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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.

Advocates, scientists, doctors, members of Congress, kids, parents, and other individuals spoke out in a series of hearings last week to let the Environmental Protection Agency know how they feel about a potential sea change in climate and environmental policy: the proposed repeal of the 2009 Endangerment Finding. 

 
Related

•  Submit Your Own Public Comment
•  EPA Releases Proposal to Rescind Endangerment Finding
•  Public Commenters Overwhelmingly Oppose EPA’s Plan to Curtail Key Climate Protections (Mother Jones)
•  What’s Changed—and What Hasn’t—Since the EPA’s Endangerment Finding
•  Get Involved: AGU Science Policy Action Center
 

In 2009, the EPA found that current and projected concentrations of greenhouse gases threatened the public health and welfare of current and future generations. The finding is the legal underpinning for many EPA greenhouse gas regulations. The EPA announced a proposal to rescind the finding on 29 July at an auto dealership in Indiana. If finalized, the proposed rule would repeal “all greenhouse gas emissions regulations for motor vehicles,” according to the EPA.

Day 1 of public hearings, 19 August, opened with remarks from Aaron Szabo, assistant administrator in the Office of Air and Radiation. Szabo indicated the EPA’s proposal to reconsider the Endangerment Finding was aligned with President Trump’s commitment to “unleash American energy, lower costs for Americans, [and] revitalize the American auto industry.”

The proposal was open for public comment from 19-22 August, and remains open for written submissions.

The following nearly 12 hours of testimonies included a series of comments from state attorneys general, pleas from parents and children concerned about respiratory health, and physicians arguing that the Endangerment Finding protects their patients. 

Leslie Glustrom, a biochemist from Colorado, is speaking with a hoarse voice. Wildfire smoke in the state “makes it very difficult for me to speak, so hopefully you will take that as part of the evidence in this record,” she said.

— Eos (@eos.org) 2025-08-19T13:08:58.771Z

The vast majority of speakers asked the EPA not to revoke the Endangerment Finding, and many said the proposal to do so countered EPA’s mission to protect human health and the environment.

@agu.org's own Elizabeth Landau is next up. “I am testifying on behalf of AGU and its scientists, who affirm that climate change, which is unequivocally driven by human activities that increase greenhouse gas emissions, is endangering human health and welfare in the US and globally,” she said.

— Eos (@eos.org) 2025-08-19T18:39:10.743Z

The next day, hearings resumed after additional comments from Szabo and the EPA’s Bill Charmley, director of the agency’s Assessment and Standards Division. Charmley said even after the hearings, anyone could still send the EPA written comments, and that the EPA would provide a written response to the testimonies in the near future.

Representatives from multiple religious organizations provided testimonies against the EPA proposal, arguing that members of certain faiths have a religious responsibility to protect the environment and keep children and vulnerable people safe from the health harms that climate change brings. 

Victoria Goebel, also EEN, says that the Bible calls us to ask justly, and that we cannot do that while ignoring the unequal impacts of climate change.Heat waves cause >12,000 deaths every year & that number will only grow. She says the proposal is a threat to life & calls this a pro-life issue.

— Eos (@eos.org) 2025-08-20T14:54:53.134Z

Melanie Aron, co-chair of the Jewish Earth Alliance, said her mother, uncle, and many members of her congregation have asthma."Air quality is key to their survival," she said. "I believe it is our duty to preserve God's creation and to act as stewards, passing that gift on to future generations."

— Eos (@eos.org) 2025-08-21T14:16:55.804Z

Days 3 and 4 included hour upon hour of additional testimonies, still almost entirely against the proposal. 

Clean air advocacy groups, such as Moms Clean Air Force, had a strong showing at the hearings. Many parents affiliated with such groups recounted stories of watching their children suffer from asthma attacks, heat-related health problems, and the stress of growing up in a quickly changing world. 

Stephanie Hernandez from D.C. laments that she couldn't let her daughter play outside this summer due extreme heat & last summer due to smokey skies. "Climate change has influenced our family planning," saying she and her husband don't know if they want to have another child in a worsening climate.

— Eos (@eos.org) 2025-08-21T12:24:12.532Z

Charlie Inglis, age 13, said the repeal would mean "moving backwards" as a country."I speak for my generation when I say that the world we will inherit will be in shambles if we permit actions such as this," he said. "Climate change isn’t some far-off future problem. It’s happening right now."

