Ocean temperatures hit record highs in 2025, underscoring need for climate action

Ocean temperatures reached record highs in 2025, showing global heating is accelerating and increasingly affecting weather worldwide

Global ocean temperatures reached their highest levels on record in 2025, according to a new analysis by an international team of scientists who track Earth’s climate indicators each year.

The ocean absorbs more than 90 percent of the excess heat trapped by greenhouse gases, making it the primary heat reservoir in the climate system. Ocean heat content, which measures the accumulation of heat stored in the ocean, is thereby one of the clearest indicators of long-term climate change.

The study, published in Advances in Atmospheric Sciences, found that ocean warming was widespread but uneven. About 16 percent of the world’s oceans recorded their highest-ever ocean heat content in 2025, while roughly 33 percent ranked among the three warmest years in their historical records. The strongest warming occurred in the tropical and South Atlantic, the North Pacific and the Southern Ocean.

Researchers also reported that ocean warming trends have intensified since the 1990s. Heat stored in the upper 2,000 meters of the ocean has continued to rise steadily in recent decades, with evidence of a slight acceleration in the rate of warming.

Global average sea surface temperatures in 2025 ranked as the third warmest year on record and remained about 0.5 degrees Celsius (approximately 1 degree Fahrenheit) above the 1981 to 2010 baseline. Sea surface temperatures were slightly lower than in 2023 and 2024, a change the researchers attributed primarily to the transition from El Niño to La Niña conditions in the tropical Pacific.

Sea surface temperatures play a key role in shaping global weather patterns. Warmer oceans increase evaporation and atmospheric moisture, contributing to heavier rainfall and more intense storms. In 2025, the study linked these conditions to flooding across parts of Southeast Asia, drought in the Middle East and flooding in Mexico and the Pacific Northwest.

Rising ocean heat is also driving sea-level rise through thermal expansion and intensifying heatwaves and extreme weather, the researchers said. As long as Earth continues to accumulate heat, ocean heat content is expected to keep increasing and new records are likely to follow.

Read the fully study.