EOS

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A pair of new climate studies suggest an intensification of strong storms called nor’easters and other disruptive extremes affecting the East Coast of North America on an overheated planet.

Nor’easters generally form within about 100 miles of the East Coast between North Carolina and Massachusetts, often when cooler air from Canada meets warm, moist air over Gulf Stream waters. Those contrasting air masses can start to spin with a nudge from the jet stream, fueling storms that can produce damaging winds, coastal flooding and intense, disruptive snowfall in the winter.

The strongest nor’easters are already significantly windier and rainer than they were in the middle of the 20th century, said University of Pennsylvania climate scientist Michael Mann, a coauthor of a study published on 14 July in the Proceedings of the National Academy of Sciences.

A 2022 study showed a similar trend of intensification for storms forming over the Atlantic and hitting Europe, and that the track of those storms is moving northward, potentially putting unsuspecting areas more at risk.

Mann said the increases in the intensity and precipitation rates of the strongest nor’easters have likely been fueled by increases in ocean temperatures and the increased moisture capacity of a warming atmosphere.

“There are two reasons to look at the most intense nor’easters,” Mann said via email. “First, from an impact standpoint, they do the most damage, including coastal erosion, destruction and paralyzing snowfalls. The 1962 Ash Wednesday storm, with 84 mile per hour gusts, is a great example. In today’s dollars, it did $21 billion worth of damage.”

And just last February, a classic nor’easter described at the time as a “bomb cyclone” dropped several feet of snow over parts of Virginia and North Carolina and caused damaging flooding along parts of the Massachusetts coast, Eastern Long Island, and the Jersey Shore.

Mann said the increases in the intensity and precipitation rates of the strongest nor’easters have likely been fueled by increases in ocean temperatures and the increased moisture capacity of a warming atmosphere.

The researchers tracked 900 nor’easters back to 1940 in combination with a careful reanalysis of historical climate conditions surrounding the storms, including notable events like the Perfect Storm in 1991, Storm of the Century in 1993, and Snowmaggedon in 2010.

In the very strongest storms, the wind speeds have increased about 5.4%, from 69 to 71 mph, “but since destructive potential goes as the wind speed cubed, that’s a roughly 17% increase in destructive potential,” Mann said.

Overall, he added, a lot of research suggests that extra warming in the Arctic, which reduces the temperature contrast between high latitudes and midlatitudes, will lead to less storminess overall, but the destructive potential of intensifying nor’easters warrants attention.

Compared to other types of storms, nor’easters feed more off the heat of the ocean, which remains considerable in winter, “So those storms that can make it past the obstacles to development have the potential to grow stronger than they otherwise would have,” he said. “While we don’t see any evidence of increased intensity for the ‘average’ nor’easter, the strongest ones are clearly getting stronger.”

“My interest in these storms, and how they’re being impacted by climate change has been inspired by two personal experiences,” he said, first noting the March 1993 “storm of the century,” which caused 270 deaths and $12.2 billion worth of damage across 26 states, according to the National Ocean and Atmospheric Administration.

Mann said the storm disrupted a spring break road trip in Florida, where the temperature in St. Augustine dropped from the 70s to 40s in a few hours.

“We drove past Okefenokee Swamp later that day and it was snowing,” Mann said. “Then we stopped off in Southern Georgia for the night and temperatures dropped to the mid 20s. We froze. I will never forget that.”

“The strongest nor’easters can have impacts comparable to category 1 and 2 hurricanes, with effects encompassing a larger area.”

He said he remembers another infamous nor’easter, Snowmaggedon, from February 2010 because a U.S. senator who rejects science that proves human-caused warming used the occasion to build what he called an igloo in an attempt to cast doubt on climate science. At the same time, Mann said he ended up stuck in a hotel room for three days with several feet of snow blocking most roads in Pennsylvania.

As such storms grow stronger in a warming world, said Anthony Broccoli, an atmospheric scientist at Rutgers University who was not involved in the new study but who also researches nor’easters, “it will be important to remember that the strongest nor’easters can have impacts comparable to category 1 and 2 hurricanes, with effects encompassing a larger area.”

With sea level rise accelerating along the East Coast, Broccoli added that nor’easters “will lead to greater coastal flooding even without any changes in storm intensity.”

The increased thermal energy from warming oceans is likely driving the trend toward stronger nor’easters, and there could be other large-scale changes to ocean currents and winds that could shift the tracks of nor’easters, potentially raising unexpected risks in new areas, he said.

The new research doesn’t mean that temperatures are getting colder, but that the frigid air that still does form over the Arctic in winter will still make its way south, showing up perhaps more frequently in unexpected regions, or with increased unusual seasonal extremes that can damage crops.

The Arctic Connection

Large-scale changes affecting nor’easters and cold weather extremes in the United States likely include accelerated warming of the Arctic region, climatologist Judah Cohen said in an email interview. Cohen, a visiting scientist at MIT and director of seasonal research with Atmospheric and Environmental Research, published an 11 July study in Science Advances that bolsters evidence for a climate connection.

