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ocean warming
Fossil Fuels Blamed as 84% of World's Coral Reefs Hit by Worst Bleaching Event Ever Recorded
"The magnitude and extent of the heat stress is shocking," said one marine scientist.
Apr 23, 2025
A year after scientists warned the world was seeing its fourth mass coral bleaching event, rising ocean temperatures fueled by greenhouse gas emissions have now devastated 84% of Earth's coral reefs—with likely knock-on effects for about a third of all marine species and 1 billion people whose lives and livelihoods are directly impacted by the health of the "rainforests of the sea."
Coral Reef Watch at the U.S. National Oceanic and Atmospheric Administration (NOAA) released its latest data on Wednesday, showing the current bleaching event has become the most widespread on record, impacting reefs from the Indian Ocean to the Atlantic and Pacific.
The news comes three months after scientists confirmed 2024 was the hottest year on record. Last year, meteorologists also found that sea surface temperatures in the North Atlantic were about 2°F higher than the 1990-2020 average and nearly 3°F above the average in the 1980s.
Unusually warm ocean waters cause corals to expel algae that give the reefs their bright color and deliver nutrients, supporting the immense biodiversity that is normally found within the reefs. Prolonged bleaching can kill coral reefs.
"The magnitude and extent of the heat stress is shocking," marine scientist Melanie McField, the founder of the Healthy Reefs for Healthy People initiative in the Caribbean, told Reuters. "Some reefs that had thus far escaped major heat stress and we thought to be somewhat resilient, succumbed to partial mortalities in 2024."
Derek Manzello, director of Coral Reef Watch, told The Guardian that some reefs that had been considered safe from the impact of rising ocean temperatures have now been bleached.
"Some reefs that had thus far escaped major heat stress and we thought to be somewhat resilient, succumbed to partial mortalities in 2024."
“The fact that so many reef areas have been impacted," he said, "suggests that ocean warming has reached a level where there is no longer any safe harbor from coral bleaching and its ramifications."
The current coral bleaching event began in January 2023. That same year, scientists were alarmed by an ocean heatwave off the coast of Florida that rapidly bleached the continental United States' only living barrier reef.
That event prompted NOAA to introduce a new coral bleaching alert scale from Level 1—significant bleaching—to Level 5, at which point a reef is approaching mortality.
Another ocean heatwave last year threatened Australia's Great Barrier Reef, eight years after nearly half of the coral in some northern parts of the 1,400-mile reef was killed by a mass bleaching event.
But recent major bleaching events affecting specific reefs have not compared to the current widespread devastation in the world's oceans.
“Reefs have not encountered this before," said Britta Schaffelke, coordinator of the Global Coral Reef Monitoring Network, told The Guardian. "With the ongoing bleaching it's almost overwhelming the capacity of people to do the monitoring they need to do. The fact that this most recent, global-scale coral bleaching event is still ongoing takes the world's reefs into uncharted waters."
The other three mass bleaching events on record occurred from 2014-17, with 68% of the world's reefs affected; in 2010, when 37% were impacted; and in 1998, when 21% suffered bleaching.
The report from Coral Reef Watch followed the Trump administration's under-the-radar release of climate change data that minimized NOAA's findings about the level of planet-heating carbon dioxide emissions in the atmosphere. President Donald Trump also issued an executive order demanding sunset provisions for every existing energy regulation and notified companies that they can seek exemptions to clean air regulations.
Joerg Wiedenmann, a marine biologist at the Coral Reef Laboratory at the University of Southampton in England, emphasized that taking action to stop the heating of the world's oceans could protect coral reefs, the marine species they provide habitats to, and the communities they support by protecting coastlines and providing fishing and tourism jobs.
"If we manage to decrease ocean warming," Wiedenmann told The Washington Post, "there is always a chance for corals to recover."
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Alarming Heat Streak Continues as February Shatters Temperature Record
"As remarkable as this might appear, it is not really surprising as the continuous warming of the climate system inevitably leads to new temperature extremes," said the head of the E.U. climate service.
Mar 07, 2024
Last month was the warmest February on record, the European Union’s climate service said Wednesday, marking the ninth consecutive month of unprecedented heat as the climate crisis continues to drive up global temperatures.
Climate scientists say the climate crisis, without a doubt, is to blame for increased temperatures.
Not only was it warm above sea level—global ocean temperatures also reached a record high last month. That's not just for February but for any month on record.
"Ocean warming has prompted concerns about the mass bleaching of coral reefs. It also raises global sea levels and can help to fuel higher intensity hurricanes," the BBC reports. "Unusually warm waters may also have been a factor in another exceptional month for Antarctic sea ice. The three lowest minimum extents in the satellite era have now occurred in the last three years."
