World’s Oceans Hit Record Heat in 2025, at Great Economic and Social Costs

By Oritro Karim
UNITED NATIONS, Jan 22 2026 – In 2025, global ocean temperatures rose to some of the highest levels ever recorded, signaling a continued accumulation of heat within the Earth’s climate system and raising deep concern among climate scientists. The economic toll of ocean-related impacts—including collapsing fisheries, widespread coral reef degradation, and mounting damage to coastal infrastructure—is now estimated to be nearly double the global cost of carbon emissions, placing immense strain on economies and endangering millions of lives.

On January 14, the World Meteorological Organization (WMO) confirmed that global temperatures have reached record highs over the past 11 years, with ocean heating continuing at an alarming pace. Despite the cooling influence of La Niña, 2025 became the third hottest year ever recorded. In just the past year, ocean temperatures increased by an estimated ∼23 ± 8 zettajoules—an amount of heat roughly equivalent to 200 times the world’s total electricity generation in 2024.

With an estimated 90 percent of excess heat from global warming absorbed by the world’s oceans, rising ocean temperatures have become one of the clearest indicators of the accelerating climate crisis—carrying profound risks for ecosystems and human life. The ocean is central to global prosperity, supporting livelihoods, market economies, and overall human well-being.

“Global warming is ocean warming,” said John Abraham, a professor of thermal science at the University of St. Thomas. “If you want to know how much the Earth has warmed or how fast we will warm into the future, the answer is in the oceans.”

Zeke Hausfather, a climatologist and research scientist at University of California, Berkeley, described the ocean as the “most reliable thermostat of the planet.”

According to figures from WMO, roughly 33 percent of the Earth’s total ocean area ranked among the top three warmest conditions for ocean ecosystems in history, with roughly 57 percent falling within the top five, such as the tropical and South Atlantic Ocean, Mediterranean Sea, North Indian Ocean, and Southern Oceans.

The primary impact of human-generated carbon dioxide emissions on the ocean is the rapid warming of ocean waters, which significantly reduces the ocean’s capacity to hold oxygen—a critical lifeline for species survival. Rising temperatures also drive ocean acidification—weakening marine organisms, disrupting ecosystems, altering the physiology of numerous species, and triggering mass die-offs.

These effects have catastrophic consequences for biodiversity, fueling widespread coral reef bleaching, the collapse of seagrass beds, and the decline of kelp forests—all of which directly harm the benefits that humans yield from healthy marine environments. Rising ocean temperatures also intensify extreme weather events and accelerate sea-level rise, which in turn increase coastal flooding, erosion, and displacement, placing millions of people, particularly those in low-lying coastal communities, at heightened risk.

While some ocean-based benefits—such as seafood and maritime transport—are reflected in market prices, many others, including coastal protection, recreation, and marine biodiversity, remain overlooked, becoming part of the invisible social “blue cost” of carbon emissions, despite being essential to the deeply interconnected relationship between oceans, people, and economic systems.

“If we don’t put a price tag on the harm that climate change causes to the ocean, it will be invisible to key decision makers,” said environmental economist Bernardo Bastien-Olvera, who led a Scripps Institution of Oceanography study at the University of California San Diego, examining the social cost of carbon emissions and the economic toll of ocean degradation.

“Until now, many of these variables in the ocean haven’t had a market value, so they have been absent from calculations. This study is the first to assign monetary-equivalent values to these overlooked ocean impacts,” added Bastien-Olvera.

According to findings from the Scripps Institution of Oceanography study, accounting for the social impacts of ocean-related carbon emissions nearly doubles the estimated global cost—showing that ocean degradation is a major driver of climate-related economic losses. Researchers found that without ocean impacts included in their model, the average cost per ton of carbon dioxide was roughly USD 51. When accounting for ocean losses, the total costs increased by USD 41.6 per ton, reaching a total of USD 97.2, marking a 91 percent rise.

With the WMO Global Carbon Budget estimating global carbon dioxide emissions at roughly 41.6 billion tons in 2024, this translates to nearly $2 trillion in ocean-related losses in a single year—which is currently absent from standard climate cost assessments. Furthermore, the study found that market damages as a result of ocean degradation account for the largest costs to society and could reach global annual losses of $1.66 trillion in the year 2100.

Furthermore, damages in non-use values—such as recreational benefits provided by ocean ecosystems—now amount to an estimated USD 224 billion annually, while non-market values, including nutritional losses from collapsing fisheries, contribute an additional USD 182 billion in yearly damages. Bastien-Olvera stressed that many of these losses are not traditional market losses but cultural and societal losses, which carry different and often deeper forms of significance for affected communities.

“When an industry emits a ton of carbon dioxide into the atmosphere, as a society we are paying a cost. A company can use this number to inform cost-benefit analysis — what is the damage they will be causing society through increasing their emissions?”, asked Bastien-Olvera.

In response to the rapid warming of the Earth’s oceans, governments, scientific institutions, and international organizations are mobilizing new strategies to reduce carbon emissions and protect marine ecosystems, including expanding green energy infrastructure and advancing large-scale ecosystem restoration efforts.

The United Nations (UN) has renewed pressure on member states to meet their Paris Agreement commitments, while initiatives like the Global Ocean Observing System (GOOS) and the High Seas Treaty work to strengthen ocean monitoring and protect marine biodiversity.

Scientists are also testing emerging methods to counteract climate-driven changes in the ocean. In late 2025, marine scientist Adam Subhas and his team released 16,200 gallons of sodium hydroxide into the ocean in an effort to neutralize rising acidity levels. Though controversial and still in early development, the experiment reflects a growing interest in exploring non-traditional tools that could stabilize marine ecosystems.

“As long as the Earth’s heat continues to increase, ocean heat content will continue to rise and records will continue to fall. The biggest climate uncertainty is what humans decide to do. Together, we can reduce emissions and help safeguard a future climate where humans can thrive,” said Abraham.

IPS UN Bureau Report

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