Source: AGU Advances

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

No se tienen registros suficientes en las bases de datos globales de los peligros meteorológicos extremos. Por ejemplo, los eventos donde las temperaturas son potencialmente mortales y que se ajustan a las normas climatológicas generalmente no son incluidos en los estudios de riesgos, y las inundaciones locales o regionales a menudo suelen pasar desapercibidas para los instrumentos satelitales.

En los últimos 20 años Texas ha experimentado una cantidad inusualmente alta de fenómenos climáticos extremos, incluyendo un incremento en inundaciones y olas de calor. Usando datos satelitales de fácil acceso de precipitación y temperatura tomados diariamente, Preisser y Passalacqua crearon una visión más amplia de los riesgos por inundaciones y olas de calor que han afectado al estado en los últimos años.

Al consultar los datos de precipitación del 2001 al 2020, los investigadores definieron como un evento de inundación peligrosa a aquellos que ocurren en promedio una vez cada dos años o más, lo que significa que un evento de esa magnitud ocurre en un área determinada con una frecuencia que no supera los dos años. Compararon sus resultados con los registrados en la Base de Datos de Eventos de Tormentas de la NOAA y la base de datos del Observatorio de Inundaciones de Dartmouth (DFO por sus siglas en inglés). Su análisis detectó tres veces más inundaciones que en la base de datos del DFO y se identificaron daños adicionales de $320 millones de dólares.

El equipo también amplió el análisis sobre el calor extremo. En muchos estudios previos sobre amenazas múltiples sólo se consideraron las olas de calor, donde las temperaturas superaron un percentil, como el 90 o el 95, durante tres días seguidos. Este estudio también consideró los periodos donde la temperatura de globo de bulbo húmedo (índice WBGT) supera un umbral de salud de 30°C, en lugar de un percentil determinado. Bajo esta definición, los científicos determinaron que, entre 2003 y 2020, Texas vivió 2,517 días con eventos peligrosos de calor, lo que equivale a casi el 40% de los días dentro de este periodo. Estos eventos afectaron un total de 253.2 millones de kilómetros cuadrados.

El estudio consideró como eventos de amenazas múltiples aquellos en los que coinciden inundaciones y episodios de calor extremo. Usando el método del intervalo de recurrencia promedio, junto con la definición más amplia de peligros, los investigadores encontraron que las zonas del estado con una alta concentración de poblaciones minoritarias estaban expuestas a un mayor riesgo ante este tipo de eventos multiriesgo. Esto sugiere que los métodos más antiguos pueden subestimar tanto la magnitud de los eventos de amenaza múltiple como el impacto desproporcionado en comunidades marginadas, de acuerdo con los investigadores. (AGU Advances, https://doi.org/10.1029/2025AV001667, 2025)

—Rebecca Owen (@beccapox.bsky.social), Escritora de ciencia

This translation by translator Oscar Uriel Soto was made possible by a partnership with Planeteando y GeoLatinas. Esta traducción fue posible gracias a una asociación con Planeteando and GeoLatinas.

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Sixty-seven extreme heat events have occurred since May 2024. All of these events—including a deadly Mediterranean heat wave in July 2024, an unprecedented March 2025 heat wave in central Asia, and extreme heat in South Sudan in February 2025—broke temperature records, caused major harm to people or property, or did both.

According to a new analysis, each of these extreme events was made more likely by climate change. The number of days with extreme heat is now at least double what it would have been without climate change in 195 countries and territories. Climate change added at least an extra month of extreme heat in the past year for 4 billion people—half the world’s population. 

“There’s really no corner of the globe that has been untouched by climate-driven extreme heat,” said Kristina Dahl, a climate researcher at the climate change research and communication nonprofit Climate Central who was part of the report team. “Half the world’s population is experiencing an extra month of extreme heat. The numbers are staggering.”

The authors of the report say it serves as a stark reminder of the dangers of climate change and the urgent need for better early-warning systems, heat action plans, and long-term planning for heat events across the globe. 

The report was created by scientists at Climate Central; World Weather Attribution, a climate research group; and the Red Cross Climate Centre. 

More Frequent Heat

In the new report, scientists calculated the number of days between 1 May 2024 and 1 May 2025 in which temperatures in a country or territory were above 90% of the historical temperatures from 1991 to 2020. Then, they analyzed how many of these extreme heat days were made more likely by climate change using the climate shift index, a methodology developed by Climate Central that compares actual temperatures to a simulated world without human-caused climate change. 

The team found that climate change made extreme heat events more likely in every country.

Over all the countries and territories, climate change added the greatest number of extreme heat days to the Federated States of Micronesia (57 days), and Aruba had the most extreme heat days in total over the past year, 187 days. The report’s authors estimate that in a world without climate change, Aruba would have experienced just 45 days of extreme heat.

Other Caribbean and Oceanic islands were among the countries and territories most strongly affected by climate change. People in the United States experienced 46 days of extreme heat, 24 of which were added by climate change. 

Of the 67 extreme heat events that occurred in the past year, the one most influenced by climate change was a heat wave that struck Pacific islands in May 2024. Researchers estimated the event was made at least 69 times more likely by climate change. 

The findings are not a surprise to Nick Leach, a climate scientist at the University of Oxford who was not involved in the report. “We’ve understood the impact of climate change on temperature and extreme heat for quite some time…[including] how it’s increasing the frequency and intensity of extreme heat,” he said. Research has consistently shown that heat events on Earth are made more likely, more intense, and longer lasting as a result of climate change. 

Leach said the new report gives a good overview of how climate change is influencing heat waves worldwide. However, defining extreme heat as temperatures above the 1991–2020 90th percentile creates a relatively broad analysis, he said. Studies using a more extreme definition of extreme heat may be more relevant to the impacts of extreme heat, and studies estimating those impacts are typically more policy relevant, he said.

The report’s authors chose the 90% threshold because heat-related illness and mortality begin to increase at those temperatures, Dahl said. 

Taking Action on Heat Waves

For rising global temperatures, “the causes are well known,” the report’s authors wrote. Burning of fossil fuels such as coal, oil, and gas has released enough greenhouse gases to warm the planet by 1.3°C (2.34°F; calculated as a 5-year average); 2024 marked the first year with average global temperatures exceeding 1.5°C (2.7°F) above preindustrial temperatures.

“Only comprehensive mitigation, through phasing out fossil fuels, will limit the severity of future heat-related harms,” the authors wrote.

Extreme heat puts strain on the human body as it tries to cool itself. This strain can worsen chronic conditions such as cardiovascular problems, mental health problems, and diabetes and can cause heat exhaustion and heat stroke, which can be deadly. Extreme heat is particularly dangerous for already-vulnerable populations, including those with preexisting health conditions, low-income populations lacking access to cool shelter, and outdoor workers. 

Heat Action Day on 2 June, hosted by the International Federation of Red Cross and Red Crescent Societies, raises awareness of heat risks across the globe. This year, the day of action will focus on how to recognize signs of heat exhaustion and heat stroke. Dahl recommends using the Centers for Disease Control and Prevention tips on heat and health to stay safe. “Most heat-related illness and death is preventable,” she said.

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

Citation: van Deelen, G. (2025), Climate change made extreme heat days more likely, Eos, 106, https://doi.org/10.1029/2025EO250208. Published on 30 May 2025.

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Source: AGU Advances

A translation of this article was made possible by a partnership with Planeteando. Una traducción de este artículo fue posible gracias a una asociación con Planeteando.

Not all extreme weather hazards are sufficiently documented in global databases. For instance, life-threatening high-heat events that fall within climatological norms are often not included in hazard studies, and local or regional flash flooding events frequently go undetected by satellite instruments.

Texas has experienced more than its fair share of extreme weather over the past 20 years, including increasingly frequent flooding and heat events. Using widely accessible daily precipitation and temperature satellite data, Preisser and Passalacqua created a more complete picture of the flooding and heat hazards that have affected the state in recent years.

In consulting rainfall data from 2001 to 2020, the researchers designated a hazardous flood event as one that had an average recurrence interval of 2 or more years—meaning that an event of that magnitude occurred in a given area no more often than every 2 years. They compared their findings to the flooding events documented in the NOAA Storm Events Database and Dartmouth Flood Observatory (DFO) database. Their analysis captured 3 times as many flooding events as the DFO database did and identified an additional $320 million in damages.