The #C3S's monthly climate bulletin is out now:
📈 February 2024 was globally the warmest on record;
📈 Global Sea Surface Temperatures hit record highs.
▶️https://t.co/XEmBnArhh6 pic.twitter.com/uUubVY9c05
— Copernicus ECMWF (@CopernicusECMWF) March 7, 2024
Arctic sea ice is also disappearing, and the Arctic could be virtually ice-free during the summer within a decade.
"February joins the long streak of records of the last few months," said Carlo Buentempo, director of the Copernicus Climate Change Service. "As remarkable as this might appear, it is not really surprising as the continuous warming of the climate system inevitably leads to new temperature extremes."
“The climate responds to the actual concentrations of greenhouse gases in the atmosphere so, unless we manage to stabilize those, we will inevitably face new global temperature records and their consequences,” Buentempo added.
The last year has been over 1.5°C above pre-industrial averages—1.56°C, to be exact—but that won't signify a breach of the goals set in the Paris Agreement unless temperatures remain elevated for the next few years.
"A year ago, the fact that the global temperature for a particular month would reach 1.5°C above the pre-industrial level would have been considered exceptional," Julien Nicolas, a senior scientist at Copernicus, told The New York Times.
The world will have to get off of fossil fuels in order to halt runaway warming, and this year could help determine the future of the climate, considering one of the people running to lead the nation appears destined to unleash billions of tons of additional planet-warming emissions should he return to office.
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Hurricane Lee: An Ominous Storm Even If It Doesn't Come to Land
"This is your hurricane on fossil fueled climate change."
Sep 10, 2023
Hurricane Lee, which became a monster Category 5 before weakening over the weekend and which may or may not ever make landfall, is being treated as a warning by meteorologists and climate experts who say the storm's behavior over recent days could have dire future implications.
The National Hurricane Center said Saturday that Lee would move well north of Puerto Rico and the Virgin Islands but that dangerous beach conditions may be seen along the Atlantic coastline of the United States. On Thursday, the hurricane jumped from a Category 3 storm to a Category 5 in less than 24 hours at a pace faster than what is called "rapid intensification"—when sustained winds increase by 35 mph over the course of a day.
Marshall Shepherd, director of the University of Georgia's atmospheric sciences program and a past president of the American Meteorological Society, explained to the Associated Press how Hurricane Lee intensified at more than double that rate, moving it into a category he called hyperintensification.
"This one increased by 80 mph (129 kph)," Shepherd said. "I can't emphasize this enough. We used to have this metric of 35 mph, and here's a storm that did twice that amount, and we're seeing that happen more frequently." If future storms, fueled by increasingly hotter ocean temperatures, continue with this trend it will have disastrous consequences for regions that rarely, if ever, experience such powerful storms.
As Lee became reached Category 5 status on Thursday, meteorologist Jeff Berardelli pointed out the increasing frequency of storms reaching that threshold:
Responding to the same trend and data, climate movement organizer Jamie Henn said: "This is your hurricane on fossil fueled climate change."
And it's a global phenomenon, not just for hurricanes forming in the Atlantic. For the first time since records began, Category 5 storms (or the equivalent) have been recorded in each of the world's designated cyclone basins.
"Hurricanes are getting stronger at higher latitudes," warned Shepherd in his assessment. "If that trend continues, that brings into play places like Washington, D.C., New York and Boston."
As science and environment journalist Matt Simon wrote for Wired on Saturday:
Rapid intensification makes hurricanes extra dangerous because they change so quickly and dramatically as they approach the coastline. It's a bit like watching a driver who’s cruising along at 25 miles per hour and then guns it right before hitting an obstruction. Residents might be expecting a storm they can ride out, but are instead faced with a full-scale hurricane that's quickly grown monstrous.
Exploring the science and talking with experts of rapid intensification, Simon explained why Lee is being treated as "a warning" and that people and communities should "get ready for more of this phenomenon as the planet warms."
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Ocean Warming Study So Distressing, Some Scientists Didn't Even Want to Talk About It
"This is one of those 'sit up and read very carefully' moments," said one science journalist.
Apr 25, 2023
Scientists are so alarmed by a new study on ocean warming that some declined to speak about it on the record, the BBC reported Tuesday.
"One spoke of being 'extremely worried and completely stressed,'" the outlet reported regarding a scientist who was approached about research published in the journal Earth System Science Data on April 17, as the study warned that the ocean is heating up more rapidly than experts previously realized—posing a greater risk for sea-level rise, extreme weather, and the loss of marine ecosystems.
