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Billions upon billions of soot particles enter Earth's atmosphere each second, totaling about 5.8 million metric tons a year—posing a climate-warming impact previously estimated at almost one-third that of carbon dioxide.

Terrestrial ecosystems, vital for absorbing atmospheric carbon dioxide to mitigate climate change, rely on Earth system models (ESMs) for estimating carbon uptake—a cornerstone of climate policy, carbon budgeting and land management strategies. Yet new research from the Chinese Academy of Sciences (CAS) reveals critical flaws in how these models represent a key metric of carbon absorption, raising concerns about the reliability of long-term climate projections.

University of Toledo environmental researchers trooped through the woods and wetlands of the Ottawa National Wildlife Refuge for a week in early June. Their mission? To outfit an approximately 16-acre site with nearly 300 sensors that will constantly monitor a slew of metrics related to the soil, water and plants, including the flow of sap through trees.

For the last century, Émile Argand's theory on the formation and geological support system of the massive Himalayan mountain range has remained the predominant explanation widely accepted among geologists. This theory states that the ongoing collision of the Indian and Asian continental plates forced the crusts of the two plates to double in thickness and that this ultra-thick crust alone holds up the region's mountains, which were formed from these colliding structures.

For the first time, a study maps safe areas that can practically be used for underground carbon storage, and estimates that using them all would only cut warming by 0.7°C. The result is almost ten times lower than previous estimates of around 6°C, which considered the total global potential for geological storage, including in risky zones, where storing carbon could trigger earthquakes and contaminate drinking water supplies. The researchers say the study shows that geological storage is a scarce, finite resource, and warn that countries must use it in a highly targeted way.

A study from researchers at Ben-Gurion University of the Negev reveals that desert soils can emit powerful greenhouse gases within minutes of being wetted—even in the absence of microbial life.

A new study led by Professor Jonghun Kam's team at POSTECH (Pohang University of Science and Technology) has uncovered a shocking forecast for Pakistan's future. Using a cutting-edge AI model, the research predicts that the country will face unprecedented "super floods" and "extreme droughts" on a periodic basis.

As climate change accelerates, it’s more important than ever to understand the individual drivers of sea level rise, from land subsidence and coastal erosion to changes in ocean volume. For the past 20 years, scientists have had access to high-resolution, satellite-derived maps of Earth’s gravity field, which allows them to calculate fluctuations in global ocean mass.

Recently, geodesists have found a way to extend that record back 10 more years, significantly extending the time frame by which they can consistently measure global ocean mass change.

“This is the first observation-based global ocean mass time series” from 1993 to the present, said Jianli Chen, a geodesy researcher at Hong Kong Polytechnic University in China and a coauthor on the research.

By reconciling older and newer techniques for measuring ocean mass change, the team’s work improves calculations of long-term trends and provides a potential stopgap should satellite data no longer be available.

Shooting Lasers into Space

When scientists measure sea level rise, they consider two main components: how much the ocean’s volume has grown because of changes in water density—the steric component—and how much it has grown because it has gained mass from melted ice—the barystatic component.

Past estimates of total ocean mass change have relied on indirect methods like adding up mass loss from ice sheets, glaciers, and land water storage, explained Yufeng Nie, a geodesy researcher also at Hong Kong Polytechnic University and lead researcher on the new study. Mass lost from these areas is assumed to translate to an increase in ocean mass.

“But these individual estimates are not necessarily consistent, because they are developed by different groups” with different methodologies, Nie said.

In light of this, some researchers adapted satellite laser ranging (SLR), a technique in which scientists bounce ground-based lasers off orbiting satellites to track changes in ocean mass. SLR has been used for decades to measure Earth’s nonuniform gravity field by observing shifts in satellite orbits. A satellite’s altitude depends on Earth’s gravity at any given point, and gravity in turn depends on the distribution of mass beneath that point. Measuring satellite altitudes thus provides a window into measuring ocean mass changes.

“How can you observe, for example, ocean mass change from Antarctic melting using a technique with 4,000-kilometer spatial resolution?”

However, one key drawback to using SLR to measure barystatic sea level (BSL) change is that it can measure changes only on very large spatial scales, which limits its application in climate research, Chen said.

“How can you observe, for example, ocean mass change from Antarctic melting using a technique with 4,000-kilometer spatial resolution?” asked Chen.