The team also broadened the analysis of extreme heat. Many previous multihazard studies considered only heat waves, in which temperature exceeds a percentile, such as the 90th or 95th, for three consecutive days or longer. This study also considered heat events, or periods in which the wet-bulb globe temperature exceeds a 30°C health threshold rather than a given percentile. Using this definition, the researchers determined that between 2003 and 2020, Texas experienced 2,517 days with a heat hazard event—nearly 40% of all days. Heat hazard events affected a total of 253.2 million square kilometers.

The study defined combinations of floods and extreme heat as multihazard experiences. Using the average recurrence interval method, combined with the broader definition of hazards, the researchers found that parts of the state with large minority populations faced higher risk from multihazard events. This suggests that older methods may underestimate both the extent of multihazard risks and their disproportionate impact on marginalized communities, the researchers say. (AGU Advances, https://doi.org/10.1029/2025AV001667, 2025)

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

Citation: Owen, R. (2025), Scientists reveal hidden heat and flood hazards across Texas, Eos, 106, https://doi.org/10.1029/2025EO250191. Published on 16 May 2025.

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This story was originally published by Knowable Magazine.

Ralph Loya was pretty sure he was going to lose the corn. His farm had been scorched by El Paso’s hottest-ever June and second-hottest August; the West Texas county saw 53 days soar over 100 degrees Fahrenheit in the summer of 2024. The region was also experiencing an ongoing drought, which meant that crops on Loya’s eight-plus acres of melons, okra, cucumbers and other produce had to be watered more often than normal.

Loya had been irrigating his corn with somewhat salty, or brackish, water pumped from his well, as much as the salt-sensitive crop could tolerate. It wasn’t enough, and the municipal water was expensive; he was using it in moderation and the corn ears were desiccating where they stood.

Ensuring the survival of agriculture under an increasingly erratic climate is approaching a crisis in the sere and sweltering Western and Southwestern United States, an area that supplies much of our beef and dairy, alfalfa, tree nuts and produce. Contending with too little water to support their plants and animals, farmers have tilled under crops, pulled out trees, fallowed fields and sold off herds. They’ve also used drip irrigation to inject smaller doses of water closer to a plant’s roots, and installed sensors in soil that tell more precisely when and how much to water.

In the last five years, researchers have begun to puzzle out how brackish water, pulled from underground aquifers, might be de-salted cheaply enough to offer farmers another water resilience tool. Loya’s property, which draws its slightly salty water from the Hueco Bolson aquifer, is about to become a pilot site to test how efficiently desalinated groundwater can be used to grow crops in otherwise water-scarce places.

Desalination renders salty water less so. It’s usually applied to water sucked from the ocean, generally in arid lands with few options; some Gulf, African and island countries rely heavily or entirely on desalinated seawater. Inland desalination happens away from coasts, with aquifer waters that are brackish—containing between 1,000 and 10,000 milligrams of salt per liter, versus around 35,000 milligrams per liter for seawater. Texas has more than three dozen centralized brackish groundwater desalination plants, California more than 20.

Such technology has long been considered too costly for farming. Some experts still think it’s a pipe dream. “We see it as a nice solution that’s appropriate in some contexts, but for agriculture it’s hard to justify, frankly,” says Brad Franklin, an agricultural and environmental economist at the Public Policy Institute of California. Desalting an acre-foot (almost 326,000 gallons) of brackish groundwater for crops now costs about $800, while farmers can pay a lot less—as little as $3 an acre-foot for some senior rights holders in some places—for fresh municipal water. As a result, desalination has largely been reserved to make liquid that’s fit for people to drink. In some instances, too, inland desalination can be environmentally risky, endangering nearby plants and animals and reducing stream flows.

But the US Bureau of Reclamation, along with a research operation called the National Alliance for Water Innovation (NAWI) that’s been granted $185 million from the Department of Energy, have recently invested in projects that could turn that paradigm on its head. Recognizing the urgent need for fresh water for farms—which in the US are mostly inland—combined with the ample if salty water beneath our feet, these entities have funded projects that could help advance small, decentralized desalination systems that can be placed right on farms where they’re needed. Loya’s is one of them.

US farms consume over 83 million acre-feet (more than 27 trillion gallons) of irrigation water every year—the second most water-intensive industry in the country, after thermoelectric power. Not all aquifers are brackish, but most that are exist in the country’s West, and they’re usually more saline the deeper you dig. With fresh water everywhere in the world becoming saltier due to human activity, “we have to solve inland desal for ag…in order to grow as much food as we need,” says Susan Amrose, a research scientist at MIT who studies inland desalination in the Middle East and North Africa.

That means lowering energy and other operational costs; making systems simple for farmers to run; and figuring out how to slash residual brine, which requires disposal and is considered the process’s “Achilles’ heel,” according to one researcher.

The last half-decade of scientific tinkering is now yielding tangible results, says Peter Fiske, NAWI’s executive director. “We think we have a clear line of sight for agricultural-quality water.”

Swallowing the High Cost

Fiske believes farm-based mini-plants can be cost-effective for producing high-value crops like broccoli, berries and nuts, some of which need a lot of irrigation. That $800 per acre-foot has been achieved by cutting energy use, reducing brine and revolutionizing certain parts and materials. It’s still expensive but arguably worth it for a farmer growing almonds or pistachios in California—as opposed to farmers growing lesser-value commodity crops like wheat and soybeans, for whom desalination will likely never prove affordable. As a nut farmer, “I would sign up to 800 bucks per acre-foot of water till the cows come home,” Fiske says.

Loya’s pilot is being built with Bureau of Reclamation funding and will use a common process called reverse osmosis. Pressure pushes salty water through a semi-permeable membrane; fresh water comes out the other side, leaving salts behind as concentrated brine. Loya figures he can make good money using desalinated water to grow not just fussy corn, but even fussier grapes he might be able to sell at a premium to local wineries.

Such a tiny system shares some of the problems of its large-scale cousins—chiefly, brine disposal. El Paso, for example, boasts the biggest inland desalination plant in the world, which makes 27.5 million gallons of fresh drinking water a day. There, every gallon of brackish water gets split into two streams: fresh water and residual brine, at a ratio of 83 percent to 17 percent. Since there’s no ocean to dump brine into, as with seawater desalination, this plant injects it into deep, porous rock formations—a process too pricey and complicated for farmers.

But what if desalination could create 90 or 95 percent fresh water and 5 to 10 percent brine? What if you could get 100 percent fresh water, with just a bag of dry salts leftover? Handling those solids is a lot safer and easier, “because super-salty water brine is really corrosive…so you have to truck it around in stainless steel trucks,” Fiske says.

Finally, what if those salts could be broken into components—lithium, essential for batteries; magnesium, used to create alloys; gypsum, turned into drywall; as well as gold, platinum and other rare-earth elements that can be sold to manufacturers? Already, the El Paso plant participates in “mining” gypsum and hydrochloric acid for industrial customers.

Loya’s brine will be piped into an evaporation pond. Eventually, he’ll have to pay to landfill the dried-out solids, says Quantum Wei, founder and CEO of Harmony Desalting, which is building Loya’s plant. There are other expenses: drilling a well (Loya, fortuitously, already has one to serve the project); building the physical plant; and supplying the electricity to pump water up day after day. These are bitter financial pills for a farmer. “We’re not getting rich; by no means,” Loya says.

More cost comes from the desalination itself. The energy needed for reverse osmosis is a lot, and the saltier the water, the higher the need. Additionally, the membranes that catch salt are gossamer-thin, and all that pressure destroys them; they also get gunked up and need to be treated with chemicals.

Reverse osmosis presents another problem for farmers. It doesn’t just remove salt ions from water but the ions of beneficial minerals, too, such as calcium, magnesium and sulfate. According to Amrose, this means farmers have to add fertilizer or mix in pretreated water to replace essential ions that the process took out.

