We Have Entered the Era of ‘Global Boiling’—Marine Wildlife, Ecosystems, and Economies Are Being Devastated
From The Observatory
Source: Earth Food Life Project
Marine heat waves are causing record-breaking ocean temperatures that kill animals and impact ocean-based industries.
This article was produced by Earth • Food • Life, a project of the Independent Media Institute.
“We Have Entered the Era of ‘Global Boiling’—Marine Wildlife, Ecosystems, and Economies Are Being Devastated” by David Hastings is licensed by the Observatory under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (CC BY-NC-SA 4.0).
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Introduction
We have known for decades that greenhouse gas emissions are the primary driver of long-term global warming. And every day, the ocean plays a huge role in keeping us cool: It absorbs 90 percent of the excess heat generated by burning fossil fuels and deforestation. But now, we are officially in uncharted waters. According to the Climate Change Institute at the University of Maine, in March and April 2024, the average global sea surface temperature (SST) reached 21.17 degrees Celsius (70.11 degrees Fahrenheit), the hottest temperature ever recorded for the average world ocean at the surface.
Record-breaking marine heatwaves in 2023 and 2024 have led some researchers to believe there is a fundamental shift with serious impacts for life both in the ocean and on land. Heatwaves in the North Atlantic and Pacific oceans in 2023 were exceptional in their severity, duration, and size.
Following the record-breaking year in 2023, 2024 was the warmest year ever measured for the global ocean. In fact, every decade since 1982, when scientists started measuring ocean temperatures by satellite, has been warmer than the previous one. The culprit is human-caused climate change. Modeling efforts reveal that without a human-induced warming trend, these unprecedented events would not have been possible.
The extraordinarily high sea surface temperatures recorded in 2023 provide a frightening glimpse into the planet’s future. A 2024 study by researchers at the University of Reading and Imperial College London found that temperatures in the top 100 meters of ocean basins around the world have steadily increased since 1980. The Atlantic basin, in particular, has experienced substantial heat amplification since 2016.
They concluded that extreme sea surface temperatures in the North Atlantic during 2023 “lie at the fringe of the expected mean climate change for a global surface-air temperature warming level (GWL)” of 1.5 degrees Celsius and closer to 3.0 degrees Celsius GWL. If this scenario is attained globally, it would have catastrophic consequences, including the eventual collapse of ice caps. This would lead to an uncontrollable rising sea level that would consume low-lying cities and contaminate water sources with salty seawater worldwide.
Marine heat waves are also an important factor in extreme weather events, including hurricanes, since warmer surface oceans mean increased evaporation, which in turn results in heavier rains in some areas. It is well established that the energy of warm surface water leads to hurricane formation; these storms are more likely to intensify rapidly and become more destructive with hotter surface water. In August 2023, Hurricane Idalia, sitting over unusually warm surface water in the Gulf of Mexico, intensified quickly. It strengthened from 80 mph winds to a Category 3 storm, gaining 40 mph in less than 24 hours. The warm surface water was like rocket fuel for the approaching storm.
The year 2024 did not see relief from the heat. In August 2024, the Arctic Ocean’s mean sea surface temperatures were between 2 and 4 degrees Celsius (3.6 and 7.2 degrees Fahrenheit) warmer than the 1991-2020 average August values in most Arctic Ocean marginal seas, according to the National Oceanic and Atmospheric Administration (NOAA). In the southwest Pacific, the intense heat in 2024 contributed to a record-breaking streak of tropical cyclones hitting the Philippines. We have clearly entered a new era of exceptionally high surface ocean temperatures, which is of great concern. In the first half of 2025, global sea surface temperatures were the second-warmest on record, with the mean reaching 20.89 degrees Celsius, just below the 2024 record of 21.04 degrees Celsius.
The rate of ocean warming has more than quadrupled over the past four decades, according to a 2025 study. In the 1980s, ocean surface temperatures were rising 0.06 degrees Celsius (0.1 degrees Fahrenheit) per decade, but are now increasing at 0.27 degrees Celsius (0.49 degrees Fahrenheit) per decade. El Niño, a natural warming event in the Pacific, can explain some of the variation over a short time period, but it doesn’t explain these long-term increases over decades.
Impact on Marine Wildlife
As on land, marine ecosystems are sensitive to temperature changes. Extreme heat in the oceans can destroy coral reefs, which thrive in a narrow range of temperatures. Warm water is best for corals and their symbiotic algae, ideally between 23 and 29 degrees Celsius (about 73 to 84 degrees Fahrenheit). When it gets hotter than this upper temperature, the photosynthetic algae that coexist with and provide food for the tiny coral polyps will be expelled, and the corals will lose color and bleach. Corals can die if the ocean water doesn’t return to cooler temperatures quickly or if bleaching events happen repeatedly. Between 1950 and 2021, ocean reefs have lost half of their capacity to provide ecosystem services.
The hottest ocean temperatures of 38.4 degrees Celsius (101.1°F) ever recorded occurred in the Florida Keys in 2023; this high heat, almost as hot as a hot tub, will harm coral and cause problems for all marine life.
A marine heat wave in the Gulf of Maine in 2012 underscored the risk that warmer water poses to fisheries. It turns out that squid drawn north by warmer waters were eating Northern shrimp. As a result of the predation, the shrimp population plummeted by almost 90 percent, decreasing from over 27 billion in 2010 to only 2.8 billion two years later, according to a recent 2024 assessment. The commercial shrimp fishery closed and has not yet reopened. By 2023, the Northern shrimp population was estimated to have dropped to around 200 million, less than 1 percent of the numbers before the heat wave.