Enter NASA’s Gravity Recovery and Climate Experiment (GRACE) missions. GRACE and its successor, GRACE Follow-On (GRACE-FO), each consisted of two satellites chasing each other along the same orbit, continuously sending laser beams back and forth. Like SLR, this process allowed the GRACE missions to provide maps of Earth’s surface mass, but at 10 times the resolution of SLR. And like with SLR, scientists have used GRACE gravity maps to track global ocean mass change.

But GRACE data, too, have their caveats. The first GRACE mission spanned 2002–2017, and GRACE-FO has spanned from 2018 to the present, a short time for understanding long-term trends. What’s more, the 11-month gap between GRACE and its successor meant that scientists were not able to calibrate the two satellites with each other, leaving some uncertainty about systematic differences between the missions.

A Near-Perfect Match

Nie, Chen, and their team were able to address both of these caveats by comparing SLR-based measurements of global ocean mass change with those from GRACE/-FO for the same time period, 2003–2022.

According to gravity maps provided by SLR, barystatic sea level change was 2.16 millimeters per year from 2003 to 2022, while GRACE/-FO measured 2.13 millimeters per year.

The new analysis shows that SLR and GRACE/-FO “agree quite well for the long-term trends,” Nie said. What’s more, researchers found no significant change in the calculation when the data transitioned from GRACE to GRACE-FO. “This gives us confidence that the SLR data, although it is of very low spatial resolution, can be used to tell us the ocean mass variations before 2002,” he added.

“Our SLR measurements…can provide a global constraint of the mass changes for the pre-GRACE era.”

The researchers were able to extend the time frame of their analysis back to 1993 by using SLR data, and they calculated a barystatic sea level change of 1.75 millimeters per year for 1993–2022. They attribute the lower rate of sea level rise in the past to recent acceleration of ice loss in Greenland.

“Our SLR measurements…can provide a global constraint of the mass changes for the pre-GRACE era,” Nie said.

This study was published in Proceedings of the National Academy of Sciences of the United States of America in June.

“Extending the record of measured BSL using satellite laser ranging back to 1993 is an important achievement,” said Bryant Loomis, chief of the Geodesy and Geophysics Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Md. “It allows the disaggregation of total sea level change, which is measured by altimetry, into its barystatic and steric components.”

“The long-term BSL estimate is also useful for assessing the accuracy of previous efforts to quantify the major land ice contributions to BSL prior to the launch of GRACE,” he added, referring to the method of adding together mass changes from glaciers, ice sheets, and land water storage. Loomis was not involved in the new research.

Nie, Chen, and their team are working to push the limits of SLR-derived barystatic sea level measurements to smaller spatial scales and lower uncertainties. They hope to demonstrate that SLR data can be used to measure mass change in Antarctica.

GRACE Continuity?

GRACE-FO launched in 2018 and is 7 years into its nominal 5-year mission. The satellites are in good health, and the nearly identical GRACE mission set a good precedent—it lived for more than 15 years. GRACE-FO might well overlap with its planned successor, GRACE-Continuity (GRACE-C), which is scheduled to launch in 2028.

The GRACE missions are designed to measure minute changes in Earth’s gravity at high spatial resolution. However, there was a coverage gap between the end of the GRACE mission and the start of GRACE-FO, and there may be a similar gap between GRACE-FO and GRACE-C. Credit: NASA/JPL-Caltech, Public Domain

However, recent woes for federally funded science in the United States have put GRACE-C’s future in doubt. Although NASA requested funding for GRACE-C for fiscal year 2026 through the mission’s launch, NASA’s acting administrator, Sean Duffy, recently stated his, and presumably President Donald Trump’s, desire to eliminate all Earth science at the agency (including healthy satellites). That cutback would likely nix GRACE-C.

In the near future, both Europe and China plan to launch satellite-to-satellite laser ranging missions that will provide GRACE-like measurements of Earth’s gravity, Chen said. However, the loss of GRACE-quality data would hamper climate scientists’ ability to accurately track drivers of sea level rise, he added. The SLR-derived measurements demonstrated in this recent research could help mitigate the loss, but only somewhat.