To circumvent such challenges, one NAWI-funded team is experimenting with ultra-high-pressure membranes, fashioned out of stiffer plastic, that can withstand a much harder push. The results so far look “quite encouraging,” Fiske says. Another is looking into a system in which a chemical solvent dropped into water isolates the salt without a membrane, like the polymer inside a diaper absorbs urine. The solvent, in this case the common food-processing compound dimethyl ether, would be used over and over to avoid potentially toxic waste. It has proved cheap enough to be considered for agricultural use.

Amrose is testing a system that uses electrodialysis instead of reverse osmosis. This sends a steady surge of voltage across water to pull salt ions through an alternating stack of positively charged and negatively charged membranes. Explains Amrose, “You get the negative ions going toward their respective electrode until they can’t pass through the membranes and get stuck,” and the same happens with the positive ions. The process gets much higher fresh water recovery in small systems than reverse osmosis, and is twice as energy efficient at lower salinities. The membranes last longer, too—10 years versus three to five years, Amrose says—and can allow essential minerals to pass through.

Data-Based Design

At Loya’s farm, Wei paces the property on a sweltering summer morning with a local engineering company he’s tapped to design the brine storage pond. Loya is anxious that the pond be as small as possible to keep arable land in production; Wei is more concerned that it be big and deep enough. To factor this, he’ll look at average weather conditions since 1954 as well as worst-case data from the last 25 years pertaining to monthly evaporation and rainfall rates. He’ll also divide the space into two sections so one can be cleaned while the other is in use. Loya’s pond will likely be one-tenth of an acre, dug three to six feet deep.

The desalination plant will pair reverse osmosis membranes with a “batch” process, pushing water through multiple times instead of once and gradually amping up the pressure. Regular reverse osmosis is energy-intensive because it constantly applies the highest pressures, Wei says, but Harmony’s process saves energy by using lower pressures to start with. A backwash between cycles prevents scaling by dissolving mineral crystals and washing them away. “You really get the benefit of the farmer not having to deal with dosing chemicals or replacing membranes,” Wei says. “Our goal is to make it as painless as possible.”

Another Harmony innovation concentrates leftover brine by running it through a nanofiltration membrane in their batch system; such membranes are usually used to pretreat water to cut back on scaling or to recover minerals, but Wei believes his system is the first to combine them with batch reverse osmosis. “That’s what’s really going to slash brine volumes,” he says. The whole system will be hooked up to solar panels, keeping Loya’s energy off-grid and essentially free. If all goes to plan, the system will be operational by early 2025 and produce seven gallons of fresh water a minute during the strongest sun of the day, with a goal of 90 to 95 percent fresh water recovery. Any water not immediately used for irrigation will be stored in a tank.

Spreading Out the Research

Ninety-eight miles north of Loya’s farm, along a dead flat and endlessly beige expanse of road that skirts the White Sands Missile Range, more desalination projects burble away at the Brackish Groundwater National Desalination Research Facility in Alamogordo, New Mexico. The facility, run by the Bureau of Reclamation, offers scientists a lab and four wells of differing salinities to fiddle with.

On some parched acreage at the foot of the Sacramento Mountains, a longstanding farming pilot project bakes in relentless sunlight. After some preemptive words about the three brine ponds on the property—“They have an interesting smell, in between zoo and ocean”—facility manager Malynda Cappelle drives a golf cart full of visitors past solar arrays and water tanks to a fenced-in parcel of dust and plants. Here, since 2019, a team from the University of North Texas, New Mexico State University and Colorado State University has tested sunflowers, fava beans and, currently, 16 plots of pinto beans. Some plots are bare dirt; others are topped with compost that boosts nutrients, keeps soil moist and provides a salt barrier. Some plots are drip-irrigated with brackish water straight from a well; some get a desalinated/brackish water mix.

Eyeballing the plots even from a distance, the plants in the freshest-water plots look large and healthy. But those with compost are almost as vigorous, even when irrigated with brackish water. This could have significant implications for cash-conscious farmers. “Maybe we do a lesser level of desalination, more blending, and this will reduce the cost,” says Cappelle.

Pei Xu, has been co-investigator on this project since its start. She’s also the progenitor of a NAWI-funded pilot at the El Paso desalination plant. Later in the day, in a high-ceilinged space next to the plant’s treatment room, she shows off its consequential bits. Like Amrose’s system, hers uses electrodialysis. In this instance, though, Xu is aiming to squeeze a bit of additional fresh—at least freshish—water from the plant’s leftover brine. With suitably low levels of salinity, the plant could pipe it to farmers through the county’s existing canal system, turning a waste product into a valuable resource.

Xu’s pinto bean and El Paso work, and Amrose’s in the Middle East, are all relevant to Harmony’s pilot and future projects. “Ideally we can improve desalination to the point where it’s an option which is seriously considered,” Wei says. “But more importantly, I think our role now and in the future is as water stewards—to work with each farm to understand their situation and then to recommend their best path forward…whether or not desalting is involved.”

Indeed, as water scarcity becomes ever more acute, desalination advances will help agriculture only so much; even researchers who’ve devoted years to solving its challenges say it’s no panacea. “What we’re trying to do is deliver as much water as cheaply as possible, but that doesn’t really encourage smart water use,” says NAWI’s Fiske. “In some cases, it encourages even the reverse. Why are we growing alfalfa in the middle of the desert?”

Franklin, of the California policy institute, highlights another extreme: Twenty-one of the state’s groundwater basins are already critically depleted, some due to agricultural overdrafting. Pumping brackish aquifers for desalination could aggravate environmental risks.

There are an array of measures, say researchers, that farmers themselves must take in order to survive, with rainwater capture and the fixing of leaky infrastructure at the top of the list. “Desalination is not the best, only or first solution,” Wei says. But he believes that when used wisely in tandem with other smart partial fixes, it could prevent some of the worst water-related catastrophes for our food system.

—Lela Nargi, Knowable Magazine

This article originally appeared in Knowable Magazine, a nonprofit publication dedicated to making scientific knowledge accessible to all. Sign up for Knowable Magazine’s newsletter. Read the original article here.

Source: GeoHealth

Small particulate matter (PM_2.5) in air pollution raises the risks of respiratory problems, cardiovascular disease, and even cognitive decline. Heat waves, which are occurring more often with climate change, can cause heatstroke and exacerbate conditions such as asthma and diabetes. When heat and pollution coincide, they can create a deadly combination.

Existing studies on hot and polluted episodes (HPEs) have often focused on local, urban settings, so their findings are not necessarily representative of HPEs around the world. To better understand premature mortality associated with pollution exposure during HPEs at multiple scales and settings, Huang et al. looked at a global record of climate and PM_2.5 levels from 1990 to 2019.

The team used data from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), which included hourly concentration measurements of PM_2.5 in the form of dust, sea salt, black carbon, organic carbon, and sulfate particles. Daily maximum temperatures were obtained via satellite data from ERA5 (the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis).

The researchers also conducted a meta-analysis of health literature, identifying relevant research using the search terms “PM_2.5,” “high temperature,” “heatwaves,” and “all-cause mortality” in the PubMed, Scopus, and Web of Science databases. Then, they conducted a statistical analysis to estimate PM_2.5-associated premature mortality events during HPEs.

They found that both the frequency of HPEs and maximum PM_2.5 levels during HPEs have increased significantly over the past 30 years. The team estimated that exposure to PM_2.5 during HPEs caused 694,440 premature deaths globally between 1990 and 2019, 80% of which occurred in the Global South. With an estimated 142,765 deaths, India had the highest mortality burden by far, surpassing the combined total of China and Nigeria, which had the second- and third-highest burdens. The United States was the most vulnerable of the Global North countries, with an estimated 32,227 deaths.

The work also revealed that PM_2.5 pollution during HPEs has steadily increased in the Global North, despite several years of emission control endeavors, and that the frequency of HPEs in the Global North surpassed that of the Global South in 2010. The researchers point out that the study shows the importance of global collaboration on climate change policies and pollution mitigation to address environmental inequalities. (GeoHealth, https://doi.org/10.1029/2024GH001290, 2025)

—Sarah Derouin (@sarahderouin.com), Science Writer

Citation: Derouin, S. (2025), Heat and pollution events are deadly, especially in the Global South, Eos, 106, https://doi.org/10.1029/2025EO250151. Published on 14 May 2025.