A persistent marine heat wave occupying an enormous area in the northeast Pacific Ocean, coined “the Blob,” existed from 2014 to 2016, causing a chain of events that disrupted entire ecosystems. It greatly impacted organisms, large and small, throughout the food chain, and reveals how interconnected and interdependent marine ecosystems are. High surface temperatures caused krill and forage fish populations to decline, and a harmful algal bloom spread in shellfish from Alaska to Southern California, shutting down the clam industry. Lacking krill, humpback whales fed on anchovies closer to shore, where crab traps are set, leading to whale entanglements. The Blob also led to the stranding of thousands of California sea lions and an unusual mortality event.
During “the Blob,” a shift in food web dynamics from crustaceans to gelatinous organisms with less food value to fish causes a collapse in several major fisheries, including salmon, Dungeness crab, and sardines. Humpback whales had been experiencing a good, prolonged period of recovery following the end of commercial whaling in 1976. But between 2012 and 2021, the humpback whale population in the North Pacific fell by 20 percent. This dramatic loss was attributed to the loss of food during the marine heatwave, including krill, a primary food source for humpbacks.
During and after the Blob, a catastrophic and persistent loss of more than half of Alaska’s population of common murres occurred between 2013 and 2016. Common murres are large seabirds, similar to a loon but smaller. An estimated loss of 4 million birds occurred, largely due to warmer waters disrupting fish ecosystems and their food sources. In a 2024 study published in Science, researchers found no indication of recovery since the heatwave was resolved, suggesting an entire ecosystem shift as a result of the heatwave. This is the largest documented wildlife mortality event in the modern era, according to the researchers. While it is a mistake to draw sweeping conclusions from a single event, the impacts from the Blob provide insight into what happens to marine life as the ocean temperature rises.
In February 2024, researchers from the National Oceanic and Atmospheric Administration completed a mission to assess the impact of the 2023 marine heat wave on corals in the Florida Keys Marine Sanctuary. Their preliminary findings are worrisome. The scientists found extreme heat killed nearly 80 percent of the approximately 1,500 staghorn coral (Acropora cervicornis), which provide critical habitat for a host of other marine life.
“The findings from this assessment are critical to understanding the impacts to corals throughout the Florida Keys following the unprecedented marine heat wave,” said Sarah Fangman, the Florida Keys National Marine Sanctuary superintendent. “They also offer a glimpse into coral’s future in a warming world. When the ecosystem experiences significant stress in this way, it underscores the urgency for implementing updates to our regulations, like the Restoration Blueprint, which addresses multiple threats that will give nature a chance to hold on.”
Impact on Fisheries
Marine heat waves have caused fishery disasters, affecting populations of sardines—a key feeder fish for larger marine species—and causing the collapse of select salmon and cod fisheries.
Between 2014 and 2016, the marine region along the Pacific coastline of the Baja California Peninsula in Mexico experienced an unprecedented period of intense and prolonged marine heatwaves that impacted local marine ecosystems. A team of scientists from Stanford University published an important study in Nature in November 2024 in which they determined that during this period of elevated sea temperatures, lobster, sea urchin, and sea cucumber fisheries suffered a 15 to 58 percent decrease in aggregate landings, particularly impacting small-scale fisheries.
“In the face of extreme environmental shocks such as marine heatwaves, small-scale fisheries operating near biogeographic transition zones are among the most vulnerable,” they write.
Role of Human Global Warming on Marine Heatwaves
According to a 2025 study published in the Proceedings of the National Academy of Sciences, human-induced global warming is responsible for almost half of the extreme marine heatwave events. On average, global warming has led to a threefold increase in the number of days per year that the oceans experience extreme heat conditions at the surface. These events are growing more intense, lasting longer, and occurring more frequently as a result of human-caused global warming.
Another study published in 2024 investigated the underlying causes of an unprecedented marine heatwave in the Northwest Pacific Ocean, compounded with a record-breaking land-based heatwave in the Yangtze River Basin. Using model-based simulations, the researchers concluded that the marine heatwave was extremely unlikely to happen without human-caused warming.
The Era of Global Boiling
Warmer ocean temperatures clearly have long-term impacts on the environment. This includes not just biological impacts, but also a reduction in the ability of the ocean to take up carbon dioxide. Warm water holds less gas, including carbon dioxide—the most important greenhouse gas—than cool water. So, as the ocean warms, less heat-trapping gas is removed from the air, and more stays in the atmosphere. It’s a vicious cycle leading inexorably towards a worse outcome: as the ocean warms, less carbon dioxide is absorbed and more remains in the air, which causes the planet to heat up even more.
Marine heat waves are parallel to heat waves on land, as evidenced by 2023’s record-setting terrestrial heat waves in the southeastern United States, Southern Europe, and China. Studies of these heat waves reveal that they would have been “virtually impossible” without human-caused climate change. In July 2023, United Nations Secretary-General António Guterres declared, “The era of global warming has ended; the era of global boiling has arrived.”
Still, there is some good news. When we first recognized climate change as a serious concern decades ago, there were no clear solutions or answers to the enormous challenges that climate scientists projected. However, with the falling cost of solar and wind energy, progressively better and affordable battery storage, and crucial gains in energy efficiency, viable solutions that are much less expensive than burning fossil fuels are available.
Specifically, in March 2025, less than half of U.S. electricity production was produced using fossil fuels, as clean power generation surged. Power plants that don’t burn fossil fuels, including solar, wind, batteries, biofuels, and nuclear, are planned to deliver 93 percent of all new capacity for the U.S. grid in 2025, according to the Energy Information Agency.
Exceptionally warm global waters will not disappear. However, we can avoid the worst impacts of climate change and even hotter water temperatures by taking rapid action to strengthen local, state, and national climate policy initiatives.
