversion model that inverts GNSS and GRACE observations to estimate reliable TWS changes over Brazil from January 2008 to July 2016. We evaluate the performance of the spatiotemporally constrained joint inversion model using both closed-loop simulation and independent GNSS surface displacement observations. The simulation results indicate that the joint inversion results using spatiotemporal constraints outperform GNSS-only solutions, GRACE-only solutions, yielding improved accuracy and reliability than joint inversion results with spatial constraints. The corresponding standard deviations are 45.94 mm, 57.44 mm, 52.53 mm, and 48.88 mm, respectively. Analysis from the measured data shows that vertical displacement time series simulated from TWS changes derived from spatiotemporally constrained joint inversion indicate higher consistency with GNSS-observed surface displacement time series at nine GNSS stations compared with the GNSS-only, GRACE-only (from CSR-M), and the joint inversion results with spatial constraints. The corresponding standard deviations and correlation coefficients are 1.93 mm & 0.92, 2.54 mm & 0.87, 4.45 mm & 0.74, and 1.94 mm & 0.91, respectively. Meanwhile, the joint inversion results from measured GNSS and GRACE data using spatiotemporal constraints show lower uncertainty and higher stability than those of GNSS-only and joint inversion results with spatial constraints. The proposed inversion model provides an alternative means to fully exploit the potentials of GNSS and GRACE technologies for integrated monitoring of TWS changes.

The global water cycle is becoming increasingly unbalanced. Extreme droughts and floods are the result. This is shown in this year's report by the World Meteorological Organization (WMO) on the state of global water resources, "State of Global Water Resources 2025," which was published today.

An international team of glaciologists and climate scientists, including professor Bethan Davies from Newcastle University, carried out a rapid scientific analysis and identified the role of climate change and its impacts on the high-altitude landscape.

Understanding how wind changes in response to global warming is necessary for accurately modeling climate and weather, identifying risks to infrastructure, and assessing global wind power capacity.

How deep is the deepest ocean—and how precisely can we actually measure it? A Japanese research team led by the National Institute of Polar Research (NIPR), SOKENDAI, the University of Tokyo and other Japanese institutions has mapped the Challenger Deep in the Mariana Trench using the EM124 multibeam echosounder aboard the research vessel Hakuho-maru. Their study is published in the journal Scientific Data.

Rivers across the globe in 2025 had one of the driest years in more than three decades, according to a new report from the World Meteorological Organization (WMO). It shows a continuation of the long-term decline in Earth's freshwater storage and glacier retreat—trends with serious implications for people and economies in the future.

As the 2026 El Niño intensifies across the Amazon, new research highlights the urgent need to better protect the region's remaining forests from disturbances.

Mysterious trenches stretching for kilometers across southern Australia's Nullarbor Plain have been revealed as the surface footprints of deep, hidden ancient cave systems.