— Eos (@eos.org) 2025-08-22T15:19:15.701Z

By our count, at the end of the four full days of public hearing testimony, we’d heard hundreds of Americans speak out against the EPA proposal and fewer than 20 speak in favor. Those in favor of rescinding the Endangerment Finding included representatives from the American Petroleum Institute, the CO2 Coalition, and auto industry trade groups, as well as Kathleen Sgamma, an oil and gas advocate who was under consideration to lead the U.S. Bureau of Land Management but withdrew.

—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 how changes in law or policy are affecting scientists or research? Send us a tip at eos@agu.org. Text © 2025. 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.

A new study has uncovered a surprising and concerning paradox: although Earth's vegetation cover has expanded dramatically over the past four decades, this widespread "greening" trend is often associated with a decline in soil moisture, particularly in water-scarce regions. The study is published in Communications Earth & Environment.

Plants use nitrogen to produce proteins, enzymes, and chlorophyll: all necessary components to perform photosynthesis, in which plants remove carbon from the atmosphere and store it in their leaves, roots, and soil.

However, though the atmosphere is made up of more than 78% nitrogen, the element is unusable for plants in its natural form. Tiny microorganisms called diazotrophs are responsible for “fixing” nitrogen into a form that plants can absorb and use. Diazotrophs live in the soil and in living and decaying plants, creating important partnerships with both naturally growing vegetation and agricultural crops.

Because plants need the nitrogen to grow and remove carbon from the atmosphere, understanding the global distribution of biological nitrogen fixation (BNF) is crucial for building accurate climate models.

But a new study makes a surprising update to global BNF estimates: Forests, grasslands, and other natural areas may have access to between a quarter and two thirds less biologically fixed nitrogen than previously thought. In previous studies, most field measurements of BNF in natural settings were taken from locations such as tropical forests, where nitrogen-fixing organisms are 17 times more abundant than the global average, creating an overestimation of nitrogen availability. This new work, coauthored by a team of 24 international scientists, examines a broader range of ecosystem types and provides a more detailed picture of the global distribution of nitrogen fixation.

Modernized Mapping

A group of researchers, many of whom are involved in the new study, first published a paper on how to model BNF in 1999, explained lead author Carla Reis Ely, an ecosystem ecologist at the Oak Ridge Institute for Science and Education. “But they knew that there were some issues, particularly with data on the abundance of nitrogen fixers, that needed to be addressed.”

The scientists involved with the updated project started by reviewing a compilation of field measurements and distribution data on BNF across natural ecosystems. They found that the sampling bias in past research had produced an overestimation of global nitrogen availability.

Reis Ely said that “it makes sense” that scientists hoping to measure BNF would do their research in places where they know BNF is occurring. “It’s very hard to propose a project where scientists were going to go to a place to measure nitrogen fixation where they know nitrogen fixation is not happening.”

They compiled more than 1,100 existing measurements of BNF rates from natural field sites, ranging from tropical forests to the Arctic. In doing so, they aimed to build a much larger and more representative dataset on how common nitrogen-fixing organisms and their hosts (such as shrubs and mosses) are across various regions and ecosystems. Once they had gathered and organized the measurements of BNF rates from specific sites, they upscaled those rates to estimate and map global nitrogen fixation rates for each of Earth’s biomes.

From Forests to Farms—and Beyond

According to the study’s findings, the amount of nitrogen fixation by microbes in natural environments is approximately 25 million tons lower than previously estimated.

According to the study’s findings, the amount of nitrogen fixation by microbes in natural environments is approximately 25 million tons lower than previously estimated—the equivalent of 113 fully loaded cargo ships. Most of it occurs in tropical forests and drylands, but Reis Ely noted that soils, biocrusts, mosses, and lichens also conduct high amounts of nitrogen fixation.

Though naturally occurring nitrogen fixation is lower than previous estimates, agriculturally based nitrogen fixation has actually been underestimated, the researchers discovered after sorting through thousands of measurements of agricultural BNF. When natural and agricultural datasets were combined, “we found both lower natural nitrogen fixation and higher agricultural nitrogen fixation than prior estimates, [indicating] an increasing human signal on this essential process worldwide,” said Steven Perakis, an ecologist with the U.S. Geological Survey at the Forest and Rangeland Ecosystem Science Center and one of the study’s authors.

Crops like soybeans and alfalfa host bacteria that are fixing much more nitrogen than the natural systems that they replaced were fixing. Even though agricultural nitrogen-fixing crops cover only 6% of Earth’s land, they have boosted global nitrogen fixation by 64% since preindustrial levels.

