An international annual analysis using data from NOAA and other research groups found that the upper 2,000 meters of the world’s oceans held a record amount of heat in 2023. The result reflects Earth’s continuing energy imbalance and underscores the value of sustained ocean monitoring.
TLDR: NOAA-linked research found that the upper 2,000 meters of the world’s oceans held more heat in 2023 than in any year of the modern record. The ocean’s continued heat gain is a key sign of climate change and can contribute to sea-level rise and marine heatwaves.
The world’s oceans held more heat in 2023 than at any point in the modern measurement record, according to an annual analysis. The finding offers a measure of how steadily Earth’s climate system is accumulating energy, much of it absorbed by seawater rather than remaining in the atmosphere.
Researchers estimated that the heat stored in the upper 2,000 meters of ocean reached a record high in 2023. Their analysis, published in Advances in Atmospheric Sciences in January 2024, combined measurements from multiple research groups, including data maintained by the US National Oceanic and Atmospheric Administration’s National Centers for Environmental Information. It captures heat well below the surface.
The study estimated that the upper ocean gained about 15 zettajoules of heat during 2023 compared with the previous year. A zettajoule is one sextillion joules, an amount difficult to picture in everyday terms. The researchers illustrated the scale by comparing the annual increase with the energy released by many hundreds of millions of Hiroshima-sized atomic bombs. Such comparisons convey magnitude, not a direct measure of human risk or damage.
Oceans take up more than 90 percent of the excess heat trapped by greenhouse gases, making ocean heat content a key indicator of long-term climate change. Air temperatures can fluctuate sharply from year to year under the influence of weather patterns and natural cycles. Heat stored in the ocean changes more slowly, so its continuing rise helps distinguish the sustained warming trend from short-lived variations.
The 2023 record came as global average sea-surface temperatures also reached exceptional levels. El Niño, a natural climate pattern that warms parts of the tropical Pacific, contributed to the warmth during the year. But the long-running increase in ocean heat is primarily associated with the human-caused buildup of greenhouse gases. The annual analysis does not attribute every regional temperature extreme to climate change; it documents the accumulating heat across the ocean as a whole.
Scientists assemble this picture from ship-based measurements, autonomous floats and other observing systems. Argo floats, which drift through the ocean and periodically descend to depth, now provide a major share of temperature and salinity observations in the upper ocean. NOAA and international partners also collect and quality-check records that allow researchers to compare recent conditions with earlier decades. Coverage remains uneven, particularly in some polar and deep-sea regions, and estimates carry uncertainty.
That uncertainty does not erase the main signal. Different research teams and analysis methods have found the same broad pattern: ocean heat content has risen over the period covered by modern observations, and recent years have established successive records. The 2023 figure is an annual snapshot, rather than proof that every ocean basin warmed at the same rate. Regional circulation, winds and mixing can shift heat between the surface and deeper layers, and across different parts of the sea.
The consequences extend beyond warmer water. Heating contributes to the expansion of seawater, which adds to sea-level rise alongside melting land ice. It can also intensify marine heatwaves, stress ecosystems and influence the moisture and energy available to storms. The study measures stored heat; it does not by itself predict the timing or severity of any particular coastal impact.
Researchers will need continued observations to track where the added energy goes and how ocean circulation redistributes it. Maintaining floats, ships and satellite measurements is essential, especially in regions with sparse records. The record is a reminder that reducing greenhouse-gas emissions addresses the underlying energy imbalance, while long-term monitoring can improve estimates of future sea-level rise and ocean change.
Mark Davis serves as the Senior Correspondent for Energy, Climate, and Resource Economics at Just Right News. In an era where the conversation around the environment is often dominated by alarmism and top-down mandates, Mark provides a vital, market-oriented perspective on the complex forces shaping our world. As the lead voice behind the acclaimed feature series “Power and the Planet,” he explores the intersection of environmental policy, global energy markets, and the fundamental economic principles that sustain modern civilization.
Mark’s pragmatic approach to resource management was forged in the high desert of his hometown, Albuquerque, New Mexico. Growing up in a region defined by both its breathtaking natural beauty and its rugged, resource-dependent landscape, he developed an early appreciation for the delicate balance between conservation and utilization. New Mexico’s unique position as a hub for both traditional energy production and cutting-edge scientific research provided Mark with a front-row seat to the evolution of the American energy sector. This upbringing instilled in him a deep-seated belief that true environmental stewardship is inseparable from economic prosperity and technological innovation.
Now based in Boulder, Colorado, Mark operates from the heart of the nation’s climate research community. While Boulder is often seen as a bastion of environmental idealism, Mark utilizes his post to provide a necessary counterweight, grounded in the realities of resource economics. He understands that energy policy does not exist in a vacuum; it has tangible consequences for the American taxpayer, the stability of the national power grid, and the strength of the domestic manufacturing sector. By reporting from the front lines of the climate debate, he is able to challenge prevailing narratives with hard data and a commitment to the principles of the free market.
Throughout his tenure at Just Right News, Mark has distinguished himself by focusing on the “Resource Economics” aspect of his beat. He frequently highlights the hidden costs of rapid energy transitions and advocates for an “all-of-the-above” energy strategy that prioritizes American energy independence. His work often shines a light on the geopolitical implications of resource scarcity, arguing that a secure nation must first be an energy-secure nation. Whether he is analyzing the impact of federal land-use regulations or investigating the supply chains required for new technologies, Mark remains focused on how policy decisions affect the lives and livelihoods of everyday citizens.
In “Power and the Planet,” Mark continues to bridge the gap between complex scientific concepts and the economic realities facing the country. He rejects the false choice between a healthy environment and a thriving economy, instead seeking out solutions that leverage American ingenuity and private-sector competition. For Mark, reporting on the climate is not about following the latest trends, but about ensuring that the conversation remains tethered to the foundational values of liberty, property rights, and fiscal responsibility. His contributions ensure that Just Right News readers receive a comprehensive, clear-eyed view of the challenges and opportunities defining the future of our planet.