Cohen said that, as far as he’s concerned, the new paper is “preaching to the choir,” because its conclusions are consistent with his own research showing that “Arctic change can lead to episodic increases in severe winter weather in the U.S. east of the Rockies including extreme cold and disruptive snowfalls.”

The temperature contrast between the Arctic and the midlatitudes is one of the main forces that creates key winds at different altitudes, like the jet stream and polar vortex, and moves weather systems around the Northern Hemisphere.

Cohen’s work over recent years suggests that accelerated warming of the Arctic “stretches” the polar vortex—like elongating a round rubber band—into positions that let cold polar air spill southward more frequently.

He noted that two of the most recent nor’easters specifically named in the new paper by Mann and his coauthors, in March 1993 and January 2018, occurred during stretched polar vortex events. The new paper, he said, “provides a medley of possible causes but doesn’t settle on any one cause.”

His own recent paper, he said, shows “for the first time that stretched polar vortex events are overwhelmingly associated with extreme cold and heavy snowfall in the Eastern U.S.,” compared to other polar vortex configurations.

Often the polar vortex flows in a tight coil around the North Pole, containing the Arctic air, but Cohen’s study, and other research, suggest a trend to more frequent stretched polar vortexes and the associated cold-air outbreaks and storm impacts. Taken altogether, he said the new research helps explain regional “winter cooling trends and an increased number of heavy snowfalls in the Eastern U.S. over the past two and a half decades.”

—Bob Berwyn (@bberwyn), Inside Climate News

Artificial light and higher temperatures in cities may lengthen the growing season by up to 24 days, according to a new study in Nature Cities.

Previous studies have observed that plant growth starts earlier and ends later in cities than in rural areas. But these studies haven’t concluded whether this difference depends more on heat or light, both of which regulate the growing season and are amplified in urban centers.

The new study’s authors used satellite data to estimate nighttime light pollution in cities and pinpoint the start and end of the growing season. They found that the amount of artificial light at night plays a bigger role in growing season length than temperature does, especially by delaying the end of the season.

“This study highlights artificial light at night as a powerful and independent force on plant phenology,” said Shuqing Zhao, an urban ecologist at Hainan University in China who was not involved in the research. “It marks a major step forward in our understanding of how nonclimatic urban factors influence plant life cycles.”

City Lights Trick Plants

“Plants rely on both temperature and light as environmental cues to regulate their growth,” explained Lin Meng, an environmental scientist at Vanderbilt University and a coauthor of the study. In the spring, warmer temperatures and lengthening days signal to plants that it’s time to bud and produce new leaves. In the fall, colder, shorter days prompt plants to drop their leaves and prepare for winter.

“Plants evolved with predictable cycles of light and darkness—now, cities are flipping that on its head.”

But in cities, these essential cues can be disrupted. Cities are typically hotter than surrounding rural areas—the so-called urban heat island effect—and much brighter because of the abundance of artificial light. These disrupted cues “can trick plants into thinking the growing season is longer than it actually is,” Meng said. “Plants evolved with predictable cycles of light and darkness—now, cities are flipping that on its head.”

To assess how heat and light are affecting urban plants, Meng and her coauthors used satellite data from 428 cities in the Northern Hemisphere, collected from 2014 to 2020. For each city, the researchers analyzed correlations between the amount of artificial light at night (ALAN), air temperature, and the length of the growing season.

The scientists found that on average, the growing season started 12.6 days earlier and ended 11.2 days later in city centers compared with rural areas. ALAN apparently played an important role in extending the growing season, especially in the autumn, when ALAN’s influence exceeded that of temperature.

Anna Kołton, a plant scientist at the University of Agriculture in Krakow who was not part of the research, highlighted the significance of this result. “The impact of climate change, including increased temperatures on plant functioning, is widely discussed, but light pollution is hardly considered by anyone as a significant factor affecting plant life.” The new study is among the first to bring ALAN’s effects into the spotlight.

“Every Day Needs a Night”

“The extension of urban vegetation may at first glance appear positive,” said Kołton. But this positive impression is deceiving. In reality, an extended growing season “poses a threat to the functioning of urban greenery.”

Delaying the end of the growing season may be especially disruptive. In the fall, shortening days prompt plants to reduce their metabolic activity, drop their leaves, and toughen up their cell walls to withstand the coming winter. But if they are constantly stimulated by artificial light, Kołton pointed out, urban plants may miss their cue and be unprepared when the cold hits.

“Every day needs a night, and so do our trees, pollinators, and the rhythms of nature we all depend on.”

Longer growing seasons also affect animals and people. “Flowers might bloom before their pollinators are active, or leaf-out might not align with bird migration,” said Meng. “And for people, a longer growing season means earlier and prolonged pollen exposure, which can make allergy seasons worse.”

As cities become bigger and brighter, their growing seasons will likely continue to lengthen unless the impacts of ALAN are addressed. “The good news is that unlike temperature, artificial light is something we can manage relatively easily,” said Meng. She and Zhao both suggested that swapping blue-rich LED lamps for warmer LEDs (which are less stimulating to plants), introducing motion-activated or shielded lights, and reducing lighting in green spaces could limit light pollution in cities.