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When an intense marine heat wave sent ocean temperatures soaring in 2023 and 2024, coral reefs around the world bleached. New research on the Great Barrier Reef’s One Tree Island shows that more than 50% of surveyed coral colonies that bleached died of heat stress and starvation. And even heat-resistant corals weren’t immune.

When corals are stressed by warm water, they can lose the algae that live in their tissues. This process turns the coral white, earning it the name “coral bleaching.” Sometimes corals can recover, but if the stress is too intense, they die and eventually crumble into rubble and sand.

“What we noticed in more recent times, when it gets really hot, they often die before they even fully bleach,” said marine biologist Maria Byrne at the University of Sydney.

A Global Marine Heat Wave

Record hot temperatures in 2023 were worsened by a strong El Niño. This heat triggered a global coral bleaching event that began in the Caribbean. By early 2024, it had reached the Great Barrier Reef. Australian aerial surveys showed that in some areas of the reef, more than 90% of corals were bleached.

Starting in February 2024, Byrne and her colleagues went to the One Tree Island Reef, located roughly 100 kilometers off the coast of Queensland, Australia, to document how the heat wave affected the reef in the months afterward. The island is protected from mainland coastal pollution and tourism, so the effects of the heat wave could be surveyed independently from those stressors.

Over 161 days, the researchers tracked 462 coral colonies from the peak of the Southern Hemisphere heat wave in February through to the winter of July 2024. On four occasions, they dived at two lagoon sites—a shallow channel and a bay connected to the ocean.

Wearing thin stinger suits to protect them from jellyfish stings, the researchers swam in pairs along marked transects, one researcher capturing videos and the other taking both wide-angle and close-up photos.

The scientists monitored individual corals across surveys using GPS markers and numbered tags. The tags helped them match photos and videos from different dives, allowing them to compare changes over time—whether the corals remained bleached, recovered, or succumbed to disease and algae.

“We match the corals a bit like a jigsaw puzzle,” Byrne said. “It did take a lot of time to match all the photos, thousands of them, to individual corals.”

When bleaching and algae made corals unrecognizable, Byrne’s team had to use natural landmarks—like a giant clam or a patch of soft coral—to track the reef’s changing story.

Widespread White

Reef sensors recorded a peak temperature of 30.55°C (86.99°F). That’s higher than satellite readings. This kind of on-site data should help the scientists identify coral heat stress and bleaching risks better.

In February, almost two thirds of the corals were ghostly white. Even the heat-resistant Porites, usually a refuge for turtles, was affected, with seven out of 10 colonies observed showing signs of bleaching.

By April, bleaching had intensified, affecting 80% of the 462 coral colonies under study. Though bleaching can contribute to slow starvation over weeks or months, extreme heat can lead to sudden die-offs due to heat stress before the coral even turns fully white. By July, more than half of the observed bleached colonies had died, and only 16% showed signs of recovery.

Some species fared worse: Acropora, a fast-growing branching coral, faced near-total collapse after bleaching, with 95% of colonies dead. Goniopora, known for its flowerlike polyps, was severely affected by black band disease, a fatal disorder in which a dark stripe separates the animal’s healthy tissue from an encroaching microbial mat that leaves a dead skeleton in its wake.

The results were published in Limnology and Oceanography Letters.

“The corals that live on One Tree Island Reef are very used to having extreme summers, and to a degree, it’s surprising they were pushed over the limit so easily,” said Stuart Kininmonth, a coral reef ecologist who managed the University of Queensland’s Heron Island Research Station, located 20 kilometers west of One Tree Island. Kininmonth was not associated with the study.

The scale of the die-offs and the low recovery rate at One Tree Island Reef show how hard it can be for reefs to recover amid harsh bleaching events. Although some species (the stony corals Goniastrea and Pavona) experienced lower mortalities, surveys also revealed how quickly the reef turned to rubble after coral died, transforming the underwater landscape and ecosystem.

“We’ve entered a new phase where heat intensities are so frequent—every 2 years instead of every 10—that corals may not have a chance to recover,” Byrne said. “Species that didn’t bleach may be the ones that survive, leading to a different barrier reef with altered species, ecosystem services, and predator-prey dynamics. We’re entering a brave new world.”

—Anupama Chandrasekaran (@indiantimbre), Science Writer

Citation: Chandrasekaran, A. (2025), Great Barrier Reef corals hit hard by marine heat wave, Eos, 106, https://doi.org/10.1029/2025EO250082. Published on 4 March 2025.

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Extreme heat resulting from climate change will become a growing threat in Europe over the next 75 years, new research reports. Without substantial mitigation and adaptation efforts, an additional 2.3 million lives could be lost to extreme-temperature-related causes by the end of the century, with the effects of rising heat outpacing any potential decline in cold-related deaths.

This dire projection comes from a team of researchers led by Pierre Masselot, a statistician and environmental epidemiologist at the London School of Hygiene & Tropical Medicine. Their analysis, published in Nature Medicine, examined climate projections and estimated future temperature-related mortality in 854 European cities with populations greater than 50,000 across 30 countries. The researchers used advanced climate simulations to project daily temperatures for each city and combined the results with statistical data on annual temperature-related deaths in each area.

A 2023 study also led by Masselot found that between the years 2000 and 2019, about 143,817 deaths in these cities were attributable to extreme temperatures each year. The new study considered various warming scenarios and revealed that without substantial reductions in greenhouse gas emissions, extreme-temperature-related deaths are expected to rise. The worst-case scenario—characterized by a lack of substantial emissions reductions and minimal adaptation—projects that the net death burden from climate change will rise by 50%, to about 215,000 deaths per year, by the end of the century. This scenario would result in the aforementioned 2.3 million additional deaths by 2100.

Masselot noted that the consistency of the trend across all scenarios was surprising. “The takeaway is that if cities warm as much as it is projected in the worst-case scenario, it will be very difficult to adapt,” he said.

Mitigation Versus Adaptation

The study investigated the potential effects of adaptation strategies designed to protect people from heat, such as using air-conditioning and developing cooling centers. But their results found that deaths would rise even if significant adaptation efforts were implemented.

“In [the] absence of mitigation,” Masselot said, “the adaptation to heat would need to be massive to counterbalance this trend.”

Mitigation efforts would mostly take the form of reducing greenhouse gas emissions: Masselot said that up to 70% of these extra deaths could be averted by limiting the global average temperature increase to 2°C by the end of the century through reduced emissions in line with the Paris Agreement. However, recent research suggests that Earth is on track to exceed this limit.

Mediterranean Exposure

Currently, extreme cold causes 10 times more deaths than heat in Europe. However, Masselot explained that though milder winters might mean some northern countries see a reduction in overall temperature-related deaths, the increase in heat-related deaths across the continent will far outweigh this localized effect. The team identified Mediterranean regions, including eastern Spain, southern France, Italy, and Malta, as particularly vulnerable.

The Mediterranean region is more affected because it is a climate change hot spot where temperatures are increasing faster than the global average. “We had a taste of this in 2022 and 2023 when massive heat waves occurred in the region,” Masselot said.

The study also considered expected demographic changes in the European Union. For instance, the population of adults aged 80 and above is projected to increase 2.5-fold between 2024 and 2100. Factors such as age are important given older adults’ increased vulnerability to heat.

Large cities suffer from the so-called heat island effect, in which city centers can be 4°C to 5°C warmer than their surroundings, thanks to a combination of pollution, high insolation (exposure to the Sun’s rays), and heat-absorbing materials such as asphalt and concrete. This effect makes large Mediterranean cities particularly vulnerable.

Mark Nieuwenhuijsen, an expert in air pollution and urban planning at the Barcelona Institute for Global Health who was not involved with the research, said scientists shouldn’t ignore adaptation strategies. “We could easily reduce the temperatures if we replace a lot of the asphalt with more green space.”

Particularly in more polluted cities, air pollution also plays a role by exacerbating the deadly effects of heat. Nieuwenhuijsen highlighted the importance of reducing air pollution, both to reduce heat-related deaths and to reduce heat itself, because carbon dioxide emissions drive temperature increases. Air pollution causes 300,000 deaths every year in the European Union, far more than heat or cold, and the solutions to both temperature- and pollution-related mortality go hand in hand. “We need to address both climate change and air pollution, and we can do it through the same means: the decarbonization of our economy and our transport system,” Nieuwenhuijsen said. “This is the positive message, but we can’t wait.”