Scientists from institutions including Mercator Ocean International in France, Scripps Institution of Oceanography in the United States, and Royal Netherlands Institute for Sea Research collaborated to discover that as the planet has accumulated as much heat in the past 15 years as it did in the previous 45 years, the majority of the excess heat has been absorbed by the oceans.
In March, researchers examining the ocean off the east coast of North America found that the water's surface was 13.8°C, or 24.8°F, hotter than the average temperature between 1981 and 2011.
The study notes that a rapid drop in shipping-related pollution could be behind some of the most recent warming, since fuel regulations introduced in 2020 by the International Maritime Organization reduced the heat-reflecting aerosol particles in the atmosphere and caused the ocean to absorb more energy.
But that doesn't account for the average global ocean surface temperature rising by 0.9°C from preindustrial levels, with 0.6°C taking place in the last four decades.
The study represents "one of those 'sit up and read very carefully' moments," said former BBC science editor David Shukman.
Lead study author Karina Von Schuckmann of Mercator Ocean International told the BBC that "it's not yet well established, why such a rapid change, and such a huge change is happening."
"We have doubled the heat in the climate system the last 15 years, I don't want to say this is climate change, or natural variability or a mixture of both, we don't know yet," she said. "But we do see this change."
Scientists have consistently warned that the continued burning of fossil fuels by humans is heating the planet, including the oceans. Hotter oceans could lead to further glacial melting—in turn weakening ocean currents that carry warm water across the globe and support the global food chain—as well as intensified hurricanes and tropical storms, ocean acidification, and rising sea levels due to thermal expansion.
A study published earlier this year also found that rising ocean temperatures combined with high levels of salinity lead to the "stratification" of the oceans, and in turn, a loss of oxygen in the water.
"Deoxygenation itself is a nightmare for not only marine life and ecosystems but also for humans and our terrestrial ecosystems," researchers from the Chinese Academy of Sciences, the National Center for Atmospheric Research, and the National Oceanic and Atmospheric Administration said in January. "Reducing oceanic diversity and displacing important species can wreak havoc on fishing-dependent communities and their economies, and this can have a ripple effect on the way most people are able to interact with their environment."
The unusual warming trend over recent years has been detected as a strong El Niño Southern Oscillation (ENSO) is expected to form in the coming months—a naturally occurring phenomenon that warms oceans and will reverse the cooling impact of La Niña, which has been in effect for the past three years.
"If a new El Niño comes on top of it, we will probably have additional global warming of 0.2-0.25°C," Dr. Josef Ludescher of the Potsdam Institute for Climate Research told the BBC.
The world's oceans are a crucial tool in moderating the climate, as they absorb heat trapped in the atmosphere by greenhouse gases.
Too much warming has led to concerns among scientists that "as more heat goes into the ocean, the waters may be less able to store excess energy," the BBC reported.
The anxiety of climate experts regarding the new findings, said the global climate action movement Extinction Rebellion, drives home the point that "scientists are just people with lives and families who've learnt to understand the implications of data better."
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As Planet Warms, Oceans Face Threatening Changes Unseen in 3 Million Years
New study predicts major disruptions to entire world ecology under both moderate and severe warming levels
Jun 02, 2015
Continued warming of the world's oceans may trigger disruptions to marine life not seen in 3 million years, according to a new study published Monday in the journal Nature Climate Change.
The study, put forth by scientists from the University of Science and Technology in Lille, France, and other institutions, aims to put the anticipated ecological crisis in a historical perspective.
Among the foreseen changes are extinction of some of the ocean's keystone species as well as the widespread influx of invasive plants and animals particularly in "temperate and polar biomes."
"Climate change may rapidly reorganize marine diversity over large oceanic regions," states the report. "The intensity of this reorganization will depend, unsurprisingly, on the magnitude of warming."
According to the report, a "moderate warming" scenario, with projected global warming ranging from 0.9 to 2.6 C, "will increase by threefold the changes already observed over the past 50 years."
However, of most concern is that severe warming, with a projected increase of 0.8 to 4.8degC, "will affect marine biodiversity to a greater extent than temperature changes that took place between either the Last Glacial Maximum or the mid-Pliocene and today," impacting as much as 70 percent of the world's oceans.
The effects of both the moderate and severe scenarios will ultimately impact humans, said co-author Richard Kirby with Britain's University of Plymouth, as the global ecosystem will inevitably be altered.
"When the temperature of the environment changes, animals and plants change in abundance locally or may move to new locations if the habitat is suitable," Kirby said. "These movements ultimately affect the food web and ecology, and if they are rapid, the food web may become uncoupled."
The study, Kirby continued, highlights "the changes in the Earth's biology that may lie ahead if we do not address global warming."
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