In 2025, the world’s oceans absorbed enough extra heat to equal about 365 million Hiroshima-sized atomic bombs. This finding comes from a report by 55 scientists, published in the journal Advances in Atmospheric Sciences. For the ninth consecutive year, marine heat levels hit record highs, and experts warn that this trend is worsening extreme weather, rising sea levels, and disturbing marine ecosystems. The primary cause? Increasing greenhouse gas emissions.
We’ve already felt the severe consequences of this rising ocean heat. In 2025, heavy monsoon rains took over 1,300 lives in Southeast Asia. In Central Texas, flash floods tragically claimed 138 lives, including 27 summer campers. These events highlight how marine warming can intensify storms and lead to devastating flooding.
The report’s authors are clear: global ocean heat content will keep rising until we reach net-zero greenhouse gas emissions. They stress that the oceans act as a crucial heat sink, absorbing about 90% of the excess warmth trapped by greenhouse gases. This absorption affects climate in various ways, mainly by increasing moisture in the atmosphere, which fuels stronger storms.
To measure ocean heat, the researchers looked at temperature changes in the upper 6,500 feet of the ocean. They found that in just one year, ocean heat content rose by 23 zettajoules, ensuring 2025 is the hottest year recorded. Notably, around 14% of the oceans peaked at their warmest levels on record, especially in regions like the Southern Ocean and the Mediterranean Sea. More than half of the ocean area recorded temperatures among the five highest ever.
This rising heat does more than just intensify storms; it’s also accelerating the melting of glaciers and sea ice. In 2025, Arctic sea ice hit a historic low since satellite tracking began, while Antarctic sea ice also dropped significantly. Studies suggest that parts of the Greenland and Antarctic ice sheets are at critical tipping points, meaning they could contribute significantly to rising sea levels over time.
Coral reefs are another casualty of ocean warming. When ocean temperatures exceed their tolerance levels, corals expel the algae that provide them with needed nutrients, leading to bleaching. Currently, we’re in the middle of a major global coral bleaching event. According to NOAA, around 84% of the world’s coral reefs have been impacted by heat stress this year, with significant bleaching reported in at least 83 countries.
Experts don’t expect the trend of marine warming to reverse anytime soon. Until we achieve net-zero carbon emissions, ocean heat will continue to rise. While we may not be close to reaching that goal, quick cuts to emissions can still minimize future damage. Strengthening ocean monitoring will help us understand these changes better and prepare for a new climate reality, allowing communities to adapt and build resilience.
For more insights on climate change, check out this recent NASA report on ocean warming and its implications.
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extreme weather,Global warming,greenhouse gases,oceans