Masselot noted that the next step is understanding how to build up resilience to heat, which will be necessary even with immediate mitigation efforts. “That means understanding what makes some cities more resilient to heat than others,” he said. “What are the specific characteristics of these cities that we can use to act upon later and can inform policy?”

—Javier Barbuzano (@javibarbuzano), Science Writer

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Citation: Barbuzano, J. (2025), Europe faces increased heat mortality in coming decades, Eos, 106, https://doi.org/10.1029/2025EO250074. Published on 25 February 2025.

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During the 2026 FIFA World Cup, soccer teams will play a rapid sequence of games that will take them to 16 cities across Canada, Mexico, and the United States. A team of climate scientists and environmental physiologists evaluated the environmental stress the teams will experience during the tournament, finding that players will be at very high risk of extreme heat stress during matches played at 10 of the 16 stadiums. Matches at high-elevation stadiums will also put players at risk because of the lower oxygen content in the air.

“We hope our results will enable optimization of match schedules at individual venues, taking into account the health risks associated with extreme heat stress, but also the physiological reactions to heat potentially affecting the performance of players on the pitch,” said Katarzyna Lindner-Cendrowska, a geoecologist and climatologist at the Polish Academy of Sciences in Warsaw, and lead researcher on the study, which was published in Scientific Reports.

Stadium Swaps Add to Heat Stress

In places where the risks of heat-related illnesses are already high, research has shown that people engaging in intense physical activity such as professional sports are at an even greater risk.

Hot and humid conditions cause an athlete’s body to produce more heat than it can dissipate and enhance the risks of extreme dehydration via sweating. Low levels of atmospheric oxygen make it harder to breathe and oxygenate blood, further lowering a body’s ability to dissipate heat. These physical responses slow cognitive function and reaction times, inhibit the speed and precision of movements, and reduce concentration. Prolonged activity in these environments can also lead to long-term health conditions and, in extreme cases, death.

These risks are well known by sporting groups. The Fédération Internationale de Football Association (FIFA) considers environmental risks to players, coaches, and spectators ahead of events, typically by measuring the wet-bulb globe temperature (WBGT). If WBGT exceeds 32°C (89.6°F), cooling breaks are mandatory during both halves of a FIFA match. Recent research found that just six of the 16 host cities exceed this threshold during an average year, and each less than 5% of the time. (Four more cities exceed this threshold in a hot year.)

But despite its popularity among FIFA and other sporting organizations, WBGT “is considered an imperfect measure of heat load on athletes, as it is prone to underestimating the heat stress level,” Lindner-Cendrowska said. Some stadiums don’t have a way to measure WBGT on site, and the index itself doesn’t consider the additional thermal load if there is high humidity or poor airflow, which makes it harder to cool down, she added.

Lindner-Cendrowska and her colleagues calculated a more precise measure of athletes’ heat stress risk by modifying the universal thermal climate index (UTCI) to include biometric data on core body heat, water loss, and oxygen levels of soccer players while playing. The calculation is similar to the “feels like” temperature on a weather app but for physical exertion.

“UTCI is a measure of the human physiological response to the thermal environment and is considered a better index, as it provides an estimation of how the body feels under a given environmental condition specified by the air temperature, wind, humidity, radiation, clothing, and level of physical effort,” explained George Nassis, an environmental physiologist who focuses on cardiovascular and thermoregulatory systems at the University of Kalba in Sharjah, United Arab Emirates.

Nassis, who was not involved with the study, said the researchers’ choice to evaluate heat stress risk using a modified UTCI was “most appropriate.”

The researchers evaluated hourly average heat stress risk at each 2026 World Cup stadium during the 11 June to 19 July tournament. At 10 of the 16 stadiums, UTCI levels for active athletes could exceed 46°C (114.8°F), the threshold for extreme heat stress.

Midday matches in Houston and Arlington, Texas; and Monterrey, Mexico, put players at the highest risk of heat stress from heat and humidity, with UTCI levels exceeding 50°C (122°F), but morning and evening matches at these locations were nearly as risky. In other stadiums, midday matches provided the most risk of extreme heat stress, but shifting matches to other times of day alleviated the risk.

In addition, matches played in Guadalajara and Tlalpan, Mexico, which are at elevations of 1,566 and 2,240 meters above sea level, respectively, could put athletes at risk due to lower levels of oxygen in the air. Though levels don’t vary greatly during the day, oxygen levels are the lowest just after midday in both stadiums.

“This altitude will also impose stress to the body of the coaching and supporting staff as well as to the visitors traveling to these locations from low-altitude locations,” Nassis said.

What’s more, the logistics of the 2026 World Cup present an additional complication: The 104 matches will take place in nine different Köppen-Geiger climate zones ranging from humid continental regions to subtropical deserts. The researchers called this an “unprecedented” diversity in biothermal conditions.

Teams moving from a low heat stress environment to a high heat stress environment will need to quickly adapt, Nassis said.

“This is a big challenge given that proper heat acclimatization…needs some days to take place,” Nassis added. “As a result, some players of these teams may be vulnerable to excessive heat stress that may compromise their health and performance.”

Helping Players Stay Cool

Most of the risk can be avoided by strategically scheduling matches at cooler and less humid times of day, the researchers concluded. When hot times can’t be avoided, stadiums could use air conditioning in strategic locations at the hottest times to help athletes cool down. The three stadiums that have retractable roofs could cover the fields.

Teams, too, can alter their training regimens to better prepare for the anticipated environmental stress.

“The top two priorities are acclimatization and hydration,” Nassis said. Teams could train outdoors or in artificial indoor environments to acclimatize players to anticipated heat conditions. They can also be more vigilant about monitoring hydration and teaching different ways to effectively cool down when overheated. Teams can implement different cooling strategies during halftime and during any WBGT-mandated cooling breaks, which are only 3 minutes long.

The modifications to match scheduling and training regimens would benefit soccer leagues not just for the 2026 World Cup but for future sporting events, too. The risk of heat stress is increasing around the world because of climate change, which is lengthening and intensifying heat waves and altering precipitation patterns.

“We hope that not only FIFA, but also other international sports federations and organizers of major sporting events will find our results inspiring enough to implement precautionary planning, which is essential for ensuring that sporting events are safe and satisfying experiences for everyone—athletes, spectators, and technical staff,” Lindner-Cendrowska said.

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

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Citation: Cartier, K. M. S. (2025), Soccer players risk heat stress in World Cup stadiums, Eos, 106, https://doi.org/10.1029/2025EO250066. Published on 20 February 2025.

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Climate change made the combination of high heat, dry climate, and forceful winds that drove this month’s devastating Los Angeles wildfires about 35% more likely, according to a report published today by World Weather Attribution (WWA).

The study, conducted by nearly three dozen researchers at institutions in the United States and Europe, examined the Fire Weather Index, which incorporates meteorological factors such as temperature, relative humidity, wind speed, and precipitation to estimate fire danger. Researchers compared the index and resulting likelihood and intensity of fires in a 2025 climate to how they might have been under preindustrial conditions, in which the global mean surface temperature was approximately 1.3°C cooler.

The factors that led to the Los Angeles fires are expected to coincide, on average, every 17 years, whereas in preindustrial conditions they may have occurred together only every 23 years.

The Palisades and Eaton Fires in Los Angeles County have burned nearly 40,000 acres (160 square kilometers), claiming at least 29 human lives and more than 14,000 structures. What ignited the first flames of these fires is not yet known, but they were fanned by what Chad Thackeray called “a recipe for disaster.” Thackeray is a climate scientist at the University of California, Los Angeles (UCLA), who was not involved in the new study.

Water years 2022–2024 brought Los Angeles to a 2-year rain total not seen since the highs of 1888–1890, leading to a buildup of vegetation. Then, a record-breaking heat wave in summer 2024 dried that vegetation out, and Southern California’s rainy season, usually experienced between November and March, were unusually delayed. Between 1 May 2024 and 25 January 2025, the region experienced just 0.3 inch (0.8 centimeter) of rain. Thackeray said the total is normally closer to 6 inches (15 centimeters). Then came dry Santa Ana winds, which flow toward the coast in the region between October and March.