“There’s no way SLR can reach the same [resolution] as GRACE,” Chen said. “We can only use SLR to see the long-term, the largest scale, to fill the gap. But for many of GRACE’s applications—regional water storage or glacial mass change—no, there’s no way SLR can help.”

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

Citation: Cartier, K. M. S. (2025), Bridging old and new gravity data adds 10 years to sea level record, Eos, 106, https://doi.org/10.1029/2025EO250321. Published on 3 September 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.

This is an authorized translation of an Eos article. Esta es una traducción al español autorizada de un artículo de Eos.

La reforestación es más compleja que simplemente plantar árboles. Esta incluye la evaluación de hábitats y ecosistemas, la identificación de la salud y la sostenibilidad de diferentes especies y el estudio de las estrategias para establecer nuevos asentamientos de árboles.

En regiones como Mesoamérica, donde los bosques están gravemente amenazados por las actividades humanas y el cambio climático, los conservacionistas interesados en la reforestación deben priorizar las especies cuyas poblaciones están disminuyendo. Para facilitar esta tarea, un grupo de investigadores evaluó el estado de conservación de las 4,046 especies de árboles endémicas de Mesoamérica, descritas en el proyecto Global Tree Assessment (Evaluación global de árboles). Es así como descubrieron que el 46% de estos árboles se encuentran en cierto riesgo de extinción.

Este estudio es el primero en evaluar el estado de todos los árboles endémicos en Mesoamérica.

El estudio, publicado en la revista Plants, People, Planet, es el primero en evaluar el estado de todos los árboles endémicos en Mesoamérica.

Emily Beech, autora principal del estudio y jefa de conservación en Botanic Gardens Conservation International (Conservación Internacional de Jardines Botánicos), enfatizó la importancia de enfocarse en esta región debido a sus altos niveles de biodiversidad, que con frecuencia están subrepresentados. Los países centroamericanos (Belice, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua y Panamá), dijo Beech, rara vez figuran entre los de mayor biodiversidad o como el hogar del mayor número de especies en peligro de extinción. Esta ausencia no se debe a una falta de biodiversidad, explicó, sino que es simplemente atribuible a su tamaño. El tamaño reducido de estos países hace que sean eclipsados por países grandes con bosques más extensos, como Brasil y la República Democrática del Congo. Pero, junto con México, Centroamérica alberga el 10% de la diversidad vegetal del mundo a pesar de representar menos del 1% de su superficie terrestre.

Para abordar esta brecha, los científicos primero identificaron árboles endémicos mesoamericanos a partir de evaluaciones presentadas en la Lista Roja de especies amenazadas de la Unión Internacional para la Conservación de la Naturaleza (IUCN, por sus siglas en inglés). Posteriormente, para evaluar el estado de conservación de los árboles, los investigadores superpusieron mapas de distribución de las especies arbóreas seleccionadas sobre mapas de la Base de Datos Mundial de Áreas Protegidas.

De las 4,046 especies arbóreas analizadas, encontraron que 1,867 están en peligro de extinción. México fue el único país que tenía especies arbóreas extintas en la base de datos, o extintas en estado silvestre. En los árboles existentes, México y Costa Rica presentaron el mayor número de especies amenazadas, con 888 y 227, respectivamente. La amenaza más común en general fue la pérdida de hábitat debido a la expansión agrícola.

La mayoría de las especies (3,349) contaban con al menos un punto de datos dentro de un área protegida. Sin embargo, el 72% de las especies mesoamericanas en áreas protegidas están amenazadas.

Un enfoque personalizado

Neptalí Ramírez Marcial no participó en la nueva investigación, pero como jefe del grupo de restauración del South Border College en México, trabaja con especies arbóreas que se encuentran en diferentes categorías de amenaza. Los bosques de Chiapas, donde él y sus colegas residen, solían estar repletos de encinos, que albergaban altos niveles de biodiversidad. Debido a la influencia humana, ahora hay más pinos que encinos, y el clima es menos favorable para las especies sensibles de la Lista Roja de la UICN.

A pesar del uso de la Lista Roja por parte de Ramírez Marcial, este se mantiene crítico con la herramienta y su uso en la investigación. Por ejemplo, señaló que la nueva evaluación de árboles mesoamericanos clasifica a la Furcraea macdougallii (planta del siglo de MacDougall) como extinta en México. Ramírez Marcial cree que esta planta es similar al agave y no debería considerarse un árbol en absoluto, por lo cual no debería incluirse en el estudio.