“Every day needs a night,” Meng said, “and so do our trees, pollinators, and the rhythms of nature we all depend on.”

—Caroline Hasler (@carbonbasedcary), Science Writer

Citation: Hasler, C. (2025), Artificial light lengthens the urban growing season, Eos, 106, https://doi.org/10.1029/2025EO250254. Published on 18 July 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.

A computer model drawing on satellite and climate data could give scientists an early warning of coastal marsh decline.

Using the model, scientists detected a decline in underground plant biomass across much of Georgia’s coastal marshes between 2014 and 2023. Critically, this loss occurred even though the marsh grasses appeared green and thriving at the surface.

The findings, published last month in Proceedings of the National Academy of Sciences of the United States of America, could help land managers identify targets for restoration before more severe damage takes hold.

Roots of Concern

Marshes “are not only economically but culturally and recreationally important places for the people who both live along the coast and visit the coast.”

Marshes “are not only economically but culturally and recreationally important places for the people who both live along the coast and visit the coast,” said study coauthor Kyle Runion, a landscape ecologist at the University of Georgia. They help control flooding, sequester carbon, and provide space for hunting, fishing, and wildlife spotting.

But rapid sea level rise has threatened coastal marsh grasses, as higher waters and more frequent flooding inundate the soil and choke oxygen supply at the roots. In a healthy ecosystem, underground plant biomass staves off erosion and adds organic matter that eventually decomposes into more soil, boosting the marsh’s resilience to sea level rise, so declining root systems can be an early sign of trouble in marshlands.

Marshlands can appear healthy even as their roots are dying off, said Bernard Wood, a wetland ecologist at the Coastal Protection and Restoration Authority of Louisiana who was not involved in the study.

A trip into the marsh itself tells a different story, however. “You could just pick up this huge clump of grass with one hand, and it barely has anything holding it to the ground,” Wood said.

Sea level rise can threaten the roots of smooth cordgrass, even as the leafy part of the plant can appear healthy. The exposed roots of smooth cordgrass are seen here at a marsh edge along the Folly River in Georgia. Credit: Kyle Runion/Colorado State University BERM and Biomass

To understand how Georgia’s marshes are responding to changing conditions, researchers developed and tested the Belowground Ecosystem Resilience Model (BERM) in 2021. BERM draws from satellite and climate data to estimate the belowground biomass of Spartina alterniflora, or smooth cordgrass, in coastal areas.

In the 2021 study, the team collected information on environmental conditions in Georgia salt marshes from Landsat 8, Daymet climate summaries, and other publicly available datasets. They built a machine learning model that could predict belowground biomass and trained it on field data from four marsh sites. Researchers found that elevation, vapor pressure, and flooding frequency and depth were some of the most important variables in predicting root biomass.

How a salt marsh looks on the surface isn’t necessarily an indicator of how it’s truly faring.

In the new study, Runion and his colleagues applied the model to estimate changes in S. alterniflora root biomass over nearly 700 square kilometers of Georgia coast between 2014 and 2023.

During that time, belowground biomass decreased about 1% per year on average, the team found. About 72% of the salt marsh area saw declines in underground plant mass. At the same time, aboveground biomass—the visible part of the marsh grass—increased over most of the study area.

The disparity between biomass above and below could occur because aboveground biomass is less sensitive to flooding than root systems. Or the increase might be temporary, as flooding initially delivers nutrients but eventually drowns the plant. In either case, how a salt marsh looks on the surface isn’t necessarily an indicator of how it’s truly faring.

Tool for Conservation

Early-warning signs of marsh decline provided by the model could be crucial for conservation. “Once [marsh] loss occurs, that can be irreversible,” Runion said. “By getting a sign of deterioration before loss happens, that’s when we can intervene and much more easily do something about this.”

Mapping which areas of the marsh are most vulnerable could also combat the tendency to see marshes as either “doomed” or “not doomed” and target conservation efforts to the areas most in need, said Denise Reed, a coastal geomorphologist at the University of New Orleans who was not involved in the study. Though belowground biomass is declining on average, some areas of the coast are experiencing less change than others.

“There are some complex patterns going on—probably something that it would be great to understand a little bit better,” Reed said. But “this idea of being able to detect areas which are in worse condition versus areas that are in better condition from the soil’s perspective is really helpful.”

For now, BERM can predict belowground biomass only in Georgia marshes. Other regions have different plant species and flooding dynamics that could alter the relationships BERM relies on. But with additional calibration data from other salt marshes, the team could make the model more widely applicable, Runion said.

“We are looking to expand this sort of modeling framework to include different species along the Gulf and East Coast,” Runion said.

—Skyler Ware (@skylerdware), Science Writer

Citation: Ware, S. (2025), Machine learning model flags early, invisible signs of marsh decline, Eos, 106, https://doi.org/10.1029/2025EO250253. Published on 17 July 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.