“While Southern California is no stranger to high impact wildfires, the impact of these fires and the timing of these fires in the core of what should be the wet season differentiate this event as an extreme outlier,” said John Abatzoglou, a climatologist at the University of California, Merced, in a statement. “This was a perfect storm of climate-enabled and weather-driven fires impacting the built environment.”

The Role of Climate Change

According to the report, California’s dry season has grown about 23 days longer since the preindustrial era, when global climate was 1.3°C cooler. This increase, the researchers said, is attributable to climate change, but their study did not quantify exactly to what degree. A longer dry season means there is increasing potential for overlap between the dry season, when there is lots of brush to burn, and the peak of the Santa Ana winds, which can speed the spread of fires once they ignite.

Southern California has the most volatile hydroclimate in the United States, usually experiencing either extremely high or extremely low amounts of precipitation, said Sasha Gershunov, a research meteorologist at the University of California, San Diego’s Scripps Institution of Oceanography who was not involved in the study. Previous research has shown that “climate whiplash,” or transitions between the two extremes, has also grown more common in a warming climate.

“Very wet years with lush vegetation growth are increasingly likely to be followed by drought, so dry fuel for wildfires can become more abundant as the climate warms,” said Theo Keeping, a climate and environmental scientist at the Leverhulme Centre for Wildfires, Imperial College London, in a statement.

However, Gershunov added, the rainy season has never arrived so late in the 150 years’ worth of records that exist for the region.

“I can’t say that this winter precipitation is so late because of climate change, but I can say that it’s consistent with what we expect for a warmer future,” he said. “And even in a warmer future, this would still be extreme as far as how late the precipitation is.”

The past weekend brought about 0.5 to 1.5 inches (1.3 to 3.8 centimeters) of rain across the Los Angeles Basin, more than the area has cumulatively received since May 2024. “It’s a start,” Abatzoglou said at a press conference. “Whether it’s going to really end the fire season, I don’t know. I think, temporarily, it’ll pause it.”

The researchers’ observational analysis showed that low rainfall from October to December is about 2.4 times more likely now than it was in the preindustrial climate. As with the extended length of the dry season, the researchers attribute this general shift to climate change but did not determine the quantitative impact of climate change on low rainfall in this study.

What’s Next?

The study projected that if the world warms by another 1.3°C by 2100, fire-prone conditions will grow another 35% more likely.

The authors noted that there is a high level of uncertainty in their reported numbers, which have not yet been peer reviewed, in part because Southern California has an inherently volatile hydroclimate. But their collective analysis in the form of observational results and climate modeling all points to the same conclusion: The conditions most conducive to fire activity are growing more common as the climate warms and will continue to do so under further warming.

The findings align with a report issued by a team of UCLA researchers, including Thackeray and two of the researchers on the WWA study, on 13 January that suggested that the fires were made larger and more intense by climate change because climate change made the vegetation in the region 25% drier than it otherwise would have been.

“Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier, and more flammable,” said Clair Barnes, a statistician at Imperial College London and WWA researcher, in a statement.

—Emily Dieckman (@emfurd), Science Writer

Citation: Dieckman, E. (2025), How much did climate change affect the Los Angeles wildfires?, Eos, 106, https://doi.org/10.1029/2025EO250042. Published on 28 January 2025.

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Source: Community Science

The health effects of heat waves hit some communities harder than others. People with preexisting health conditions, as well as those who have low income or are physically or socially isolated, very old or very young, from racial or ethnic minority groups, or experiencing homelessness, are more at risk for hospitalization and mortality when faced with extreme heat.

In metropolitan areas, public officials have enacted heat mitigation efforts, including providing air-conditioned cooling centers in public places such as government buildings. Watkins et al. developed a tool to identify optimal sites for these cooling centers and help ensure access for those who need it the most.

The team collaborated with groups such as the Arizona Cooling Center Working Group and focused on Phoenix and Tucson, Ariz., metropolitan areas where temperatures frequently top 100°F. Nearly 3,000 emergency room visits stemming from heat-related illnesses occur in the state each year. The researchers chose the two cities to demonstrate that their tool—developed with commercially available software and publicly available data—could be tailored to cities with different sizes, needs, and data availability.

The team used the U.S. Centers for Disease Control and Prevention’s (CDC) Building Resilience Against Climate Effects framework, which was designed to help health officials prepare for the effects of climate change. They also referred to the CDC’s Social Vulnerability Index to identify census tracts with high-risk populations and considered barriers that may prevent people from using cooling centers, including a lack of awareness that such centers exist.

After identifying the locations of existing centers, the researchers identified candidate facilities that could serve as potential cooling center locations, including churches, health care centers, hotels, schools, shelters, and government facilities. The new workflow is designed to be reproducible in other locations by governments and partners with varying resources. The researchers say the work could ultimately improve heat resilience for community members affected by extreme heat. (Community Science, https://doi.org/10.1029/2023CSJ000038, 2024)

—Sarah Derouin (@sarahderouin.bsky.social), Science Writer

Citation: Derouin, S. (2024), Helping the most vulnerable stay cool in extreme heat, Eos, 105, https://doi.org/10.1029/2024EO240472. Published on 5 November 2024.

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

El huracán Helene se originó el 24 de septiembre como una tormenta tropical en el Golfo de México. Para el 26 de septiembre evolucionó rápidamente hasta convertirse en un huracán de Categoría 4, impulsado por una intensificación acelerada sobre las aguas inusualmente cálidas del Golfo.

Los ciclones tropicales que se forman en el Golfo de México y en el noroeste del Mar Caribe presentan, en promedio, un 50% más de probabilidades de experimentar una intensificación rápida durante las olas de calor marinas, según un estudio publicado en agosto en Communications Earth and Environment. Este tipo de huracanes resultan especialmente peligrosos al tocar tierra, ya que su intensidad es más difícil de predecir.

“Si se busca un mejor indicador ambiental [para predecir la intensificación rápida], una vía efectiva consiste en utilizar las olas de calor marinas”, afirmó Soheil Radfar, experto en modelado hidrológico de la Universidad de Alabama y autor principal del estudio.

Un ciclón tropical se considera en proceso de intensificación rápida cuando la velocidad del viento máxima aumenta a razón de 35 millas por hora (56 kilómetros por hora) o más, en un lapso de 24 horas. La mayoría de los huracanes de categoría 3 a 5 experimentan al menos un evento de intensificación rápida a lo largo de su ciclo de vida, como ha ocurrido con cinco de los huracanes más destructivos y particularmente costosos que han afectado esta región: Katrina (2005), Harvey (2017), Ian (2022), Ida (2021) y Michael (2018).

Las olas de calor marinas se producen cuando la temperatura superficial del mar en una zona determinada supera un umbral específico durante 5 o más días consecutivos. Este umbral se establece en función de la temperatura promedio del océano, la cual varía según la estación del año y la ubicación geográfica.

Además de causar daños a la vida marina, las olas de calor oceánicas son uno de los varios factores que pueden contribuir a la intensificación de un ciclón tropical. Aunque las interacciones entre estos fenómenos son complejas y aún no se comprenden por completo, Radfar explicó que un factor clave que vincula ambos eventos climáticos extremos es la disponibilidad de humedad en la atmósfera. Durante una ola de calor marina, la temperatura superficial del mar se eleva por encima de lo habitual, lo que favorece la evaporación del agua y las condiciones que originan las tormentas tropicales.

Probabilidad de episodios de intensificación rápida

Para comprender mejor esta relación, Radfar y sus colegas llevaron a cabo un análisis del comportamiento de las olas de calor marinas y de los ciclones tropicales que ocurrieron entre 1950 y 2022. Luego de analizar la base de datos, el grupo de científicos identificó 738 episodios que coincidían con los criterios de intensificación rápida en el Golfo de México y en el noroeste del Caribe.

Los investigadores identificaron las olas de calor marinas mediante un reanálisis meteorológico, que es una estimación de las condiciones pasadas que integra datos observacionales y simulaciones numéricas para cubrir las áreas sin registros. En este estudio, se empleó el conjunto de datos del Reanálisis 5 del Centro Europeo de Previsiones Meteorológicas a Plazo Medio (ERA5).