This increase comes with pros and cons: Nitrogen-fixing crops can help feed Earth’s growing population, and they tend to be more eco-friendly than crops requiring chemical fertilizers. But too much nitrogen can upset the nutrient balance in soils and threaten biodiversity by feeding the growth of invasive plants. Further, excess nitrogen can be converted into the greenhouse gas nitrous oxide, and runoff from these soils can leach into groundwater and cause algal blooms.

“It’s a Goldilocks sort of thing. You want just enough, but not too much, for healthy functioning of ecosystems.”

“Less nitrogen fixation in natural areas could mean reduced capacity [for plants] to uptake carbon from the atmosphere and help mitigate climate change,” Reis Ely said. “On the other hand, if we underestimate how much agricultural nitrogen fixation is happening, we are also underestimating how much excess nitrogen we are adding to natural environments.”

Understanding this balance has implications for estimating nitrogen needs in agriculture as well as how forests grow and store carbon as carbon dioxide levels rise. “It’s a Goldilocks sort of thing. You want just enough, but not too much, for healthy functioning of ecosystems,” said Eric Davidson, a biogeochemist at the University of Maryland Center for Environmental Science who was not involved in the study.

With this new dataset, researchers can now update their models, which may have been under- or overestimating the nitrogen fixation occurring in natural and agricultural settings. Correct estimates can factor into plans for mitigating climate change. “Could these numbers, these global estimates, change in the future?” Davidson said. “Yes, they could with better understanding. But for the time being, it would appear that this is a significant improvement.”

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

Citation: Owen, R. (2025), Nitrogen needs could be limiting nature’s carbon capacity, Eos, 106, https://doi.org/10.1029/2025EO250312. Published on 25 August 2025. Text © 2025. 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: Journal of Advances in Modeling Earth Systems

What determines whether a cloud produces rain? This question has been challenging atmospheric scientists for decades due to difficulties in validation with real-world observations alone.

Chen et al. [2025] used the Pi Cloud Chamber at Michigan Technological University to provide steady, repeatable laboratory measurements for a range of aerosol injection rates. The scientists tested high-resolution numerical models of varying complexity, from a one-dimensional turbulence model to 3D large-eddy-simulations. Each model simulated how rapidly injected aerosols activate into droplets, grow, and fall out within the turbulent, moist chamber.

All models exhibited similar trends in droplet number concentration and mean droplet size in response to variations in the aerosol injection rates, but the exact values for a given injection rate differed greatly. These differences arose from how models represented processes such as droplet formation, particle loss through chamber’s bottom and sidewalls, near-wall moisture exchange, and turbulence properties. Despite these disparities, the models agreed on key scaling relationships between aerosol injection rates and droplet properties, consistent with both chamber measurements and theory.

The results highlight the unique value of laboratory facilities for benchmarking and improving cloud microphysics in models and point to priorities for future work to better constrain models and reduce uncertainty. More broadly, this first-of-its-kind model intercomparison demonstrates how laboratory measurements can inform and improve model representation of cloud-aerosol interactions.

Citation: Chen, S., Krueger, S. K., Dziekan, P., Enokido, K., MacMillan, T., Richter, D., et al. (2025). A model intercomparison study of aerosol-cloud-turbulence interactions in a cloud chamber: 1. Model results. Journal of Advances in Modeling Earth Systems, 17, e2024MS004562. https://doi.org/10.1029/2024MS004562

—Jiwen Fan, Editor, JAMES

Text © 2025. 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.

New research shows that isotopic signatures of the EASM (East Asian Summer Monsoon) during Dansgaard-Oeschger (DO) events are not uniform but rather reflect diverse changes in response to subtle variations of the Westerlies' position.

Worldwide, an estimated 440 million people were exposed to a wildfire encroaching on their home at some point between 2002 and 2021, new research shows. That's roughly equivalent to the entire population of the European Union, and the number has been steadily rising—up 40% over those two decades.

The wetlands found across the Rocky Mountains of Colorado just below tree line are magical places. Dripping with mosses and deep green sedges, these open expanses flanked by evergreens are a breathtaking sight for passing hikers. Moose graze there, and elk gather during their mating season.

