Oceans Reach Record-Breaking Temperatures
▼ Summary
– Since 2018, global researchers have measured record-breaking ocean heat absorption each year, with 2025 marking the eighth consecutive annual record.
– A 2025 study found the world’s oceans absorbed 23 zettajoules of excess heat, a significant increase from the 16 zettajoules absorbed in 2024.
– A zettajoule is an immense unit of energy, with 23 zettajoules equaling 23 sextillion joules.
– A researcher illustrates the scale by comparing the 2025 ocean heat increase to the energy of 12 Hiroshima atomic bombs exploding every second.
– Oceans act as the planet’s primary heat sink, absorbing over 90% of excess atmospheric warming and distributing heat to deeper waters.
The world’s oceans have reached a new and alarming milestone, absorbing more heat in 2025 than in any previous year on record. This marks the eighth consecutive year of record-breaking ocean heat content, a clear signal of the accelerating pace of planetary warming. A comprehensive international study published in Advances in Atmospheric Science reveals that the oceans absorbed an additional 23 zettajoules of heat in 2025. This staggering figure represents a significant jump from the 16 zettajoules absorbed just the year before, underscoring a rapid and concerning trend.
To grasp the scale of this energy, it helps to understand the units. A joule is a standard measure of energy, but a zettajoule is an almost unimaginably large number: one sextillion joules. The 23 zettajoules absorbed last year can be written as 23 followed by 21 zeros. Researchers often struggle to find analogies that make such colossal numbers relatable to the public. John Abraham, a professor of thermal science and co-author of the study, offers a striking comparison. He notes that the amount of heat added to the oceans in 2025 is energetically equivalent to the detonation of 12 Hiroshima atomic bombs every single second of the year. Other calculations equate it to the energy needed to boil two billion Olympic-sized swimming pools.
“The past year was a bonkers, crazy warming year, that’s the technical term,” Abraham remarked with a touch of dark humor. “The peer-reviewed scientific term is ‘bonkers’.” His comment highlights the profound surprise and concern within the scientific community regarding the intensity of recent warming. The data comes from a collaborative effort by more than fifty scientists across the United States, Europe, and China, who have been meticulously tracking ocean heat since 2018.
Oceans act as the planet’s primary heat sink, soaking up over ninety percent of the excess warmth trapped in the atmosphere by greenhouse gases. This absorption plays a critical role in moderating global air temperatures, but it comes at a severe cost to marine ecosystems. The heat doesn’t just stay at the surface; ocean currents and circulation patterns slowly transport this excess energy into deeper waters. This process has far-reaching consequences, including more intense and frequent marine heatwaves, coral bleaching, sea-level rise from thermal expansion, and disruptions to global weather patterns. The relentless year-on-year increase in ocean heat content is a definitive measure of the Earth’s growing energy imbalance, with profound implications for climate stability now and in the future.
(Source: Ars Technica)