Posteriormente, los investigadores se enfocaron en la identificación de las olas de calor que ocurrieron en un plazo de 10 días y dentro de un radio de 125 millas (200 kilómetros) de un evento de intensificación rápida. Aproximadamente el 70% de las tormentas tropicales durante ese período atravesaron al menos una ola de calor marina.

Los datos revelaron tres zonas críticas donde las olas de calor marinas parecían incrementar hasta cinco veces la probabilidad de intensificación rápida: cerca de la Cuenca Caimán en el noroeste del Mar Caribe, la Bahía de Campeche y el Canal de Yucatán en el Golfo de México.

Los autores del estudio también observaron que la duración de las olas de calor marinas en la región se ha incrementado de 36.5 días por año a 49.5 días por año.

Radfar indicó que, como consecuencia del calentamiento global, la influencia de las olas de calor marinas sobre los huracanes podría intensificarse. Sin embargo, también señaló que estas olas pueden no tener un impacto significativo en la cantidad total de tormentas.

David Francisco Bustos Usta, oceanógrafo físico de la Universidad de Concepción en Chile y ajeno a esta investigación, coincidió con la mayoría de las conclusiones del estudio. “A medida que el calentamiento global aumenta, evidentemente hay más energía disponible para potenciar los huracanes”, afirmó. El trabajo de Bustos Usta ha demostrado que es probable que las olas de calor marinas sean más prolongadas y con temperaturas mayores en el futuro. Además, él considera que la frecuencia de los ciclones tropicales también podría aumentar.

Estas olas de calor complican la predicción de los ciclones tropicales y el tiempo de preparación para sus posibles impactos en tierra. Radfar señaló que “cuando se presenta un entorno favorable, la previsión de huracanes se vuelve más difícil, no más sencilla”. Por esta razón, enfatiza la importancia de continuar investigando las olas de calor marinas. Los científicos necesitan comprender cómo las olas de calor marinas interactúan con las tormentas tropicales “para mejorar nuestros modelos de predicción de intensificación rápida, así como para proporcionar información más precisa a los gobiernos y agencias federales”, afirmó.

—Roberto González (@ggonzalitos), Escritor de ciencia

This translation by Emilia Belia was made possible by a partnership with Planeteando and Geolatinas. Esta traducción fue posible gracias a una asociación con Planeteando y Geolatinas.

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Source: Geophysical Research Letters

Because small changes in atmospheric and surface conditions can have large, difficult-to-predict effects on future weather, traditional weather forecasts are released only about 10 days in advance. A longer lead time could help communities better prepare for what’s to come, especially extreme events such as the record-breaking June 2021 U.S. Pacific Northwest heat wave, which melted train power lines, destroyed crops, and caused hundreds of deaths.

Meteorologists commonly use adjoint models to determine how sensitive a forecast is to inaccuracies in initial conditions. These models help determine how small changes in temperature or atmospheric water vapor, for example, can affect the accuracy of conditions forecast for a few days later. Understanding the relationship between the initial conditions and the amount of error in the forecast allows scientists to make changes until they find the set of initial conditions that produces the most accurate forecast.

However, running adjoint models requires significant financial and computing resources, and the models can measure these sensitivities only up to 5 days in advance. Vonich and Hakim tested whether a deep learning approach could provide an easier and more accurate way to determine the optimal set of initial conditions for a 10-day forecast.

To test their approach, they created forecasts of the June 2021 Pacific Northwest heat wave using two different models: the GraphCast model, developed by Google DeepMind, and the Pangu-Weather model, developed by Huawei Cloud. They compared the results to see whether the models behaved similarly, then compared the forecasts to what actually happened during the heat wave. (To avoid influencing the results, data from the heat wave were not included in the dataset used to train the forecasting models.)

The team found that using the deep learning method to identify optimal initial conditions led to a roughly 94% reduction in 10-day forecast errors in the GraphCast model. The approach resulted in a similar reduction in errors when used with the Pangu-Weather model. The team noted that the new approach improved forecasting as far as 23 days in advance. (Geophysical Research Letters, https://doi.org/10.1029/2024GL110651, 2024)

—Sarah Derouin (@sarahderouin.bsky.social), Science Writer

Citation: Derouin, S. (2024), Machine learning could improve extreme weather warnings, Eos, 105, https://doi.org/10.1029/2024EO240452. Published on 11 October 2024.

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Hurricane Helene started out on 24 September as a tropical storm churning through the Gulf of Mexico. By 26 September, it had grown into a category 4 hurricane, experiencing rapid intensification over the abnormally warm waters of the Gulf.

Tropical cyclones in the Gulf of Mexico and northwestern Caribbean Sea are 50% more likely to undergo rapid intensification on average during such marine heat waves, according to a study published in August in Communications Earth and Environment. These types of hurricanes are more dangerous as they make landfall because their intensity is harder to predict.

“If you’re looking for a better environmental predictor [for rapid intensification], a clear path is to use marine heat waves,” said Soheil Radfar, a hydrologic modeling expert at the University of Alabama and first author of the study.

A tropical cyclone is said to be undergoing rapid intensification when it experiences a 35-mile-per-hour (56-kilometer) or greater increase in maximum wind speed over a 24-hour period. Most category 3–5 hurricanes experience at least one such event during their lifetime, including five particularly costly U.S. storms that passed through this region: Katrina (2005), Harvey (2017), Ian (2022), Ida (2021), and Michael (2018).

Marine heat waves occur when sea surface temperatures in a given area exceed a threshold for 5 or more consecutive days. The threshold is based on the baseline temperature of the ocean and varies by season and location.

Along with causing damage to marine life, ocean heat waves are one of several factors that can intensify a tropical cyclone. Although these interactions are complex and not fully understood, Radfar explained that a key factor linking both extreme climate events is the availability of moisture in the air. During a marine heat wave, the sea surface is warmer than usual, making it easier for water to evaporate and fuel tropical storms.

More Likely Intensification

To better understand this relationship, Radfar and his colleagues analyzed the behavior of marine heat waves and tropical cyclones that occurred from 1950 to 2022. They used a database of tropical storms to identify 738 events that matched the criteria for rapid intensification in the Gulf of Mexico and northwestern Caribbean.

They identified marine heat waves from a weather reanalysis—an estimate of past conditions that combines data and simulations to fill areas without records. In this study, the researchers used the European Centre for Medium-Range Weather Forecasts Reanalysis 5 (ERA) data set.

Then they isolated heat waves that occurred within 10 days and 125 miles (200 kilometers) of a rapid intensification event. Roughly 70% of tropical storms during the time period passed over at least one marine heat wave.

The data highlighted three hot spots where marine heat waves appeared to increase the likelihood of rapid intensification up to fivefold: near the Cayman Basin in the northwestern Caribbean Sea and the Bay of Campeche and the Yucatán Channel in the Gulf of Mexico.

The researchers also found that the duration of marine heat waves in the area has increased from 36.5 days per year to 49.5 days per year.

Because of global warming, the influence of marine heat waves on hurricanes may become stronger, Radfar said, though he pointed out that heat waves may not affect the number of storms.

David Francisco Bustos Usta, a physical oceanographer at the Universidad de Concepción in Chile who was not involved in this research, agreed with most of the study’s conclusions. “As global warming increases, you obviously have more energy to power hurricanes,” he said. Bustos Usta’s own work has shown that marine heat waves are likely to be longer and warmer in the future. He thinks the frequency of tropical cyclones could indeed increase.

These heat waves make predicting tropical cyclones and preparing for their landfall challenging. Radfar explained that “when we have a favorable environment, hurricane forecasting is harder, not easier.” That’s why he thinks it’s important to continue studying marine heat waves. Scientists need to understand how they interact with tropical storms “to better inform our rapid intensification prediction models, as well as governments and federal agencies,” he said.

—Roberto González (@ggonzalitos), Science Writer

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Citation: González, R. (2024), Marine heat waves make tropical storm intensification more likely, Eos, 105, https://doi.org/10.1029/2024EO240446. Published on 4 October 2024.

