Explaining and anticipating global temperature surges by tracking heat
This study demonstrates that a heat budget model driven by Earth's energy imbalance and El Niño-related subsurface heat release successfully explains global temperature variations during the Argo era and projects that a potential 1997/98-like El Niño in 2026–2027 could push global temperatures to a record 1.80 K above the pre-industrial baseline.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
The Earth is constantly balancing a delicate ledger of energy. On one side, sunlight pours in, warming the planet. On the other, the planet radiates heat back out into space. For most of human history, these two sides were nearly equal, keeping global temperatures relatively stable. However, as greenhouse gases have accumulated in the atmosphere, they act like a thickening blanket, trapping more heat than escapes. This creates a persistent surplus of energy known as Earth's energy imbalance. While this imbalance drives long-term warming, the temperature we feel from year to year is also influenced by the ocean's ability to store and release heat. Specifically, the tropical Pacific Ocean acts as a massive thermal battery, shifting vast amounts of warm water between its surface and its depths in a cycle known as El Niño and La Niña. Understanding how these two forces—the steady accumulation of trapped energy and the rhythmic shifting of ocean heat—interact is crucial for predicting why some years become significantly hotter than others.
A team of researchers has developed a new way to track this heat, offering a clearer picture of why global temperatures surged to record levels recently and what might happen next. Instead of looking at surface temperatures alone, the scientists built a "heat budget" that follows the energy as it moves between the atmosphere and the upper layers of the ocean. They focused on a specific reservoir of heat: the air above the Earth and the top 100 meters of the ocean. By combining data on how much extra energy the Earth is absorbing from space with measurements of how much heat is moving up or down in the tropical Pacific, they created a model that explains nearly all of the temperature changes observed over the last 18 years. This approach allowed them to see exactly how much of the recent heat spike came from the planet trapping more sunlight and how much came from the ocean releasing stored warmth.
The study reveals that the record-breaking warmth of 2023 and 2024 was not caused by a single factor, but by a rare alignment of two drivers. First, the Earth's energy imbalance reached unusually high levels, meaning the planet was absorbing significantly more solar energy than it was releasing. Second, the tropical Pacific Ocean shifted from a cool phase to a strong El Niño, pumping a massive amount of heat from the deep ocean up to the surface. These two forces worked together to create an exceptional surge in heat. The researchers found that after this peak, global temperatures began to decline in 2024 and 2025, but not because the Earth stopped warming. Instead, the ocean began to absorb heat again, pulling energy away from the surface. However, this cooling effect was not strong enough to return temperatures to pre-2023 levels, leaving the planet in a permanently elevated state of warmth.
Looking ahead, the researchers used their heat-tracking framework to forecast the coming year. They started their outlook in August 2026, a time when a new El Niño event was developing. They considered two possible futures. In the first scenario, they assumed the tropical Pacific would release no additional heat from its depths. Even in this conservative case, the continued accumulation of energy from the sun would push global temperatures higher than the previous records. In the second, more extreme scenario, they assumed the ocean would release heat at a rate similar to the massive 1997/98 event, which was one of the strongest El Niños on record. If this happens, the study suggests that the average global temperature for the 12-month period from July 2026 to June 2027 could reach 1.80 K above the pre-industrial baseline. This would be 0.25 K above the previous record, representing a significant new milestone in global warming.
The findings underscore the importance of keeping a close watch on the ocean's hidden heat. The researchers emphasize that their ability to make these predictions relies entirely on a global network of observing instruments, including satellites that measure radiation from space and thousands of floating sensors that dive into the ocean to measure temperature and salinity. Without these continuous observations, it would be impossible to know how much heat is being stored or released. The study suggests that while the long-term trend of warming is driven by the Earth's energy imbalance, the year-to-year jumps in temperature are heavily influenced by the ocean's rhythm. By tracking the flow of heat through the climate system, scientists can now provide a more reliable, physics-based outlook for the near future, offering a clearer warning of the extremes to come.
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