También señaló que el nuevo estudio considera a todo México como parte de Mesoamérica. Desde el punto de vista ecológico, dijo, la región biogeográfica mesoamericana se extiende solamente por el centro de México y excluye la parte norte del país, la cual tiene ecosistemas discretos no compartidos con Centroamérica.

Ocotea monteverdensis “pasó de no estar siquiera incluido en la lista a estar en la categoría de conservación más vulnerable”.

Ramírez Marcial coincidió con las conclusiones del nuevo estudio, sin embargo, argumenta que: las estrategias de restauración deben considerar la biodiversidad de las áreas que se desean proteger. Por ejemplo, señaló que los programas del gobierno mexicano priorizan la distribución de pinos para la reforestación en todo el país, en lugar de diseñar estrategias definidas para cada región.

Daniela Quesada, conservacionista del Instituto Monteverde en Costa Rica, afirmó que el nuevo estudio ofrece una visión más completa del estado de los árboles en Mesoamérica. No obstante, al igual que Ramírez Marcial, considera la información de la Lista Roja de la UICN como un punto de partida para la investigación. La exactitud de la Lista Roja, explicó, depende de la cantidad de información que se le presente.

Quesada apuntó que el siguiente paso para la conservación de los árboles en Mesoamérica es que los científicos “analicen con más detalle cada especie que apareció” en el nuevo estudio. Un análisis riguroso de la presencia e influencia de cada especie en cada región podría influir en el desarrollo de proyectos de conservación determinados.

Como ejemplo, mencionó el caso de Ocotea monteverdensis, un árbol que “pasó de no estar siquiera incluido en la lista a estar en la categoría de conservación más vulnerable” (en peligro crítico) gracias al trabajo del ecólogo John Devereux Joslin Jr. Este reconocimiento condujo al desarrollo de un programa comunitario de conservación específico y continuo para este árbol.

—Roberto González (@perrobertogg.bsky.social), Escritor de ciencia

This translation by translator Oriana Venturi Herrera (@OrianaVenturiH) was made possible by a partnership with Planeteando y GeoLatinas. Esta traducción fue posible gracias a una asociación con Planeteando and GeoLatinas.

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.

The world's methane emissions continue to rise steadily with no signs of slowing, as global trade contributes some 30% to the total amount of the greenhouse gas swirling around the planet, a new study reveals.

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

Being an experienced researcher can come with a lot of heavy professional responsibilities, such as leading grant proposals, managing research teams or labs, supervising doctoral students and postdoctoral scientists, serving on committees, mentoring younger colleagues … the list goes on. This may also be a time filled with greater personal responsibilities beyond the job. Why add to the workload by taking on a book project? In the third installment of career-focused articles, three scientists who wrote or edited books as experienced researchers reflect on their motivations and how their networks paved the way for—and grew during—the publishing process.

Douglas Alsdorf co-edited Congo Basin Hydrology, Climate, and Biogeochemistry: A Foundation for the Future, which discusses new scientific discoveries in the Congo Basin and is published in both English and French. Nancy French co-edited Landscape Fire, Smoke, and Health: Linking Biomass Burning Emissions to Human Well-Being, which presents a foundational knowledge base for interdisciplinary teams to interact more effectively in addressing the impacts of air pollution. Michael Liemohn authored Data Analysis for the Geosciences: Essentials of Uncertainty, Comparison, and Visualization, a textbook on scientific data analysis and hypothesis testing in the Earth, ocean, atmospheric, space, and planetary sciences. We asked these scientists why they decided to write or edit a book, what impacts they saw as a result, and what advice they would impart to prospective authors and editors.

Why did you decide to write or edit a book? Why at that point in your career?

ML: I was assigned to develop a new undergraduate class on data-model comparison techniques. I realized that the best textbooks for it were either quite advanced or rather old. One book I love included the line, “if the student has access to a computer…” in one of the homework questions. I also was not finding a book with the content set that I wanted to cover in the class. So, I developed my own course content set and note pack, which provided the foundation for the chapters of the book.