Text © 2024. 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.

Trees in northern cities are feeling the impacts of climate change. Heat and water stress might be hindering tree growth more severely in Boston’s and New York City’s forests than in surrounding rural areas—although experts say more work is needed to know for sure. That’s according to a new study published in Ecological Applications.

If trees struggle to grow in a warmer future, they may not offer cities the same benefits that trees today provide, said environmental ecologist Andrew Reinmann of the City University of New York, who supervised the work.

“There is a lot of research in natural or near-natural environments that are dwindling on our planet, and there is not enough research in managed and urban areas,” said forest ecologist Flurin Babst of the University of Arizona, who was not involved with the research. The new study begins to fill that gap.

A Tale of Three Cities

Urban trees bring a plethora of benefits, from providing shade to removing pollutants from the air to improving mental health. But urban trees also experience unique stresses. Cities tend to be hotter than surrounding areas, their soil tends to be more compacted, and city air tends to be drier and contain more particulate matter.

These stresses are compounded by heat waves and droughts brought on by climate change, according to the new study. In his previous research as a postdoc at Boston University, Reinmann and his colleagues found that unusually hot weather affected the growth of trees in Boston’s urban forests more strongly than that of trees in nearby rural forests. He wondered whether the same was true in other cities.

In 2020, Barnard College undergraduate student Kayla Warner used her time during COVID lockdown to dig into this question by analyzing tree cores that had been collected for other research prior to the pandemic. The cores came from several dozen trees in each of three cities—Boston, New York, and Baltimore—as well as from nearby rural forests. The researchers selected these locales because they have similarly humid, temperate climates, but a wide geographic span.

Warner correlated the growth rings of three species that are common in these cities—red oak, white oak, and red maple—with climate data going back to the 1990s.

Distinct Behavior

During much of the year, the growth rates of oak trees in Boston and New York suffered more from hot, dry weather than the growth rates of trees in surrounding areas, the researchers found. For all trees in Massachusetts and New York, the distance between rings grown during hot, dry years was smaller than between those grown during wetter, cooler years. But that distance was reduced more significantly for city trees than for their rural counterparts.

Baltimore’s urban forests also suffered from water stress, but unlike in the other two cities, they were not strongly affected by heat stress.

“I don’t have a clear answer for why Maryland behaves a little bit differently than New York and Boston,” Reinmann said.

“It reminds me of some research on people’s experiences of heat stress,” said quantitative ecologist Ailene Ettinger of The Nature Conservancy. “People in northern latitude cities also tend to be much more sensitive to high heat events because we’re not as well acclimated.”

It’s possible that each city contains genetically distinct subspecies of maples and oaks that have adapted to different weather patterns, Reinmann said. Given that hypothesis, Babst said it could make sense to compare the growth of trees derived from all three cities side by side under a range of climate conditions—a “common garden experiment,” as it’s called in the field. “That would be a really, really cool project,” he added.

The study is a nice start, but scientists have a way to go before they fully understand how urban trees are responding to climate. “Sample size in this research is relatively small,” said forest ecologist and postdoc Jiejie Wang of Université Laval. Analyzing more trees will help researchers draw robust conclusions. Babst suggested analyzing longer time series.

Measuring water stress also can be tricky because it can be difficult to say exactly how much of the water in the environment is actually available to trees. Wang said she thinks analyzing soil moisture would be the most appropriate way to determine how much water is available to trees. Instead, the researchers used a combined measure of heat and water. “I would have liked to see a water-only metric, like simply precipitation, for example,” Babst said.

The sooner follow-up work can happen, the better, Ettinger said. “Urban trees are critical for bolstering our climate change resilience.”

—Saima May Sidik (@saimamaysidik), Science Writer

Citation: Sidik, S. M. (2024), Some urban trees suffer under climate stress, Eos, 105, https://doi.org/10.1029/2024EO240415. Published on 17 September 2024.

Text © 2024. 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.

With near-constant reports of wildfire catastrophes in the media, it seems like extreme fires are occurring more regularly. And a recent study in Nature Ecology and Evolution confirms it—showing that intense wildfires are now twice as common as they were 2 decades ago.

Many scientists had suspected that extreme fires were getting worse, said Calum Cunningham, a pyrogeographer from the University of Tasmania who led the study. “But we’ve not had the evidence to prove this at a global scale before,” he said.

Periodic, small wildfires can help maintain healthy ecosystems by clearing dead vegetation. But extreme blazes burn hotter and more uncontrollably, causing significant damage to the environment, people’s health, and economies. Large wildfires also emit vast stores of carbon, exacerbating global warming—in turn fueling conditions for more wildfires.

“We focused on the energetically extreme fires,” Cunningham said. Global wildfire patterns are usually established by counting pixels of burned land on satellite images. But the traditional approach overlooks the most dangerous fires, he said. “The intensity of fires, particularly the extreme ones, also matters.”

Cunningham and his colleagues mapped the intensity of more than 30 million wildfire events (made up of clusters and individual fires) detected by NASA’s MODIS (Moderate Resolution Imaging Spectroradiometer) satellites between 2003 and 2023, homing in on the most intense burns.

Using infrared sensors, MODIS satellites can see the heat released by wildfires. “That heat energy directly relates to the amount of biomass burned and the emissions released,” explained Cunningham. “It’s essentially a measure of environmental damage.”

The researchers took daily snapshots of wildfires around the world by summing the heat energy measured within 20- × 20-kilometer (12- × 12-mile) blocks across Earth’s surface. Then they isolated which of these blocks contained the top 0.01% of wildfires according to their radiative power (about 2,900 fire events, made up of clusters and individual fires).

“The analysis is impressive,” said Virginia Iglesias, a wildfire ecologist from the University of Colorado Boulder who was not involved in the study. With long-term satellite records now available, handling the abundance of data poses a challenge, she added. “Pinpointing the extreme events meant they could tease out an important trend.”

An Exponential Rise

Cunningham said that 6 of the past 7 years experienced the highest number of extreme fires. Last year saw the most extreme fires and was also the hottest year on record.

That uptick in extreme fires fits with existing observations of worsening fire activity in specific regions, Iglesias said. In a 2022 study, Iglesias showed that wildfires had become larger and more frequent across the United States since the early 2000s.

However, the global picture of wildfire had been less clear because records that were long enough were not available. Scientists have previously shown a long-term reduction in the acreage burned by wildfires around the world. That pattern reflects changing agricultural practices (and a decline in the use of fire to clear land) in the savanna grasslands of Africa, where around 70% of the world’s burning by land area occurs.

Savanna fires typically burn at lower intensity, Cunningham said, and once those fires were filtered from the global data set, the steep rise in extreme wildfires was clear.

Cunningham and his colleagues found that the global trend was driven by a dramatic worsening of extreme wildfires in the western United States, Canada, and Russia. They noted an elevenfold increase in extreme fires in the coniferous forests of North America since 2003. High-latitude boreal forests experienced a sevenfold increase over the same period.

Fanning the Flames

“Climate change is unambiguously making the conditions required for an extreme fire more common,” said Cunningham. The study didn’t try to make the link to climate change, but, he said, scientists have a wealth of evidence to show that hotter, drier conditions are turning landscapes into tinderboxes, making wildfires more likely and more energetic.

Iglesias said that legacies of land management are likely compounding the effects of climate change. Particularly in North America, aggressive fire suppression policies during the 20th century have allowed dead vegetation to pile up. “All that excess fuel, coupled with a drying climate, stacks the odds in favor of intense fires,” she said.

As climate change accelerates and wildfires burn with more intensity, our relationship with fire needs to change too, Cunningham said. “We’ve moved beyond a period where suppressing all fire was the objective. It’s now time to learn to live in fire-prone landscapes.” Using frequent, low-intensity fires as a tool to reduce fuel loads and mitigate against larger fires, just as Indigenous peoples have for millennia, could be one way forward.

—Erin Martin-Jones, Science Writer

Citation: Martin-Jones, E. (2024), Extreme wildfires are getting more extreme and occurring more often, Eos, 105, https://doi.org/10.1029/2024EO240310. Published on 26 July 2024.

Text © 2024. The authors. CC BY-NC-ND 3.0
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