SummaryPermafrost degradation in the Arctic is both an indicator of, and contributor to warming global temperatures. In addition to the global impact of thawing permafrost, at the local scale permafrost degradation can result in infrastructure damage, ecosystem changes, chemical and microbial releases, landfill leaks, and river bank erosion. As such, accurate mapping and monitoring of the in-situ permafrost extent is crucial. Differentiation of frozen and thawed arctic soils is commonly achieved through electrical geophysical imaging methods; however, recently a hysteresis-like phenomenon was observed in the electrical conductivity of soils undergoing freezing followed by thawing. This phenomenon can result in over an order of magnitude difference in conductivity when measured on the same sample at precisely the same temperature. Here, we explore this effect in a clean sand with low surface conduction and a frost-susceptible clay-rich soil with relatively higher surface conduction. The unsaturated samples were prepared at a moisture content of 16.5 per cent by weight. Each soil was evaluated under four different NaCl pore-fluid conductivities 10 ppm, 100 ppm, 1000 ppm, 1000 ppm. We then developed a model to simulate the full hysteresis loop for the soil. In both cases the hysteresis effect was clearly observed in the real component of the conductivity. In the frequency dependent imaginary conductivity response only the frost-susceptible soil demonstrated consistent signs of hysteresis along with a soil-specific frequency response.

SummaryDownward continuation is a very interesting approach to enhance the information content of potential field data. However, the calculation of the downward continuation represents a fundamental challenge due to its inherent instability. In this study, a strategy to perform high-order vertical derivatives using the β-VDR method is introduced, called the generalized β-VDR method. Testing on a noisy synthetic model shows that the proposed strategy has the lowest noise compared to other methods. Based on stable vertical derivatives computed by using the generalized β-VDR method, a stable downward continuation method is also presented to enhance the information content of potential field data. The applicability of the generalized β-VDR downward continuation algorithm is demonstrated on both synthetic and real field gravity anomalies and compared to other downward continuation algorithms. In the case of synthetic examples, the proposed method provides sharper images and estimates more accurate amplitudes than other algorithms, even continuing the field to a level close to causative bodies. The real application shows that the proposed algorithm can give a meaningful result that agrees well with seismic data along a profile in the area.

Publication date: Available online 7 August 2025

Source: Advances in Space Research

Author(s): Ifeoluwa Adawa, Yuichi Otsuka, Moataz Abdelwahab, Ayman Mahrous

Global sea-level change has now been measured by satellites for more than 30 years, and a comparison with climate projections from the mid-1990s shows that they were remarkably accurate, according to two Tulane University researchers whose findings were published in Earth's Future.

Phytoplankton—microscopic algae that form the base of ocean food webs—have long been viewed as transient players in the global carbon cycle: They bloom, die, and the carbon they contain is quickly recycled back into the ecosystem.

The power of a tornado can inflict tremendous damage on residential property, but the impact is also felt by nearby homeowners, even when their property is unscathed.

All the critical minerals the U.S. needs annually for energy, defense and technology applications are already being mined at existing U.S. facilities, according to a new analysis published in the journal Science.

Source: Global Biogeochemical Cycles

Throughout the first half of 2020, average monthly temperatures in Siberia reached 6°C above the norm. The situation climaxed on 20 June, when the temperature in the town of Verkhoyansk climbed to 38°C (100.4°F), the highest temperature ever recorded north of the Arctic Circle. With the extreme heat came wildfires, insect outbreaks, and thawing permafrost.

Now Kwon et al. suggest that the effects of the 2020 heat wave were still detectable the following year in the form of warmer- and wetter-than-usual soils.

The researchers obtained data on temperatures, precipitation, and other climatic factors from the European Centre for Medium-Range Weather Forecasts and incorporated them into a model of high-latitude ecosystems. To capture the effect of the 2020 Siberian heat wave, they replaced data from 2020 with data from each of the previous 5 years (2015 to 2019), which provided five estimates of what regional ecosystems might have looked like in 2021 had the heat wave not occurred.

The analysis indicated that the high heat caused soil temperature to remain roughly 1.2°C, or about 150%, warmer in 2021 than it would have been without the heat wave, even though air temperatures had returned to normal. The warmer temperatures also melted soil ice, resulting in wetter soil than usual. Root zone soil water availability, a measure of how much water soil can hold in the rooting depth of plants, increased by 10.9% in forests in 2021 and by 9.3% in grasslands. However, some of this meltwater left the soil via runoff.

In response to warmer, wetter soil, microbes proliferated and caused the soil ecosystem to emit more carbon dioxide than usual, the modeling indicated. In forests, this effect was largely offset by an increase in photosynthesis as plants flourished under the new conditions. In grasslands, on the other hand, photosynthesis initially increased during the heat wave event but then quickly decreased until 2021 as plants used up the available water and died off. As a result of the 2020 heat wave, the researchers reported, forests gained an additional 6 grams of carbon per square meter in the first half of 2021, whereas grasslands lost 10.9 grams of carbon per square meter. (Global Biogeochemical Cycles, https://doi.org/10.1029/2025GB008607, 2025)

—Saima May Sidik (@saimamay.bsky.social), Science Writer

Citation: Sidik, S. M. (2025), In the Arctic, consequences of heat waves linger, Eos, 106, https://doi.org/10.1029/2025EO250313. Published on 22 August 2025. Text © 2025. 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.