DA: Our 2022 book was a result of a 2018 AGU Chapman Conference in Washington, DC, that I was involved in organizing. About 100 researchers, including 25 from sub-Saharan Africa, attended the conference, and together we decided that an edited book in the AGU Geophysical Monograph Series would become a launching point for the next decade of research in the Congo Basin.

The motivation for the book was not to advance my career, but because the topic was important to get out there.

NF: The motivation for the book was not to advance my career, but because the topic was important to get out there. The book looks at how science is trying to better inform how to manage smoke from wildland fires. The work was important because people in fire, smoke modeling, and health sciences do not work together often, and there were some real misconceptions about how others do the research and how detailed the topics can be.

What were some benefits of completing a book as an experienced researcher? 

NF: Once you have been working in a field for a while you want to see how your deep expertise can benefit more than just the community of researchers that you know or know of. Reaching into other disciplines allows you to understand how your work can have broader impact. And, you are ready to know more about other, adjacent topics, rather than a deeper view of what you know already. I think these feelings grow more true as you move to later stages of a career.

I think that I would have greatly struggled with this breadth of content if I had tried to write this particular book 10 years earlier.

ML: I was developing my data-model comparison techniques course and textbook for all students in my department, so I wanted to include examples across that diverse list of disciplines—Earth, atmosphere, space, and planetary sciences. Luckily, over the years I had taught a number of classes spanning these topics. Additionally, I had attended quite a few presentations across these fields, not only at seminars on campus but also at the annual AGU meeting. I felt comfortable including examples and assignments from all these topics. Also, I knew colleagues in these fields, and I called on them for advice when I got stuck. I think that I would have greatly struggled with this breadth of content if I had tried to write this particular book 10 years earlier.

What impact do you hope your book will have?

The next great discoveries will happen in the Congo Basin and our monograph motivates researchers toward those exciting opportunities. 

DA: There are ten times fewer peer-reviewed papers on the Congo Basin compared to the Amazon Basin. Our monograph changes that! We have brought new attention to the Congo Basin, demonstrating to the global community of Earth scientists that there is a large, vibrant group of researchers working daily in the Congo Basin. The next great discoveries will happen in the Congo Basin and our monograph motivates researchers toward those exciting opportunities. 

ML: I hope that the book has two major impacts. The first expected benefit is to the students that use it with a course on data-model comparison methods. I want it to be a useful resource regardless of their future career direction. The second impact I wish for is on Earth and space scientist researchers; I hope that our conversations about data-model comparisons are ratcheted up to a higher level, allowing us to more thoughtfully conduct such assessments and therefore maximize scientific progress.

What advice would you give to experienced researchers who are considering pursuing a book project?

NF: Here are a few thoughts: One: Choose co-authors, editors, and contributors that you can count on. Don’t try to “mend fences” with people you have not been able to connect with. That said, if you do admire a specific person or know their point of view is valuable, this is the time to overcome any barriers to your relationship. Two: Give people assignments, and they will better understand your point of view. Three: Listen to your book production people. They are all skilled professionals who know more about this than you do. They can be great allies in getting it done!

DA: Do it! Because we publish papers, our thinking tends to focus on the one topic of a particular paper. A book, however, broadens our thinking so that we more fully understand the larger field of work. Each part of that bigger space has important advances as well as unknowns that beg for answers. A book author who can see each one of these past solutions and future challenges becomes a community resource who provides insights and directions for new research. 

—Douglas Alsdorf (alsdorf.1@osu.edu, 0000-0001-7858-1448), The Ohio State University, USA; Nancy French (nhfrench@mtu.edu, 0000-0002-2389-3003), Michigan Tech Research Institution, USA; and Michael Liemohn (liemohn@umich.edu, 0000-0002-7039-2631), University of Michigan, USA

This post is the third in a set of three. Learn about leading a book project as an early-career or mid-career researcher.

Citation: Alsdorf, D., N. French, and M. Liemohn (2025), Experienced researcher book publishing: sharing deep expertise, Eos, 106, https://doi.org/10.1029/2025EO255028. Published on 3 September 2025. This article does not represent the opinion of AGU, Eos, or any of its affiliates. It is solely the opinion of the author(s). Text © 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.

Rare rocks buried deep beneath central Australia have revealed the origins of one of the world's most promising new deposits of niobium—a metal vital for producing high-strength steel and clean energy technologies—and how it formed during the breakup of an ancient supercontinent.

