The Oceans Were Hotter Than Ever in 2025
Here's why that matters.
The Earth’s oceans were hotter in 2025 than in any year since modern measurements began, marking a dangerous new record.
New analysis published in the peer-reviewed journal Advances in Atmospheric Sciences on Friday found that the upper 2,000 meters (6,561 ft.) of the ocean absorbed a record-setting 23 zettajoules more energy than in 2024—equivelant to roughly 37 times more energy than the world consumed in 2023.
The study examined ocean heat content, which measures how much excess heat energy the world’s oceans store over time. Tracking ocean temperatures is a key way scientists can monitor long-term climate change. That’s because our oceans play a key role in regulating the impact of global carbon emissions in our atmosphere—absorbing about 90% of the excess heat from planetary warming trapped by greenhouse gases over the past century.
Researchers also noted that global average sea-surface temperatures, where the ocean water and atmosphere meet, in 2025 were the third highest on record and remained about 0.5°C (1°F) above the 1981–2010 average baseline. Some areas are warming faster than others—the warmest areas included the South Atlantic and North Pacific Oceans, and the Southern Ocean.
As oceans get hotter, a range of climate impacts are being unleashed. Warmer oceans contribute to rising sea levels (due in part to the expansion of water molecules as they heat up) and fuels more extreme weather. This includes increasing the intensity of hurricanes while decreasing the speed at which they travel—meaning they can linger longer in one location when they make landfall, potentially leaving more destruction in their wake. We’re already seeing the impacts—last year was only the second year in recorded history in which at least three Category 5 hurricanes formed in the Atlantic basin.
Read More: The World’s First Climate Tipping Point Has Been Crossed, Scientists Say
Rising ocean temperatures also contribute to the loss of coral reefs, which help support fisheries, and protect coastlines from storm surges and rising sea levels. A 2025 report found that warm-water coral reefs are passing their tipping point, with 80% experiencing unprecedented heat waves, bleaching events, and die back.
Today’s report raises alarm bells about the climate impacts the world stands to face due to ocean warming. The authors note that, without global efforts to reduce emissions, temperatures will only continue to rise.