SummaryThere are two fundamental probabilities in the seismic phase picking process – the probability of the existence of a seismic phase (detection probability) and the probability associated with the phase arrival time estimation (timing probability). The nearly ubiquitous approach in developing deep learning phase picking models is to use a kernel, such as a truncated Gaussian, to mask the labeled phase arrival time and train a segmentation model. Once a model is trained, the times of the peaks in the output are taken as phase arrival times (picks), and the height of the peaks are taken as “probability” of the picks. Here, we show that this “probability” represents neither the detection nor the timing probability because this approach forces the output to follow the shape of the kernel. We introduce an approach using two models to estimate these two distinct probabilities. We use a binary classifier with a calibrated confidence to address the detection probability and a multi-class classifier to obtain a probability mass function to address the timing probability. This new approach can make the deep learning-based phase picking process more interpretable and provide options to logically control seismic monitoring workflows.

SummaryThis study introduces a new method for calculating acoustic-gravity waves in a spherically layered atmosphere. The method introduces a model assumption and divides the atmosphere into finely stratified layers to solve the PDE with respect to the radial coordinate. The time-domain synthetic signal is obtained by summing over the orders of the associated Legendre functions and then applying the FFT. The method is applied to numerically simulate wave behaviour, including Earth curvature effects, and compares with the horizontally layered model (HLM). Results show that at near-field distances, our method aligns closely with HLM, but significant differences emerge in the far field, particularly beyond an epicentral distance of 50°, where Earth curvature becomes critical. Our method successfully simulates head waves of seismic phases, and Rayleigh waves, even for waves travelling multiple times around the Earth, which HLM cannot achieve. Simulations using a homogeneous Earth model reveal head wave characteristics consistent with previous studies, with the strongest energy observed in Rayleigh head waves. The application of the AK135 Earth model highlights the visibility of seismic phases through the Earth’s core. We validate our method by comparing synthetic records with actual data from the 1999 Chi-Chi earthquake. The synthetic records show good agreement with observed seismic signals and ionospheric perturbations in terms of arrival time and wave envelope. These results demonstrate the accuracy of our method in simulating acoustic-gravity waves at large epicentral distances.

SummaryThe widespread, multi-year crustal deformation induced by megathrust earthquakes (Mw8+) is primarily controlled by the combined effects of continuous aseismic slip on the fault plane (afterslip) and viscoelastic relaxation driven by coseismic stress perturbations in the upper mantle. However, till today it remains a considerable challenge to separate these two mechanisms in geodetic observations. We derived the first 3-year GNSS observations following the 2021 Chignik Mw8.2 earthquake to investigate the mechanisms of postseismic deformation. We established a model capable of simultaneously simulating afterslip and viscoelastic relaxation, and constrained the upper mantle rheology beneath the Alaska Peninsula. The best-fit model effectively reproduces the GNSS observations and reveals a notable viscosity difference between the mantle wedge and the oceanic asthenosphere, with steady-state viscosities of $3 \times {{10}^{18}}$ Pa s and $4 \times {{10}^{19}}$ Pa s, respectively. The inferred mantle wedge viscosity beneath the Alaska Peninsula is lower than the values reported for south-central and southeastern Alaska, suggesting an eastward increase in viscosity along the subduction zone. Two main patches of afterslip are identified during the first 3 years. The patch of up-dip afterslip overlaps with the 1938 Chignik Mw8.3 earthquake rupture zone, and demonstrates a close spatial correlation with the slow slip event in 2018. The above new results enhance our insights into the spatial variability of regional rheology and slip behavior along the Alaska-Aleutian subduction zone.

A team of Johns Hopkins researchers is using an innovative X-ray imaging approach to reveal how compression reshapes the tiny spaces and stresses within sandstone—findings that could predict how this common rock used for fuel reservoirs behaves under deep subterranean pressure. The results appear in the Journal of Geophysical Research: Solid Earth.

New research from Purdue University reveals how moisture influences atmospheric blocking, a phenomenon that often drives heat waves, droughts, cold outbreaks and floods, helping solve a mystery in climate science and improving future extreme weather predictions.