SummaryWe revisit the challenge of estimating velocities from global navigation satellite system (GNSS) coordinate time series by incorporating stochastic processes to address the quasi-periodic oscillations (QPOs) in weighted least-squares estimation. We examine two advanced stochastic seasonal models (i.e., Fractional Sinusoidal Waveform (FSW) and Varying Periodic Band-Pass (VPBP)) and evaluate their efficacy on mitigating velocity biases by using both synthetic data and 14 Antarctic GNSS stations. The result shows that pure FSW cannot fully capture the spectral shape of the QPOs since the FSW's spectral shape is controlled by the fractional parameter d, which is unfortunately dependent on the global spectra slope of the GNSS data. In contrast, VPBP can fit the QPOs more freely by using the parameter phi. Nevertheless, both FSW and VPBP models, when used without augmentation, tend to underestimate velocity uncertainties due to spectral flattening at low frequencies. This poses a risk for applications requiring high-confidence geodetic velocity estimates. To solve this issue, adopting a hybrid noise model that is compensated with an additional appropriate noise background (e.g., power law) is recommended. This knowledge can guide future research on secular velocity estimation of GNSS stations.

SummarySpectral induced polarization (SIP) aims to characterize geological materials by measuring the dispersion of their complex conductivity in the frequency domain. Despite the complex-valued nature of SIP data, most machine learning models used for its analysis rely on real-valued representations that discard phase information and may limit performance. This study investigates the benefits of complex-valued neural networks (CVNN) for SIP applications by comparing their performance against real-valued neural networks (RVNN) across three tasks: mineral classification, Cole-Cole parameter estimation, and mechanistic modelling of ionic and electric potential perturbations around polarizable minerals. To ensure fair comparisons and emphasize the effect of complex-valued representations, we design CVNN and RVNN models with matched capacity, aspect ratio, and training duration. Our numerical experiments show that CVNNs consistently outperform RVNNs in the classification task, achieving lower validation loss and up to 5 percent higher classification metrics (p-value = 2.9 × 10−7). We test the Cole-Cole inversion networks on laboratory SIP measurements and validate the parameter estimation accuracy using synthetic data. Test results indicate that CVNNs produce curve fits that are ≈4 % more accurate for the imaginary part of resistivity (p-value = 3.1 × 10−4), and validation results show accuracy improvements of up to 2 percent for chargeability, relaxation time, and the Cole-Cole exponent (p-value = 1.7 × 10−7). CVNNs also yield more accurate approximations of mechanistic model variables, with error reductions of up to 1 percent for ionic concentrations (p-value = 1.6 × 10−4). Our experiments suggest that CVNNs provide modest but statistically significant benefits in SIP applications involving laboratory or synthetic data. While RVNNs may eventually reach comparable predictive accuracy if trained longer, we observe that CVNNs converge more rapidly under matched training conditions. This study provides a reproducible framework for benchmarking neural network architectures in SIP and supports the integration of CVNNs into geophysical workflows where phase responses encode physically meaningful information.

A research team led by Prof. Chen Cheng from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has retrieved global aerosol and surface properties using advanced polarization data from China's GF-5(02) satellite.

Nearly 40 years after breaking off Antarctica, a colossal iceberg ranked among the oldest and largest ever recorded is finally crumbling apart in warmer waters, and could disappear within weeks.

Deforestation in the Brazilian Amazon is responsible for approximately 74.5% of the reduction in rainfall and 16.5% of the temperature increase in the biome during the dry season. For the first time, researchers have quantified the impact of vegetation loss and global climate change on the forest.

The Amazon is the world's largest tropical forest, home to unmatched biodiversity and one of the planet's longest rivers. Besides the Amazon River, the Amazon rainforest also features "flying rivers:" invisible streams of vapor that travel through the atmosphere, fueling rainfall both within the forest and far beyond its boundaries.

U.S. cities are facing a growing threat that goes beyond hot weather or hazy air. New research from the University of Oklahoma reveals that "compound events"—periods when heat wave conditions coincide with high air pollution levels—are becoming more frequent and intense in urban areas across the United States.

Along the coast, waves break with a familiar sound. The gentle swash of the surf on the seashore can lull us to sleep, while the pounding of storm surge warns us to seek shelter.